Novel Regulation of V‐ATPase by PKA and AMPK in Kidney Intercalated Cells

Abstract

The metabolic sensor AMP‐activated kinase (AMPK) regulates several transport proteins, potentially coupling ion transport to cellular metabolism. The Vacuolar H+‐ATPase (V‐ATPase) regulates pH homeostasis in intracellular compartments and in the whole organism. Apical membrane V‐ATPase in collecting duct Type‐A intercalated cells (A‐ICs) contributes to net urinary acid excretion and to acid‐base homeostasis. In epididymal proton‐secreting clear cells, AMPK activation prevents alkaline pH and cAMP‐mediated V‐ATPase apical membrane accumulation. To study the effects of AMPK on V‐ATPase subcellular localization in A‐ICs, we exposed kidney slices to two distinct AMPK activators, AICAR and A‐769662. Compared to control kidney slices, each AMPK activator inhibited baseline V‐ATPase apical accumulation in A‐ICs as monitored by immunofluorescence labeling and confocal microscopy. In addition, preincubation of kidney slices with AICAR prevented PKA‐mediated V‐ATPase apical accumulation. Moreover, both PKA and AMPK phosphorylated the V‐ATPase A subunit in vitro and in vivo in HEK‐293 cells. AMPK knockdown enhanced PKA‐dependent A‐subunit phosphorylation in vivo, suggesting an antagonistic effect of AMPK on the regulation of V‐ATPase by PKA. We propose that V‐ATPase activity in kidney is coupled to the sensing of acid‐base status via PKA and to metabolic status via AMPK. (Support by NIH)