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Abstract #25734 Published in IGR 12-2
Mechanistic basis of Rho GTPase-induced extracellular matrix synthesis in trabecular meshwork cells
Pattabiraman PP; Rao PVAmerican Journal of Physiology and Cell Physiology 2010; 298: C749-C763
Elevated intraocular pressure arising from impaired aqueous humor drainage through the trabecular pathway is a major risk factor for glaucoma. To understand the molecular basis for Rho GTPase-mediated resistance to aqueous humor drainage, we investigated the possible interrelationship between actomyosin contractile properties and extracellular matrix (ECM) synthesis in human trabecular meshwork (TM) cells expressing a constitutively active form of RhoA (RhoAV14). TM cells expressing RhoAV14 exhibited significant increases in fibronectin, tenascin C, laminin, (alpha)-smooth muscle actin ((alpha)-SMA) levels, and matrix assembly in association with increased actin stress fibers and myosin light-chain phosphorylation. RhoAV14-induced changes in ECM synthesis and actin cytoskeletal reorganization were mimicked by lysophosphatidic acid and TGF-(beta)(2), known to increase resistance to aqueous humor outflow and activate Rho/Rho kinase signaling. RhoAV14, lysophosphatidic acid, and TGF-(beta)(2) stimulated significant increases in Erk1/2 phosphorylation, paralleled by profound increases in fibronectin, serum response factor (SRF), and (alpha)-SMA expression. Treatment of RhoA-activated TM cells with inhibitors of Rho kinase or Erk, on the other hand, decreased fibronectin and (alpha)-SMA levels. Although suppression of SRF expression (both endogenous and RhoA, TGF-(beta)(2)-stimulated) via the use of short hairpin RNA decreased (alpha)-SMA levels, fibronectin was unaffected. Conversely, fi-bronectin induced (alpha)-SMA expression in an SRF-dependent manner. Collectively, data on RhoA-induced changes in actomyosin contractile activity, ECM synthesis/assembly, and Erk activation, along with fibronectin-induced (alpha)-SMA expression in TM cells, reveal a potential molecular interplay between actomyosin cytoskeletal tension and ECM synthesis/assembly. This interaction could be significant for the homeostasis of aqueous humor drainage through the pressure-sensitive trabecular pathway.
P. V. Rao. Dept. of Ophthalmology, AERI Bldg., Duke Univ. School of Medicine, Durham, NC 27710, United States. rao00011@mc.duke.edu
Classification:
3.6 Cellular biology (Part of: 3 Laboratory methods)
3.5 Molecular biology incl. SiRNA (Part of: 3 Laboratory methods)
1.3 Pathogenesis (Part of: 1 General aspects)
2.5.1 Trabecular meshwork (Part of: 2 Anatomical structures in glaucoma > 2.5 Meshwork)
