Molecular Basis for Increased Risk for Late-onset Alzheimer Disease Due to the Naturally Occurring L28P Mutation in Apolipoprotein E4

ApoE variants with lower thermodynamic stability and changes in conformational plasticity have been shown to have altered interdomain interactions and defective physiological functions.

“ApoE variants with lower thermodynamic stability and changes in conformational plasticity have been shown to have altered interdomain interactions and defective physiological functions (19, 24 -28).”

• cites [19] Hatters, 2006, Apolipoprotein E structure: insights into function, Trends Biochem. Sci sourceNot checked — no full text of the source
• cites [24] Mahley, 2009, Apolipoprotein E: structure determines function, from atherosclerosis to Alzheimer's disease to AIDS, J. Lipid Res sourcePartly supported

  The section on apoE4 domain interaction reports that structural differences alter interactions between domains, lipid-binding preference, and some detrimental effects. The copy does not establish that these variants have lower thermodynamic stability or variant-specific changes in conformational plasticity; its discussion of conformational change concerns apoE binding to lipid. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [25] Chroni, 2008, Biophysical analysis of progressive C-terminal truncations of human apolipoprotein E4: insights into secondary structure and unfolding properties, Biochemistry sourcePartly supported

  The Discussion’s “Functional Properties of apoE4 C-Terminal Truncation Mutants” section links altered unfolding behavior to impaired lipid interactions and cholesterol efflux. But it describes a correlation between structural stabilization—not lower stability—and loss of function. The paper discusses N- and C-terminal domain interactions, but does not establish that the functionally impaired truncation variants have altered interdomain interactions. Page numbers are unavailable in our copy. (LLM, conf=0.87)

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• cites [26] Saito, 2001, Lipid binding-induced conformational change in human apolipoprotein E: evidence for two lipid-bound states on spherical particles, J. Biol. Chem sourcePartly supported

  The ApoE Conformation on Emulsion section reports that apoE4 adopts different lipid-bound conformations and discusses their effects on LDL-receptor binding. The Effects of Particle Size section also discusses interaction between its N- and C-terminal domains. Neither section establishes that variants with lower thermodynamic stability have altered interdomain interactions and defective physiological functions; the measured thermodynamics concern lipid binding, not protein stability. Page numbers are unavailable in our copy. (LLM, conf=0.84)

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• cites [27] Georgiadou, 2011, Biophysical analysis of apolipoprotein E3 variants linked with development of type III hyperlipoproteinemia, PLoS ONE sourcePartly supported

  The Results report altered stability and conformational behavior in apoE3 variants, and the Discussion proposes that some mutations perturb interdomain interactions (pages not specified). But stability was not uniformly lower, and the Discussion says further functional analysis is needed to establish the role of these changes in apoE3 dysfunction. The claim presents those proposed links and defective physiological function more definitively than this paper does. (LLM, conf=0.88)

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• cites [28] Georgiadou, 2013, Thermodynamic and structural destabilization of apoE3 by hereditary mutations associated with the development of lipoprotein glomerulopathy, J. Lipid Res sourcePartly supported

  The Thermodynamic stability section reports that the studied apoE3 variants are less stable than wild-type, and Mutations cause N-terminus misfolding describes structural changes that perturb normal function (page numbers unavailable). The paper discusses interdomain interactions and proposes conformational changes between domains, but the cited passages do not show that these variants have altered interdomain interactions. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

The concentration 0.375 M is similar to the reported concentration of apoE in human cerebrospinal fluid (0.365-0.395 M).

“More importantly, toxicity (28% decrease in cell viability) was evident even when lipidated apoE4[L28P] was used at the lower concentration of 0.375 M, which is similar to the reported concentration of apoE in human cerebrospinal fluid (0.365-0.395M) (47,48).”

• cites [47] Kay, 2003, Cerebrospinal fluid apolipoprotein E concentration decreases after traumatic brain injury, J. Neurotrauma sourceNot checked — no full text of the source
• cites [48] Wang, 2010, Cerebrospinal fluid apolipoprotein E concentration decreases after seizure, Seizure sourcePartly supported

  The Results report apoE in control subjects’ cerebrospinal fluid at 13.60 ± 12.11 mg/L, and the Introduction gives apoE’s molecular mass as 32 kDa. That mean converts to approximately 0.425 µM, broadly comparable to 0.375 µM, but the paper does not report the claimed 0.365–0.395 µM range. If the citing sentence’s printed unit “M” is literal rather than an omitted micro symbol, the concentrations are not comparable. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Recent genome-wide association studies of LOAD identified several common variants of new genes, but with the exception of variants of triggering receptor expressed on myeloid cells 2, no rare variants were identified.

