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Y. Gribanova, N. B. Akhmedov, C. K. Yamashita, C. Njoku, D. B. Farber; Potential Role of the Novel 7R Protein in Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3423.
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© ARVO (1962-2015); The Authors (2016-present)
The 7R gene maps to human Chromosome 7 and segregates with disease in a family with autosomal recessive retinitis pigmentosa. 7R is predicted to encode a novel protein with seven transmembrane domains that we previously localized to the cis-Golgi membranes of transfected HEK 293 cells. In adult mouse retina, 7R is distributed predominantly in cone outer segments and in the perinuclear region of photoreceptors, all cell types of the inner nuclear layer and ganglion cells. The objective of this study was to identify the role of the 7R protein in retina.
Retinas were isolated from P5, P14, P21, P30, P90 and P330 C57BL/6 mice. Nuclear and cytoplasmic proteins were extracted and separated by SDS gel electrophoresis. Immunoprecipitation of retinal proteins with the 7R antibody was used to identify 7R-interacting proteins. These were resolved by PAGE, sypro-ruby stained bands were excised, digested with trypsin and subjected to MALDI TOF mass-spectrometry. Data was analyzed using ProteinPilot software. Cryosections of P5, P11 and P30 mouse retinas were immunostained with 7R antibody and examined by confocal microscopy.
Western blots of retinal proteins using the 7R antibody revealed two major immunoreactive bands: a 38 kDa band was detected predominantly in P5 and P14 retinas and a 115 kDa band in P21 through P330 retinas. In P5 and P14 retinas 7R was only in the nuclear fraction, but in retinas from mice older than P21 it was present in both nuclear and cytoplasmic fractions. Immunohistochemistry of mouse retina confirmed these results. Furthermore, immunoprecipitation of retinal proteins with the 7R antibody and mass spectrometry analysis of the putative 7R-interacting proteins identified a subset of proteins implicated in nucleocytoplasmic transport and membrane vesicle trafficking.
Based on the distribution of 7R in differentiating and adult mouse retinas as well as the 7R immunoprecipitation results we hypothesize that the 7R protein may participate in transport of macromolecules in mammalian retina.
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