title: Expression of Cataract-linked γ-Crystallin Variants in Zebrafish Reveals a Proteostasis Network That Senses Protein Stability.
abstract: The refractivity and transparency of the ocular lens is dependent on the stability and solubility of the crystallins in the fiber cells. A number of mutations of lens crystallins have been associated with dominant cataracts in humans and mice. Of particular interest were γB- and γD-crystallin mutants linked to dominant cataracts in mouse models. Although thermodynamically destabilized and aggregation-prone, these mutants were found to have weak affinity to the resident chaperone α-crystallin in vitro To better understand the mechanism of the cataract phenotype, we transgenically expressed different γD-crystallin mutants in the zebrafish lens and observed a range of lens defects that arise primarily from the aggregation of the mutant proteins. Unlike mouse models, a strong correlation was observed between the severity and penetrance of the phenotype and the level of destabilization of the mutant. We interpret this result to reflect the presence of a proteostasis network that can "sense" protein stability. In the more destabilized mutants, the capacity of this network is overwhelmed, leading to the observed increase in phenotypic penetrance. Overexpression of αA-crystallin had no significant effects on the penetrance of lens defects, suggesting that its chaperone capacity is not limiting. Although consistent with the prevailing hypothesis that a chaperone network is required for lens transparency, our results suggest that αA-crystallin may not be efficient to inhibit aggregation of lens γ-crystallin. Furthermore, our work implicates additional inputs/factors in this underlying proteostasis network and demonstrates the utility of zebrafish as a platform to delineate mechanisms of cataract.
authors: From the Departments of Molecular Physiology and Biophysics and.
authors: Shu-Yu
authors: SY
authors: Wu
authors: From the Departments of Molecular Physiology and Biophysics and.
authors: Ping
authors: P
authors: Zou
authors: From the Departments of Molecular Physiology and Biophysics and.
authors: Alexandra W
authors: AW
authors: Fuller
authors: From the Departments of Molecular Physiology and Biophysics and.
authors: Sanjay
authors: S
authors: Mishra
authors: Biochemistry and.|the Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
authors: Zhen
authors: Z
authors: Wang
authors: Biochemistry and.|the Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
authors: Kevin L
authors: KL
authors: Schey
authors: From the Departments of Molecular Physiology and Biophysics and hassane.mchaourab@vanderbilt.edu.
authors: Hassane S
authors: HS
authors: Mchaourab
mesh_terms: D000818:Animals; D002386:Cataract / Q000235:genetics*; D007903:Lens Capsule, Crystalline / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D066329:Protein Aggregates; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000096:biosynthesis* / Q000235:genetics; D038202:alpha-Crystallin A Chain / Q000096:biosynthesis / Q000235:genetics; D038222:gamma-Crystallins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D066329:Protein Aggregates; D029961:Zebrafish Proteins; D038202:alpha-Crystallin A Chain; D038222:gamma-Crystallins
keywords: aggregation; cataract; chaperone; crystallin; lens; proteostasis; small heat shock protein (sHsp); zebrafish