IMMUNOLOCALIZATION OF N-ACETYLGALACTOSAMINYLPHOSPHOTRANSFERASE IN THE ADULT RETINA AND SUBRETINAL SPACE

The cell surface N-acetylgalactosaminylphosphotransferase (GalNAcPTase) modulates N-cadherin-mediated adhesion among embryonic chick retinal cells (Balsamo et al., 1990). We are investigating the potential role of this transferase in modulating adhesive interactions in the adult retina. Using a previously characterized monoclonal anti-GalNAcPTase, we have used immunohistochemical and immunoblot techniques to localize and characterize the transferase in the retinas of the post metamorphic frog (Xenopus laevis), adult cow, and adult cynomolgus macaque. On frozen sections, anti-GalNAcPTase specifically labels the outer segments of photoreceptors in all species. Immunolabel appears at the surface of, or between rod outer segments in all species. The nerve fiber layer also shows high immunoreactivity in all species. Monkey cone outer segments are also highly immunoreactive. Photoreceptor inner segments are clearly immunoreactive in the cow retina. Immunoblots of purified cow rod outer segments show immunolabeled bands near 220 kDa, which is the molecular mass of the GalNAcPTase used as immunogen. Purified Xenopus rod outer segments are not immunoreactive on blots, while soluble interphotoreceptor matrix (IPM) shows immunoreactive bands principally at 113-130, and 166 kDa. Cow soluble IPM shows immunoreactivity at 180 kDa. Based on these findings, we propose that the GalNAcPTase, or a fragment thereof, is a component of the IPM, and perhaps of the photoreceptor outer segment as well. © 1991.