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The Human 343delT HSPB5 Chaperone Associated with Early-onset Skeletal Myopathy Causes Defects in Protein Solubility. J Biol Chem 2016 07 15;291(29):14939-53

Date

05/27/2016

Pubmed ID

27226619

Pubmed Central ID

PMC4946913

DOI

10.1074/jbc.M116.730481

Scopus ID

2-s2.0-84978431927   8 Citations

Abstract

Mutations of HSPB5 (also known as CRYAB or αB-crystallin), a bona fide heat shock protein and molecular chaperone encoded by the HSPB5 (crystallin, alpha B) gene, are linked to multisystem disorders featuring variable combinations of cataracts, cardiomyopathy, and skeletal myopathy. This study aimed to investigate the pathological mechanisms involved in an early-onset myofibrillar myopathy manifesting in a child harboring a homozygous recessive mutation in HSPB5, 343delT. To study HSPB5 343delT protein dynamics, we utilize model cell culture systems including induced pluripotent stem cells derived from the 343delT patient (343delT/343delT) along with isogenic, heterozygous, gene-corrected control cells (WT KI/343delT) and BHK21 cells, a cell line lacking endogenous HSPB5 expression. 343delT/343delT and WT KI/343delT-induced pluripotent stem cell-derived skeletal myotubes and cardiomyocytes did not express detectable levels of 343delT protein, contributable to the extreme insolubility of the mutant protein. Overexpression of HSPB5 343delT resulted in insoluble mutant protein aggregates and induction of a cellular stress response. Co-expression of 343delT with WT prevented visible aggregation of 343delT and improved its solubility. Additionally, in vitro refolding of 343delT in the presence of WT rescued its solubility. We demonstrate an interaction between WT and 343delT both in vitro and within cells. These data support a loss-of-function model for the myopathy observed in the patient because the insoluble mutant would be unavailable to perform normal functions of HSPB5, although additional gain-of-function effects of the mutant protein cannot be excluded. Additionally, our data highlight the solubilization of 343delT by WT, concordant with the recessive inheritance of the disease and absence of symptoms in carrier individuals.

Author List

Mitzelfelt KA, Limphong P, Choi MJ, Kondrat FD, Lai S, Kolander KD, Kwok WM, Dai Q, Grzybowski MN, Zhang H, Taylor GM, Lui Q, Thao MT, Hudson JA, Barresi R, Bushby K, Jungbluth H, Wraige E, Geurts AM, Benesch JL, Riedel M, Christians ES, Minella AC, Benjamin IJ

Authors

Ivor J. Benjamin MD Center Director, Professor in the Medicine department at Medical College of Wisconsin
Aron Geurts PhD Associate Professor in the Physiology department at Medical College of Wisconsin
Wai-Meng Kwok PhD Professor in the Anesthesiology department at Medical College of Wisconsin




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

Cardiomyopathies
Cataract
Female
Homozygote
Humans
Induced Pluripotent Stem Cells
Male
Models, Biological
Muscle Fibers, Skeletal
Muscular Diseases
Mutant Proteins
Myocytes, Cardiac
Pedigree
Protein Aggregation, Pathological
RNA, Messenger
Recombinant Proteins
Sequence Deletion
Solubility
alpha-Crystallin B Chain
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a