title: Fetuin-A and cystatin C are endogenous inhibitors of human meprin metalloproteases.
abstract: Meprin α and β, zinc metalloproteinases, play significant roles in inflammation, including inflammatory bowel disease (IBD), possibly by activating cytokines, like interleukin 1β, interleukin 18, or tumor growth factor α. Although a number of potential activators for meprins are known, no endogenous inhibitors have been identified. In this work, we analyzed the inhibitory potential of human plasma and identified bovine fetuin-A as an endogenous meprin inhibitor with a K(i) (inhibition constant) of 4.2 × 10(-5) M for meprin α and a K(i) of 1.1 × 10(-6) M meprin β. This correlated with data obtained for a fetuin-A homologue from carp (nephrosin inhibitor) that revealed a potent meprin α and β inhibition (residual activities of 27 and 22%, respectively) at a carp fetuin concentration of 1.5 × 10(-6) M. Human fetuin-A is a negative acute phase protein involved in inflammatory diseases, thus being a potential physiological regulator of meprin activity. We report kinetic studies of fetuin-A with the proteolytic enzymes astacin, LAST, LAST_MAM, trypsin, and chymotrypsin, indeed demonstrating that fetuin-A is a broad-range protease inhibitor. Fetuin-A inhibition of meprin α activity was 40 times weaker than that of meprin β activity. Therefore, we tested cystatin C, a protein structurally closely related to fetuin-A. Indeed, cystatin C was an inhibitor for human meprin α (K(i) = 8.5 × 10(-6) M) but, interestingly, not for meprin β. Thus, the identification of fetuin-A and cystatin C as endogenous proteolytic regulators of meprin activity broadens our understanding of the proteolytic network in plasma.
authors.affiliation: Institute of Zoology, Cell and Matrix Biology, Johannes Gutenberg-University, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Hedrich
authors.forename: Daniel
authors.initials: D
authors.lastname: Lottaz
authors.forename: Katharina
authors.initials: K
authors.lastname: Meyer
authors.forename: Irene
authors.initials: I
authors.lastname: Yiallouros
authors.forename: Willi
authors.initials: W
authors.lastname: Jahnen-Dechent
authors.forename: Walter
authors.initials: W
authors.lastname: Stöcker
authors.forename: Christoph
authors.initials: C
authors.lastname: Becker-Pauly
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002347:Carps; D002417:Cattle; D055316:Cystatin C / Q000378:metabolism*; D006801:Humans; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008969:Molecular Sequence Data; D010949:Plasma / Q000378:metabolism*; D016415:Sequence Alignment; D060749:alpha-2-HS-Glycoprotein
chemical_list: C556354:AHSG protein, human; D001798:Blood Proteins; D055316:Cystatin C; D060749:alpha-2-HS-Glycoprotein; D008666:Metalloendopeptidases; C053833:meprin A