Molecular Determinants Mediating Gating of Transient Receptor Potential Canonical (TRPC) Channels by Stromal interaction molecule 1 (STIM1) [Signal Transduction]

January 24th, 2014 by Lee, K. P., Choi, S., Hong, J. H., Ahuja, M., Graham, S., Ma, R., So, I., Shin, D. M., Muallem, S., Yuan, J.

Transient Receptor Potential Canonical channels (TRPCs) mediate critical part of the receptor-evoked Ca2+ influx. TRPCs are gated open by the ER Ca2+ sensor STIM1. Here, we how STIM1 and TRPCs interact and how the interaction opens the channels. We report that the STIM1 Orai1 Activating region (SOAR) interacts with the TRPCs coiled-coil domains (CCDs) to open the channels. Thus, disruption of the N terminus (NT) CCDs by triple mutations eliminated all TRPCs surface localization, reduced binding of STIM1 to TRPC1 and TRPC5 while increasing binding to TRPC3 and TRPC6. Single mutations in TRPC1 NT or C-terminus (CT) CCDs reduced interaction and activation by STIM1. Remarkably, single mutations in TRPC3 NT-CCD enhanced interaction and regulation by STIM1. Disruption of TRPC3 CT-CCD eliminated regulation by STIM1 and the enhanced interaction caused by NT-CCD mutations. The NT-CCD mutations converted TRPC3 from TRPC1-dependent to TRPC1-independent, STIM1-regulated channel. TRPC1 reduced FRET between BFP-TRPC3 and TRPC3-YFP and between CFP-TRPC3-YFP upon stimulation. Accordingly, knockdown of TRPC1 made TRPC3 STIM1-independent, which was reconstituted by TRPC1 CT-CCD alone. Knockout of Trpc1 and Trpc3 similarly inhibited Ca2+ influx and inhibition of Trpc3 had no further effect on Ca2+ influx in Trpc1-/- cells. Cell stimulation enhanced the formation of Trpc1-Stim1-Trpc3 complexes. These findings support a model in which the TRPC3 NT and CT CCDs interact to shield the CT-CCD from interaction with STIM1. TRPC1 CT-CCD dissociates this interaction to allow SOAR access to the TRPC3 CT-CCD and channel opening. These studies provide evidence that the TRPC channels CCDs participate in channels gating.
  • Posted in Journal of Biological Chemistry, Publications
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