title: Regulation of transforming growth factor-beta activation by discrete sequences of thrombospondin 1.
abstract: Transforming growth factor-beta (TGF-beta) is a potent growth regulatory protein secreted by virtually all cells in a latent form. A major mechanism of regulating TGF-beta activity occurs through factors that control the processing of the latent to the biologically active form of the molecule. We have shown previously that thrombospondin 1 (TSP1), a platelet alpha-granule and extracellular matrix protein, activates latent TGF-beta via a protease- and cell-independent mechanism and have localized the TGF-beta binding/activation region to the type 1 repeats of platelet TSP1. We now report that recombinant human TSP1, but not recombinant mouse TSP2, activates latent TGF-beta. Activation was further localized to the unique sequence RFK found between the first and the second type 1 repeats of TSP1 (amino acids 412-415) by the use of synthetic peptides. A peptide with the corresponding sequence in TSP2, RIR, was inactive. In addition, a hexapeptide GGWSHW, based on a sequence present in the type 1 repeats of both TSP1 and TSP2, inhibited the activation of latent TGF-beta by TSP1. This peptide bound to 125I-active TGF-beta and inhibited interactions of TSP1 with latent TGF-beta. TSP2 also inhibited activation of latent TGF-beta by TSP1, presumably by competitively binding to TGF-beta through the WSHW sequence. These studies show that activation of latent TGF-beta is mediated by two sequences present in the type 1 repeats of TSP1, a sequence (GGWSHW) that binds active TGF-beta and potentially orients the TSP molecule and a second sequence (RFK) that activates latent TGF-beta. Peptides based on these sites have potential therapeutic applications for modulation of TGF-beta activation.
authors.affiliation: Department of Pathology, University of Alabama at Birmingham 35294-0019, USA.
authors.forename: S
authors.initials: S
authors.lastname: Schultz-Cherry
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: D F
authors.initials: DF
authors.lastname: Mosher
authors.forename: T M
authors.initials: TM
authors.lastname: Misenheimer
authors.forename: H C
authors.initials: HC
authors.lastname: Krutzsch
authors.forename: D D
authors.initials: DD
authors.lastname: Roberts
authors.forename: J E
authors.initials: JE
authors.lastname: Murphy-Ullrich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002448:Cell Adhesion / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000494:pharmacology; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D018411:Spodoptera; D013329:Structure-Activity Relationship; D019699:Thrombospondins; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology*
chemical_list: D015815:Cell Adhesion Molecules; D008562:Membrane Glycoproteins; D009842:Oligopeptides; D010446:Peptide Fragments; D010455:Peptides; D011994:Recombinant Proteins; D019699:Thrombospondins; D016212:Transforming Growth Factor beta; D006493:Heparin