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An alternative splice variant of human ?A-crystallin modulates the oligomer ensemble and the chaperone activity of ?-crystallins.

ABSTRACT: In humans, ten genes encode small heat shock proteins with lens ?A-crystallin and ?B-crystallin representing two of the most prominent members. The canonical isoforms of ?A-crystallin and ?B-crystallin collaborate in the eye lens to prevent irreversible protein aggregation and preserve visual acuity. ?-Crystallins form large polydisperse homo-oligomers and hetero-oligomers and as part of the proteostasis system bind substrate proteins in non-native conformations, thereby stabilizing them. Here, we analyzed a previously uncharacterized, alternative splice variant (isoform 2) of human ?A-crystallin with an exchanged N-terminal sequence. This variant shows the characteristic ?-crystallin secondary structure, exists on its own predominantly in a monomer-dimer equilibrium, and displays only low chaperone activity. However, the variant is able to integrate into higher order oligomers of canonical ?A-crystallin and ?B-crystallin as well as their hetero-oligomer. The presence of the variant leads to the formation of new types of higher order hetero-oligomers with an overall decreased number of subunits and enhanced chaperone activity. Thus, alternative mRNA splicing of human ?A-crystallin leads to an additional, formerly not characterized ?A-crystallin species which is able to modulate the properties of the canonical ensemble of ?-crystallin oligomers.

SUBMITTER: Preis W

PROVIDER: S-EPMC5465031 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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An alternative splice variant of human αA-crystallin modulates the oligomer ensemble and the chaperone activity of α-crystallins.

Preis Waldemar W Bestehorn Annika A Buchner Johannes J Haslbeck Martin M

Cell stress & chaperones 20170218 4

In humans, ten genes encode small heat shock proteins with lens αA-crystallin and αB-crystallin representing two of the most prominent members. The canonical isoforms of αA-crystallin and αB-crystallin collaborate in the eye lens to prevent irreversible protein aggregation and preserve visual acuity. α-Crystallins form large polydisperse homo-oligomers and hetero-oligomers and as part of the proteostasis system bind substrate proteins in non-native conformations, thereby stabilizing them. Here, ...[more]

PMID: 28214988

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Project description:BackgroundA substitution mutation in human ?A-crystallin (?AG98R) is associated with autosomal dominant cataract. The recombinant mutant ?AG98R protein exhibits altered structure, substrate-dependent chaperone activity, impaired oligomer stability and aggregation on prolonged incubation at 37 °C. Our previous studies have shown that ?A-crystallin-derived mini-chaperone (DFVIFLDVKHFSPEDLTVK) functions like a molecular chaperone by suppressing the aggregation of denaturing proteins. The present study was undertaken to determine the effect of ?A-crystallin-derived mini-chaperone on the stability and chaperone activity of ?AG98R-crystallin.Methodology/principal findingsRecombinant ?AG98R was incubated in presence and absence of mini-chaperone and analyzed by chromatographic and spectrometric methods. Transmission electron microscope was used to examine the effect of mini-chaperone on the aggregation propensity of mutant protein. Mini-chaperone containing photoactive benzoylphenylalanine was used to confirm the interaction of mini-chaperone with ?AG98R. The rescuing of chaperone activity in mutant?-crystallin (?AG98R) by mini-chaperone was confirmed by chaperone assays. We found that the addition of the mini-chaperone during incubation of ?AG98R protected the mutant crystallin from forming larger aggregates that precipitate with time. The mini-chaperone-stabilized ?AG98R displayed chaperone activity comparable to that of wild-type ?A-crystallin. The complexes formed between mini-?A-?AG98R complex and ADH were more stable than the complexes formed between ?AG98R and ADH. Western-blotting and mass spectrometry confirmed the binding of mini-chaperone to mutant crystallin.Conclusion/significanceThese results demonstrate that mini-chaperone stabilizes the mutant ?A-crystallin and modulates the chaperone activity of ?AG98R. These findings aid in our understanding of how to design peptide chaperones that can be used to stabilize mutant ?A-crystallins and preserve the chaperone function.

Dataset Information

An alternative splice variant of human ?A-crystallin modulates the oligomer ensemble and the chaperone activity of ?-crystallins.

Publications

An alternative splice variant of human αA-crystallin modulates the oligomer ensemble and the chaperone activity of α-crystallins.

Similar Datasets

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