The SNARE protein VAMP2 but not VAMP3 mediates cAMP‐stimulated renin release from juxtaglomerular cells

Abstract

Exocytosis of renin containing granules mediates renin release from juxtaglomerular (JG) cells, a process stimulated by cAMP. We found that the SNARE protein SNAP23 is involved in renin release. To mediate exocytosis, SNAP23 must interact with a vesicle associated membrane protein (VAMP). We found that VAMP2 and VAMP3 are expressed in JG cells but their role is not known. We hypothesized that VAMP2 mediates cAMP-stimulated renin release from mouse JG cells. To study the role of VAMP2 and 3 in JG cells we generated adenoviruses expressing shRNAs for these proteins. Transducing primary cultures of JG cells with either VAMP2 shRNA (n=4) or shVAMP3 (n=3) specifically decreased VAMP2 and VAMP3 respectively, without affecting other VAMPs or GAPDH. In control cells transduced with scrambled shRNA, increasing cAMP with Forskolin/IBMX stimulated renin release by 226±31% (p<0.05). However, in JG cells transduced with VAMP2-shRNA, cAMP increased renin release only by 81±27%, a 64% blockade (p<0.05). In contrast, silencing VAMP3 did not affect the stimulatory effect of cAMP on renin release (n=9). Confocal microscopy showed that VAMP2 colocalized with renin containing granules, whereas VAMP3 was expressed in JG cells but did not colocalize with renin. We concluded that VAMP2 but not VAMP3 mediates in part cAMP-stimulated renin release, identifying for the first time a specific granule protein involved in renin release. NIH/NRSA to M. Mendez.