Phosphatidylinositol-(4, 5)-bisphosphate regulates calcium gating of small-conductance cation channel TMEM16F.

Abstract

TMEM16F, which is activated by elevation of intracellular calcium to trigger phospholipid scrambling and the collapse of lipid bilayer asymmetry to mediate important cellular functions such as blood coagulation, also generates a small-conductance calcium-activated cation current. How TMEM16F activation may be regulated is an open question. By recording TMEM16F Ca²⁺-activated current, we found that the TMEM16F Ca²⁺-response is desensitized by a brief exposure to high intracellular Ca²⁺, which is associated with depletion of phosphatidylinositol-(4, 5)-bisphosphate (PIP₂) from the inner leaflet of the membrane. Application of artificial or natural PIP₂ restores TMEM16F channel activity. PIP₂ modulation of TMEM16F requires the presence of several positively charged amino acids in its cytoplasmic N-terminal domain. TMEM16F interaction with PIP₂ works synergistically with membrane depolarization to facilitate Ca²⁺-gating of TMEM16F. Our study reveals the dependence of TMEM16F activity on phosphoinositides and provides one mechanism for TMEM16F activation to be strictly regulated in the cell membrane.