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J.G. Hollyfield, K.G. Shadrach, K.A. West, J. Sun, J.W. Crabb; The Human Interphotoreceptor Matrix Proteome-Initial Results . Invest. Ophthalmol. Vis. Sci. 2003;44(13):944.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The interphotoreceptor matrix (IPM) serves important roles in retinal physiology yet less than a dozen IPM proteins have been documented to date. Additional proteins must function in this critical retinal extracellular matrix and we have initiated efforts to define the IPM proteome. Methods: Human IPM was isolated from dissected retina and posterior eye cup containing RPE by sequential rinses with PBS pH 7 and extractions with TBS at pH 8. Four IPM fractions were obtained: 1) the retina rinse and 2) the eye cup/RPE rinse containing readily soluble IPM components; 3) the retina extraction and 4) eye cup/RPE extraction containing less soluble IPM components. Extracted IPM samples were digested with Chondroitinase ACII to remove chondroitin sulfate-type GAGs from proteoglycans. Proteins were separated by SDS-PAGE, excised from the gel, digested in situ with trypsin and identified by LC MS/MS sequence analysis using Swiss Pro and NCBI databases. Results: Over 100 different proteins have been identified from initial analyses of the IPM, including interphotoreceptor retinoid-binding protein, SPACR and SPACRCAN. Particularly striking is the number of hypothetical and unknown proteins, accounting for about 15% of these initial protein identifications. Conclusions: Proteomic methods are revealing the identity of proteins in the IPM. Hypothetical and unknown proteins may be possible candidate genes for inherited retinal disease. Complete definition of the IPM proteome will lead to a better understanding of the molecular interactions taking place in this important compartment supporting photoreceptor and RPE functions.
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