Activation of the Cl ⁻ Channel ANO1 by Localized Calcium Signals in Nociceptive Sensory Neurons Requires Coupling with the IP ₃ Receptor

Abstract

We report that ANO1 (also known as TMEM16A) Ca 2+ -activated Cl − channels in small neurons from dorsal root ganglia are preferentially activated by particular pools of intracellular Ca 2+ . These ANO1 channels can be selectively activated by the G protein-coupled receptor (GPCR)-induced release of Ca 2+ from intracellular stores, but not by Ca 2+ influx through voltage-gated Ca 2+ channels. This ability to discriminate between Ca 2+ 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 C-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 Ca 2+ signals rather than to global changes in intracellular Ca 2+ .

Activation of Ca2+‐activated Cl− channel ANO1 by localized Ca2+ signals

“…Our data suggest that in sensory neurons ANO1 may physically interact with the IP 3 R (Jin et al . 2013), but we do not yet know if these interactions are direct nor if they are constitutive. Likewise, we do not yet know what other components exist within such signalling complexes or what interactions hold these together.…”

“…2010; Jin et al . 2013). Thus, in patch‐clamp recordings from cultured capsaicin‐sensitive DRG neurons we found that activation of VGCCs with voltage pulses rarely resulted in a CaCC current activation, even in same neurons in which B 2 or PAR‐2 receptor triggering did activate CaCCs (Jin et al .…”

“…In accord with these reports we found that B 2 and PAR‐2 receptors co‐immunoprecipitated with the IP 3 R and with the lipid raft marker caveolin‐1 (Jin et al . 2013). Thus, we hypothesized that a functional signalling unit that produces CaCC‐mediated depolarization in response to inflammatory mediators in nociceptive sensory neurons may be assembled at the plasma membrane–ER junctions.…”

“…The authors reported that CaCCs were not distributed homogenously in the plasma membrane of the smooth muscle cells but instead were clustered in the proximity of ER‐localized RyRs, possibly in a fashion similar to that reported for nociceptive sensory neurons (Jin et al . 2013; see above); the fact that IP 3 Rs and RyRs belong to the same protein family (Amador et al . 2013) adds to the analogy.…”

“…2012; Jin et al . 2013). It is thought that in these neurons CaCCs amplify signals generated by Ca 2+ ‐permeable channels in response to the respective sensory events.…”