Myocilin binding to Hep II domain of fibronectin inhibits cell spreading and incorporation of paxillin into focal adhesions

Exp Cell Res. 2005 Feb 15;303(2):218-28. doi: 10.1016/j.yexcr.2004.09.026. Epub 2004 Nov 2.


Myocilin, a novel matricellular protein found in the human eye, can modify signaling events mediated by the Heparin II domain of fibronectin. Using myocilin produced in sf9 insect cells, myocilin inhibited spreading of cycloheximide-treated human skin fibroblasts plated on substrates co-coated with myocilin and either fibronectin or its Heparin II domain. Cell spreading could be rescued by adding back either substrate adsorbed or soluble Heparin II domains. Myocilin did not inhibit cell attachment to fibronectin even in the presence of a 2400 M excess of myocilin. Myocilin impaired focal adhesion formation and specifically blocked the incorporation of paxillin, but not vinculin, into focal adhesions. The Heparin II domain mediated the incorporation of paxillin into focal adhesions, since paxillin was not assembled into focal adhesions unless the Heparin II domain was present. The effect of myocilin on focal adhesions could be overcome by treating cells with either phorbol 12-myristate (PMA) or oleoyl-L-alpha-lysophosphatidic acid (LPA). Myocilin bound to the fibroblast cell surface, but its binding could not be competed with excess fibronectin, suggesting that myocilin does not compete for cell surface binding sites of fibronectin. Myocilin therefore appears to specifically block functions mediated by the Heparin II domain possibly through direct interactions with it.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Cells, Cultured
  • Cycloheximide / pharmacology
  • Cytoskeletal Proteins / metabolism*
  • Eye Proteins / metabolism*
  • Fibroblasts / drug effects
  • Fibroblasts / physiology
  • Fibronectins / chemistry*
  • Fibronectins / metabolism*
  • Focal Adhesions / drug effects
  • Focal Adhesions / physiology*
  • Glycoproteins / metabolism*
  • Humans
  • Paxillin
  • Phosphoproteins / metabolism*
  • Protein Structure, Tertiary
  • Recombinant Proteins / metabolism
  • Signal Transduction


  • Cytoskeletal Proteins
  • Eye Proteins
  • Fibronectins
  • Glycoproteins
  • PXN protein, human
  • Paxillin
  • Phosphoproteins
  • Recombinant Proteins
  • trabecular meshwork-induced glucocorticoid response protein
  • Cycloheximide