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Selective degradation of aggregate-prone CryAB mutants by HSPB1 is mediated by ubiquitin-proteasome pathways. J Mol Cell Cardiol 2010 Dec;49(6):918-30

Date

09/25/2010

Pubmed ID

20863832

Pubmed Central ID

PMC2975794

DOI

10.1016/j.yjmcc.2010.09.004

Scopus ID

2-s2.0-78149416783   33 Citations

Abstract

Disease-causing mutations of genes encoding small MW heat shock proteins (sHSPs) constitute a growing family of inherited myofibrillar disorders. In the present work, we found that three structurally-distinct CryAB mutants R120G, 450delA and 464delCT are mostly present in the detergent-insoluble fractions when overexpressed in H9c2 rat heart cells. We found that either over-expression or knockdown of HSPB1, a related sHSP, affects the solubility, stability, and degradation of aggregation-prone CryAB mutants. HSPB1 overexpression has negligible effects on the solubility and protein aggregates of either R120G and/or 450delA but increased the solubility and prevented formation of 464delCT aggregates. HSPB1 knockdown decreased solubility and increased protein aggregates of all CryAB mutants, indicating a key role for HSPB1 in clearance of CryAB mutants under basal conditions. We provide four lines of evidence that such selective clearance of R120G, 450delA and 464delCT mutants by HSPB1 is mediated by the ubiquitin-proteasome system (UPS). First, we found that treatment with the proteasome inhibitors increased the levels of all CryAB mutants. Second, R120G and 450delA overexpression corresponded to the accumulation of their specific ubiquitin conjugates in H9c2 cells. Third, HSPB1 knockdown directly increased the levels of all polyubiquitin conjugates. And fourth, the selective attenuation of 464delCT expression by HSPB1 over-expression was abrogated by the proteasome inhibition. We conclude that such selective interactions between CryAB mutants and HSPB1 overexpression might have important implications for the clinical manifestations and potential treatment.

Author List

Zhang H, Rajasekaran NS, Orosz A, Xiao X, Rechsteiner M, Benjamin IJ

Author

Ivor J. Benjamin MD Center Director, Professor in the Medicine department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Animals
Autophagy
Cytoplasm
Down-Regulation
Gene Knockdown Techniques
HSP27 Heat-Shock Proteins
Humans
Mice
Molecular Sequence Data
Mutant Proteins
Myocytes, Cardiac
Polyubiquitin
Proteasome Endopeptidase Complex
Protein Processing, Post-Translational
Protein Structure, Quaternary
Rats
Signal Transduction
Solubility
Subcellular Fractions
Ubiquitin
alpha-Crystallin B Chain
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a