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Cited by 67Fungal and yeast genetics researchHeat shock proteins researchAntifungal resistance and susceptibility

Cdc28 provides a molecular link between Hsp90, morphogenesis, and cell cycle progression in Candida albicans

Open access
Senn, Heather, Shapiro, Rebecca S., Cowen, Leah E.·2012·Molecular Biology of the Cell
DOI 10.1091/mbc.e11-08-0729PMC PMC3258172
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Abstract

The trimorphic fungus Candida albicans is the leading cause of systemic candidiasis, a disease with poor prognosis affecting immunocompromised individuals. The capacity of C. albicans to transition between morphological states is a key determinant of its ability to cause life-threatening infection. Recently the molecular chaperone heat shock protein 90 (Hsp90) was implicated as a major regulator of temperature-dependent C. albicans morphogenesis; compromising Hsp90 function induces filamentation and relieves repression of Ras1–protein kinase A (PKA) signaling, although the mechanism involved remains unknown. Here we demonstrate that filaments generated by compromise of Hsp90 function are neither pseudohyphae nor hyphae but closely resemble filaments formed in response to cell cycle arrest. Closer examination revealed that these filaments exhibit a delay in mitotic exit mediated by the checkpoint protein Bub2. Furthermore, Hsp90 inhibition also led to a distinct morphology with defects in cytokinesis. We found that the cyclin-dependent kinase Cdc28 was destabilized in response to depletion of Hsp90 and that Cdc28 physically interacts with Hsp90, implicating this major cell cycle regulator as a novel Hsp90 client protein in C. albicans. Taken together, our results suggest that Hsp90 is instrumental in the regulation of cell division during yeast-form growth in C. albicans and exerts its major effects during late cell cycle events.

AI snapshot

Written from the paper’s full text.

TL;DR

Hsp90 inhibition in *Candida albicans* produces filaments and two-lobed cells that reflect distinct cell cycle defects, including delayed mitotic exit and cytokinesis failure. The cyclin-dependent kinase Cdc28 is destabilized and physically interacts with Hsp90, identifying it as an Hsp90 client linking Hsp90 to morphogenesis and cell cycle progression.

Key findings

  • Geldanamycin-induced filaments were neither canonical pseudohyphae nor hyphae; after 8 h, almost all filaments contained two nuclei and no septa, and 76% (n = 85) had elongated microtubule structures resembling mitotic spindles, suggesting a delay in late mitosis.
  • A second two-lobed morphology was multinucleate and showed cytokinesis defects: Mlc1-YFP actomyosin rings were present at the mother/daughter junction in 96% of cells (n = 79) but variable/absent at the daughter-cell constriction, and Cdc3-YFP septin rings were present at the mother/daughter junction in 97% (n = 69) but mostly absent at the daughter constriction.
  • Hsp90 depletion reduced Cdc28 protein levels without changing *CDC28* transcript levels, and Hsp90-HA coimmunoprecipitated Cdc28, identifying Cdc28 as an Hsp90 client; Clb4 levels fell while Clb2 levels remained unchanged, and Cdc5 levels increased rather than decreased.
  • Deletion of *BUB2* dampened the geldanamycin-induced filamentous and two-lobed phenotypes, implicating the Bub2/Bfa1 mitotic exit checkpoint in the morphological response to Hsp90 compromise.

Methods

  • Used *C. albicans* strains including wild type, *MAL2p-HSP90/hsp90Δ*, *hsp90Δ/tetO-HSP90*, *bub2Δ/bub2Δ*, and tagged strains for Mlc1, Cdc3, Clb2, Clb4, Cdc5, Hsp90, and Cdc28; Hsp90 was compromised pharmacologically with geldanamycin (10–30 μM) or genetically by promoter repression.
  • Assessed morphology and cell cycle phenotypes by microscopy with propidium iodide/calcofluor white staining, rhodamine-phalloidin, indirect tubulin immunofluorescence, FACS for DNA content, checkerboard assays for hydroxyurea/doxycycline sensitivity, Western blotting, coimmunoprecipitation, and quantitative RT-PCR.

Limitations

  • The paper states that mitotic exit events are poorly understood in *C. albicans* and that considerable divergence from *S. cerevisiae* MEN architecture makes predictions impractical; it also notes that Cdc28 depletion was incomplete, leaving likely residual Cdc28 function, and that other Hsp90 client proteins critical for S phase and mitotic exit remain unidentified.
  • Evident from the text: the study relies on in vitro laboratory media, pharmacological inhibition, and promoter-depletion strains, with no in vivo infection model or direct demonstration of the proposed stochastic spindle-breakdown/cell-separation decision point.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1091/mbc.e11-08-0729

Cites

75 of 75 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 90 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Geldanamycin-induced filaments almost always contained exactly two nuclei even in filaments with multiple branches.

