Expression of Guanylyl Cyclase-A/Atria1 Natriuretic Peptide Receptor Blocks the Activation of Protein Kinase C in Vascular Smooth Muscle Cells Role of cGMP and cGMP-Dependent Protein Kinase

To understand the molecular mechanisms of cellular stgnalmg of atria1 natrmrettc pepttde (ANP), we have studied Its effect on the enzymatrc activrty of endogenous and overexpressed protein kmase C (PKC) m rat thoracrc aortrc vascular smooth muscle (RTASM) cells Angrotensm II (ANG II), endothelm-1 (ET-l), and 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated fourfold to fivefold PKC acttvny m PKC-a cDNA-transfected RTASM cells However, pretreatment of these cells with ANP significantly mhlbtted the agonist-stimulated PKC actlvrty m a dose-dependent manner The mhtbltory effect of ANP was more effective If cells were transfected wrth both PKC-a and guanylyl cyclase-A/atria1 natrmrettc pepttde receptor (Npra) cDNAs The agomst-strmulated PKC actrvrty was also mhrbtted rf RTASM cells were pretreated with cGMP analog 8-bromo-cGMP, however, the treatment of cells with a CAMP analog, dtbutyryl-CAMP, did not show any dtscermble effect The pretreatment of cells with Npra antagonist A-71915, srgmficantly blocked the productron of cGMP as well as the mhtbttory effect A trial natrmretic peptide is an endogenous and potent hypotensive hormone that regulates sodmm excretion, water balance, steroidogenesis, and cell proliferation. l-4 One of the prmcipal components mvolved m the regulatory action of ANP is the guanylyl cyclase-linked atria1 natriuretic peptide receptor (GC-A), also designated as Npra.5 Natnuretic peptide receptor/ guanylyl cyclase-A is a unique class of cell surface receptors that contam an extracellular hgand-bmdmg domain, a single transmembrane spanning region and mtracellular protein kmase-hke and guanylyl cyclase catalytic domains that synthesizes the intracellular second messenger cGMP m response to ANP bmdmg.6*7 In addition to Npra, another natrmretic peptide receptor with guanylyl cyclase activity (GC-B) has been cloned and designated as Nprb.5 The evidence suggests that both ANP and BNP selectively bmd to Npra, and CNP has been shown pnmanly to bmd Nprb. 899 However, all three natriuretic peptides (ANP, BNP, and CNP) mdiscnmmately bmd to naProm the Department of Brochemistry and Molecular Brology (R K , W A C , K N P ), Medical College of Georgra, School of Medacme, Augusta, and the Department of Pathology (T M L ), Umversrty of Alabama at Brrmmgham Correspondence to Dr Karlash N Pandey, Department of BIOchemistry and Molecular Biology, Medrcal College of Georgia School of Medrcme, Augusta, GA 30912-2100