Résumé :
|
Dystrophin is an integral structural component of skeletal and cardiac muscles. It provides mechanical stability during muscle contraction and has a crucial signaling role. The absence of dystrophin in DMD leads to calcium homeostasis dysregulation. Cytoskeleton and scaffolding proteins have been shown to be essential for maintaining calcium homeostasis by regulating the calcium influxes through the sarcolemma. Store-Operated Calcium entry supported by TRPCs is involved in abnormal calcium influx due to the absence of dystrophin, however the mechanisms of this mishandling aren't completely elucidated. This study aims to investigate the implication of PLC and PKC pathways in the TRPC1-dependent cation entry dysregulation in dystrophin-deficient muscle cells using fura-2 imaging and pharmacological tools. It also explores the contribution of STIM1 and ORAI1 to this TRPC1-dependent cation influx.We observed that STIM1 silencing using siRNA is responsible for a large percentage of this cation entry, which shows that the TRPC-dependent influx recorded in myotubes is store-operated. We also found that the inhibition of PLC or PKC results in a significant decrease of the abnormal cation influx in dystrophin-deficient cells. We also achieved to decrease this influx by chelating the cytoplasmic free calcium using BAPTA 2-AM, a membrane-permeable selective chelator of intracellular Calcium. Moreover, double treatment with BAPTA-AM and PLC or PKC inhibitor suggested that these compounds affect the same cation influx. We demonstrated thus, for the first time, an involvement of Calcium/PLC/PKC pathway in impaired store-operated calcium influx through TRPC1 in dystrophin-deficient cells.
|