    “Of interest, geldanamycin-induced filaments almost always contained exactly two nuclei even in filaments with multiple branches (Supplemental Figure S1).”
    Quote in the paperSubstantial claim
  • Findingown data

    A second distinct morphology in geldanamycin-treated cultures consists of a single yeast cell (mother) attached to a daughter cell consisting of two lobes with an obvious constriction between them, which is consistently wider than the mother/daughter cell junction.

    “A second, distinct morphology was found in geldanamycin-treated cultures (Figure 2C). This form consists of a single yeast cell, believed to be the mother cell, attached to a daughter cell consisting of two lobes with an obvious constriction between them. This constriction was consistently wider than the mother/daughter cell junction.”
    Quote in the paperNot a substantial claim
  • Findingown data

    At 4 and 6 h of geldanamycin treatment there was an enrichment of large-budded yeast cells compared with the untreated sample, occurring prior to the emergence of a large population of filaments at later time points.

    “Notably, at 4 and 6 h there was an enrichment of large-budded yeast cells compared with the untreated sample, and this occurred prior to the emergence of a large population of filaments at later time points (Figure 3A).”
    Quote in the paperSubstantial claim
  • Findingnone given

    Hsp90 inhibition induces filaments with a delay in mitotic exit mediated by the checkpoint protein Bub2.

    “Hsp90 inhibition induces filaments with a delay in mitotic exit mediated by the checkpoint protein Bub2.”
    Quote in the paperSubstantial claim
  • Findingown data

    FACS analysis of nuclear DNA content identifies major populations of 4n and higher-ploidy DNA content following geldanamycin treatment.

    “FACS analysis of nuclear DNA content identifies major populations of 4n and higher-ploidy DNA content following GdA treatment.”
    Quote in the paperSubstantial claim
  • May combine two claims. 55
  • The quote only partly states this claim. 1
  • Classified as probably not a substantial claim. 36

  • May combine two claims.

    Findingown data

    After 8 h of geldanamycin treatment, almost all filaments contained two nuclei and no septa.

    “After 8 h of treatment, almost all filaments contained two nuclei and no septa (Figure 2B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At 6 h of geldanamycin treatment, there was not an appreciable recovery of the 2n peak compared with the untreated control, the 4n peak represented the largest proportion of the population, and the higher-ploidy peak persisted and became larger.

    “At 6 h there was not an appreciable recovery of the 2n peak compared with the untreated control, the 4n peak (Figure 3B, white arrowheads) represented the largest proportion of the population, and the higher-ploidy peak persisted and became larger.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    After 2 h of geldanamycin treatment, a higher proportion of the treated population had 2n nuclear content compared with the untreated sample; by 3 and 4 h, the treated population was highly enriched for 4n cells, and a third peak indicative of higher ploidy appeared after 4 h.

    “After 2 h of treatment, a higher proportion of the geldanamycin-treated population had 2n nuclear content compared with the untreated sample (Figure 3B, black arrowheads). By 3 and 4 h, the geldanamycin-treated population is highly enriched for 4n cells and, in addition, a third peak indicative of cells at higher ploidy appeared after 4 h in the geldanamycin-treated samples (Figure 3B, gray arrowh”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Genetic depletion of Hsp90 phenocopies pharmacological inhibition of Hsp90, producing both elongated binucleate cells and multinucleate two-lobed cells.

    “After 6 h of growth, cells grown in maltose were primarily of the budding yeast form, whereas cells grown in glucose displayed both of the prominent morphologies found in response to geldanamycin treatment—elongated, binucleate cells and multinucleate, two-lobed cells (Figure 2E).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Filaments induced by growth in the presence of the Hsp90 inhibitor geldanamycin have a clear constriction between the filament and the attached yeast-form cell like pseudohyphae, but lack subsequent constrictions and have approximately parallel walls more closely resembling hyphae.

    “Like pseudohyphae, filaments induced by geldanamycin had a clear constriction between the filament and the attached yeast-form cell. Unlike pseudohyphae, however, the highly elongated filaments had no obvious subsequent constrictions at cell junctions. In fact, the walls of the filament were approximately parallel and more closely resembled hyphae than pseudohyphae.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In a randomly selected population of cells scored after 4, 6, and 8 h of geldanamycin treatment, filaments were the most prominent response, the two-lobed morphology formed a much smaller proportion of the total cell population, and a population of yeast cells was present at all time points.

    “This analysis revealed that filaments were the most prominent response, with the two-lobed morphology forming a much smaller proportion of the total cell population. In addition, a population of yeast cells was present at all time points.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The two-lobed daughter cell constriction contains no septum, and propidium iodide staining suggests this form is multinucleate, with cells containing between two and four discernible nuclei.

