title: Characterization of the dimerization interface of membrane type 4 (MT4)-matrix metalloproteinase.
abstract: MT4-MMP (MMP17) belongs to a unique subset of membrane type-matrix metalloproteinases that are anchored to the cell surface via a glycosylphosphatidylinositol moiety. However, little is known about its biochemical properties. Here, we report that MT4-MMP is displayed on the cell surface as a mixed population of monomeric, dimeric, and oligomeric forms. Sucrose gradient fractionation demonstrated that these forms of MT4-MMP are all present in lipid rafts. Mutational and computational analyses revealed that Cys(564), which is present within the stem region, mediates MT4-MMP homodimerization by forming a disulfide bond. Substitution of Cys(564) results in a more rapid MT4-MMP turnover, when compared with the wild-type enzyme, consistent with a role for dimerization in protein stability. Expression of MT4-MMP in Madin-Darby canine kidney cells enhanced cell migration and invasion of Matrigel, a process that requires catalytic activity. However, a serine substitution at Cys(564) did not reduce MT4-MMP-stimulated cell invasion of Matrigel suggesting that homodimerization is not required for this process. Deglycosylation studies showed that MT4-MMP is modified by N-glycosylation. Moreover, inhibition of N-glycosylation by tunicamycin diminished the extent of MT4-MMP dimerization suggesting that N-glycans may confer stability to the dimeric form. Taken together, the data presented here provide a new insight into the characteristics of MT4-MMP and highlight the common and distinct properties of the glycosylphosphatidylinositol-anchored membrane type-matrix metalloproteinases.
authors.affiliation: Department of Pathology and the Karmanos Cancer Institute, Wayne State University, Detroit, Michigan 48201, USA.
authors.forename: Anjum
authors.initials: A
authors.lastname: Sohail
authors.forename: Marta
authors.initials: M
authors.lastname: Marco
authors.forename: Huiren
authors.initials: H
authors.lastname: Zhao
authors.forename: Qicun
authors.initials: Q
authors.lastname: Shi
authors.forename: Scott
authors.initials: S
authors.lastname: Merriman
authors.forename: Shahriar
authors.initials: S
authors.lastname: Mobashery
authors.forename: Rafael
authors.initials: R
authors.lastname: Fridman
mesh_terms: D000818:Animals; D003545:Cysteine / Q000378:metabolism; D004285:Dogs; D004795:Enzyme Stability; D006031:Glycosylation; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated / Q000737:chemistry / Q000378:metabolism*; D021962:Membrane Microdomains / Q000201:enzymology; D056004:Molecular Dynamics Simulation; D050505:Mutant Proteins / Q000378:metabolism; D009361:Neoplasm Invasiveness; D010455:Peptides / Q000378:metabolism; D055503:Protein Multimerization
chemical_list: D007527:Isoenzymes; D050505:Mutant Proteins; D010455:Peptides; C402225:MMP17 protein, human; D053504:Matrix Metalloproteinases, Membrane-Associated; D003545:Cysteine