TRPC1 contributes to the Ca2+-dependent regulation of adenylate cyclases.

SOCE (store-operated Ca2+ entry) is mediated via specific plasma membrane channels in response to ER (endoplasmic reticulum) Ca2+ store depletion. This route of Ca2+ entry is central to the dynamic interplay between Ca2+ and cAMP signalling in regulating the activity of Ca2+-sensitive adenylate cyclase isoforms (AC1, AC5, AC6 and AC8). Two proteins have been identified as key components of SOCE: STIM1 (stromal interaction molecule 1), which senses ER Ca2+ store content and translocates to the plasma membrane upon store depletion, where it then activates Orai1, the pore-forming component of the CRAC (Ca2+ release-activated Ca2+) channel. Previous studies reported that co-expression of STIM1 and Orai1 in HEK-293 (human embryonic kidney 293) cells enhances Ca2+-stimulated AC8 activity and that AC8 and Orai1 directly interact to enhance this regulation. Nonetheless, the additional involvement of TRPC (transient receptor potential canonical) channels in SOCE has also been proposed. In the present study, we evaluate the contribution of TRPC1 to SOCE-mediated regulation of Ca2+-sensitive ACs in HEK-293 cells stably expressing AC8 (HEK-AC8) and HSG (human submandibular gland) cells expressing an endogenous Ca2+-inhibited AC6. We demonstrate a role for TRPC1 as an integral component of SOCE, alongside STIM1 and Orai1, in regulating Ca2+ fluxes within AC microdomains and influencing cAMP production. Abbreviations: AC, adenylate cyclase; 2APB, 2-aminoethoxydiphenyl borate; CRAC, Ca2+ release-activated Ca2+; DAG, diacylglycerol; ER, endoplasmic reticulum; Fsk, forskolin; HA, haemagglutinin; HEK, human embryonic kidney; HSG, human submandibular gland; NFAT, nuclear factor of activated T-cells; ROI, region of interest; RT-PCR, reverse transcription–PCR; SOCE, store-operated Ca2+ entry; STIM1, stromal interaction molecule 1; Tg, thapsigargin; TIRF, total internal reflection fluorescence; TRPC, transient receptor potential canonical