title: Matriptase is inhibited by extravascular antithrombin in epithelial cells but not in most carcinoma cells.
abstract: Antithrombin, a major anticoagulant, is robustly transported into extravascular compartments where its target proteases are largely unknown. This serpin was previously detected in human milk as complexes with matriptase, a membrane-bound serine protease broadly expressed in epithelial and carcinoma cells, and under tight regulation by hepatocyte growth factor activator inhibitor (HAI)-1, a transmembrane Kunitz-type serine protease inhibitor that forms heat-sensitive complexes with active matriptase. In the current study, we detect, in addition to matriptase-HAI-1 complexes, heat-resistant matriptase complexes generated by nontransformed mammary, prostate, and epidermal epithelial cells that we show to be matriptase-antithrombin complexes. These findings suggest that in addition to HAI-1, interstitial antithrombin participates in the regulation of matriptase activity in epithelial cells. This physiological mechanism appears, however, to largely be lost in cancer cells since matriptase-antithrombin complexes were not detected in all but two of a panel of seven breast, prostate, and ovarian cancer cell lines. Using purified active matriptase, we further characterize the formation of matriptase-antithrombin complex and show that heparin can significantly potentiate the inhibitory potency of antithrombin against matriptase. Second-order rate constants for the inhibition were determined to be 3.9 × 10(3) M(-1)s(-1) in the absence of heparin and 1.2 × 10(5) M(-1)s(-1) in the presence of heparin, a 30-fold increase, consistent with the established role of heparin in activating antithrombin function. Taken together these data suggest that normal epithelial cells employ a dual mechanism involving HAI-1 and antithrombin to control matriptase and that the antithrombin-based mechanism appears lost in the majority of carcinoma cells.
authors.affiliation: Greenebaum Cancer Center, University of Maryland, Baltimore, MD 21201, USA.
authors.forename: Feng-Pai
authors.initials: FP
authors.lastname: Chou
authors.forename: Han
authors.initials: H
authors.lastname: Xu
authors.forename: Ming-Shyue
authors.initials: MS
authors.lastname: Lee
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Chen
authors.forename: O X Durand
authors.initials: OX
authors.lastname: Richards
authors.forename: Richard
authors.initials: R
authors.lastname: Swanson
authors.forename: Steven T
authors.initials: ST
authors.lastname: Olson
authors.forename: Michael D
authors.initials: MD
authors.lastname: Johnson
authors.forename: Chen-Yong
authors.initials: CY
authors.lastname: Lin
mesh_terms: D034961:Antigens, Nuclear / Q000378:metabolism; D000990:Antithrombin III / Q000378:metabolism*; D001943:Breast Neoplasms / Q000201:enzymology; D002277:Carcinoma / Q000201:enzymology*; D045744:Cell Line, Tumor; D004817:Epidermis / Q000201:enzymology; D004847:Epithelial Cells / Q000201:enzymology*; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008297:Male; D042361:Mammary Glands, Human / Q000201:enzymology; D010051:Ovarian Neoplasms / Q000201:enzymology; D011467:Prostate / Q000201:enzymology; D011471:Prostatic Neoplasms / Q000201:enzymology; D053491:Proteinase Inhibitory Proteins, Secretory / Q000378:metabolism*; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D034961:Antigens, Nuclear; D053491:Proteinase Inhibitory Proteins, Secretory; C542513:SERPINC1 protein, human; C102470:SP140 protein, human; C109149:SPINT1 protein, human; D014157:Transcription Factors; D000990:Antithrombin III; D006493:Heparin