Functional involvement of VAMP/synaptobrevin-2 in cAMP-stimulated aquaporin 2 translocation in renal collecting duct cells.

The involvement of soluble N-ethylmaleimide sensitive factor-attachment protein receptor (SNARE) proteins in the cAMP-induced exocytosis of aquaporin 2 (AQP2)-containing vesicles was investigated in AQP2-transfected renal CD8 cells. RT-PCR and western blot analysis confirmed the presence of the SNARE homologs VAMP/synaptobrevin-2, syntaxin-1, syntaxin-4 and SNAP-23 in CD8 cells. Tetanus neurotoxin (TeNT) was efficient in cleaving synaptobrevin-like protein both in vitro and in intact CD8 cells incubated with the toxin. TeNT treatment in intact CD8 cells completely abolished cAMP-stimulated AQP2 targeting to the plasma membrane, as assessed by quantification of cell-surface immunoreactivity to an anti-AQP2 antibody raised against a peptide reproducing the extracellular AQP2 C-loop. These results represent the first evidence for the functional involvement of VAMP-2 in cAMP-induced AQP2 exocytosis in renal cells.