LTBP-2 Has a Single High-Affinity Binding Site for FGF-2 and Blocks FGF-2-Induced Cell Proliferation

PLoS One. 2015 Aug 11;10(8):e0135577. doi: 10.1371/journal.pone.0135577. eCollection 2015.

Abstract

Latent transforming growth factor-beta-1 binding protein-2 (LTBP-2) belongs to the fibrillin-LTBP superfamily of extracellular matrix proteins. LTBPs and fibrillins are involved in the sequestration and storage of latent growth factors, particularly transforming growth factor β (TGF-β), in tissues. Unlike other LTBPs, LTBP-2 does not covalently bind TGF-β, and its molecular functions remain unclear. We are screening LTBP-2 for binding to other growth factors and have found very strong saturable binding to fibroblast growth factor-2 (FGF-2) (Kd = 1.1 nM). Using a series of recombinant LTBP-2 fragments a single binding site for FGF-2 was identified in a central region of LTBP-2 consisting of six tandem epidermal growth factor-like (EGF-like) motifs (EGFs 9-14). This region was also shown to contain a heparin/heparan sulphate-binding site. FGF-2 stimulation of fibroblast proliferation was completely negated by the addition of 5-fold molar excess of LTBP-2 to the assay. Confocal microscopy showed strong co-localisation of LTBP-2 and FGF-2 in fibrotic keloid tissue suggesting that the two proteins may interact in vivo. Overall the study indicates that LTBP-2 is a potent inhibitor of FGF-2 that may influence FGF-2 bioactivity during wound repair particularly in fibrotic tissues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites*
  • Cell Line
  • Cell Proliferation / drug effects
  • Fibrillins
  • Fibroblast Growth Factor 2 / antagonists & inhibitors*
  • Fibroblast Growth Factor 2 / chemistry*
  • Fibroblast Growth Factor 2 / pharmacology
  • Fibroblasts / metabolism
  • Heparin / metabolism
  • Humans
  • Keloid / metabolism
  • Latent TGF-beta Binding Proteins / chemistry*
  • Latent TGF-beta Binding Proteins / metabolism*
  • Latent TGF-beta Binding Proteins / pharmacology
  • Microfilament Proteins / metabolism
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Transport
  • Receptor, Fibroblast Growth Factor, Type 1 / agonists
  • Receptor, Fibroblast Growth Factor, Type 1 / metabolism
  • Recombinant Proteins
  • Skin / metabolism

Substances

  • Fibrillins
  • LTBP2 protein, human
  • Latent TGF-beta Binding Proteins
  • Microfilament Proteins
  • Recombinant Proteins
  • Fibroblast Growth Factor 2
  • Heparin
  • Receptor, Fibroblast Growth Factor, Type 1

Grant support

This work was supported by the National Health and Medical Research Council of Australia project grant number 519211. Part of the work was supported by a scholarship to MAS from the Internatinal Islamic University of Malaysia and the Malaysian Government.