Two helices in the third intracellular loop determine anoctamin 1 (TMEM16A) activation by calcium

• Authors: Jesun Lee, Seoul National University; Jooyoung Jung, Seoul National University; Min Ho Tak, Seoul National University; Jungwon Wee, Seoul National University; Byeongjoon Lee, Seoul National University; Yongwoo Jang, Seoul National University; Hyeyeon Chun, Seoul National University; Dong-Jin Yang, Seoul National University; Young Duk Yang, CHA University; Sang Ho Park, Seoul National University; Byung Woo Han, Seoul National University; Soonsil Hyun, Seoul National University; Jaehoon Yu, Seoul National University; Hawon Cho, Seoul National University; Harrison Hartzell Jr., Emory University; Uhtaek Oh, Seoul National University
• Journal Title: Pflügers Archiv European Journal of Physiology
• Volume: Volume 467, Number 8
• Publisher: SpringerOpen | 2015-08-01, Pages 1677-1687
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1007/s00424-014-1603-2
• Subjects: Health Sciences, Pharmacy; Chemistry, Pharmaceutical
• Keywords: Science & Technology; Life Sciences & Biomedicine; Physiology; Anoctamin 1; Anoctamin 2; Calcium; Activation; Helix; Structure; CA2+-ACTIVATED CL-CHANNELS; CHLORIDE CHANNELS; ENDOTHELIAL-CELLS; GNATHODIAPHYSEAL-DYSPLASIA; PROTEIN; CURRENTS; AMPLIFICATION; EXPRESSION; CLONING; NEURONS

Abstract

Anoctamin 1 (ANO1)/TMEM16A is a Cl⁻ channel activated by intracellular Ca²⁺ mediating numerous physiological functions. However, little is known of the ANO1 activation mechanism by Ca²⁺. Here, we demonstrate that two helices, “reference” and “Ca²⁺ sensor” helices in the third intracellular loop face each other with opposite charges. The two helices interact directly in a Ca²⁺-dependent manner. Positively and negatively charged residues in the two helices are essential for Ca²⁺-dependent activation because neutralization of these charges change the Ca²⁺ sensitivity. We now predict that the Ca²⁺ sensor helix attaches to the reference helix in the resting state, and as intracellular Ca²⁺ rises, Ca²⁺ acts on the sensor helix, which repels it from the reference helix. This Ca²⁺-dependent push-pull conformational change would be a key electromechanical movement for gating the ANO1 channel. Because chemical activation of ANO1 is viewed as an alternative means of rescuing cystic fibrosis, understanding its gating mechanism would be useful in developing novel treatments for cystic fibrosis.