V‐ATPase membrane accumulation and activity are stimulated by cAMP in A‐type intercalated cells

Abstract

Recycling of the vacuolar proton (H+) pumping ATPase (V‐ATPase) between intracellular vesicles and the plasma membrane in H+‐secreting cells is central to acid‐base regulation by the kidney. Collecting duct (CD) A‐type intercalated cells (A‐IC) respond to systemic acidosis by accumulating the V‐ATPase in their apical membrane, which correlates with higher rates of H+ secretion and increased microvillar extension. We show that CPT‐cAMP infused in vivo results in an almost two‐fold increase in apical V‐ATPase accumulation in A‐IC within 15 min, and that these cells develop an extensive array of apical microvilli. The cAMP effect on A‐IC is direct, as shown in vitro in cells isolated from the medulla of transgenic mice expressing EGFP in IC (driven by the V‐ATPase B1‐subunit promoter). 3D‐reconstructions of confocal images showed that cAMP induced a dramatic, time dependent growth of microvilli in isolated IC. These morphological changes were paralleled by increased cAMP‐mediated H+ extrusion rates by A‐IC in isolated outer medullary CD measured using the ratiometric probe BCECF. These results support the idea that cAMP, generated by the soluble adenylyl cyclase (sAC ‐ which is enriched in IC) or other effectors, is part of the signal transduction mechanism for acid‐base sensing and V‐ATPase trafficking in IC. Funding source: NIH DK‐73266, DK‐42956, DK‐38452 and HD‐40793.