The Basigin gene encodes two glycoproteins, Basigin and Basigin-2. These gene products are the result of differential splice variations. Basigin can be found in various areas of the body, including the Müller glial cells of the retina. Basigin-2 is found only in the retina on the photoreceptor cells. Basigin-2 has an extra loop domain at the N-terminus, as compared to its counterpart Basigin. This extracellular domain is thought to participate in cell adhesion. We hypothesized that the N-terminal domain of Basigin-2, expressed on photoreceptors binds to the extracellular domain(s) of Basigin on Müller glial cells and essentially adheres the two cell types together. Therefore, we sought to determine whether Basigin-2 binds to Basigin. The cDNA coding the N-terminal loop region of Basigin-2 was cloned into the pET102 vector (Invitrogen), which generates six-histidine (6X-His)-tagged proteins in bacterial cells. The recombinant Basigin-2 loop was then used as a probe in ELISA analysis. Endogenous Basigin, from either retina or kidney lystates was trapped using an antibody specific for Basigin gene products and probed with the recombinant Basigin-2 loop probe. The ELISA analyses showed binding of the N-terminal loop to Basigin in retina lysates, as well as the kidney lysates. Since the kidney has been shown to only express Basigin, this suggests that Basigin-2 binds Basigin. This is a significant finding, as it supports our hypothesis that Basigin gene products are important glycoproteins for photoreceptor-Muller cell interactions.
Support for this work provided by UNF Academic Affairs (to JDO).
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