Depolarization-induced slow calcium transients activate early genes in skeletal muscle cells

Abstract

The signaling mechanisms by which skeletal muscle electrical activity leads to changes in gene expression remain largely undefined. We have reported that myotube depolarization induces calcium signals in the cytosol and nucleus via inositol 1,4,5-trisphosphate (IP(3)) and phosphorylation of both ERK1/2 and cAMP-response element-binding protein (CREB). We now describe the calcium dependence of P-CREB and P-ERK induction and of the increases in mRNA of the early genes c-fos, c-jun, and egr-1. Increased phosphorylation and early gene activation were maintained in the absence of extracellular calcium, while the increase in intracellular calcium induced by caffeine could mimic the depolarization stimulus. Depolarization performed either in the presence of the IP(3) inhibitors 2-aminoethoxydiphenyl borate or xestospongin C or on cells loaded with BAPTA-AM, in which slow calcium signals were abolished, resulted in decreased activation of the early genes examined. Both early gene activation and CREB phosphorylation were inhibited by ERK phosphorylation blockade. These data suggest a role for calcium in the transcription-related events that follow membrane depolarization in muscle cells.

NFAT activation by membrane potential follows a calcium pathway distinct from other activity-related transcription factors in skeletal muscle cells

“…4, A-F). 2-APB abolished the IP 3 R-dependent Ca 2ϩ transient, as did the PLC inhibitor (5,11,31). In C2C12 subcellular fractions, a significant decrease in NFATc1 translocation occurred mainly in the presence of ryanodine (Fig.…”

“…The experimental protocol complied with the "Guiding Principles for Research Involving Animals and Human Beings" of the American Physiological Society and was approved by the Bioethics Committee for Investigation in Animals of the Facultad de Medicina, Universidad de Chile. Primary cultures of rat skeletal muscle cells were prepared from Sprague-Dawley neonates as previously reported (5,38). Briefly, muscle tissue dissected from the hindlimbs was minced and treated with collagenase for 15 min at 37°C and grown in medium composed of F-12-DMEM (1: 1), 10% BSA, 2.5% FBS, 100 U/ml penicillin, and 10 mg/ml streptomycin in 60-mm plates.…”

“…We have already reported a highly specific activation of transcriptional regulators ERK, cAMP response element-binding protein (CREB), c-fos, c-jun, and egr-1 associated with K ϩ depolarization-induced IP 3 R-mediated Ca 2ϩ release in skeletal muscle cells in primary culture (2,4,5,31). Recently, we determined that both RyR and IP 3 R-mediated Ca 2ϩ transients regulate the increase of NF-B activity by depolarization in primary myotubes and C2C12 cells (38).…”

Mechanisms of exercise-induced muscle damage and fatigue: Intracellular calcium accumulation

“…Changes in [Ca 2+ ] i regulate transcriptional activation through the calcineurin/CaMK pathways. In turn, these trigger the signaling pathway that ultimately results in muscle growth and hypertrophy 25,70) . Activated calcineurin dephosphorylates the nuclear factor of activated T-cell (NFAT) resulting in translocation of NFAT from the cytoplasm to the nucleus.…”

Altered Gene Expression Pathways in Duchenne Muscular Dystrophy

“…Slow Ca 2+ transients are involved in the "E-T coupling" mechanism, which relates membrane depolarization with gene expression (Powell et al 2001;Araya et al 2003;Carrasco et al 2003;Juretic et al 2006;Juretic et al 2007). The signaling pathway begins at the DHPR, which by a mechanism involving G protein (Eltit et al 2006), activates PI3 kinase and PLC to produce inositol 1,4,5-trisphosphate (IP 3 ) that diffuses in the cytosol and reaches IP 3 receptors (IP 3 Rs) located both at the SR membrane and at the nuclear envelope, promoting Ca 2+ release (Araya et al 2003).…”