title: Activation of procollagenase IV by cytochalasin D and concanavalin A in cultured rat mesangial cells: linkage to cytoskeletal reorganization.
abstract: The secretion and activation of procollagenase IV were studied in cultured rat mesangial cells. Under resting conditions, mesangial cells secrete predominantly a protein that, by gel zymography, exhibits gelatinase activity and also reacts with an anti-72-kd procollagenase IV antibody raised against a conserved region of the activation site of the enzyme. Cytochalasin D or concanavalin A treatment of mesangial cells causes disruption of actin stress fibers and results in the activation of procollagenase IV, yielding two lower molecular mass forms with gelatinase activity. Concanavalin A-induced actin filament disruption and procollagenase IV activation can be blocked by alpha-methyl-D-mannopyranoside but not by D(+)-galactose. Procollagenase IV as well as the activated forms all exhibit Ca2+ and Zn2+ dependency, characteristic of metalloproteinases. Mesangial cells in culture also secrete a specific tissue inhibitor of metalloproteinase, TIMP-2. Cytochalasin D treatment of mesangial cells reduces TIMP-2 expression. Cytochalasin D and concanavalin A both inhibited the serum-induced contraction of collagen gels embedded with mesangial cells. It was concluded that cytochalasin D-induced cytoskeletal disruption in mesangial cells may activate procollagenase IV by inhibiting TIMP-2 expression and that there is a concanavalin A-binding site on mesangial cells that is part of a transmembrane signaling system altering mesangial cell cytoskeletal organization and metalloproteinase secretion and activation.
authors.affiliation: Department of Medicine, University of Toronto, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Allenberg
authors.forename: T
authors.initials: T
authors.lastname: Weinstein
authors.forename: I
authors.initials: I
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Silverman
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D017364:Collagenases / Q000378:metabolism*; D003208:Concanavalin A / Q000494:pharmacology*; D003285:Contractile Proteins / Q000187:drug effects; D015638:Cytochalasin D / Q000494:pharmacology*; D003599:Cytoskeleton / Q000187:drug effects* / Q000648:ultrastructure; D004247:DNA / Q000032:analysis; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000378:metabolism*; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008297:Male; D008766:Methylmannosides / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019716:Tissue Inhibitor of Metalloproteinase-2
chemical_list: D003285:Contractile Proteins; D004792:Enzyme Precursors; D008766:Methylmannosides; D011506:Proteins; D003208:Concanavalin A; D019716:Tissue Inhibitor of Metalloproteinase-2; D015638:Cytochalasin D; C008466:methylmannoside; D004247:DNA; D017364:Collagenases; C022440:procollagenase