ANP, BNP and CNP: Physiology and Pharmacology of the Cardiorenal Axis

The three mammalian natriuretic peptides (NPs), A-type natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and C-type natriuretic peptide (CNP), are genetically distinct but share structural similarities. Human ANP, BNP, and CNP are synthesized as preprohormones, which are subsequently split into prohormones by proteolytic cleavage of an N-terminal signal peptide. Human prepro-ANP is a 151-amino acid (AA) peptide that is cleaved to the 126-AA pro-ANP, whereas human prepro-BNP is a 134-AA peptide that is cleaved to the 108-AA pro-BNP. Pro-ANP and pro-BNP are stored in secretory granules in atrial cardiomyocytes and are cleaved to form ANP and BNP, respectively, upon secretion. The conversion of pro-ANP to ANP is mediated by corin, a transmembrane cardiac serine protease. Both human ANP, a 28-AA peptide, and human BNP, a 32-AA peptide, are released from the myocardium in response to various physiologic and pathophysiologic stimuli, such as myocardial wall stretch. Human pro-CNP consists of 103 AA residues and is processed by furin, an intracellular endoprotease, to the mature 53-AA CNP. CNP-53, which is found primarily in the brain, the heart, and endothelial cells, may be further cleaved to CNP-22.