Calpain 3 deficiency affects SERCA expression and function in the skeletal muscle

Expert Rev Mol Med. 2016 Apr 8;18:e7. doi: 10.1017/erm.2016.9.

Abstract

Limb-girdle muscular dystrophy type 2A (LGMD2A) is a form of muscular dystrophy caused by mutations in calpain 3 (CAPN3). Several studies have implicated Ca2+ dysregulation as an underlying event in several muscular dystrophies, including LGMD2A. In this study we used mouse and human myotube cultures, and muscle biopsies in order to determine whether dysfunction of sarco/endoplasmatic Ca2+-ATPase (SERCA) is involved in the pathology of this disease. In CAPN3-deficient myotubes, we found decreased levels of SERCA 1 and 2 proteins, while mRNA levels remained comparable with control myotubes. Also, we found a significant reduction in SERCA function that resulted in impairment of Ca2+ homeostasis, and elevated basal intracellular [Ca2+] in human myotubes. Furthermore, small Ankyrin 1 (sAnk1), a SERCA1-binding protein that is involved in sarcoplasmic reticulum integrity, was also diminished in CAPN3-deficient fibres. Interestingly, SERCA2 protein was patently reduced in muscles from LGMD2A patients, while it was normally expressed in other forms of muscular dystrophy. Thus, analysis of SERCA2 expression may prove useful for diagnostic purposes as a potential indicator of CAPN3 deficiency in muscle biopsies. Altogether, our results indicate that CAPN3 deficiency leads to degradation of SERCA proteins and Ca2+ dysregulation in the skeletal muscle. While further studies are needed in order to elucidate the specific contribution of SERCA towards muscle degeneration in LGMD2A, this study constitutes a reasonable foundation for the development of therapeutic approaches targeting SERCA1, SERCA2 or sAnk1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Ankyrins / genetics
  • Ankyrins / metabolism
  • Calcium / metabolism*
  • Calpain / deficiency
  • Calpain / genetics*
  • Female
  • Gene Expression Regulation
  • Humans
  • Male
  • Mice
  • Middle Aged
  • Muscle Fibers, Skeletal / metabolism*
  • Muscle Fibers, Skeletal / pathology
  • Muscle Proteins / deficiency
  • Muscle Proteins / genetics*
  • Muscle, Skeletal / metabolism*
  • Muscle, Skeletal / pathology
  • Muscular Dystrophies, Limb-Girdle / genetics*
  • Muscular Dystrophies, Limb-Girdle / metabolism
  • Muscular Dystrophies, Limb-Girdle / pathology
  • Mutation
  • Primary Cell Culture
  • Proteolysis
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Sarcoplasmic Reticulum / metabolism
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / genetics*
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
  • Signal Transduction

Substances

  • Ank1 protein, mouse
  • Ankyrins
  • Atp2a1 protein, mouse
  • Muscle Proteins
  • RNA, Messenger
  • Calpain
  • Capn3 protein, mouse
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Atp2a2 protein, mouse
  • Calcium

Supplementary concepts

  • Limb-girdle muscular dystrophy type 2A