Characterization of the RDC1 Gene Which Encodes the Canine Homolog of a Proposed Human VIP Receptor Expression Does Not Correlate with an Increase in VIP Binding Sites
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Federation of European Biochemical Societies (FEBS)
We have isolated a portion of the canine gene encoding the orphan receptor RDC1 . The complete coding sequence is contained in a single exon, and an intron divides the 5′ untranslated region of RDC1 mRNA. The RDC1 protein is 94% homologous to the gene product of GPRN1, which has been proposed to serve as a VIP receptor when expressed in CHO-K1 and COS-7 cells (Sreedharan, S.P. et al. (1991) Proc. Natl. Acad. Sci. USA 88, 4986–4990). Northern analysis indicates that CHO-K1 cells endogenously express a 2.1 kb RDC1 mRNA. However, while CHO-K1 cells possess detectable low affinity [125I]VIP binding sites, VIP binding is not altered in membranes of CHO-K1 cells expressing varying amounts of the RDC1 gene construct. Further, endogenous VIP binding is not increased by transient expression of RDC1 in COS-7 cells. Taken together, the data suggest that RDC1 is not a canine homolog of the proposed VIP receptor.