“These studies have identified several common variants of several new genes to be associated with LOAD, but, with the exception of variants of triggering receptor expressed on myeloid cells 2, no rare variants were identified (49,50).”

• cites [49] European Alzheimer's Disease Initiative (EADI), Genetic and Environmental Risk in Alzheimer's Disease, Alzheimer's Disease Genetic Consortium, and Cohorts for Heart and Aging Research in Genomic Epidemiology, 2013, Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimer's disease, Nat. Genet sourcePartly supported

  The paper’s Abstract (page unavailable) reports newly associated LOAD loci and notes a previously identified rare susceptibility variant in TREM2. It does not establish the broader claim that no rare variants other than TREM2 variants had been identified. (LLM, conf=0.85)

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• cites [50] Guerreiro, 2013, TREM2 variants in Alzheimer's disease, N. Engl. J. Med sourcePartly supported

  The introduction lists several loci identified by genome-wide association studies of late-onset Alzheimer’s disease, and the Conclusions identify rare TREM2 variants associated with Alzheimer’s risk. However, the Methods say the rare TREM2 variant was excluded from previously reported GWAS and was investigated here using sequencing and imputed GWAS data. The paper does not establish the broader claim that no other rare variants had been identified. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

Both apoE4[L28P] and apoE4[Δ(166-299)] display the loss of a key unfolding intermediate during chemical denaturation.

“Furthermore, both variants display one common characteristic, namely the loss of a key unfolding intermediate during chemical denaturation (25).”

• cites [25] Chroni, 2008, Biophysical analysis of progressive C-terminal truncations of human apolipoprotein E4: insights into secondary structure and unfolding properties, Biochemistry sourcePartly supported

  The Results section (‘Chemical Unfolding of apoE4’; page not provided) reports that the chemical-denaturation intermediate is essentially absent in apoE4[Δ166–299]. The paper examines C-terminal deletion variants, but our copy does not report this finding for apoE4[L28P], so it supports only one of the two variants named. (LLM, conf=0.89)

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Rare variants such as apoE4[L28P] are seldom found by initial genome-wide association studies, primarily because of their low representation in the cohort, and require resequencing of large populations or targeted family-based studies and linkage analysis to be identified.

“Rare variants, like apoE4[L28P], although equally important as common variants for disease pathogenesis, are seldom found by initial genome-wide association studies, primarily because of the low representation in the cohort, and require resequencing of large populations or targeted family-based studies and linkage analysis to be identified (51,52).”

• cites [51] Bush, 2012, Chapter 11: Genome-wide association studies, PLoS Comput. Biol sourcePartly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

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• cites [52] Gibson, 2011, Rare and common variants: twenty arguments, Nat. Rev. Genet sourcePartly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured

The single-amino acid L28P mutation gives apoE4 the ability to promote the intracellular accumulation of amyloid beta 42.

“More importantly this single-amino acid mutation gives apoE4 the ability to promote the intracellular accumulation of A␤42, a function that has also been found previously in a heavily truncated apoE4 variant, apoE4[(⌬(166 -299)] (10)”

• cites [10] Dafnis, 2010, An apolipoprotein E4 fragment can promote intracellular accumulation of amyloid peptide β 42, J. Neurochem sourceSupported

The truncated apoE4 variant apoE4[Δ(166-299)] has a similar molecular weight to carboxyl-terminal truncated apoE4 fragments found in the brain of Alzheimer disease patients.

“which has a similar molecular weight as carboxyl-terminal truncated apoE4 fragments found in the brain of AD patients (54,55)”

• cites [54] Huang, 2001, Apolipoprotein E fragments present in Alzheimer's disease brains induce neurofibrillary tangle-like intracellular inclusions in neurons, Proc. Natl. Acad. Sci. U.S.A sourceNot checked — no full text of the source
• cites [55] Jones, 2011, Apolipoprotein E: isoform specific differences in tertiary structure and interaction with amyloid-β in human Alzheimer brain, PLoS ONE sourcePartly supported

  The Results (page unavailable) report 17–34 kDa apoE fragments in Alzheimer brain and identify that band as a mixture containing N-terminal fragments, consistent with carboxyl-terminal truncation. The paper does not identify apoE4[Δ(166–299)] or directly compare its molecular weight with those fragments. (LLM, conf=0.78)

  Experimental — accuracy not yet measured

Rare variants in genes associated with Alzheimer disease pathogenesis could explain a significant proportion of the genetic heritability of Alzheimer disease that is not detected by genome-wide association studies.