    “Calcofluor white staining revealed that the daughter cell constriction contained no septum, although the mother/daughter cell junction tended to have brighter staining. Propidium iodide staining suggested that this form is multinucleate (Figure 2D). Cells contained between two and four discernible nuclei.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Hsp90 depletion destabilizes the cyclin-dependent kinase Cdc28, providing a link between Hsp90, cell cycle regulation, and morphogenesis.

    “Hsp90 depletion destabilizes the cyclin-dependent kinase Cdc28, providing a link between Hsp90, cell cycle regulation, and morphogenesis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In geldanamycin-induced filaments with multiple branches, not all tips had equal intensity of staining, and some tips had no evidence of polarized actin.

    “Of interest, in filaments with multiple branches not all tips had equal intensity of staining, with some tips having no evidence of polarized actin.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The 8n group sorted by FACS was highly enriched for two-lobed cells, and this cell type was found almost exclusively in this group.

    “Consistent with our hypothesis, the 8n group was highly enriched for two-lobed cells, and this cell type was found almost exclusively in this group.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    After 24 h, many geldanamycin-induced filaments took up propidium iodide, but some were able to exclude it.

    “Although many filaments took up the propidium iodide stain, some were easily able to exclude it after 24 h (Supplemental Figure S4B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Mother and daughter cells remained attached after sonication, and anucleate mother cells or nuclei spanning the mother/daughter cell junction were observed, indicating nuclear migration across the site.

    “Mother and daughter cells remained attached after sonication, and it was not uncommon to observe anucleate mother cells or nuclei spanning the mother/daughter cell junction, indicating nuclear migration across the site (data not shown).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Genetic depletion of Hsp90 phenocopied pharmacological inhibition with respect to Clb4 and Clb2 levels.

    “Genetic depletion of Hsp90 phenocopied pharmacological inhibition.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cdc3-YFP was almost ubiquitously present at the junction between mother and daughter cells (97%, n = 69) but its presence was variable at the daughter cell constriction, with the majority of cells having no visible septin ring.

    “Similar to Mlc1-YFP fluorescence, Cdc3-YFP was almost ubiquitously present at the junction between mother and daughter cells (97%, n = 69) but its presence was variable at the daughter cell constriction, with the majority of cells having no visible septin ring (Figure 5C).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Cells with decreased levels of Hsp90 are hypersensitive to hydroxyurea, and the combined activity of doxycycline-mediated Hsp90 depletion and hydroxyurea is synergistic.

    “The combined activity of the two drugs was synergistic, suggesting that cells with decreased levels of Hsp90 were hypersensitive to hydroxyurea.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In response to Hsp90 inhibition with geldanamycin for 5 h, levels of Clb4 are reduced and levels of Clb2 are not.

    “In response to Hsp90 inhibition with GdA for 5 h, levels of Clb4 are reduced and levels of Clb2 are not.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The presence of Mlc1-YFP fluorescence at the daughter cell constriction was variable; the majority of cells had no ring, whereas some cells contained bright, faint, or partial rings.

    “The presence of Mlc1-YFP fluorescence at the daughter cell constriction, however, was variable. The majority of cells had no ring, whereas some cells contained bright, faint, or partial rings (Figure 5B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    bub2Δ/Δ cells responded normally to growth in 10% serum at 37°C by forming hyphae, ruling out a general filamentation defect.

    “bub2Δ/Δ cells responded normally to growth in 10% serum at 37°C by forming hyphae, ruling out the possibility of a general filamentation defect.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    C. albicans is a trimorphic fungus that can grow as unicellular budding yeast and in two filamentous, multicellular forms: hyphae and pseudohyphae.

    “This trimorphic fungus can grow as unicellular budding yeast and in two filamentous, multicellular forms: hyphae and pseudohyphae.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Sudbery et al., 2004 source

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    • cites Sudbery, 2011 source

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    • cites Berman, 2006 source

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  • Classified as probably not a substantial claim.

    Premisecitation

    Hsp90 is an essential molecular chaperone that stabilizes a diverse but select set of inherently unstable client proteins, including many regulators of cell signaling.

    “Hsp90 is an essential molecular chaperone that stabilizes a diverse but select set of inherently unstable client proteins, including many regulators of cell signaling (Wandinger et al., 2008; Taipale et al., 2010).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Wandinger et al., 2008

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    • cites Taipale et al., 2010 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Activation of cell cycle checkpoints through DNA damage, DNA replication stress, or spindle damage stalls cell cycle progression and causes strongly polarized growth.

    “Finally, activation of cell cycle checkpoints through DNA damage, DNA replication stress, or spindle damage stall cell cycle progression and cause strongly polarized growth (Shi et al., 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Shi et al., 2007

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  • May combine two claims.

    Premisecitation

    Hsp90 is a key temperature sensor governing morphogenesis, given that reduction of Hsp90 function bypasses the requirement for elevated temperature for cues such as serum to induce filamentous growth and that Hsp90 function is partially compromised in conditions that induce hyphal morphogenesis.

