SNAP-23 in rat kidney: colocalization with aquaporin-2 in collecting duct vesicles
Takeaki Inoue, Søren Nielsen, Beatrice Mandon, James Terris, Bellamkonda K. Kishore, Mark A. Knepper
1998
AJP - Renal Physiology
SNAP-23 in rat kidney: colocalization with aquaporin-2 in collecting duct vesicles. Am. J. Physiol. 275 (Renal Physiol. 44): F752-F760, 1998.-Vesicle targeting proteins ("SNAREs") have been proposed to direct vasopressininduced trafficking of aquaporin-2 water channels in kidney collecting ducts. A newly identified SNARE protein, SNAP-23, is proposed to mediate vesicle targeting to the plasma membrane in diverse tissues. The current studies were done to determine whether SNAP-23 is expressed in
more »
... collecting ducts with an intracellular distribution compatible with a role in aquaporin-2 trafficking. RT-PCR demonstrated SNAP-23 mRNA in microdissected collecting ducts and other tubular segments including the proximal tubule and thick ascending limb. Immunoblotting using a polyclonal antibody raised against a COOH-terminal peptide revealed a solitary band at an apparent molecular mass of 30 kDa in renal medullary membrane fractions and inner medullary collecting duct suspensions. Differential centrifugation revealed that SNAP-23 is present in membrane fractions including the low-density fraction enriched in intracellular vesicles. Immunocytochemistry revealed SNAP-23 labeling at both the apex and the cytoplasm of collecting duct principal cells. Immunoblotting of intracellular vesicles immunoisolated using an aquaporin-2 antibody revealed the presence of both SNAP-23 and synaptobrevin-2 (VAMP-2) in aquaporin-2-bearing vesicles. We conclude that SNAP-23 is strongly expressed in collecting duct principal cells, consistent with a role in vasopressin-regulated trafficking of aquaporin-2. However, localization of SNAP-23 in both intracytoplasmic vesicles and plasma membranes suggests a function different from that originally proposed for SNAP-25 in synaptic vesicle targeting. syntaxin-4; VAMP-2; synaptobrevin-2; exocytosis The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
doi:10.1152/ajprenal.1998.275.5.f752
fatcat:3olhbf67lngkdkzemlviq33z3e