Alpha‐crystallin expression affects microtubule assembly and prevents their aggregation

Xi, Jing; Bai, Fang; McGaha, Rebecca; Andley, Usha P.

doi:10.1096/fj.05-5532com

Cited by 65 publications

(58 citation statements)

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“…Previous studies have shown that ␣A-crystallin is essential for maintaining unpolymerized tubulin in an assembly competent conformation (43). Studies in the literature show that ␣A-crystallin forms co-aggregates with ␥-crystallin (44,45).…”

Section: Discussionmentioning

confidence: 99%

Mechanism of Small Heat Shock Protein Function in Vivo

Bai

Gross

et al. 2008

Journal of Biological Chemistry

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␣A-crystallin (Cryaa/HSPB4) is a small heat shock protein and molecular chaperone that prevents nonspecific aggregation of denaturing proteins. Several point mutations in the ␣A-crystallin gene cause congenital human cataracts by unknown mechanisms. We took a novel approach to investigate the molecular mechanism of cataract formation in vivo by creating gene knock-in mice expressing the arginine 49 to cysteine mutation (R49C) in ␣A-crystallin (␣A-R49C). This mutation has been linked with autosomal dominant hereditary cataracts in a four-generation Caucasian family. Homologous recombination in embryonic stem cells was performed using a plasmid containing the C to T transition in exon 1 of the cryaa gene. ␣A-R49C heterozygosity led to early cataracts characterized by nuclear opacities. Unexpectedly, ␣A-R49C homozygosity led to small eye phenotype and severe cataracts at birth. Wild type littermates did not show these abnormalities. Lens fiber cells of ␣A-R49C homozygous mice displayed an increase in cell death by apoptosis mediated by a 5-fold decrease in phosphorylated Bad, an anti-apoptotic protein, but an increase in Bcl-2 expression. However, proliferation measured by in vivo bromodeoxyuridine labeling did not decline. The ␣A-R49C heterozygous and homozygous knock-in lenses demonstrated an increase in insoluble ␣A-crystallin and ␣B-crystallin and a surprising increase in expression of cytoplasmic ␥-crystallin, whereas no changes in ␤-crystallin were observed. Co-immunoprecipitation analysis showed increased interaction between ␣A-crystallin and lens substrate proteins in the heterozygous knock-in lenses. To our knowledge this is the first knock-in mouse model for a crystallin mutation causing hereditary human cataract and establishes that ␣A-R49C promotes protein insolubility and cell death in vivo.

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Section: Discussionmentioning

confidence: 99%

Mechanism of Small Heat Shock Protein Function in Vivo

Bai

Gross

et al. 2008

Journal of Biological Chemistry

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“…The fiber cells contain several intermediate filaments, which include vimentin, phakinin (CP49), and filensin (13), and these have been found to associate with membranes (14). ␣-Crystallins have also been reported to be associated with cytoskeletal proteins (actin, microtubules, and intermediate filaments) (15,16). A FRET photobleaching study showed the ␣B R120G mutant facilitated aggregation of vimentin by altering protein-protein interactions (17).…”

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confidence: 99%

The Common Modification in αA-Crystallin in the Lens, N101D, Is Associated with Increased Opacity in a Mouse Model

