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L. Wu, M. Forbes, J.C. Tsai; Erythropoietin Receptor Protein Expression in the Rat Brain and Visual System . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2068.
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Erythropoietin receptor (EPOR) have been recently reported to be expressed (Western blotting) in neuronal and tumor cell lines. To our knowledge, EPOR expression has not been assessed in ocular tissues. To better understand the neuro–protective function of the EPO/EPOR complex in the eye, we investigated protein expression of EPOR in non–hematopoietic cells including brain and ocular tissues in the normal rat.
Brain (cerebral cortex, spinal cord and cerebellum, superior colliculus, inferior colliculus and optical chiasma) and ocular tissues were collected to assess EPO and EPOR protein expression via Western blotting. The ocular tissues comprised 5 distinct components: retina, anterior segment (AS), posterior segment (PS), lens, and lacrimal gland. The erythroleukemia cells lysate (TF–1) served as the positive control for tissue preparation and the blocking peptide against the anti–EPOR antibody for the competition study.
In positive control erythroleukemia cells, the anti–EPOR antibody detected two dominant protein bands of approximately 28 and 60 kDa and a weak protein band of approximately 40 kDa. In the collected brain tissues, the 28 and 40 kDa forms of EPOR protein were predominantly expressed, whereas the 60 kDa form was not detected. In contrast, the 28 kDa signal was the dominant EPOR form in ocular tissues (except the lens).The 40 kDa form was also strongly observed in retina and lacrimal gland, but weakly observed in the AS and PS. Of interest, the lens displayed a unique signal of approximately 51 kDa (neither 28 nor 40 kDa bands were observed). Moreover, neither the 59 kDa size band reported in tumor cells nor the anticipated 66∼100 kDa bands were observed in the central nervous system tissues (brain and eye). Competition experiments performed via pre–incubation of anti–EPOR antibody and its blocking peptide confirmed that all signals detected represented various forms of the EPOR protein.
We report the first description of EPOR protein forms (approximately 28, 40 and 51 kDa) in ocular tissues. Two dominant EPOR protein forms (28 and 40 kDa) were expressed in neuronal tissues (brain and retina), but the 40 kDa form was not as evident in other ocular tissues. The lens had expression of a distinct EPOR form (51 kDa).
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