Calmodulin binding is required for calcium mediated TRPA1 desensitization

TRPA1 is an essential calcium (Ca2+)-permeable channel involved in nociception and inflammation. It exhibits complex and mechanistically elusive Ca2+ regulation with initial potentiation then rapid desensitization. We find that the universal Ca2+ sensor Calmodulin (CaM) binds TRPA1 in cells at rest and suppresses channel activity. Combining biochemical, biophysical, modeling, NMR spectroscopy, and functional approaches, we identify an evolutionarily conserved, high-affinity Ca2+/CaM binding element in the TRPA1 distal C-terminus. Genetic or biochemical perturbation of Ca2+/CaM binding to this site yields hyperactive channels that exhibit drastic slowing of desensitization with minor effect on potentiation. Higher extracellular Ca2+ partially rescues slowed desensitization. Our results identify a critical regulatory element in an unstructured TRPA1 region highlighting the importance of these domains, they reveal Ca2+/CaM is an essential TRPA1 auxiliary subunit required for proper channel function, and they suggest that Ca2+/CaM binding at this distal site stabilizes a long-range allosteric mechanism to drive rapid desensitization. For pain signaling to be useful, sensory receptors must rapidly detect noxious stimuli and efficiently turn off once the threat has passed. Here, the authors uncover a critical role for the universal calcium sensor calmodulin in properly turning off the TRPA1 pain receptor.