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AK Ball, MT Duong, BA van Adel, B Zhang, RK Mishra; Expression Of A 40-kda Catecholamine-regulated Protein In The Inner Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):756.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: A 40 kDa catecholamine regulated protein (CRP40), which is related to the 70 kDa heat shock protein and may similarly act as a molecular chaperone, has recently been identified in the CNS. CRP40 has been shown to be modulated by dopamine, a retinal neuromodulator. In the present study we used immunohistochemistry to localize CRP40 in the rat retina and examined CRP40 expression in the retina after optic nerve transection. Methods: Eyes were fixed, cryostat sectioned, and sections incubated overnight in antisera against CRP40. Double-label immunohistochemistry was performed to evaluate colocalization between CRP40 and markers for specific retinal cells: PGP9.5 (GABA amacrine cells, horizontal cells, and ganglion cells), TH (dopaminergic cells), GFAP (astrocytes), vimentin (Muller cells). Some retinas that were labeled with only CRP40 were counterstained with YO-PRO-1 to label nuclei. Retinal ganglion cells (RGCs) were identified by applying Dextran-FITC to the cut optic nerve. To evaluate the expression of CRP40 after injury, the optic nerve of adult rats were severed and the retinas extracted 1, 2, 4, 7, and 14 days post axotomy and prepared for Western blotting. Results: CRP40 was localized only to cells in the proximal retina. The nuclear envelope of all cells in the proximal retina were intensely labeled. The cytoplasm of vimentin-labeled end-feet of Muller cells was also labeled by CRP40. There was no cytoplasmic labeling of GFAP labeled astrocytes, Dextran-FITC labeled RGCs, PGP9.5 labeled amacrine or horizontal cells, or TH labeled dopaminergic cells. The cytoplasm of a subpopulation of amacrine cells, located near the retinal margin, was intensely labeled by CRP40. These cells had small nuclei and neurites that were narrowly stratified in IPL S1. Immunoblot results showed that CRP40 expression decreased in a time-dependent fashion after optic nerve transection. There was no significant change in CRP40 expression until 2 days after optic nerve transection. CRP40 expression was reduced by 70% at 2 days postaxotomy. CRP40 expression continued to gradually decrease at 4, 7, and 14 days postaxotomy. Conclusion: These results demonstrate that CRP40 is localized to the nuclear envelope of all proximal retinal cells, the cytoplasm of Muller cells, and a subpopulation of amacrine cells. The expression of CRP40 was markedly decreased after optic nerve transection, suggesting that CRP40 plays an important role in the retina's response to injury.
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