Local Ca ²⁺ signals couple activation of TRPV1 and ANO1 sensory ion channels

Abstract

ANO1 (TMEM16A) is a Ca2+-activated Cl− channel (CaCC) expressed in peripheral somatosensory neurons that are activated by painful (noxious) stimuli. These neurons also express the Ca2+-permeable channel and noxious heat sensor TRPV1, which can activate ANO1. Here, we revealed an intricate mechanism of TRPV1-ANO1 channel coupling in rat dorsal root ganglion (DRG) neurons. Simultaneous optical monitoring of CaCC activity and Ca2+ dynamics revealed that the TRPV1 ligand capsaicin activated CaCCs. However, depletion of endoplasmic reticulum (ER) Ca2+ stores reduced capsaicin-induced Ca2+ increases and CaCC activation, suggesting that ER Ca2+ release contributed to TRPV1-induced CaCC activation. ER store depletion by plasma membrane–localized TRPV1 channels was demonstrated with an ER-localized Ca2+ sensor in neurons exposed to a cell-impermeable TRPV1 ligand. Proximity ligation assays established that ANO1, TRPV1, and the IP3 receptor IP3R1 were often found in close proximity to each other. Stochastic optical reconstruction microscopy (STORM) confirmed the close association between all three channels in DRG neurons. Together, our data reveal the existence of ANO1-containing multichannel nanodomains in DRG neurons and suggest that coupling between TRPV1 and ANO1 requires ER Ca2+ release, which may be necessary to enhance ANO1 activation.

Cyst growth in ADPKD is prevented by pharmacological and genetic inhibition of TMEM16A in vivo

“…4i, j ). Thus, Ca 2+ release and SOCE are coupled and are augmented by deletion of Pkd1 , probably due to upregulation of TMEM16A 23 , 25 – 27 . SOCE is potently blocked by the inhibitors of Orai channels and transient receptor potential (Trp) channels, YM58483 and SK&F96365, respectively, suggesting a contribution of both channels to enhanced SOCE in Pkd1 −/− cells (Fig.…”

Molecular mechanisms of activation and regulation of ANO1-Encoded Ca2+-Activated Cl- channels

“…In addition, the TRPV1-ANO1 coupling led to enhanced action potential firing in response to CAP, a response that was also blocked by the ANO1 blocker T16 Inh -A01. Shah et al [ 218 ] reported a similar interaction between TRPV1 and ANO1 in peripheral somatosensory neurons. They also showed that the CAP-induced ANO1 conductance involved ER Ca 2+ release through an additional interaction with type 1 IP 3 R (IP 3 R1).…”

Dorsal root ganglia control nociceptive input to the central nervous system

“…The fluorescence of EYFP-QL is quenched by iodide and since Clchannels (e.g. GABAA) are permeable to this anion, EYFP-QL fluorescence quenching by Ican be used to monitor Clchannel activation (40)(41)(42)(43). We co-cultured these 'GABA indicator' HEK293 cells with DRG neurons and measured EYFP-QL fluorescence quenching induced by the addition of 5 mM NaI to the extracellular solution (Fig.…”