title: Calmodulin inhibitors trigger the proteolytic processing of membrane type-1 matrix metalloproteinase, but not its shedding in glioblastoma cells.
abstract: Most transmembrane proteins are subjected to limited proteolysis by cellular proteases, and stimulation of cleavage of membrane proteins by calmodulin (CaM) inhibitors was recently shown. The present study investigated the ability of several CaM inhibitors to induce the proteolytic cleavage of the membrane type-1 matrix metalloproteinase (MT1-MMP) from the cell surface of highly invasive U-87 glioblastoma cells. Although no shedding of a soluble MT1-MMP form was induced by CaM inhibitors in the conditioned media, we showed that these inhibitors induced MT1-MMP proteolytic processing to the 43 kDa membrane-bound inactive form that was not correlated with an increase in proMMP-2 activation but rather with an increase in tissue inhibitor of MMPs (TIMP)-2 expression levels. Moreover, this proteolytic processing was sensitive to marimastat suggesting the involvement of MMPs. Interestingly, CaM inhibitors antagonized concanavalin A- and cytochalasin D-induced proMMP-2 activation, and affected the cytoskeletal actin organization resulting in the loss of migratory potential of U-87 glioblastoma cells. Cytoplasmic tail-truncated MT1-MMP constructs expressed in COS-7 cells were also affected by CaM inhibitors suggesting that these inhibitors stimulated MT1-MMP proteolytic processing by mechanisms independent of the CaM-substrate interaction. We also propose that TIMP-2 acts as a negative regulator of MT1-MMP-dependent activities promoted by the action of CaM inhibitors in U-87 glioblastoma cells.
authors.affiliation: Centre de Cancérologie Charles-Bruneau, Hôpital Sainte-Justine, 3175 Côte Ste-Catherine, Montréal, Québec, Canada H3T 1C5.
authors.forename: B
authors.initials: B
authors.lastname: Annabi
authors.forename: A
authors.initials: A
authors.lastname: Pilorget
authors.forename: N
authors.initials: N
authors.lastname: Bousquet-Gagnon
authors.forename: D
authors.initials: D
authors.lastname: Gingras
authors.forename: R
authors.initials: R
authors.lastname: Béliveau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D018076:DNA, Complementary / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism; D018093:Gelatinases / Q000235:genetics / Q000378:metabolism; D005909:Glioblastoma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism; D014268:Trifluoperazine / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D002147:Calmodulin; D018076:DNA, Complementary; D004792:Enzyme Precursors; D011994:Recombinant Proteins; D019716:Tissue Inhibitor of Metalloproteinase-2; D014268:Trifluoperazine; D018093:Gelatinases; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases; C069860:progelatinase