Characterization of human prorenin expressed in mammalian cells from cloned cDNA.

Human preprorenin was synthesized in Chinese hamster ovary (CHO) cells transfected with an expression vector containing renin cDNA sequences. These cells secrete an inactive form of renin (EC 3.4.23.15) that can be activated by trypsin. This inactive renin is precipitable by antibody generated against purified human renal renin and also by antisera generated to a synthetic peptide derived from the amino acid sequence of the pro segment of preprorenin (anti-propeptide), indicating that the secreted inactive enzyme is a form of prorenin. Analysis of [35S]methionine-labeled proteins immunoprecipitated from CHO cell conditioned culture medium indicates that prorenin is expressed in CHO cells as two distinct forms that differ in their degree of glycosylation. In vitro trypsin activation of prorenin cleaves approximately 4.5 kDa from the protein, rendering it unreactive with the antipropeptide antiserum but still recognizable by anti-renal renin antibody. These results show directly that the prorenin expressed by CHO cells is an inactive enzyme that is activated by trypsin cleavage of the pro segment. The ability to express human renin in this form will allow for the purification of both active and inactive forms of the enzyme in quantities sufficient for detailed physiological and structural studies.