Molecular cloning and expression of murine guanylate cyclase/atrial natriuretic factor receptor cDNA

The potent diuretic and natriuretic peptide hormone atrial natriuretic factor (ANF), with vasodilatory activity also stimulates steroidogenic responsiveness in Leydig cells. The actions of ANF are mediated by its interaction with specific cell surface receptors and the membrane-bound form of guanylate cyclase represents an atrial natriuretic factor receptor (ANF-R). To understand the mechanism of ANF action in testicular steroidogenesis and to identify guanylate cyclase/ANF-R that is expressed in the Leydig cells, the primary structure of murine guanylate cyclase/ANF-R has been deduced from its cDNA sequence. A cDNA library constructed from poly(A+) RNA of murine Leydig tumor (MA-10) cell line was screened for the membrane-bound form of ANF-R/guanylate cyclase sequences by hybridization with a rat brain guanylate cyclase/ANF-R cDNA probe. The amino acid sequence deduced from the cDNA shows that murine guanylate cyclase/ANF-R cDNA consists of 1057 amino acids with 21 amino acids comprising the transmembrane domain which separates an extracellular ligand-binding domain (469 amino acid residues) and an intracellular guanylate cyclase domain (567 amino acid residues). Upon transfection of the murine guanylate cyclase/ANF-R cDNA in COS-7 cells, the expressed protein showed specific binding to 125I-ANF, stimulation of guanylate cyclase activity and production of intracellular cGMP in response to ANF. The expression of guanylate cyclase/ANF-R cDNA transfected in rat Leydig tumor cells stimulated the production of testosterone and intracellular cGMP after treatment with ANF. The results presented herein directly show that ANF can regulate the testicular steroidogenic responsiveness in addition to its known regulatory role in the control of cardiovascular homeostasis.