Journal of Neuroscience, Vol 10, 1486-1494, Copyright © 1990 by Society for Neuroscience
Immunological characterization and localization of the Na+/Ca2(+)- exchanger in bovine retina
W Haase, W Friese, RD Gordon, H Muller and NJ Cook
Max-Planck-Institut fur Biophysik, Abteilung fur Physiologie, Frankfurt/Main, Federal Republic of Germany.
The sodium/calcium exchanger was purified from bovine retinal rod outer
segment membranes and used for the immunization of New Zealand White
rabbits. A polyclonal antibody was produced which was found to bind
specifically to the 230 kDa Na+/Ca2(+)-exchanger protein as assessed by
Western blotting. The antibody did not bind to the high-molecular- weight
"rim protein," thereby demonstrating that this protein is distinct from the
rod outer segment of Na+/Ca2(+)-exchanger. We used the polyclonal antibody
for immunohistochemically localizing the exchange protein in bovine retina.
Fluorescent light microscopy revealed intensive immunolabeling of the
photoreceptor outer segments, whereas other retinal cell layers exhibited
minimal binding. Using the electron microscopic immunogold method, we found
specific antibody binding to the extracellular side of rod outer segment
plasma membrane. Rod disk membranes, rod inner segments, and cone
photoreceptors displayed no significant labeling. We therefore conclude
that the Na+/Ca2(+)-exchanger is localized primarily in the rod outer
segment plasma membrane, the most appropriate localization considering its
proposed role in the process of vertebrate phototransduction.
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