Cited by 126Heat shock proteins researchEstrogen and related hormone effectsGenomics and Chromatin Dynamics

Role for Hsp90-Associated Cochaperone p23 in Estrogen Receptor Signal Transduction

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Knoblauch, Roland, Garabedian, Michael J.·1999·Molecular and Cellular Biology

Abstract

The mechanism of signal transduction by the estrogen receptor (ER) is complex and not fully understood. In addition to the ER, a number of accessory proteins are apparently required to efficiently transduce the steroid hormone signal. In the absence of estradiol, the ER, like other steroid receptors, is complexed with Hsp90 and other molecular chaperone components, including an immunophilin, and p23. This Hsp90-based chaperone complex is thought to repress the ER's transcriptional regulatory activities while maintaining the receptor in a conformation that is competent for high-affinity steroid binding. However, a role for p23 in ER signal transduction has not been demonstrated. Using a mutant ER (G400V) with decreased hormone binding capacity as a substrate in a dosage suppression screen in yeast cells (Saccharomyces cerevisiae), we identified the yeast homologue of the human p23 protein (yhp23) as a positive regulator of ER function. Overexpression of yhp23 in yeast cells increases ER transcriptional activation by increasing estradiol binding in vivo. Importantly, the magnitude of the effect of yhp23 on ER transcriptional activation is inversely proportional to the concentration of both ER and estradiol in the cell. Under conditions of high ER expression, ER transcriptional activity is largely independent of yhp23, whereas at low levels of ER expression, ER transcriptional activation is primarily dependent on yhp23. The same relationship holds for estradiol levels. We further demonstrate that yhp23 colocalizes with the ER in vivo. Using a yhp23-green fluorescent protein fusion protein, we observed a redistribution of yhp23 from the cytoplasm to the nucleus upon coexpression with ER. This nuclear localization of yhp23 was reversed by the addition of estradiol, a finding consistent with yhp23's proposed role as part of the aporeceptor complex. Expression of human p23 in yeast partially complements the loss of yhp23 function with respect to ER signaling. Finally, ectopic expression of human p23 in MCF-7 breast cancer cells increases both hormone-dependent and hormone-independent transcriptional activation by the ER. Together, these results strongly suggest that p23 plays an important role in ER signal transduction.

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Authors
Knoblauch, R., & Garabedian, M. J.
Affiliations
New York University (US)
Venue
Molecular and Cellular Biology
Published
1999-05
Volume
19
Issue
5
Pages
3748-3759
ISSN
  • 0270-7306 (ISSN-L)
  • 1098-5549
OpenAlex
W2105740297
Cited by
126
References
59
Citations by year
2026: 1 · 2025: 4 · 2024: 5 · 2023: 5 · 2022: 2 · 2020: 1 · 2019: 2 · 2018: 5 · 2016: 5 · 2015: 3 · 2014: 4 · 2013: 4 · 2012: 5
FWCI
3.34
Type
journal article
Language
en
Open access
Locations
  • Molecular and Cellular Biology (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • Irma T. Hirschl Trust
  • National Institutes of Health
  • National Institute of General Medical Sciences (2T32 GM-07308, T32GM007308)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Heat shock proteins research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Estrogen and related hormone effects
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Chromatin Dynamics
Keywords
p23, estrogen receptor, HSP90, signal transduction, steroid hormone signaling, chaperone complex, immunophilins, estradiol binding, transcriptional activation, nuclear localization, MCF-7 cells
MeSH terms
Estradiol, Fluorescent Antibody Technique, Humans, Luminescent Proteins, Mutation, Nuclear Proteins, Receptors, Estrogen, Recombinant Fusion Proteins, Saccharomyces cerevisiae, Suppression, Genetic, Tumor Cells, Cultured, Signal Transduction, Transcriptional Activation, Gene Expression Regulation, Fungal, Molecular Chaperones, HSP90 Heat-Shock Proteins, Green Fluorescent Proteins

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