Processing of pro-B-type natriuretic peptide: furin and corin as candidate convertases.
BACKGROUND
B-type natriuretic peptide (BNP) and its N-terminal fragment (NT-proBNP) are the products of the enzyme-mediated cleavage of their precursor molecule, proBNP. The clinical significance of proBNP-derived peptides as biomarkers of heart failure has been explored thoroughly, whereas little is known about the mechanisms of proBNP processing. We investigated the role of 2 candidate convertases, furin and corin, in human proBNP processing.


METHODS
We measured proBNP expression in HEK 293 and furin-deficient LoVo cells. We used a furin inhibitor and a furin-specific small interfering RNA (siRNA) to explore the implication of furin in proBNP processing. Recombinant proBNPs were incubated with HEK 293 cells transfected with the corin-expressing plasmid. We applied mass spectrometry to analyze the products of furin- and corin-mediated cleavage.


RESULTS
Reduction of furin activity significantly impaired proBNP processing in HEK 293 cells. Furin-deficient LoVo cells were unable to process proBNP, whereas coexpression with furin resulted in effective proBNP processing. Mass spectrometric analysis revealed that the furin-mediated cleavage of proBNP resulted in BNP 1-32, whereas corin-mediated cleavage led to the production of BNP 4-32. Some portion of proBNP in the plasma of heart failure patients was not glycosylated in the cleavage site region and was susceptible to furin-mediated cleavage.


CONCLUSIONS
Both furin and corin are involved in the proBNP processing pathway, giving rise to distinct BNP forms. The significance of the presence of unprocessed proBNP in circulation that could be cleaved by the endogenous convertases should be further investigated for better understanding BNP physiology.
Semenov
Alexander G
AG
HyTest Ltd., Turku, Finland. alexander.semenov@hytest.fi
Tamm
Natalia N
NN
Seferian
Karina R
KR
Postnikov
Alexander B
AB
Karpova
Natalia S
NS
Serebryanaya
Daria V
DV
Koshkina
Ekaterina V
EV
Krasnoselsky
Mihail I
MI
Katrukha
Alexey G
AG
D019208:Brain-Derived Neurotrophic Factor / Q000097:blood / Q000378:metabolism*; D002460:Cell Line; D045683:Furin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006333:Heart Failure / Q000097:blood; D006801:Humans; D011498:Protein Precursors / Q000097:blood / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*
D019208:Brain-Derived Neurotrophic Factor; D011498:Protein Precursors; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C426674:brain-derived neurotrophic factor precursor; C119812:CORIN protein, human; D012697:Serine Endopeptidases; D045683:Furin