    “Hsp90 is a key temperature sensor governing morphogenesis, given that reduction of Hsp90 function bypasses the requirement for elevated temperature for cues such as serum to induce filamentous growth and that Hsp90 function is partially compromised in conditions that induce hyphal morphogenesis (Shapiro et al., 2009).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Shapiro et al., 2009 source

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  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Several key regulators of cell cycle progression have been implicated as Hsp90 interactors, including the mammalian tyrosine kinase Wee1 and its budding yeast homologue Swe1, the polo-like kinase Plk1 and its yeast homologue Cdc5, and the cyclin-dependent kinase Cdc2 and its budding yeast homologue Cdc28.

    “Several key regulators of cell cycle progression have been implicated as Hsp90 interactors, including the mammalian tyrosine kinase Wee1 and its budding yeast homologue Swe1, the polo-like kinase Plk1 and its yeast homologue Cdc5, and the cyclin-dependent kinase Cdc2 and its budding yeast homologue Cdc28 (Aligue et al., 1994; Munoz and Jimenez, 1999; de Carcer et al., 2001; Goes and Martin, 2001;”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Aligue et al., 1994 source

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    • cites Munoz and Jimenez, 1999

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    • cites de Carcer et al., 2001 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The two C. albicans mitotic cyclins, Clb2 and Clb4, both negatively regulate polarized growth, and depletion of either results in filamentous growth.

    “The two C. albicans mitotic cyclins, Clb2 and Clb4, both negatively regulate polarized growth, and depletion of either results in filamentous growth (Bensen et al., 2005).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bensen et al., 2005

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  • Classified as probably not a substantial claim.

    Premisecitation

    Hsp90 has been implicated as an important regulator of the temperature-dependent switch between yeast and filamentous growth in C. albicans.

    “Recently the molecular chaperone heat shock protein 90 (Hsp90) has been implicated as an important regulator of the temperature-dependent switch between yeast and filamentous growth in C. albicans (Shapiro et al., 2009).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Shapiro et al., 2009 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Pseudohyphae and hyphae are distinct morphologies: pseudohyphae resemble chains of elongated yeast cells, are wider than hyphae, and have clear constrictions at cellular junctions; hyphae are thinner, lack a constriction between mother and daughter cell, and have unconstricted septa.

    “Pseudohyphae and hyphae are distinct morphologies. Pseudohyphae resemble chains of elongated yeast cells; they are wider than hyphae and have clear constrictions at cellular junctions. Hyphae are thinner, lack a constriction between the mother and daughter cell, and have unconstricted septa.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Sudbery et al., 2004 source

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    • cites Berman, 2006 source

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    Premisecitation

    Hsp90 itself is subject to posttranslational modification in a cell cycle-dependent manner.

    “Recently it was demonstrated that Hsp90 itself is subject to posttranslational modification in a cell cycle–dependent manner. In S. cerevisiae, during S phase of the cell cycle the tyrosine kinase Swe1 phosphorylates a residue in the N-terminus of Hsp90 that facilitates chaperone interaction with numerous client proteins (Mollapour et al., 2010).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Mollapour et al., 2010 source

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  • May combine two claims.

    Premisecitation

    Cell shape in C. albicans is tightly linked to regulation of cell cycle progression, and disruption of components of the cell cycle regulatory machinery has dramatic morphological consequences.

    “Cell shape in C. albicans is tightly linked to regulation of cell cycle progression, and disruption of components of the cell cycle regulatory machinery has dramatic morphological consequences (Berman, 2006; Shapiro et al., 2011).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Berman, 2006 source

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    • cites Shapiro et al., 2011 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The G1 cyclin Cln3 is required to maintain yeast-form growth, whereas another G1 cyclin, Ccn1, is required for hyphal extension.

    “The G1 cyclin Cln3, for example, is required to maintain yeast-form growth, whereas another G1 cyclin, Ccn1, is required for hyphal extension (Loeb et al., 1999; Bachewich and Whiteway, 2005; Chapa y Lazo et al., 2005).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Loeb et al., 1999 source

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    • cites Bachewich and Whiteway, 2005

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    • cites Chapa y Lazo et al., 2005

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Hsp90 is indispensable for appropriate regulation of cell cycle progression in many organisms.

    “Among Hsp90's many roles in the cell, it is indispensable for appropriate regulation of cell cycle progression in many organisms.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Srethapakdi et al., 2000

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    • cites Hostein et al., 2001

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    • cites de Carcer, 2004 source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data

    Hsp90 could be required for Clb4 stability.

    “Alternatively, Hsp90 could be required for Clb4 stability.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    In S. cerevisiae, the CDK Cdc28 interacts with Hsp90 and with the cochaperone Cdc37.