“suggesting that rare variants in genes associated with AD pathogenesis could explain a significant proportion of genetic heritability of AD, which is not detected by genomewide association studies (53)”

• cites [53] Cruchaga, 2012, Rare variants in APP, PSEN1 and PSEN2 increase risk for AD in late-onset Alzheimer's disease families, PLoS ONE sourceSupported

The circular dichroism spectrum of lipid-free apoE4[L28P] had overall a similar shape to the spectrum of WT apoE4.

“The circular dichroism spectrum of lipid-free apoE4[L28P] was found to overall have a similar shape to the spectrum of the WT apoE4, which is identical to spectra reported previously for that molecule (25,29,42,43).”

ANS binding analysis suggested that the L28P mutation resulted in an increase of the solvent-accessible hydrophobic surface of apoE4.

“The ANS binding analysis suggested that the L28P mutation resulted in an increase of the solvent-accessible hydrophobic surface of apoE4, a finding that could be consistent with exposure of the N-terminal four-helix bundle hydrophobic core because of misfolding (Fig. 2E).”

ApoE4[L28P] displayed a loss of about 10% of helical content compared with WT apoE4.

“ApoE4[L28P] displayed a loss of about 10% of helical content compared with the WT apoE4 (Fig. 2A).”

WT apoE4 had an α-helical content of 53.1% based on the CD signal at 222 nm.

“The calculated ␣-helical content, on the basis of the CD signal at 222 nm, for WT apoE4 was 53.1%, in the middle of the range of 44 -62% that has been reported for the helical content of apoE4 and apoE3, produced by bacterial or mammalian expression systems (22,25,29,(43)(44)(45).”

Lipoprotein particles containing apoE4[L28P] had on average larger diameters (17.8 ± 0.3 nm) compared with WT apoE4 particles (13.8 ± 0.2 nm).

“Statistical analysis of the diameter distribution of those particles revealed that the mutant protein resulted in particles that had, on average, larger diameters (13.8 Ϯ 0.2 nm versus 17.8 Ϯ 0.3 nm) (Fig. 5C).”

Lipoprotein particles containing mutant apoE4 had a slightly perturbed thermal denaturation profile.

“CD analysis of the lipoprotein particles revealed that the lipoprotein particles that contain the mutant apoE4 had a statistically significant but minor reduction in helical content (Fig. 6A) and also a slightly perturbed thermal denaturation profile (Fig. 6B), which may indicate some minor perturbation because of mutation.”

Limited proteolysis with elastase, chymotrypsin, and trypsin revealed that the introduction of the L28P mutation further sensitizes apoE4 toward proteolysis.

“Limited proteolysis with elastase, chymotrypsin, and trypsin revealed that the introduction of the L28P mutation further sensitizes apoE4 toward proteolysis.”

Lipoprotein particles containing mutant apoE4 had a statistically significant but minor reduction in helical content.

“CD analysis of the lipoprotein particles revealed that the lipoprotein particles that contain the mutant apoE4 had a statistically significant but minor reduction in helical content (Fig. 6A) and also a slightly perturbed thermal denaturation profile (Fig. 6B), which may indicate some minor perturbation because of mutation.”

Lipidated apoE4[L28P] resulted in significantly less cell viability compared with lipidated WT apoE4 at both concentrations assayed.

“However, when using the lipidated forms of the proteins and at both concentrations assayed, lipidated apoE4[L28P] resulted in significantly less cell viability compared with lipidated WT apoE4 (Fig. 7B).”

The larger average diameter of apoE4[L28P] particles was primarily due to the presence of several larger-diameter outliers.

“This, however, was primarily due to the presence of several larger-diameter outliers (Fig. 5C, insets).”

Lipidated apoE4[L28P] at 0.375 M caused a 28% decrease in cell viability.

“More importantly, toxicity (28% decrease in cell viability) was evident even when lipidated apoE4[L28P] was used at the lower concentration of 0.375 M, which is similar to the reported concentration of apoE in human cerebrospinal fluid (0.365-0.395M) (47,48).”

