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ME Rayborn, H Sakaguchi, Q Chen, KG Shadrach, K Nishiyama, JW Crabb, JG Hollyfield; Annexin II is Present in the RPE . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2429.
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Purpose: In a study of the proteome of drusen, annexin II ( lipocortin II) was identified by liquid chromatography tandem mass spectrometry as a possible drusen protein. To establish the distribution of annexin II in drusen, samples of Bruch's membrane containing drusen were evaluated with immunocytochemistry at the light and EM levels. Methods: Tissues from elderly ( 70-90 years of age) human eyes were used. Tissues fixed in 4% formaldehyde were used for light and electron microscopy. Tissues were embedded in paraffin for immunocytochemistry and in LR White for immunoelectron microscopy. A commercially available annexin II antibody was used: for light microscopy, the ABC method was employed; and for electron microscopy, colloidal gold particles were used. RT-PCR and western blots were performed to demonstrate annexin II in retina, RPE, Bruch's membrane and choroid. Results: Annexin II immunoreactivity was present in the RPE but not in drusen. In tissues where the RPE had been brushed from Bruch's membrane before tissue processing, annexin II immunoreactivity was present on the surface of drusen associated with RPE remnants. No immunoreactivity was present in the interior of drusen. Annexin II immunoreactivity was observed in the capillary endothelium of the retina, the choriocapillaris, and in the larger blood vessels of the choroid. RT-PCR results indicated that the RPE, as well as the retina and choroid, expressed annexin II; western blots identify annexin II in the RPE, and in retina, although higher signals were found in the Bruch's membrane/choroid complex. In an independent study, proteomic analysis of the caveolae/raft fraction from RPE identified annexin II as a protein present in that complex. Conclusion: Annexin II is not present in drusen, but is present in the RPE. Annexin II is a well recognized molecule in the vascular system, but this is the first demonstration of annexin II in the RPE.
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