Functional roles of glutamic acid E143 and E705 residues in the N-terminus and transmembrane domain 7 of Anoctamin 1 in calcium and noxious heat sensing

Anoctamin 1 (ANO1) is an anion channel that is activated by changes in cytosolic $Ca^{2+}$ concentration and noxious heat. Although the critical roles of ANO1 have been elucidated in various cell types, the control of its gating mechanisms by $Ca^{2+}$ and heat remain more elusive. To investigate critical amino acid residues for modulation of $Ca^{2+}$ and heat sensing, we constructed a randomized mutant library for ANO1. Among 695 random mutants, reduced $Ca^{2+}$ sensitivity was observed in two mutants (mutant 84 and 87). Consequently, the E143A mutant showed reduced sensitivity to $Ca^{2+}$ but not to high temperatures, whereas the E705V mutant exhibited reduced sensitivity to both $Ca^{2+}$ and noxious heat. These results suggest that the glutamic acids (E) at 143 and 705 residues in ANO1 are critical for modulation of $Ca^{2+}$ and/or heat responses. Furthermore, these findings help to provide a better understanding of the $Ca^{2+}$-mediated activation and heat-sensing mechanism of ANO1.