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CS Boehlke, C Yuan, Y Sawada, AJ W Huang; Distribution of G Proteins and RGS Proteins on Ocular Surface Epithelia . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1646.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Heterotrimeric G proteins effect a wide range of intracellular events via ligand-activated G protein coupled receptors. Regulators of G protein signaling (RGS) proteins can regulate G protein activation via accelaration of GTP hydrolysis by Gα subunits. Little is known about the roles of G proteins and RGS proteins in regulating epithelial differentiation. We herein characterized the distribution of G proteins and RGS proteins on the ocular surface epithelia. Methods:Immunohistochemistry with a battery of polyclonal antibodies against human Gαq, Gαi, Gαs, and RGS proteins was performed on cryosectioned human ocular tissues from donor corneal buttons. Alkaline-phosphatase conjugated secondary antibodies were used as chromophores. Results:Diffuse expression of Gαi and Gαs was noted throughout epithelial cells, but not in the stroma of, cornea, limbus, and conjunctiva. Preferential staining of Gαq was noted in all layers of corneal epithelial cells and the suprabasal epithelial cells of the limbus. Absent staining was noted in the basal layers of the limbal epithelium as well as the entire conjunctival epithelium. Among RGS, RGS4 showed a preferential staining of the conjunctival epithelium over the cornea and limbus. Conclusion:The presence of Gα subunits and RGS proteins on the cornea and conjunctiva suggests that they may be responsible for cell signaling in the ocular surface epithelia. More importantly, Gαq may serve as a differentiation marker for the epithelial development. Absence of Gαq in the basal limbus and conjunctiva suggests that alternative signaling pathways may be used in the less differentiated, or more proliferative, epithelial cells. RGS4 may play a regulatory role in the secretory functions of conjunctival epithelia.
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