201. Regulation of Transforming Growth Factor-β Activation by Discrete Sequences of Thrombospondin 1
- Author
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Hui Chen, Joanne E. Murphy-Ullrich, David D. Roberts, Tina M. Misenheimer, Stacey Schultz-Cherry, Deane F. Mosher, and Henry C. Krutzsch
- Subjects
Thrombospondin-2 ,Molecular Sequence Data ,Enzyme-Linked Immunosorbent Assay ,Peptide ,Spodoptera ,Biology ,Transfection ,Biochemistry ,Cell Line ,law.invention ,Mice ,Structure-Activity Relationship ,Transforming Growth Factor beta ,law ,Thrombospondin 1 ,Cell Adhesion ,Animals ,Humans ,Amino Acid Sequence ,Binding site ,Thrombospondins ,Molecular Biology ,Peptide sequence ,chemistry.chemical_classification ,Binding Sites ,Membrane Glycoproteins ,Heparin ,Cell Biology ,Peptide Fragments ,Recombinant Proteins ,Rats ,Kinetics ,chemistry ,Recombinant DNA ,Peptides ,Cell Adhesion Molecules ,Oligopeptides ,Transforming growth factor - 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.
- Published
- 1995