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R. Ambasudhan, X.F. Wang, M.M. Jablonski, R.N. Fariss, P.W. Wong, P.A. Sieving, R. Ayyagari; Subcellular Localization of ELOVL4 Gene Product in Cultured Cells and Mammalian Retinae and Intracellular Misrouting of its Mutant . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5096.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: ELOVL4 is a novel member of the fatty acid elongase (ELO) family of genes. A 5bp deletion in this gene, that may lead to C-terminal truncation of the putative protein, was shown to be associated with dominant Stargardt disease. Also, we had previously shown that ELOVL4 gene product localizes to photoreceptor layer of mammalian retinae. Towards understanding the function of the wild type protein and to discern the molecular basis for the pathogenic effect of the above mutation, we studied the subcellular distribution of the wild type and the mutant protein in cultured cells and mammalian retinae. Methods: GFP or 6- His tagged wild type and mutant (5bp deletion) full length ELOVL4 fusion protein were expressed in Cos-7 or CHO cell lines, by lipofectamine mediated transfection of corresponding plasmid expression constructs. Live or methanol fixed above cells were used for immunofluorescence double/single labeling using antibodies against ELOVL4 and organelle specific (ER, Golgi etc.) marker proteins. Immunoflurescence double labeling, as above, and immunoelectron microscopy for ELOVL4 were carried out on human or other mammalian retinal tissues. Immunoblot analysis of fractionated or total cell extracts was done to confirm the above expression. Results: In the cultured cells, wild type ELOVL4 protein tagged to GFP/His showed a perinuclear distribution and localized predominantly to ER. Significant difference in the localization pattern was observed for the mutant protein. Predominant ER localization of the wild type ELOVL4 was also observed in the photoreceptor inner segment of various mammalian retinae studied. Conclusions: ER localization of ELOVL4 is in agreement with its predicted localization pattern deduced from its primary structure. The consistent ER localization, in cell lines as well as in the photoreceptor of different mammals, support the suggested function of this protein in the elongation of very long chain fatty acids. Alteration in the localization observed for the mutant protein suggest that consequences of the defective protein localization could be the basis for macular dystrophy in the patients carrying this mutation.
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