Identification of a Unique Monocarboxylate Transporter (MCT3) in Retinal Pigment Epithelium (original) (raw)
1997, Biochemical and Biophysical Research Communications
The retinal pigment epithelium transports lactate photoreceptor metabolism and viability (1,4,7). between two tissue compartments, the interphotore-Recently, we identified an integral membrane proceptor matrix and the choriocapillaris. In this report tein in the basolateral membrane of differentiated we describe a 2.45-kb cDNA isolated from a chick cDNA chick RPE cells (11). The protein was identified using RPE library that encodes a membrane protein found a monoclonal antibody (MAb 3C4) and called REMP only in RPE cells. The deduced protein has 542 amino (retinal epithelial membrane protein). REMP was acids with twelve putative membrane spanning dofound only in chick RPE cells and not in other chick mains. The cDNA has been designated MCT3 based on tissues such as neural retina, intestine, kidney or liver its 45% identity in amino acid sequence and structural (11). In this report, we describe the heterologous exsimilarity with the monocarboxylate transporters pression of a full length cDNA clone that encodes this MCT1 and MCT2. Stable transfectants (pCl-neo/MCT3), protein. The deduced amino-acid sequence of the cDNA made in a rat thyroid epithelial cell line (FRTL-5), ex-(isolated from a chick RPE expression library) is homolpress MCT3 RNA. Transfectants had enhanced pyrogous with the recently cloned monocarboxylate transuvate uptake (used as a measure of lactate uptake) porters MCT1 and MCT2 (12,13). The heterologous exwhich was proton-dependent and inhibited by a-cyano-4-hydroxycinnamate. In summary, MCT3's unique pression of a cDNA in FRTL-5 cells demonstrated that expression in RPE cells, multiple potential phosphory-REMP is a proton coupled monocarboxylate translation sites, and basolateral distribution suggest that porter and is designated MCT3. MCT3 may regulate lactate levels in the interphotoreceptor space.
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