Lipoprotein particle-associated apoE4[L28P] induces ROS formation inside SK-N-SH cells to a much higher degree than wild-type apoE4.

“Our analysis showed that lipoprotein particle-associated apoE4[L28P] was capable to induce ROS formation inside SK-N-SH cells to a much higher degree than WT apoE4 (Fig. 11D).”

• Also stated in: § DISCUSSION · plain

  “whereas the lipoprotein-associated apoE4[L28P] increases ROS formation and reduces the viability of SK-N-SH cells.”

Incubation of SK-N-SH cells with Aβ42 and lipoprotein particles containing apoE4[L28P] did not promote the cellular uptake of Aβ42.

“Incubation of SK-N-SH cells with A␤42 and lipoprotein particles containing the apoE4[L28P] variant did not promote the cellular uptake of A␤42.”

Lipid-free apoE4[L28P] induces the intracellular accumulation of amyloid beta 42 in SK-N-SH human neuroblastoma cells and in mouse primary neurons.

“We show here that the lipid-free apoE4[L28P] induces the intracellular accumulation of A␤42 in SK-N-SH human neuroblastoma cells and mouse primary neurons as well as ROS formation, whereas the lipoprotein-associated apoE4[L28P] increases ROS formation and reduces the viability of SK-N-SH cells.”

Aβ42 accumulation inside the cells was persistent even 24 h post-removal of both Aβ42 and apoE4 from the medium.

“Furthermore, A␤42 accumulation inside the cells was persistent even 24 h post-removal of both A␤42 and apoE4 from the medium (Fig. 8, g-i).”

The L28P apoE4 mutation introduces a proline residue into a highly helical segment of the protein.

“The L28P apoE4 mutation is characterized by the fact that it introduces a proline residue into a highly helical segment of the protein.”

Lipoprotein-associated apoE4[L28P] reduces the viability of SK-N-SH cells.

“We show here that the lipid-free apoE4[L28P] induces the intracellular accumulation of A␤42 in SK-N-SH human neuroblastoma cells and mouse primary neurons as well as ROS formation, whereas the lipoprotein-associated apoE4[L28P] increases ROS formation and reduces the viability of SK-N-SH cells.”

Lipid-free apoE4[L28P] induces ROS formation.

“We show here that the lipid-free apoE4[L28P] induces the intracellular accumulation of A␤42 in SK-N-SH human neuroblastoma cells and mouse primary neurons as well as ROS formation, whereas the lipoprotein-associated apoE4[L28P] increases ROS formation and reduces the viability of SK-N-SH cells.”

In primary mouse cortical neurons, apoE4[L28P] but not WT apoE4 induced the intracellular accumulation of Aβ42 peptide.

“Similar to the SK-N-SH cells, the apoE4[L28P] variant, but not WT apoE4, induced the intracellular accumulation of A␤42 peptide (Fig. 10, a-c).”

No toxicity was evident for lipidated WT apoE4 at 0.375 M.

“No toxicity was evident for lipidated WT apoE4 at that concentration.”

SK-N-SH cells incubated with Aβ42 and physiological concentrations of apoE4[L28P] for 24 h resulted in internalization of the Aβ42 peptide.

“SK-N-SH cells incubated with A␤42 and physiological concentrations of apoE4[L28P] for 24 h resulted in internalization of the A␤42 peptide (Fig. 8c).”

There was no Aβ42 internalization in the presence of lipoprotein particles containing WT apoE4.

“Similarly, there was no A␤42 internalization in the presence of lipoprotein particles containing WT apoE4 (Fig. 9).”

The increase in ROS formation was persistent for at least 24 h after removal of the medium that contained Aβ42 and apoE4[L28P].

“This phenomenon was persistent for at least 24 h after removal of the medium that contained A␤42 and apoE4[L28P] (Fig. 11B).”

A naturally occurring point mutation in apoE4, L28P (apoE4 Pittsburgh), was found in a heterozygous state in patients with sporadic LOAD and related controls.

“Screening for apoE variants in patients with sporadic LOAD and related controls revealed a naturally occurring point mutation in apoE4, L28P (denoted as apoE4 Pittsburgh), in a heterozygous state (6,7).”

