PIP2 and Ca2+ regulation of TMEM16A currents in excised inside-out patches

The Ca 2+ activated Cl − channel formed by transmembrane member 16A (TMEM16A) is broadly expressed and regulates diverse processes. In addition to Ca 2+ , TMEM16A channels require the acidic phospholipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) to open. Like other channels regulated by PI(4,5)P 2 , TMEM16A-conducted currents recorded in excised patches slowly decay overtime. Here we assessed how intracellular Ca 2+ alters the rate of this current rundown, using the channels endogenously expressed in oocytes from the African clawed frog, Xenopus laevis . We found that in excised, inside-out patches, the concentration of applied Ca 2+ alters the rate of rundown, with high Ca 2+ concentrations speeding rundown by activating membrane associated phospholipase C (PLC). Together, these results clarify our understanding of how Ca 2+ regulates both TMEM16A directly, and targets PLC to regulate the membrane PI(4,5)P 2 content.