Membrane depolarization induces calcium-dependent upregulation of Hsp70 and Hmox-1 in skeletal muscle cells.
Heat shock proteins (HSPs) are a conserved family of cytoprotective polypeptides, synthesized by cells in response to stress. Hsp70 and heme oxygenase 1 (Hmox-1) are induced by a variety of cellular stressors in skeletal muscle, playing a role in long-term adaptations and muscle fibers regeneration. Though HSPs expression after exercise has been intensely investigated, the molecular mechanisms concerning Hsp70 and Hmox-1 induction are poorly understood. The aim of this work was to investigate the involvement of calcium in Hsp70 and Hmox-1 expression upon depolarization of skeletal muscle cells. We observed that depolarization of myotubes increased both mRNA levels and protein expression for Hsp70 and Hmox-1. Stimulation in the presence of intracellular calcium chelator BAPTA-AM resulted in a complete inhibition of Hsp70-induced expression. It is known that inositol-1,4,5-trisphophate (IP(3))-mediated slow Ca(2+) transients, evoked by membrane depolarization, are involved in the regulation of gene expression. Here we demonstrated that inhibition of IP(3)-dependent calcium signals decreased both Hsp70 mRNA induction and Hsp70 and Hmox-1 protein expression. Inhibitors of calcium-dependent protein kinase C also abolished Hsp70 mRNA induction. Our results provide evidence that membrane depolarization increases Hsp70 and Hmox-1 expression in cultured skeletal muscle cells, which the effect is critically dependent on Ca(2+) released from IP(3)-sensitive intracellular stores and that it involves PKC as an upstream effector in Hsp70 mRNA-induced expression.
Jorquera
Gonzalo
G
Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago 7, Chile.
Juretić
Nevenka
N
Jaimovich
Enrique
E
Riveros
Nora
N
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004558:Electric Stimulation; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology*; D018485:Muscle Fibers, Skeletal; D018482:Muscle, Skeletal / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015854:Up-Regulation
D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat; D011188:Potassium; D002118:Calcium