    “In S. cerevisiae, the CDK Cdc28 has been shown to interact with both Hsp90 and one of its cochaperones, Cdc37 (Mort-Bontemps-Soret et al., 2002; Mollapour et al., 2010).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Mort-Bontemps-Soret et al., 2002

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    • cites Mollapour et al., 2010 source

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  • May combine two claims.

    Interpretationreasoning

    At the mother/daughter cell junction septum deposition appears to be the primary defect, whereas septin ring establishment appears to be aberrant at the daughter cell constriction.

    “At the mother/daughter cell junction septum deposition appears to be the primary defect, whereas septin ring establishment appears to be aberrant at the daughter cell constriction.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data

    The multiple branches in these filaments may not all be actively growing at the same time.

    “This may indicate that the multiple branches are not all actively growing at the same time.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Polarized growth initiated by cell cycle arrest typically results in cytoskeletal organization reminiscent of growing hyphae.

    “Polarized growth initiated by cell cycle arrest typically results in cytoskeletal organization reminiscent of growing hyphae (Bachewich et al., 2003; Bensen et al., 2005; Andaluz et al., 2006; Umeyama et al., 2006).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Bachewich et al., 2003

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    • cites Bensen et al., 2005

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    • cites Andaluz et al., 2006

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  • Classified as probably not a substantial claim.

    Premisecitation

    Clb4 plays a major role in S phase progression.

    “Clb4 plays a major role in S phase progression, whereas Clb2 functions in G2/M phase and is elevated in cells arrested in late mitosis (Bensen et al., 2005; Chou et al., 2011; Ofir and Kornitzer, 2010).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Bensen et al., 2005

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    • cites Chou et al., 2011 source

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    • cites Ofir and Kornitzer, 2010

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  • May combine two claims.

    Premisecitation

    Clb2 and Clb4 are expressed from S phase through G2 and M phases and are degraded at the end of mitosis.

    “These proteins are expressed from S phase through G2 and M phases and are degraded at the end of mitosis (Bensen et al., 2005; Cote et al., 2009).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Bensen et al., 2005

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    • cites Cote et al., 2009

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  • May combine two claims.

    Interpretationown data

    These two cells are continuous and both constrictions have defects in cytokinesis despite their differing appearances.

    “This strongly suggests that these two cells are continuous and that both constrictions have defects in cytokinesis despite their differing appearances.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Clb2 functions in G2/M phase and is elevated in cells arrested in late mitosis.

    “Clb4 plays a major role in S phase progression, whereas Clb2 functions in G2/M phase and is elevated in cells arrested in late mitosis (Bensen et al., 2005; Chou et al., 2011; Ofir and Kornitzer, 2010).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Bensen et al., 2005

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    • cites Chou et al., 2011 source

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    • cites Ofir and Kornitzer, 2010

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The possibility of slowed S phase progression observed in FACS analysis is consistent with Hsp90 being required for Clb4 stability.

    “This would be consistent with the possibility of slowed S phase progression observed in the FACS analysis (Figure 3B).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    When these unidentified client proteins are unable to function due to Hsp90 compromise, the cell may be unable to cope with the additional stress of reduced Cdc28 levels, culminating in prominent cell cycle arrest phenotypes.

    “When these client proteins that remain to be identified are unable to function due to Hsp90 compromise, the cell may be unable to cope with the additional stress of reduced Cdc28 levels, culminating in prominent cell cycle arrest phenotypes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    Both mitotic exit and cell separation may proceed normally after Hsp90 inhibition, forming a new G1 yeast cell.

    “Given that a population of yeast cells typically persists after Hsp90 inhibition, the final possibility is that both mitotic exit and cell separation proceed normally and a new G1 yeast cell is formed (not depicted).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Depletion of Cdc5 in C. albicans results in cell elongation due to arrest in earlier events of mitosis and is likely involved in mitotic exit.

    “Depletion of Cdc5 in C. albicans results in cell elongation due to arrest in earlier events of mitosis and is likely involved in mitotic exit as well (Bachewich et al., 2003; Chou et al., 2011).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Bachewich et al., 2003

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    • cites Chou et al., 2011 source

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  • May combine two claims.

    Premisecitation

    Deletion of BUB2 diminishes the cell cycle arrest and cell elongation phenotype typically observed upon Cdc5 depletion, suggesting that regulation of the Bub2/Bfa1 checkpoint by Cdc5 is conserved in C. albicans.

    “Deletion of BUB2 diminishes the cell cycle arrest and cell elongation phenotype typically observed upon Cdc5 depletion, suggesting that regulation of the Bub2/Bfa1 checkpoint by Cdc5 is conserved in C. albicans (Bachewich et al., 2005).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bachewich et al., 2005

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  • May combine two claims.

    Interpretationown data

    Stochasticity determines which morphology will occur, favoring a higher proportion of filaments.