• cites [6] Kamboh, 1999, A novel mutation in the apolipoprotein E gene (APOE*4 Pittsburgh) is associated with the risk of late-onset Alzheimer's disease, Neurosci. Lett sourceNot checked — no full text of the source
• cites [7] Scacchi, 2003, Screening of two mutations at exon 3 of the apolipoprotein E gene (sites 28 and 42) in a sample of patients with sporadic late-onset Alzheimer's disease, Neurobiol. Aging sourceNot checked — no full text of the source

The loss of the unfolding intermediate for apoE4[L28P] is not due to incomplete equilibration after each addition of GndHCl but due to a destabilized structure.

“The overall shape of the denaturation curve for apoE4[L28P] was unchanged, indicating that the loss of the intermediate state is not due to incomplete equilibration after each addition of GndHCl but due to a destabilized structure.”

The increase in solvent-accessible hydrophobic surface could be consistent with exposure of the N-terminal four-helix bundle hydrophobic core because of misfolding.

“The ANS binding analysis suggested that the L28P mutation resulted in an increase of the solvent-accessible hydrophobic surface of apoE4, a finding that could be consistent with exposure of the N-terminal four-helix bundle hydrophobic core because of misfolding (Fig. 2E).”

Larger-sized malformed lipoprotein particles may indicate aggregation tendencies because of structural defects brought about by the mutation.

“Such larger-sized malformed lipoprotein particles may indicate aggregation tendencies because of structural defects brought about by the mutation.”

The slower kinetics of DMPC remodeling by apoE4[L28P] suggests possible defects in the ability of the protein to undergo the necessary conformational changes to bind lipids.

“Although apoE4[L28P] was also able to remodel DMCP vesicles, it did so with slower kinetics compared with the WT protein, suggesting possible defects in the ability of the protein to undergo the necessary conformational changes to bind lipids (Fig. 4).”

Because proline is not the preferred residue for any of the proteases used, the finding is consistent with local or even generalized unfolding that exposes protease-sensitive sites in the variant apoE4.

“Because proline is not the preferred residue for any of the proteases used, this finding is consistent with local or even generalized unfolding that exposes protease-sensitive sites in the variant apoE4.”

The apparent paradox that two opposite thermodynamic stability changes are associated with the same gain of function can be reconciled by apoE4 being a thermodynamically metastable and structurally plastic protein that relies for its function on its ability to change conformational states, an ability that necessitates an optimized thermodynamic stability.

“This apparent paradox, that two opposite thermodynamic stability changes are associated with the same gain of function, can be reconciled in the context that apoE4 is a thermodynamically metastable and structural plastic protein that relies, for its function, on its ability to change conformational states, an ability that necessitates an optimized thermodynamic stability.”

The structural integrity of apoE4 is almost certainly an important component of its role in the pathogenesis of late-onset Alzheimer disease.

“The structural integrity of apoE4 is almost certainly an important component of its role in the pathogenesis of LOAD, and analysis of structurally defective apoE4 variants may hold clues regarding the pathogenic mechanisms behind this disease.”

• AssumptionRests on an assumption: The mechanism by which apoE4 promotes late-onset Alzheimer disease pathogenesis is not clear.
• AssumptionRests on an assumption: The differences between the three common apoE isoforms are structural, and these structural differences underlie changes in function that affect disease predisposition.

The structural integrity of apoE4 is an important component of its role in AD pathogenesis.

“The structural integrity of apoE4 is an important component of its role in AD pathogenesis.”

These structural and functional changes underlie the observed added risk for AD development in carriers of apoE4[L28P].

“We propose that these structural and functional changes underlie the observed added risk for AD development in carriers of apoE4 [L28P].”

• AssumptionRests on an assumption: The structural and functional defects observed in vitro for apoE4[L28P] translate to the increased AD risk in human carriers.

The differences among the study of Huber et al. and other studies of apoE4 transgenic mice, including the presence or absence of endogenous mouse apoE and the different cellular expression sites for the apoE transgenes (glia versus neurons), seem to be critical for the development of an Alzheimer disease phenotype in mice.

“Therefore, the number of important differences among the study of Huber et al. (61) and other studies of apoE4 transgenic mice, including the presence or absence of endogenous mouse apoE, which could compensate or mask certain biological effects as well as the different cellular expression sites for the apoE transgenes (glia versus neurons), seem to be critical for the development of an AD pheno”

• cites [61] Huber, 2000, Characterization of transgenic mice expressing apolipoprotein E4(C112R) and apolipoprotein E4(L28P; C112R), Neuroscience sourceNot checked — no full text of the source

Functional analyses of rare variants can provide additional validation of their association with late-onset Alzheimer disease, even in the absence of their identification from genome-wide association studies.

