TMEM16A is a newly identified Ca2+-activated Cl- channel in biliary epithelial cells (BECs) that is important in biliary secretion. While extracellular ATP stimulates TMEM16A via binding P2 receptors and increasing [Ca2+]i, the regulatory pathways have not been elucidated. Protein Kinase C (PKC) contributes to ATP-mediated secretion in BECs, though its potential role in TMEM16A regulation is unknown. To determine whether PKCα regulates the TMEM16A-dependent membrane Cl- transport in BECs, studies were performed in human biliary Mz-cha-1 cells. Addition of extracellular ATP induced a rapid translocation of PKCα from the cytosol to the plasma membrane and activation of whole cell Ca2+-activated Cl- currents. Currents demonstrated outward rectification, reversal at 0 mV (properties consistent with TMEM16A) and were inhibited by either molecular (siRNA) or pharmacologic (PMA or Gö6976) inhibition of PKCα. Intracellular dialysis with recombinant PKCα activated Cl- currents with biophysical properties identical to TMEM16A in control cells, but not in cells after transfection with TMEM16A siRNA. In conclusion, our studies demonstrate that PKCα is coupled to ATP-stimulated TMEM16A activation in BECs. Targeting this ATP-Ca2+-PKCα signaling pathway may represent a therapeutic strategy to increase biliary secretion and promote bile formation.
- Cl- channel
- Copyright © 2015, American Journal of Physiology- Gastrointestinal and Liver Physiology