    “The other, more likely possibility is that stochasticity determines which morphology will occur, favoring a higher proportion of filaments (Figure 3A).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The reduction in Cdc28 levels may not be sufficient to cause a phenotype on its own but may sensitize the cell to further cell cycle perturbations.

    “The reduction in Cdc28 levels may not be sufficient to cause a phenotype on its own but may sensitize the cell to further cell cycle perturbations.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    When the Bub2/Bfa1 complex is activated, signaling through the MEN is inhibited and cells cannot progress to G1 of the next cell cycle.

    “Central to the MEN is the Bub2/Bfa1 checkpoint complex. When this complex is activated, signaling through the MEN is inhibited and cells cannot progress to G1 of the next cell cycle (Wang et al., 2000).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Wang et al., 2000

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In S. cerevisiae, the polo-like kinase Cdc5 is expressed during G2/M phase and regulates numerous steps of mitosis.

    “In S. cerevisiae, the polo-like kinase Cdc5 is expressed during G2/M phase and regulates numerous steps of mitosis (van Vugt and Medema, 2005).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites van Vugt and Medema, 2005

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    One Hsp90-inhibition morphology is binucleate filaments, which exhibit a delay in late mitosis.

    “One morphology is binucleate filaments, which exhibit a delay in late mitosis (Figures 2 and 6).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    Cell cycle delay could be the causative agent of filament induction, with the daughter cell representing a hyperelongated yeast-form cell.

    “Given the phenotypic similarity between these filaments and those induced by cell cycle arrest, cell cycle delay could be the causative agent of filament induction, with the daughter cell representing a hyperelongated yeast-form cell (Figure 9, top path).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The Bub2/Bfa1 checkpoint complex is central to the MEN.

    “Central to the MEN is the Bub2/Bfa1 checkpoint complex. When this complex is activated, signaling through the MEN is inhibited and cells cannot progress to G1 of the next cell cycle (Wang et al., 2000).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Wang et al., 2000

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Hsp90 interacts with approximately 10% of the S. cerevisiae proteome.

    “That Hsp90 may influence more than one process in cell cycle progression is not surprising, since it interacts with ∼10% of the S. cerevisiae proteome (Zhao et al., 2005).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zhao et al., 2005 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Reduction of Cdc28 levels in C. albicans results in filamentous growth, but reduced Cdc28 leads to a mixture of pseudohyphae, hyphal-like filaments, and hyperelongated aseptate cells with one or two nuclei, in contrast to Hsp90 inhibition's specific binucleate phenotype.

    “Reduction of Cdc28 levels in C. albicans results in filamentous growth, but in contrast to Hsp90 inhibition, in which a very specific binucleate phenotype is obtained, reduced Cdc28 leads to a mixture of pseudohyphae, hyphal-like filaments, and hyperelongated aseptate cells with one or two nuclei (Umeyama et al., 2006).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Umeyama et al., 2006

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In S. cerevisiae, mitotic exit involves two major signaling cascades: the Cdc14 early anaphase release (FEAR) in early anaphase and the mitotic exit network (MEN) in late anaphase.

    “Events involved in mitotic exit are poorly understood in C. albicans, but in S. cerevisiae, this process has been well studied and involves two major signaling cascades: the Cdc14 early anaphase release (FEAR) in early anaphase and the mitotic exit network (MEN) in late anaphase (de Gramont and Cohen-Fix, 2005).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites de Gramont and Cohen-Fix, 2005

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    In S. cerevisiae, Cdc15 and Dbf2, two kinases in the MEN cascade, were identified in screens for Hsp90 interactors, and bub2 null mutants are hypersensitive to Hsp90 inhibitors, as are strains lacking the major MEN targets Sic1 and Cdh1.

    “In S. cerevisiae, Cdc15 and Dbf2, two kinases in the MEN cascade, were identified in screens for Hsp90 interactors, and bub2 null mutants are hypersensitive to Hsp90 inhibitors, as are strains lacking the major MEN targets Sic1 and Cdh1 (Zhao et al., 2005; McClellan et al., 2007).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Zhao et al., 2005 source

      Not checked in the free run.

    • cites McClellan et al., 2007 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    If the cell is able to exit mitosis, the daughter cell may fail to separate from the mother cell and proceed to the next cell cycle, where cytokinetic defects lead to the production of the two-lobed form.

    “If, however, the cell is able to exit mitosis, the daughter cell may fail to separate from the mother cell and proceed to the next cell cycle, where cytokinetic defects lead to the production of the two-lobed form (Figure 9).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The multiple nuclei in the two-lobed form suggest that this cell type may undergo one successful round of nuclear division before becoming delayed in mitosis during its second round, which could explain the formation of polarized projections off this form at later stages.

