title: Caveolin-1 mediates the expression and localization of cathepsin B, pro-urokinase plasminogen activator and their cell-surface receptors in human colorectal carcinoma cells.
abstract: Cathepsin B and pro-urokinase plasminogen activator (pro-uPA) localize to the caveolae of HCT 116 human colorectal carcinoma cells, an association mediated by active K-RAS. In this study, we established a stable HCT 116 cell line with a gene encoding antisense caveolin-1 (AS-cav-1) to examine the effects of caveolin-1, the main structural protein of caveolae, on the expression and localization of cathepsin B and pro-uPA, and their cell-surface receptors p11 and uPA receptor (uPAR), respectively. AS-cav-1 HCT 116 cells secreted less procathepsin B than control (empty vector) cells as measured by immunoblotting and pepsin activation of the proenzyme. Expression and secretion of pro-uPA was also downregulated in AS-cav-1 HCT 116 cells. Localization of cathepsin B and pro-uPA to caveolae was reduced in AS-cav-1 HCT 116 cells, and these cells expressed less total and caveolae-associated p11 and uPAR compared with control cells. Previous studies have shown that uPAR forms a complex with caveolin-1 and beta1-integrin, and we here show that downregulation of caveolin-1 also suppressed the localization of beta1-integrin to caveolae of these cells. Finally, downregulation of caveolin-1 in HCT 116 cells inhibited degradation of the extracellular matrix protein collagen IV and the invasion of these cells through Matrigel. Based on these results, we hypothesize that caveolin-1 affects the expression and localization of cathepsin B and pro-uPA, and their receptors, thereby mediating cell-surface proteolytic events associated with invasion of colon cancer cells.
authors.affiliation: Department of Pharmacology, Wayne State University, School of Medicine, Detroit, MI 48201, USA. dcavallo@med.wayne.edu
authors.forename: Dora
authors.initials: D
authors.lastname: Cavallo-Medved
authors.forename: Jianxin
authors.initials: J
authors.lastname: Mai
authors.forename: Julie
authors.initials: J
authors.lastname: Dosescu
authors.forename: Mansoureh
authors.initials: M
authors.lastname: Sameni
authors.forename: Bonnie F
authors.initials: BF
authors.lastname: Sloane
mesh_terms: D000818:Animals; D002401:Cathepsin B / Q000235:genetics / Q000378:metabolism*; D051242:Caveolin 1; D022461:Caveolins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D024141:Collagen Type IV / Q000378:metabolism; D003110:Colonic Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D045325:HCT116 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism*
chemical_list: C495540:CAV1 protein, human; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D024141:Collagen Type IV; C524898:PLAUR protein, human; C524899:Plaur protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D011994:Recombinant Proteins; D014568:Urokinase-Type Plasminogen Activator; D002401:Cathepsin B; C067551:saruplase