Regulation of TRPC1 and TRPC4 Cation Channels Requires an α1-Syntrophin-dependent Complex in Skeletal Mouse Myotubes

Abstract

The dystrophin-associated protein complex (DAPC) is essential for skeletal muscle, and the lack of dystrophin in Duchenne muscular dystrophy results in a reduction of DAPC components such as syntrophins and in fiber necrosis. By anchoring various molecules, the syntrophins may confer a role in cell signaling to the DAPC. Calcium disorders and abnormally elevated cation influx in dystrophic muscle cells have suggested that the DAPC regulates some sarcolemmal cationic channels. We demonstrated previously that minidystrophin and ␣1-syntrophin restore normal cation entry in dystrophin-deficient myotubes and that sarcolemmal TRPC1 channels associate with dystrophin and the bound PDZ domain of ␣1-syntrophin. This study shows that small interfering RNA (siRNA) silencing of ␣1-syntrophin dysregulated cation influx in myotubes. Moreover, deletion of the PDZcontaining domain prevented restoration of normal cation entry by ␣1-syntrophin transfection in dystrophin-deficient myotubes. TRPC1 and TRPC4 channels are expressed at the sarcolemma of muscle cells; forced expression or siRNA silencing showed that cation influx regulated by ␣1-syntrophin is supported by TRPC1 and TRPC4. A molecular association was found between TRPC1 and TRPC4 channels and the ␣1-syntrophin-dystrophin complex. TRPC1 and TRPC4 channels may form sarcolemmal channels anchored to the DAPC, and ␣1-syntrophin is necessary to maintain the normal regulation of TRPC-supported cation entry in skeletal muscle. Cation channels with DAPC form a signaling complex that modulates cation entry and may be crucial for normal calcium homeostasis in skeletal muscles.

TRPC3 cation channel plays an important role in proliferation and differentiation of skeletal muscle myoblasts

“…TRPC4 anchors to the dystrophin-associated protein complex and is necessary to maintain the normal regulation of extracellular Ca 2+ -entry in skeletal muscle (Sabourin et al, 2009). Possibly the decreased TRPC4 expression in myoblast state is one of auxiliary factors inducing high Ca 2+ content in the SR of MDG/TRPC3 KD myoblasts.…”

“…TRPC1 is involved in maintaining the force during sustained repeated contractions in mouse skeletal muscle (Zanou et al, 2010). TRPC1 and TRPC4 form channels anchoring to the dystrophin-associated protein complex and are necessary to maintain the normal regulation of extracellular Ca 2+ -entry in skeletal muscle (Sabourin et al, 2009). Not much is known about TRPC6 function in skeletal muscle.…”

During post-natal human myogenesis, normal myotube size requires TRPC1 and TRPC4 mediated Ca2+ entry

“…We found that human primary myoblasts expressed TRPC1, TRPC3, TRPC4 and TRPC6 isoforms, an expression profile similar to what was reported in mouse skeletal muscle cells (Brinkmeier, 2011 negative constructs, we showed that TRPC1 and TRPC4 isoforms participated to SOCE in human primary myoblasts. The implication of TRPC1 in SOCE was already reported in mouse myoblasts (C2C12 cells; Louis et al, 2008) and myotubes (Sabourin et al, 2009), while the same channel was shown to be store-independent in adult mouse fibers (Zanou et al, 2010). Few studies analyzed the implication of TRPC4 in muscle cells, except one reporting that TRPC4 functions as a SOCE channel in myotubes (Sabourin et al, 2009).…”

“…The implication of TRPC1 in SOCE was already reported in mouse myoblasts (C2C12 cells; Louis et al, 2008) and myotubes (Sabourin et al, 2009), while the same channel was shown to be store-independent in adult mouse fibers (Zanou et al, 2010). Few studies analyzed the implication of TRPC4 in muscle cells, except one reporting that TRPC4 functions as a SOCE channel in myotubes (Sabourin et al, 2009).…”

“…Signaling pathways leading to TRPC activation is still a debated issue, but it was shown that TRPC1, TRPC4 and TRPC5 participate to SOCE in several cell types (Ambudkar, 2007;Worley et al, 2007;Yuan et al, 2007;Salido et al, 2011), including primary mouse myotubes and C2C12 mouse muscle cell line (Vandebrouck et al, 2007;Louis et al, 2008;Sabourin et al, 2009). In addition, TRPC1 was shown to play an important role to sustain skeletal muscle contraction (Zanou et al, 2010) and, in C2C12 cell line, TRPC1 silencing decreased SOCE and the fusion process (Louis et al, 2008;Formigli et al, 2009;Meacci et al, 2010), hence impairing muscle formation.…”