When the cornea is wounded, there is a dramatic conversion of quiescent stromal keratocytes, first into motile, secretory fibroblasts, and then into contraction-ready, actin-rich myofibroblasts in response to TGF-beta. Myofibroblasts promote wound closure but few, if any, remain in a successfully-healed wound. We are exploring the role of urokinase-type plasminogen activator (uPA) in these phenotype conversions. uPA is a serine protease that promotes extracellular matrix degradation, cell migration, growth factor release, and tissue invasion by cancer cells and leukocytes. I will test the hypothesis that corneal stroma cells use uPA to regulate corneal healing analogous to its activity in invasive cells. The paradigm is that uPA, activated by binding to its receptor; uPAR, generates localized plasmin from plasminogen, which in turn releases biologically-active FGF. FGF increases uPA secretion, generating more plasmin from plasminogen. When plasmin levels are significantly elevated, plasmin activity releases active TGF-beta, which inhibits uPA secretion, and stimulates secretion of a uPA inhibitor, PAI, thus turning off growth factor signaling. uPAR, in addition to binding uPA, associates with integrins and extracellular matrix proteins uPAR/integrin/matrix association may be required for coordinated migration and extracellular protease activity.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
5F32EY007049-03
Application #
6518392
Study Section
Visual Sciences C Study Section (VISC)
Program Officer
Fisher, Richard S
Project Start
2002-04-01
Project End
Budget Start
2002-04-01
Budget End
2003-03-31
Support Year
3
Fiscal Year
2002
Total Cost
$44,212
Indirect Cost
Name
Mount Sinai School of Medicine
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
114400633
City
New York
State
NY
Country
United States
Zip Code
10029
Bernstein, Audrey M; Twining, Sally S; Warejcka, Debra J et al. (2007) Urokinase receptor cleavage: a crucial step in fibroblast-to-myofibroblast differentiation. Mol Biol Cell 18:2716-27
Greenberg, Roseanne S; Bernstein, Audrey M; Benezra, Miriam et al. (2006) FAK-dependent regulation of myofibroblast differentiation. FASEB J 20:1006-8
Taliana, Lavinia; Benezra, Miriam; Greenberg, Roseanne S et al. (2005) ZO-1: lamellipodial localization in a corneal fibroblast wound model. Invest Ophthalmol Vis Sci 46:96-103
Bernstein, Audrey M; Greenberg, Roseanne S; Taliana, Lavinia et al. (2004) Urokinase anchors uPAR to the actin cytoskeleton. Invest Ophthalmol Vis Sci 45:2967-77