Role of AMPK and PKA in the trafficking of V‐ATPase in kidney intercalated cells

Abstract

Vacuolar ATPases (V‐ATPase) are expressed at the plasma membrane of type A intercalated cells (ICs) that acidify the lumen of kidney collecting duct. V‐ATPase function is important for acid excretion and defective V‐ATPase in ICs causes metabolic acidosis. V‐ATPase regulation by direct phosphorylation in mammalian epithelial cells is not well characterized. We have shown that in epididymal clear cells V‐ATPase accumulation at the apical membrane is regulated by cAMP/PKA and AMP‐activated kinase (AMPK). We hypothesized that V‐ATPase subcellular localization in ICs depends on phosphorylation of V1 sector subunits and that V‐ATPase regulation is coupled to acid‐base status via PKA and to metabolic status via AMPK. Apical V‐ATPase accumulation in ICs requires cAMP/PKA, as evidenced immunofluorescence labeling of the V‐ATPase in kidney slices treated with various agonists and antagonists. In addition, AMPK activators prevented cAMP/PKA‐mediated V‐ATPase apical accumulation in ICs. Through mass spectrometry, mutagenesis and expression in cultured cells, we have identified several candidate PKA and AMPK phosphorylation sites in V1 sector subunits that may have functional effects on V‐ATPase localization. We propose that subcellular localization and activity of the V‐ATPase in ICs depends on the direct phosphorylation of V1 sector subunits by PKA and AMPK.