Activation of the Cl- Channel ANO1 by Localized Calcium Signals in Nociceptive Sensory Neurons Requires Coupling with the IP3 Receptor

We report that anoctamin 1 (ANO1; also known as TMEM16A) Ca2+-activated Cl-channels in small neurons from dorsal root ganglia are preferentially activated by particular pools of intracellular Ca2+. These ANO1 channels can be selectively activated by the G protein-coupled receptor (GPCR)-induced release of Ca2+ from intracellular stores but not by Ca2+ influx through voltage-gated Ca2+ channels. This ability to discriminate between Ca2+ pools was achieved by the tethering of ANO1-containing plasma membrane domains, which also contained GPCRs such as bradykinin receptor 2 and protease-activated receptor 2, to juxtamembrane regions of the endoplasmic reticulum. Interaction of the carboxyl terminus and the first intracellular loop of ANO1 with IP(3)R1 (inositol 1,4,5-trisphosphate receptor 1) contributed to the tethering. Disruption of membrane microdomains blocked the ANO1 and IP(3)R1 interaction and resulted in the loss of coupling between GPCR signaling and ANO1. The junctional signaling complex enabled ANO1-mediated excitation in response to specific Ca2+ signals rather than to global changes in intracellular Ca2+.