EF-hand like Region in the N-terminus of Anoctamin 1 Modulates Channel Activity by Ca²⁺ and Voltage
- Author:
Min Ho TAK
1
;
Yongwoo JANG
;
Woo Sung SON
;
Young Duk YANG
;
Uhtaek OH
Author Information
- Publication Type:Original Article
- Keywords: Anoctamin-1; Chloride channels; Calcium; Mutagenesis; Site-directed
- MeSH: Amino Acids, Acidic; Animals; Calcium; Calmodulin; Chloride Channels; Cryoelectron Microscopy; Crystallography, X-Ray; EF Hand Motifs; Mice; Models, Molecular; Mutagenesis; Nectria; Protein Isoforms
- From:Experimental Neurobiology 2019;28(6):658-669
- CountryRepublic of Korea
- Language:English
- Abstract: Anoctamin1 (ANO1) also known as TMEM16A is a transmembrane protein that functions as a Ca²⁺ activated chloride channel. Recently, the structure determination of a fungal Nectria haematococca TMEM16 (nhTMEM16) scramblase by X-ray crystallography and a mouse ANO1 by cryo-electron microscopy has provided the insight in molecular architecture underlying phospholipid scrambling and Ca²⁺ binding. Because the Ca²⁺ binding motif is embedded inside channel protein according to defined structure, it is still unclear how intracellular Ca²⁺ moves to its deep binding pocket effectively. Here we show that EF-hand like region containing multiple acidic amino acids at the N-terminus of ANO1 is a putative site regulating the activity of ANO1 by Ca²⁺ and voltage. The EF-hand like region of ANO1 is highly homologous to the canonical EF hand loop in calmodulin that contains acidic residues in key Ca²⁺-coordinating positions in the canonical EF hand. Indeed, deletion and Ala-substituted mutation of this region resulted in a significant reduction in the response to Ca²⁺ and changes in its key biophysical properties evoked by voltage pulses. Furthermore, only ANO1 and ANO2, and not the other TMEM16 isoforms, contain the EF-hand like region and are activated by Ca²⁺. Moreover, the molecular modeling analysis supports that EF-hand like region could play a key role during Ca²⁺ transfer. Therefore, these findings suggest that EF-hand like region in ANO1 coordinates with Ca²⁺ and modulate the activation by Ca²⁺ and voltage.