“Furthermore, functional analyses of rare variants, like the one presented in this study, can provide additional validation of their association with LOAD, even in the absence of their identification from genome-wide association studies.”

It is possible that apoE4[L28P], regardless of its lipidation status, affects processes that lead to chronic oxidative stress and in that manner contributes to the pathogenesis of Alzheimer disease.

“Therefore, it is possible that apoE4[L28P], regardless of its lipidation status, affects processes that lead to chronic oxidative stress and, in that manner, contributes to the pathogenesis of AD.”

Transgenic wild-type apoE4 mice lacking endogenous mouse apoE and expressing human apoE transgenes in neurons under the neuron-specific enolase promoter showed impairments in learning a water maze task and in vertical exploratory behavior that increased with age compared with neuron-specific enolase-apoE3 transgenic mice and control non-transgenic mice.

“In contrast, in another study, transgenic WT apoE4 mice lacking endogenous mouse apoE and expressing human apoE transgenes in neurons, under the control of the neuron-specific enolase promoter, showed impairments in learning a water maze task and in vertical exploratory behavior that increased with age compared with neuron-specific enolase-apoE3 transgenic mice and control non-transgenic mice (62)”

• cites [62] Raber, 1998, Isoform-specific effects of human apolipoprotein E on brain function revealed in ApoE knockout mice: increased susceptibility of females, Proc. Natl. Acad. Sci. U.S.A sourceNot checked — no full text of the source

The findings suggest a molecular basis that may underlie the genetic association of a naturally occurring mutation in apoE4 with the development of late-onset Alzheimer disease.

“Our findings suggest a molecular basis that may underlie the genetic association of a naturally occurring mutation in apoE4 with the development of LOAD.”

• AssumptionRests on an assumption: The mechanism by which apoE4 promotes late-onset Alzheimer disease pathogenesis is not clear.

The common functional properties of apoE4[L28P] and the C-terminal truncated apoE4 support the idea that amyloid beta internalization by neuronal cells is an early event in Alzheimer disease pathogenesis that is exacerbated in the case of the apoE4[L28P] variant.

“The common functional properties of apoE4[L28P] and the C-terminal truncated apoE4 further support the idea that A␤ internalization by neuronal cells is an early event in AD pathogenesis that is exacerbated in the case of the apoE4[L28P] variant.”

A rare hereditary mutation in apoE4, L28P, has been associated with an increased risk for late-onset Alzheimer disease in patients.

“A rare hereditary mutation in apoE4, L28P, has been associated with an increased risk for LOAD in patients (6,7).”

• cites [6] Kamboh, 1999, A novel mutation in the apolipoprotein E gene (APOE*4 Pittsburgh) is associated with the risk of late-onset Alzheimer's disease, Neurosci. Lett sourceNot checked — no full text of the source
• cites [7] Scacchi, 2003, Screening of two mutations at exon 3 of the apolipoprotein E gene (sites 28 and 42) in a sample of patients with sporadic late-onset Alzheimer's disease, Neurobiol. Aging sourceNot checked — no full text of the source

Previous attempts to model the effect of apoE4[L28P] in experimental animals have yielded conflicting results.

“Although the genetic association of apoE4 and, more specifically, apoE4[L28P] with LOAD has been established, previous attempts to model this effect in experimental animals have yielded conflicting results.”

• cites [61] Huber, 2000, Characterization of transgenic mice expressing apolipoprotein E4(C112R) and apolipoprotein E4(L28P; C112R), Neuroscience sourceNot checked — no full text of the source
• cites [62] Raber, 1998, Isoform-specific effects of human apolipoprotein E on brain function revealed in ApoE knockout mice: increased susceptibility of females, Proc. Natl. Acad. Sci. U.S.A sourceNot checked — no full text of the source

This finding links the functional properties of apoE4[L28P] with a previously reported property of proteolytic fragments of apoE4 that may be associated with AD pathogenesis.

“This finding links the functional properties of this apoE4 variant with a property reported previously (intracellular accumulation of A␤42) of proteolytic fragments of apoE4 that may be associated with AD pathogenesis.”

These findings suggest that lipoproteins containing apoE4[L28P] may negatively affect neuronal cell viability.

“These findings suggest that lipoproteins containing apoE4[L28P] may negatively affect neuronal cell viability.”