Gupta

Asomugha

Srivastava

2011

Journal of Biological Chemistry

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To elucidate the morphological and cellular changes due to introduction of a charge during development and the possible mechanism that underlies cataract development in humans as a consequence of an additional charge, we generated a transgenic mouse model mimicking deamidation of Asn at position 101. The mouse model expresses a human ␣A-crystallin gene in which Asn-101 was replaced with Asp, which is referred to as ␣AN101D-transgene and is considered to be "deamidated" in this study. Mice expressing ␣AN101D-transgene are referred to here CRYAA N101D mice. All of the lines showed the expression of ␣AN101D-transgene. Compared with the lenses of mice expressing wild-type (WT) ␣A-transgene (referred to as CRYAA WT mice), the lenses of CRYAA N101D mice showed (a) altered ␣A-crystallin membrane protein (aquaporin-0 (AQP0), a specific lens membrane protein) interaction, (b) extracellular spaces between outer cortical fiber cells, (c) attenuated denucleation during confocal microscopic examination, (d) disrupted normal fiber cell organization and structure during scanning electron microscopic examination, (e) distorted posterior suture lines by bright field microscopy, and (f) development of a mild anterior lens opacity in the superior cortical region during the optical coherence tomography scan analysis. Relative to lenses with WT ␣A-crystallin, the lenses containing the deamidated ␣A-crystallin also showed an aggregation of ␣A-crystallin and a higher level of water-insoluble proteins, suggesting that the morphological and cellular changes in these lenses are due to the N101D mutation. This study provides evidence for the first time that expression of deamidated ␣A-crystallin caused disruption of fiber cell structural integrity, protein aggregation, insolubilization, and mild cortical lens opacity.The ocular lens has a unique cellular architecture consisting of a single layer of cuboidal epithelial cells, which divide and differentiate at the equator into fiber cells (1). The fiber cells elongate, and they synthesize fiber cell-specific proteins, such as AQP0 (aquaporin-0)/MIP (main intrinsic protein), cytoskeletal proteins, and crystallins (1-4). As the new fiber cells are laid down at the lens equator, the older fiber cells are pushed toward the lens core and simultaneously lose their nuclei and organelles while exhibiting very little protein turnover. Among the three classes of the vertebrate lens crystallins (␣-, ␤-, and ␥-crystallins), ␣-crystallins are composed of two primary gene products, A and B, known as ␣A-and ␣B-crystallins, that show ϳ60% amino acid homology and constitute up to 50% of the total lens proteins. Both ␣A-and ␣B-crystallins belong to a family of small heat shock proteins with "chaperone" activity (5, 6). These crystallins are constitutively expressed in both lens epithelial and fiber cells (7) and undergo numerous age-related post-translational modifications (PTMs) 2 that lead to their unfolding, aggregation, and insolubilization. These PTMs eventually lead to accumulation of damaged crystal...

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“…Under stress conditions, HspB1 and HspB5 stabilize microtubules (Hino et al 2000 ;Preville et al 1996 ;Xi et al 2006 ). HspB5 is also very active in maintaining intermediate fi laments homeostasis, particularly in muscle cells where it associates with desmin (Bennardini et al 1992 ;Djabali et al 1999 ).…”

Section: Stress Conditions Chaperone Activity and Anti-aggregation Pmentioning

confidence: 99%

Immense Cellular Implications Associated to Small Stress Proteins Expression: Impacts on Human Pathologies

Arrigo

Ducarouge

Lavial

et al. 2015

Heat Shock Proteins

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In addition to being potent chaperones that protect cells against the accumulation of unfolded proteins under stress conditions, mammalian small heat shock proteins (small Hsps) regulate many vital cellular processes in normal and pathological cells. Indeed, these Hsps are constitutively expressed in many tissues and show dramatic changes in their levels of expression in most human pathologies. They are characterized by a large spectrum of activities and are particularly active in protein conformational and infl ammatory diseases as well as in cancer pathologies. It is now believed that the immense cellular implications of small Hsps results from their ability to interact, through particular structural changes, with many different client proteins that are subsequently modulated in their activities or half-lifes. Here, we have integrated functionally and structurally the recent data in the literature concerning the interactions of mammalian small Hsps with specifi c clients. Further analysis with geneMANIA software and database confi rmed the incredibly large number of functions associated with these Hsps. The consequences for human pathologies as well as putative therapeutic strategies are discussed, particularly when the expression of small Hsps is harmful (as in some cancer pathologies) or when it appears benefi cial for patients.

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Alpha‐crystallin expression affects microtubule assembly and prevents their aggregation

Cited by 65 publications

References 48 publications

Mechanism of Small Heat Shock Protein Function in Vivo

Mechanism of Small Heat Shock Protein Function in Vivo

The Common Modification in αA-Crystallin in the Lens, N101D, Is Associated with Increased Opacity in a Mouse Model

Immense Cellular Implications Associated to Small Stress Proteins Expression: Impacts on Human Pathologies

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