Calmodulin binding is required for calcium mediated TRPA1 desensitization

Abstract

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.