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S. Morales, M. Wadehra, J. Braun, L. Gordon; Epithelial Membrane Protein 2 (EMP2) Alters Cell Surface Expression of Integrins in Retinal Pigment Epithelium . Invest. Ophthalmol. Vis. Sci. 2004;45(13):644.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Epithelial membrane protein 2 (EMP2), a four transmembrane protein, plays an important role in the recruitment and cell surface delivery of proteins, including specific integrin isoforms and MHC class I molecules, in NIH3T3 cells. EMP2 is highly expressed in certain cell types of the eye, including the retinal pigment epithelium (RPE). Integrins are key to the cell biology of RPE, including extracellular matrix interactions, and RPE expression of certain integrin isoforms has been associated with significant retinal pathology. The purpose of this project was to determine if EMP2 regulates cell surface expression of specific integrin isoforms in RPE. Methods:ARPE–19, a human cell line derived from retinal pigment epithelium, was obtained from ATCC. Immunologic methods, including immunofluorescence and Western blot, as well as RT–PCR confirmed a high level of EMP2 expression in ARPE–19. Modulation of EMP2 protein expression was achieved with transient transfections using an EMP2 overexpressing construct, EMP2 ribozyme, or vector alone. All constructs also produced GFP as an internal control for transfection. Cells transfection efficiency and expression of integrins were identified using flow cytometry and immunofluorescence studies. EMP2 expression was quantified using Western blot. Results:ARPE–19 cells contain high levels of EMP2 protein and confocal microscopy demonstrated co–localization of EMP2 and B1 integrin. Transfection efficiencies of about 50% were obtained. Overexpression of EMP2 was associated with an increase in cell surface expression of α6 and a slight decrease in α5 integrin. Decrease of EMP2 through a specific ribozyme produced a corresponding decrease in α6 integrin cell surface expression. Conclusions:EMP2 regulates the levels and isoforms of cell surface integrins in the ARPE–19 cell line. In addition, EMP2 modulates the levels of specific integrin isoforms linked to retinal disease processes. We hypothesize that alteration of EMP2 expression may provide a control point for the normal cell physiology and pathobiology of the RPE.
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