    “The multiple nuclei suggest that this cell type may undergo one successful round of nuclear division before becoming delayed in mitosis during its second round (Figures 6 and 9, bottom path), which could explain the formation of polarized projections off this form at later stages.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Cdc28-depletion filaments have variable morphologies and do not consistently arrest with a specific number of nuclei, unlike the response to geldanamycin.

    “Unlike the response to geldanamycin, these filaments have variable morphologies and do not consistently arrest with a specific number of nuclei.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Umeyama et al., 2006

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The second Hsp90-inhibition morphology is the multinucleate, two-lobed form, which primarily has defects in cytokinesis.

    “The second morphology is the multinucleate, two-lobed form, which primarily has defects in cytokinesis (Figures 2 and 5).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In late mitosis, Cdc5 phosphorylates and inactivates the Bub2/Bfa1 checkpoint to facilitate activation of the MEN.

    “In late mitosis it phosphorylates and inactivates the Bub2/Bfa1 checkpoint to facilitate activation of the MEN (Hu et al., 2001).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hu et al., 2001

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In S. cerevisiae, an additional, unidentified kinase also regulates Bub2/Bfa1, and this kinase may represent the more likely candidate for a fungal Hsp90 client protein.

    “In S. cerevisiae, an additional, unidentified kinase also regulates Bub2/Bfa1, and this kinase may represent the more likely candidate for a fungal Hsp90 client protein (Hu and Elledge, 2002).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hu and Elledge, 2002

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Plk1, the mammalian homologue of Cdc5, is an Hsp90 client protein, and Cdc5 interacts with an Hsp90 cochaperone, Cdc37, in S. cerevisiae.

    “This is intriguing, as Plk1, the mammalian homologue of Cdc5, is an Hsp90 client protein, and Cdc5 interacts with an Hsp90 cochaperone, Cdc37, in S. cerevisiae (de Carcer et al., 2001; de Carcer, 2004; Mort-Bontemps-Soret et al., 2002).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites de Carcer et al., 2001 source

      Not checked in the free run.

    • cites de Carcer, 2004 source

      Not checked in the free run.

    • cites Mort-Bontemps-Soret et al., 2002

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The phenomenon of Ras-PKA signaling enhancing mitotic exit defects may be conserved in C. albicans and play an important role in the effect of Hsp90 inhibition on mitotic exit.

    “This phenomenon may be conserved in C. albicans and play an important role in the effect of Hsp90 inhibition on mitotic exit.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Hsp90 is instrumental in the evolution and maintenance of antifungal drug resistance, and compromise of C. albicans Hsp90 function enhances the efficacy of azoles and echinocandins in a mouse model of disseminated disease.

    “It is instrumental in the evolution and maintenance of antifungal drug resistance, and compromise of C. albicans Hsp90 function enhances the efficacy of the two leading classes of antifungal drugs for the treatment of invasive fungal infections—the azoles and echinocandins—in a mouse model of disseminated disease (Cowen et al., 2009; Singh et al., 2009).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Cowen et al., 2009 source

      Not checked in the free run.

    • cites Singh et al., 2009 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Cdc37 functions both in consort with and independent of Hsp90, so Cdc5's function may not necessarily rely on Hsp90 in fungi.

    “Of note, Cdc37 has been demonstrated to function both in consort with and independent of Hsp90, so Cdc5's function may not necessarily rely on Hsp90 in fungi (MacLean and Picard, 2003).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites MacLean and Picard, 2003

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Quantitative RT-PCR reactions were performed in triplicate.

    “Reactions were performed in triplicate, with oLC752 and oLC753 (GPD1); oLC754 and oLC755 (HSP90); and oLC1476 and oLC1477 (CDC28).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationreasoning

    This work highlights the importance of Hsp90 in fungal growth and development through its role in chaperoning major regulators of cell signaling, illuminates novel circuitry through which Hsp90 regulates morphogenesis, and provides a new facet to the therapeutic potential of targeting Hsp90 in the treatment of life-threatening fungal disease.

    “This work highlights the importance of Hsp90 in fungal growth and development through its role in chaperoning major regulators of cell signaling, illuminates novel circuitry through which Hsp90 regulates morphogenesis, and provides a new facet to the therapeutic potential of targeting Hsp90 in the treatment of life-threatening fungal disease.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    There is considerable divergence between S. cerevisiae and C. albicans MEN architecture, so it would be impractical to predict how Hsp90 interacts with this pathway based on the S. cerevisiae model.

    “There does appear, however, to be considerable divergence between S. cerevisiae and C. albicans MEN architecture, so it would be impractical to make any predictions as to how Hsp90 interacts with this pathway based on the S. cerevisiae model (Bensen et al., 2005; Clemente-Blanco et al., 2006; Gonzalez-Novo et al., 2009; Chou et al., 2011).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Bensen et al., 2005

      Not checked in the free run.

