ProBNP processing into BNP and NT-proBNP is suppressed by O-glycosylation at the T71 residue near the cleavage site, and only deglycosylated or mutant (T71A) proBNP is effectively cleaved.
O-glycosylation at T71 suppresses the processing of proBNP into active BNP and NT-proBNP, providing mechanistic insight into natriuretic peptide processing in heart failure.
BACKGROUND: Processing of the brain natriuretic peptide (BNP) precursor, proBNP, is a convertase-dependent reaction that produces 2 molecules--the active BNP hormone and the N-terminal part of proBNP (NT-proBNP). Although proBNP was first described more than 15 years ago, very little is known about the cellular mechanism of its processing. The study of proBNP processing mechanisms is important, because processing impairments could be associated with the development of heart failure (HF). METHODS: The biochemical properties of recombinant proBNP and NT-proBNP and the same molecules derived from the blood of HF patients were analyzed by gel-filtration chromatography, site-directed mutagenesis, and different immunochemical methods with a panel of monoclonal antibodies (MAbs). RESULTS: Part of the proBNP molecule (amino acid residues 61-76) located near the cleavage site was inaccessible to specific MAbs because of the presence of O-glycans, whereas the same region in NT-proBNP was completely accessible. We demonstrated that a convertase (furin) could effectively cleave deglycosylated (but not intact) proBNP. Of several mutant proBNP forms produced in a HEK 293 cell line, only the T71A variant was effectively processed in the cell. CONCLUSIONS: Only proBNP that was not glycosylated in the region of the cleavage site could effectively be processed into BNP and NT-proBNP. Site-directed mutagenesis enabled us to ascertain the unique suppressing role of T71-bound O-glycan in proBNP processing.
Semenov et al. (Fri,) conducted a other in Heart failure. Deglycosylation or T71A mutation of proBNP vs. Intact (glycosylated) proBNP was evaluated on Cleavage/processing of proBNP by convertase (furin). ProBNP processing into BNP and NT-proBNP is suppressed by O-glycosylation at the T71 residue near the cleavage site, and only deglycosylated or mutant (T71A) proBNP is effectively cleaved.