Abstract
Transient receptor potential melastatin 3 ion channel (TRPM3) belongs to the TRP family of cation-permeable ion channels involved in many important biological functions such as pain transduction, thermosensation, and mechanoregulation. The channel was reported to play an important role in Ca(2+) homeostasis, but its gating mechanisms, functions, and regulation are still under research. Utilizing biophysical and biochemical methods, we characterized two independent domains, Ala-35-Lys-124 and His-291-Gly-382, on the TRPM3 N terminus, responsible for interactions with the Ca(2+)-binding proteins calmodulin (CaM) and S100A1. We identified several positively charged residues within these domains as having a crucial impact on CaM/S100A1 binding. The data also suggest that the interaction is calcium-dependent. We also performed competition assays, which suggested that CaM and S100A1 are able to compete for the same binding sites within the TRPM3 N terminus. This is the first time that such an interaction has been shown for TRP family members.