Renin is a rate-limiting enzyme in the formation of Angiotensin-ll and plays a dominant role in the control of blood pressure. Abnormally enhanced circulating renin induces a pathological increase in blood pressure, ultimately leading to cardiovascular dysfunction and kidney disease. The kidney secretes most circulating renin. Renin is stored in granules in kidney pre-glomerular juxtaglomerular (JG) cells and it secreted mainly after stimulation of intracellular cAMP. Renin release from JG cells occurs by exocytosis, however the mechanism and proteins involved in cAMP-stimulated renin release are not known. In most cells, exocytosis is mediated by """"""""soluble NSF attachment protein receptors"""""""" (SNAREs).There are 3 essential SNARE proteins required to form a complex that mediate exocytosis: one vesicle associated membrane protein (VAMP), one SNAP and one syntaxin. The expression and function of SNAREs in juxtaglomerular cells have not been studied. Our preliminary data suggest that VAMP-2, VAMP-3, syntaxin-4 and SNAP-23 are expressed in primary cultures of mouse JG cells. Our main hypothesis is that VAMP-2, syntaxin-4 and SNAP-23 form the essential SNARE complex that mediates cAMP-stimulated renin release from juxtaglomerular cells. First, we will study the localization of VAMP-2, syntaxin-4 and SNAP-23 in primary cultures of mouse JG cells. Second, we will study their individual involvement on cAMP-stimulated renin release by using a) clostridial toxins that specifically cleave and inactivate VAMP-2 and SNAP-23;b) adenoviral-mediated short interfering RNA (siRNA) c) adenoviral expression of dominant negative truncated syntaxin-4 and SNAP-23. We will also determine whether VAMP-2 physically interacts with syntaxin-4and SNAP-23 in JG cells before and after stimulation of endogenous cAMP.
Hypertension affects 29% of the adult population in the U.S. and is a major risk factor for kidney and cardiovascular disease. In a large percentage of hypertensive patients plasma renin is elevated. The proteins involved in renin exocytosis are not known. Identifying the specific proteins required for renin exocytosis will increase our understanding of the basic mechanism of renin release and will provide new targets for pharmacological intervention aimed at inhibiting the renin-angiotensin system. This would provide more effective alternatives to current therapies for the treatment of High Blood Pressure, making this area of basic research critical for future advances.
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|Caceres, Paulo S; Mendez, Mariela; Ortiz, Pablo A (2014) Vesicle-associated membrane protein 2 (VAMP2) but Not VAMP3 mediates cAMP-stimulated trafficking of the renal Na+-K+-2Cl- co-transporter NKCC2 in thick ascending limbs. J Biol Chem 289:23951-62|
|Mendez, Mariela; Gross, Kenneth W; Glenn, Sean T et al. (2011) Vesicle-associated membrane protein-2 (VAMP2) mediates cAMP-stimulated renin release in mouse juxtaglomerular cells. J Biol Chem 286:28608-18|