Complex pattern of membrane type 1 matrix metalloproteinase shedding. Regulation by autocatalytic cells surface inactivation of active enzyme.
Membrane type 1 matrix metalloproteinase (MT1-MMP) is a type I transmembrane MMP shown to play a critical role in normal development and in malignant processes. Emerging evidence indicates that MT1-MMP is regulated by a process of ectodomain shedding. Active MT1-MMP undergoes autocatalytic processing on the cell surface, leading to the formation of an inactive 44-kDa fragment and release of the entire catalytic domain. Analysis of the released MT1-MMP forms in various cell types revealed a complex pattern of shedding involving two major fragments of 50 and 18 kDa and two minor species of 56 and 31-35 kDa. Protease inhibitor studies and a catalytically inactive MT1-MMP mutant revealed both autocatalytic (18 kDa) and non-autocatalytic (56, 50, and 31-35 kDa) shedding mechanisms. Purification and sequencing of the 18-kDa fragment indicated that it extends from Tyr(112) to Ala(255). Structural and sequencing data indicate that shedding of the 18-kDa fragment is initiated at the Gly(284)-Gly(285) site, followed by cleavage between the conserved Ala(255) and Ile(256) residues near the conserved methionine turn, a structural feature of the catalytic domain of all MMPs. Consistently, a recombinant 18-kDa fragment had no catalytic activity and did not bind TIMP-2. Thus, autocatalytic shedding evolved as a specific mechanism to terminate MT1-MMP activity on the cell surface by disrupting enzyme integrity at a vital structural site. In contrast, functional data suggest that the non-autocatalytic shedding generates soluble active MT1-MMP species capable of binding TIMP-2. These studies suggest that ectodomain shedding regulates the pericellular and extracellular activities of MT1-MMP through a delicate balance of active and inactive enzyme-soluble fragments.
Toth
Marta
M
Department of Pathology, Wayne State University, Detroit, Michigan 48201, USA.
Hernandez-Barrantes
Sonia
S
Osenkowski
Pamela
P
Bernardo
M Margarida
MM
Gervasi
David C
DC
Shimura
Yoichiro
Y
Meroueh
Oussama
O
Kotra
Lakshmi P
LP
Gálvez
Beatriz G
BG
Arroyo
Alicia G
AG
Mobashery
Shahriar
S
Fridman
Rafael
R
D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D000882:Haplorhini; D006801:Humans; D007091:Image Processing, Computer-Assisted; D053504:Matrix Metalloproteinases, Membrane-Associated; D008566:Membranes / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011487:Protein Conformation; D013499:Surface Properties; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014616:Vaccinia virus
D019716:Tissue Inhibitor of Metalloproteinase-2; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases