Abstract Calmodulin (CaM) is the principal calcium (Ca 2+ ) sensor in eukaryotic cells, orchestrating hundreds of signalling pathways that regulate excitability, contraction, secretion, gene expression and many other essential processes. This small, highly conserved protein binds four Ca 2+ ions and undergoes conformational changes that enable versatile interactions with a wide range of effector proteins, including numerous ion channels. Among these the transient receptor potential (TRP) channels constitute the second‐largest family of cation channels and respond to diverse chemical, mechanical and thermal stimuli. Although TRP channels share a conserved transmembrane core their variable cytosolic domains confer extensive regulatory diversity and tissue‐specific function. Across the TRP superfamily CaM acts as a widespread yet mechanistically diverse modulator, with at least one CaM‐regulated member in four of the six major subfamilies. In most cases CaM exerts an inhibitory, Ca 2+ ‐dependent braking mechanism that promotes channel closure or desensitization, contrasting with the activating or anti‐inactivating roles CaM plays in several other ion channel families. This review integrates structural, biochemical and functional evidence from eight representative TRP channels to identify common motifs and mechanisms that define CaM‐dependent regulation. By mapping known CaM‐binding elements onto available cryo‐EM structures we contextualize current models of TRP channel calmodulation and highlight structural principles that unify otherwise disparate regulatory behaviours. This structure‐guided framework highlights emerging mechanistic themes, details unresolved questions and suggests new hypotheses for how CaM shapes TRP channel function across diverse cellular contexts. image
Alemayhu et al. (Fri,) studied this question.