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M.E. Rayborn, V.L. Bonilha, K.G. Shadrach, Å. Lundwall, J. Malm, J.G. Hollyfield; Characterization of Semenogelin Proteins in the Human Retinas of AMD Donors . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2568.
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Semenogelin I (SgI) and II (SgII) are the major structural protein components of semen coagulum. Their function is not fully understood, but several activities have been ascribed to semenogelin or semenogelin–derived peptides, e.g. inhibition of sperm motility and capacitation, activation of sperm hyaluronidase and antibacterial properties. Recently, we reported the presence and localization of both SgI and SgII in the RPE, neural retina (choroid, photoreceptors, inner nuclear layer and ganglion cell layer) and vitreous of human donors not diagnosed with any eye disease. In the present study, we further analyzed the expression of these proteins in the retinal cells of AMD eyes in vivo.
Cryo and paraffin sections of human retina were processed for both immunofluorescence and DAB reaction with an antibody that recognizes both forms of semenogelin proteins. The presence of both proteins was analyzed in retina and RPE total lysates.
Both proteins were detected by western blot in human RPE. However, the intensity of expression was significantly lower in the AMD eyes. In AMD eyes immune reaction was detected only in the tips of the photoreceptor outer segments.
Semenogelin I and II are expressed in the normal human retina and in the retina of AMD donor eyes. The expression of semenogelins in the AMD eyes is substantially lower than that observed in the normal retina. A recent report indicates that both SgI and SgII bind zinc. Earlier clinical trial data found a significant decrease in the progression of AMD in individuals supplemented with antioxidants and zinc. Our observations that Sgs are localized to photoreceptors and the RPE, the two cellular targets in AMD, may point to a function related to the ability of these cells to sequester zinc for protection against AMD.
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