    • cites Clemente-Blanco et al., 2006

      Not checked in the free run.

    • cites Gonzalez-Novo et al., 2009

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In S. cerevisiae, the Bub2/Bfa1 checkpoint is involved in response to both DNA and spindle damage, but its roles in these processes in C. albicans have not been studied.

    “In S. cerevisiae this checkpoint is involved in response to both DNA and spindle damage, but its roles in these processes in C. albicans have not been studied (Wang et al., 2000; Hu et al., 2001).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Wang et al., 2000

      Not checked in the free run.

    • cites Hu et al., 2001

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    By both facilitating MEN signaling and inhibiting Ras1-PKA signaling, Hsp90 would be poised to regulate mitotic exit through two pathways.

    “By both facilitating MEN signaling and inhibiting Ras1-PKA signaling, Hsp90 would be poised to regulate mitotic exit through two pathways.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Hsp90 compromise may result in a genotoxic stress that causes activation of the Bub2/Bfa1 checkpoint.

    “Another possibility is that Hsp90 compromise may result in a genotoxic stress that causes activation of the Bub2/Bfa1 checkpoint.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Although the C. albicans Bub2/Bfa1 checkpoint may play a role in mitotic delay in response to Hsp90 inhibition, Cdc5 does not.

    “Although the C. albicans Bub2/Bfa1 checkpoint may play a role in mitotic delay in response to Hsp90 inhibition, Cdc5, a kinase that inactivates Bub2/Bfa1, does not.”
    Quote in the paperNot a substantial claim
72 of 72

  • The paper relies on this without support.

    A role for Hsp90 in C. albicans cell cycle progression has not been established.

    “A role for Hsp90 in C. albicans cell cycle progression has not been established, and properties of filaments induced upon Hsp90 inhibition remain enigmatic.”

  • The paper relies on this without support.

    Properties of filaments induced upon Hsp90 inhibition remain enigmatic.

    “A role for Hsp90 in C. albicans cell cycle progression has not been established, and properties of filaments induced upon Hsp90 inhibition remain enigmatic.”

  • The authors state this as an assumption.

    In the context of hyphal growth, additional factors exist to promote activity of the APC/C even in the presence of activated Ras1-PKA signaling, and these factors are not activated when Hsp90 is pharmacologically or genetically compromised.

    “The critical assumption for this model is that, in the context of hyphal growth, additional factors exist to promote activity of the APC/C even in the presence of activated Ras1-PKA signaling, and these factors simply are not activated when Hsp90 is pharmacologically or genetically compromised.”
3 of 3

Claims other papers make about this one

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Cites

Flagged first, then by citations

Research works printed but not linked: 4

  1. Burt ET, 2003, Ann Clin Lab Sci, 33, 86
  2. Hostein I, 2001, Cancer Res, 61, 4003
  3. Hu F, 2002, Cell Cycle, 1, 351
  4. Srethapakdi M, 2000, Cancer Res, 60, 3940

Cited by

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Related

Authors
Senn, H., Shapiro, R. S., & Cowen, L. E.
Affiliations
University of Toronto (CA)
Corresponding author
Cowen, Leah E.
ORCID
Venue
Molecular Biology of the Cell
Publisher
American Society for Cell Biology (ASCB)
Published
2012-01-15
Volume
23
Issue
2
Pages
268-283
ISSN
  • 1059-1524 (ISSN-L)
  • 1939-4586
DOI
10.1091/mbc.e11-08-0729
PMC
PMC3258172
OpenAlex
W2144737284
Cited by
67
References
75
Citations by year
2026: 3 · 2025: 2 · 2024: 3 · 2023: 5 · 2022: 2 · 2021: 8 · 2020: 5 · 2019: 5 · 2018: 3 · 2017: 5 · 2016: 7 · 2015: 3 · 2014: 5 · 2013: 5 · 2012: 6
FWCI
2.08
Type
journal article
Language
en
Open access
Licence
cc-by-nc-sa
Locations
  • Molecular Biology of the Cell (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by-nc-sa)
  • PubMed Central (publishedVersion, cc-by-nc-sa)
  • PubMed (publishedVersion)
Funders
  • Canadian Institutes of Health Research (MOP-86452)
  • Natural Sciences and Engineering Research Council of Canada
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Fungal and yeast genetics research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Heat shock proteins research
  • Health Sciences › Medicine › Infectious Diseases › Antifungal resistance and susceptibility
Keywords
Candida albicans, HSP90, Cdc28, cyclin-dependent kinases, morphogenesis, cell cycle progression, mitotic exit, cytokinesis, Hsp90 client proteins, fungal dimorphism, pseudohyphae, molecular chaperones
MeSH terms
Candida albicans, Mitosis, HSP90 Heat-Shock Proteins, Hyphae, CDC2-CDC28 Kinases, Cell Cycle Checkpoints

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

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