TRPC3-like protein and vitamin D receptor mediate 1alpha,25(OH)2D3-induced SOC influx in muscle cells.

1alpha,25-Dihydroxy-Vitamin-D3 (1alpha,25(OH)2-Vitamin D3) stimulates in skeletal muscle cells Ca2+ release from inner stores and influx through both voltage-dependent and store-operated Ca2+ (SOC, CCE) channels. We investigated the involvement of TRPC proteins and Vitamin D receptor (VDR) in CCE induced by 1alpha,25(OH)2D3 in chick muscle cells. Two fragments were amplified by RT-PCR, exhibiting approximately 80% sequence homology with mammalian TRPC3/6/7. Northern and Western blots employing a TRPC3-probe and anti-TRPC3 antibodies, respectively, confirmed endogenous expression of a TRPC3-like protein of 140 kDa. Spectrofluorimetric measurements in Fura-2 loaded cells showed reduced CCE and Mn2+ entry in response to either thapsigargin or 1alpha,25(OH)2D3 upon transfection with anti-TRPC3/6/7 antisense oligodeoxynucleotides (ODNs). Transfection with anti-VDR antisense ODNs diminished 1alpha,25(OH)2D3-dependent Ca2+ and Mn2+ influx. Co-immunoprecipitation of TRPC3-like protein and VDR under non-denaturating conditions was observed. We propose that endogenous TRPC3-like proteins and the VDR participate in the modulation of CCE by 1alpha,25(OH)2D3 in muscle cells, which could be mediated by an interaction between these proteins.