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
09/25/2010Pubmed ID
20863832Pubmed Central ID
PMC2975794DOI
10.1016/j.yjmcc.2010.09.004Scopus ID
2-s2.0-78149416783 33 CitationsAbstract
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 IJAuthor
Ivor J. Benjamin MD Center Director, Professor in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAnimals
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
