title: Corin is co-expressed with pro-ANP and localized on the cardiomyocyte surface in both zymogen and catalytically active forms.
abstract: The multi-domain transmembrane serine protease corin cleaves pro-atrial natriuretic peptide (pro-ANP) in vitro to generate an active hormone, ANP. Corin may also contribute to the regulation of the natriuretic peptide system in vivo, and might be an attractive target for treatment of cardiovascular diseases. In order for corin to cleave its substrate pro-ANP, it should be catalytically active and located proximally. However, because knowledge of native corin is limited, we examined the expression, cardiac localization and molecular forms of the native corin protein. Immunofluorescence studies using a series of anti-corin antibodies directed against the stem and protease domains reveal that corin is present on the cell-surface of rat neonatal cardiomyocytes and murine HL-1 cardiomyocyte-like cells. Furthermore, we immunolocalized native corin in pro-ANP expressing cardiomyocytes. Immunoprecipitation of the membrane fraction of mouse heart extract showed that native corin had a relative mass of 205-210 kDa. Under reducing conditions native corin migrates as several different molecular weight forms corresponding to zymogen (uncleaved) and active (cleaved) forms. Studies using a FITC-tagged chloromethyl ketone that mimics the corin cleavage sequence in pro-ANP, suggest that an enzymatically active form of corin is localized to the cell surface of myocardial cells in vivo. Additionally, we showed that the 205-210 kDa form of corin is a glycosylated protein. Treatment of HL-1 cells with tunicamycin reduced the relative mass of expressed corin. We conclude that native corin is a glycosylated protease that is localized on the cell surface of pro-ANP-expressing cardiomyocytes in both zymogen and catalytically active forms.
authors.affiliation: Cardiovascular Research Center, Division of Cardiology, Medical College of Georgia, Augusta, GA 30912, USA. igladysheva@mcg.edu
authors.forename: Inna P
authors.initials: IP
authors.lastname: Gladysheva
authors.forename: Brian R
authors.initials: BR
authors.lastname: Robinson
authors.forename: Aiilyan K
authors.initials: AK
authors.lastname: Houng
authors.forename: Tímea
authors.initials: T
authors.lastname: Kováts
authors.forename: Sarah M
authors.initials: SM
authors.lastname: King
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D015153:Blotting, Western; D002384:Catalysis; D002460:Cell Line; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D005260:Female; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D004792:Enzyme Precursors; D011498:Protein Precursors; D009320:Atrial Natriuretic Factor; C485617:Corin protein, mouse; D012697:Serine Endopeptidases