Alpha-crystallin can function as a molecular chaperone.

Horwitz, Joseph

doi:10.1073/pnas.89.21.10449

Cited by 1,699 publications

(1,250 citation statements)

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“…In protein refolding assays in vitro (Horwitz, 1992; Jakob et al ., 1993), aggregation prevention by the ATP‐independent small HSPs has been shown to occur independent of the ATP‐dependent HSP70 machinery, but for efficient refolding, substrate transfer to the HSP70 machine is required (Lee & Vierling, 2000; Mogk et al ., 2003). Also, in living cells, refolding assistance by HSPB1 was found to require a functional HSP70 machinery (Bryantsev et al ., 2007), and in this study, a similar scenario was found to be true for the best refolding stimulating D. melanogaster small HSP, CG14207.…”

Section: Discussionmentioning

confidence: 99%

Specific protein homeostatic functions of small heat‐shock proteins increase lifespan

et al. 2015

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SummaryDuring aging, oxidized, misfolded, and aggregated proteins accumulate in cells, while the capacity to deal with protein damage declines severely. To cope with the toxicity of damaged proteins, cells rely on protein quality control networks, in particular proteins belonging to the family of heat‐shock proteins (HSPs). As safeguards of the cellular proteome, HSPs assist in protein folding and prevent accumulation of damaged, misfolded proteins. Here, we compared the capacity of all Drosophila melanogaster small HSP family members for their ability to assist in refolding stress‐denatured substrates and/or to prevent aggregation of disease‐associated misfolded proteins. We identified CG14207 as a novel and potent small HSP member that exclusively assisted in HSP70‐dependent refolding of stress‐denatured proteins. Furthermore, we report that HSP67BC, which has no role in protein refolding, was the most effective small HSP preventing toxic protein aggregation in an HSP70‐independent manner. Importantly, overexpression of both CG14207 and HSP67BC in Drosophila leads to a mild increase in lifespan, demonstrating that increased levels of functionally diverse small HSPs can promote longevity in vivo.

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Section: Discussionmentioning

confidence: 99%

Specific protein homeostatic functions of small heat‐shock proteins increase lifespan

et al. 2015

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“…The small heat shock protein α-crystallin, which is the major protein of the mammalian lens, is an aggregate assembled from two polypeptides (αA and αB). Each polypeptide has a molecular weight around 20,000 kDa and these structural proteins are known to act as molecular chaperones (Horwitz, 1992). Both proteins appear to have extensive nonlens roles (Nagineni and Bhat, 1992).…”

Section: Mitochondrial Protective and Repair Systemsmentioning

confidence: 99%

Mitochondrial function and redox control in the aging eye: Role of MsrA and other repair systems in cataract and macular degenerations

Brennan¹,

Kantorow²

2009

Experimental Eye Research

164

141

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Oxidative stress occurs when the level of prooxidants exceeds the level of antioxidants in cells resulting in oxidation of cellular components and consequent loss of cellular function. Oxidative stress is implicated in wide range of age related disorders including Alzheimer's disease, Parkinson's disease amyotrophic lateral sclerosis (ALS), Huntington's disease and the aging process itself (Lin and Beal, 2006). In the anterior segment of the eye, oxidative stress has been linked to lens cataract (Truscott, 2005) and glaucoma (Tezel, 2006) while in the posterior segment of the eye oxidative stress has been associated with macular degeneration (Hollyfield et al., 2008). Key to many oxidative stress conditions are alterations in the efficiency of mitochondrial respiration resulting in superoxide (O 2 -) production. Superoxide production precedes subsequent reactions that form potentially more dangerous reactive oxygen species (ROS) species such as the hydroxyl radical (˙OH), hydrogen peroxide (H 2 O 2 ) and peroxynitrite (OONO -). The major source of ROS in the mitochondria, and in the cell overall, is leakage of electrons from complexes I and III of the electron transport chain. It is estimated that 0.2-2% of oxygen taken up by cells is converted to ROS, through mitochondrial superoxide generation, by the mitochondria (Hansford et al., 1997). Generation of superoxide at complex I and III has been shown to occur at both the matrix side of the inner mitochondrial membrane and the cytosolic side of the membrane (Kakkar and Singh 2007). While exogenous sources of ROS such as UV light, visible light, ionizing radiation, chemotherapeutics, and environmental toxins may contribute to the oxidative milieu, mitochondria are perhaps the most significant contribution to ROS production affecting the aging process. In addition to producing ROS, mitochondria are also a target for ROS which in turn reduces mitochondrial efficiency and leads to the generation of more ROS in a vicious self-destructive cycle. Consequently, the mitochondria have evolved a number of antioxidant and key repair systems to limit the damaging potential of free oxygen radicals and to repair damaged proteins (Figure 1.0). The aging eye appears to be at considerable risk from oxidative stress. This review will outline the potential role of mitochondrial function and redox balance in age-related eye diseases, and detail how the methionine sulfoxide reductase (Msr)

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“…Among the molecular chaperones, α-crystallins are utilized during protein synthesis and to prevent aggregation of misfolded or damaged proteins during oxidative stress (Horwitz, 1992). Loss of chaperone activity occurs in ocular tissues following a significant decrease in the crystallin content (Kapphahn et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Exacerbation of retinal degeneration in the absence of alpha crystallins in an in vivo model of chemically induced hypoxia

Yaung

Kannan

Wawrousek

et al. 2008

Experimental Eye Research

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This study evaluated the role of crystallins in retinal degeneration induced by chemical hypoxia. Wild type, αA-crystallin (−/−), and αB-crystallin (−/−) mice received intravitreal injection of 12 nmol (low dose), 33 nmol (intermediate dose) or 60 nmol (high dose) cobalt chloride (CoCl 2 ). Hematoxylin and eosin and TdT-mediated dUTP nick-end labeling (TUNEL) stains were performed after 24 hours, 96 hours, and 1 week post-injection, while immunofluorescent stains for αA-and αB-crystallin were performed 1 week post-injection. The in vitro effects of CoCl 2 on αB-crystallin expression in ARPE-19 cells were determined by real time RT-PCR, Western blot, and confocal microscopy and studies evaluating subcellular distribution of αB-crystallin in the mitochondria and cytosol were also performed. Histologic studies revealed progressive retinal degeneration with CoCl 2 injection in wild type mice. Retinas of CoCl 2 injected mice showed transient increased expression of HIF-1α which was maximal 24 hours after injection. Intermediate dose CoCl 2 injection was associated with increased retinal immunofluorescence for both αA-and αB-crystallin; however, after high dose injection, increased retinal degeneration was associated with decreased levels of crystallin expression. Injection of CoCl 2 at either intermediate or high dose in αA-crystallin (−/−) and αB-crystallin (−/−) mice resulted in much more severe retinal degeneration compared to wild type eyes. A decrease in ARPE-19 total and cytosolic αB-crystallin expression with increasing CoCl2 treatment and an increase in mitochondrial αB-crystallin were found. We conclude that lack of α-crystallins accentuates retinal degeneration in chemically-induced hypoxia in vivo.

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Alpha-crystallin can function as a molecular chaperone.

Cited by 1,699 publications

References 48 publications

Specific protein homeostatic functions of small heat‐shock proteins increase lifespan

Specific protein homeostatic functions of small heat‐shock proteins increase lifespan

Mitochondrial function and redox control in the aging eye: Role of MsrA and other repair systems in cataract and macular degenerations

Exacerbation of retinal degeneration in the absence of alpha crystallins in an in vivo model of chemically induced hypoxia

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