Regulation of acidosis‐induced V‐ATPase trafficking in salivary ducts by protein phosphorylation

Redistribution of acid‐base transporters is a crucial regulatory mechanism for many cells to cope with extracellular pH changes. Moreover, in epithelial cells, translocation of acid‐base transporters ultimately leads to changes in vectorial transport of H + and HCO 3 − . In the present study we have investigated the impact of protein phosphorylation on the acidosis‐induced trafficking of V‐ATPase in salivary duct cells in vitro using the human submandibular cell line of ductal origin HSG as an experimental model. The results show that administration of exogenous cAMP significantly increased movement of V‐ATPase‐containing vesicles from the Golgi apparatus towards the plasma membrane in controls. Co‐localization of V‐ATPase with TGN38, a marker for trans ‐Golgi network, was significantly increased in acidosis, compared to the controls, a process that could be prevented after blocking of PKA, sAC or Src. In addition, the amount of V‐ATPase‐containing vesicles reaching the plasma membrane was significantly decreased in acidotic HSG cells, compared to the controls. The data suggest protein phosphorylation as regulator of acidosis‐induced V‐ATPase trafficking in salivary gland cells and underscore redistribution of acid‐base transporters as the major adaptive mechanism after acid‐base disturbances. Funded by the Deutsche Forschungsgemeinschaft.