title: Oligomerization through hemopexin and cytoplasmic domains regulates the activity and turnover of membrane-type 1 matrix metalloproteinase.
abstract: The formation of multimeric complexes by membrane-type 1 matrix metalloproteinase (MT1-MMP) may facilitate its autocatalytic inactivation or proMMP-2 activation on the cell surface. To characterize these processes, we expressed various glutathione S-transferase/MT1-MMP fusion proteins in human HT-1080 fibrosarcoma cells and SV40-transformed lung fibroblasts and analyzed their effects on MT1-MMP activity and potential homophilic interactions. We report here that MT1-MMP is expressed on the cell surface as oligomeric 200--240-kDa complexes containing both the active 60-kDa and autocatalytically processed 43-kDa species. Overexpression of a glutathione S-transferase/MT1-MMP fusion protein containing the transmembrane and cytoplasmic domains of MT1-MMP inhibited the phorbol 12-myristate 13-acetate-induced autocatalytic cleavage of endogenous MT1-MMP to the 43-kDa species, but not proMMP-2 activation. On the other hand, a similar fusion protein with the hemopexin, transmembrane, and cytoplasmic domains inhibited proMMP-2 activation in a dominant-negative fashion. These results suggest that both the autocatalytic cleavage of MT1-MMP and proMMP-2 activation may be regulated by oligomerization through the cytoplasmic and hemopexin domains. Indeed, either domain, when attached to the cell membrane by a transmembrane domain, formed stable homophilic complexes. Copurification of MT1-MMP with these fusion proteins correlated with their cell-surface co-localization. Thus, MT1-MMP oligomerization through the hemopexin, transmembrane, and cytoplasmic domains controls its catalytic activity.
authors.affiliation: Department of Virology, Haartman Institute, Biomedicum Helsinki, University of Helsinki and Helsinki University Hospital, FIN-00014 Helsinki, Finland.
authors.forename: Kaisa
authors.initials: K
authors.lastname: Lehti
authors.forename: Jouko
authors.initials: J
authors.lastname: Lohi
authors.forename: Minna M
authors.initials: MM
authors.lastname: Juntunen
authors.forename: Duanqing
authors.initials: D
authors.lastname: Pei
authors.forename: Jorma
authors.initials: J
authors.lastname: Keski-Oja
mesh_terms: D001667:Binding, Competitive; D002384:Catalysis; D020134:Catalytic Domain; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003593:Cytoplasm / Q000201:enzymology* / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes; D005799:Genes, Dominant; D005982:Glutathione Transferase / Q000378:metabolism; D006466:Hemopexin / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D020781:Matrix Metalloproteinase 1 / Q000737:chemistry* / Q000378:metabolism*; D009154:Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D000939:Epitopes; D011993:Recombinant Fusion Proteins; D006466:Hemopexin; D005982:Glutathione Transferase; D020781:Matrix Metalloproteinase 1