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Mark S. Filla, Xuyang Liu, Thai D. Nguyen, Jon R. Polansky, Curtis R. Brandt, Paul L. Kaufman, Donna M. Peters; In Vitro Localization of TIGR/MYOC in Trabecular Meshwork Extracellular Matrix and Binding to Fibronectin. Invest. Ophthalmol. Vis. Sci. 2002;43(1):151-161.
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purpose. To determine whether trabecular meshwork–inducible glucocorticoid
response/myocilin (TIGR/MYOC) protein associates with the extracellular
matrix (ECM) of human trabecular meshwork (HTM) cells.
methods. The extracellular localization of TIGR/MYOC was examined by
immunofluorescence microscopy in HTM cultures treated with and without
dexamethasone and ascorbate and in a transformed HTM cell line, TM-1,
transiently transfected with TIGR/MYOC cDNA. Antibodies to TIGR/MYOC,
fibronectin, laminin, type IV collagen, or thrombospondin were used to
determine the extracellular localization of TIGR/MYOC. Solid phase
binding assays using 125I-recombinant TIGR/MYOC and types I
and IV collagens, fibronectin, and laminin were done to examine the
association of TIGR/MYOC with these proteins and to identify a specific
TIGR/MYOC binding site within fibronectin. The domains of fibronectin
tested were the fibrin/collagen binding domain, the RGD domain, and the
Heparin II (Hep II) domain.
results. TIGR/MYOC colocalized with fibronectin, laminin, and type IV collagen,
but not thrombospondin in both dexamethasone and
dexamethasone/ascorbate-treated HTM cultures and in TM-1 cultures
transfected with TIGR/MYOC cDNA. In solid phase binding assays, 125I-TIGR/MYOC bound fibronectin but not laminin or type IV
collagen. Binding to fibronectin could be competed with excess
TIGR/MYOC or fibronectin. Specific binding was found for the Hep II
domain of fibronectin.
conclusions. TIGR/MYOC can associate with components of the ECM via interactions
with the Hep II domain of fibronectin. The interactions with the Hep II
domain of fibronectin could alter cell–matrix interactions in the TM
and provides an interesting lead to explore the role(s) of TIGR/MYOC in
both steroid-induced and primary open angle
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