WATER CHANNEL-CARRYING VESICLES IN THE RAT IMCD CONTAIN CELLUBREVIN

Antidiuretic hormone (arginine vasopressin) induces a cyclic process o f docking, fusion, and endocytosis of water channel-containing vesicle s in the collecting duct. There is now evidence that docking and endoc ytosis are mediated by an array of proteins associated with vesicles a nd target membranes. In recent studies, we have shown that cellubrevin , a member of the vesicle-associated membrane protein family, as well as other docking proteins, are expressed in the rat inner medullary co llecting duct. We now show by immunogold electron microscopy that cell ubrevin is present on vesicles containing water channels, that it is a ssociated with both coated and uncoated vesicles, and that it is prese nt on the apical membrane. Cellubrevin, therefore, is in a position to mediate one or more steps in arginine vasopressin-induced water chann el cycling.