Corin is present in the normal human heart, kidney, and blood, with Pro-B-type natriuretic peptide processing in the circulation

BACKGROUND: B-type natriuretic peptide (BNP), which is activated in heart failure (HF), is processed to an active form by corin. The corin gene is expressed in the human heart and kidney, but corin protein expression in the heart, kidney, and circulation, along with whether proBNP is processed by circulating corin, remains unknown. METHODS: We examined corin protein expression by immunostaining and Western blot in human heart and kidney, and we assessed the circulating corin concentration by ELISA. We examined histidine-tagged (Histag) proBNP1-108 processing in serum and plasma by immunoprecipitation and Western blot and sequenced the processed form. RESULTS: Normal human heart and kidney displayed the presence of corin, especially in cells around the vasculature. Both corin and proBNP1-108 were present in the plasma of healthy human subjects, with circulating corin significantly higher in men than women (P < 0.0001) and a positive correlation of corin to age (P<0.0497, r<0.27). In fresh normal plasma and serum, His-tag proBNP1-108 was processed to a lower molecular weight form confirmed to be BNP. Processed BNP was higher in men than women (P<0.041) and was positively correlated to plasma corin concentrations (P<0.041, r<0.65). CONCLUSIONS: Our results support the concept that proBNP1-108 may be processed outside of the heart in the circulation where the proprotein convertase is present. Moreover, sex may impact this process, since corin concentrations are higher in men. These findings\ may have important physiologic and pathophysiologic implications for the proBNP/corin system in the human.