CREMI, CHU de Québec Research Center, Quebec, Quebec G1V 4G2, Canada; Department of Molecular Medicine, Faculty of Medicine, Laval University, Quebec, Quebec G1V 4G2, Canada. Electronic address: [Email]
OBJECTIVE : Secreted protein acidic and rich in cysteine, (SPARC), is a matricellular protein implicated in the modulation of the extracellular matrix (ECM) and mitochondrial proteins expression. METHODS : To study the mechanism through which SPARC is involved in the possible link between ECM and mitochondria, C2C12 myoblasts were cultured with/without the exogenous addition/inhibition of SPARC as well as activation/inhibition of adenosine monophosphate-activated protein kinase (AMPK). Electrical pulse stimulation (EPS), was applied for 2 days in myotubes. RESULTS : The expressions of ECM-related (integrin-linked kinase (ILK), glycogen synthase kinase-3 beta (GSK-3ß), phosphorylated-GSK-3ß (p-GSK-3ß) and collagen 1a1), mitochondrial-related (AMPK, phosphorylated-AMPK (p-AMPK), succinate dehydrogenase (SDHB) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc1α)) and SPARC proteins and/or genes were measured after modulation of SPARC and/or AMPK as well as with or without EPS. The addition of SPARC in C2C12 myoblast increased the expression of ILK, p-GSK-3ß and p-AMPK whereas anti-SPARC antibody decreased them at different incubation times (0, 10, and 30 min, and 6 h). The AMPK activation increased SPARC, collagen 1a1, p-AMPK and SDHB proteins level, however, AMPK inhibition blunted the effects. EPS induced Sparc and Pgc1a genes expression. CONCLUSIONS : Sparc, an EPS-induced gene, may be involved in the link between ECM remodeling and mitochondrial function in muscle via its interaction with ILK/AMPK.
