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JCS ePress online publication date 27 May 2008
doi: 10.1242/jcs.022210

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Research Article

AQP2 exocytosis in the renal collecting duct - involvement of SNARE isoforms and the regulatory role of Munc18b


Giuseppe Procino, Claudia Barbieri, Grazia Tamma, Leonarda De Benedictis, Jeffrey E. Pessin, Maria Svelto, and Giovanna Valenti*
* Author for correspondence (e-mail: g.valenti{at}biologia.uniba.it)

Vasopressin regulates the fusion of the water channel aquaporin 2 (AQP2) to the apical membrane of the renal collecting-duct principal cells and several lines of evidence indicate that SNARE proteins mediate this process. In this work MCD4 renal cells were used to investigate the functional role of a set of Q- and R-SNAREs, together with that of Munc18b as a negative regulator of the formation of the SNARE complex. Both VAMP2 and VAMP3 were associated with immunoisolated AQP2 vesicles, whereas syntaxin 3 (Stx3), SNAP23 and Munc18 were associated with the apical plasma membrane. Co-immunoprecipitation experiments indicated that Stx3 forms complexes with VAMP2, VAMP3, SNAP23 and Munc18b. Protein knockdown coupled to apical surface biotinylation demonstrated that reduced levels of the R-SNAREs VAMP2 and VAMP3, and the Q-SNAREs Stx3 and SNAP23 strongly inhibited AQP2 fusion at the apical membrane. In addition, knockdown of Munc18b promoted a sevenfold increase of AQP2 fused at the plasma membrane without forskolin stimulation.




© The Company of Biologists Ltd 2008