CLONING OF A HUMAN HEPTAHELICAL RECEPTOR CLOSELY-RELATED TO THE P2Y(5) RECEPTOR

The 6H1 receptor cloned from activated chicken T cells was initially c onsidered an orphan G-coupled receptor, but was later included in the P2Y family of receptors for purine and pyrimidine nucleotides on the b asis of a significant amino acid identity and was renamed P2Y(5). Anal ysis of the expressed sequence tag database revealed the presence of a related sequence exhibiting 63% amino acid identity with this recepto r. Starting from this partial sequence, we have isolated a complete cl one and identified a 1113 base pair open reading frame encoding a new G-coupled receptor that we have caned P2Y(5)-like. This sequence exhib its 61% identity with the chicken P2Y(5) sequence and 30-33% with Othe r P2Y subtypes. A construct encoding this P2Y(5)-like receptor was tra nsfect;ed into COS-7, 1321N1, and CHO-K1 cells, and expression was doc umented by Northern blotting. None of the 40 nucleotides and nucleosid es tested was able to elicit a response in any of four functional assa ys: inositol phosphate formation, stimulation or inhibition of cAMP fo rmation, and extracellular acidification measured with a microphysiome ter. These results suggest either that the natural ligand of the P2Y(5 )-like receptor is an uncommon nucleotide or alternatively that despit e its structural similarity to the P2Y family it is not a nucleotide r eceptor. (C) 1997 Academic Press.