Cloning and characterization of cDNA encoding a novel human leukotriene B(4) receptor

By homology screening using BLAST searches of expressed sequence tags (ESTs), we have found a previously unidentified cDNA encoding a putative seven-transmembrane receptor with highest similarity to the leukotriene B(4) receptor, BLTR. Analysis of calcium flow in transfected cells, along with sequence analysis, revealed that the EST encoded a functionally inactive protein, lacking the segment corresponding to the C-terminal part of the putative receptor protein. The missing segment was obtained by PCR amplification of a human leukocyte cDNA library and ligated to the truncated EST cDNA. The novel cDNA encodes a full-length receptor with 39% identity to the previously cloned BLTR. Studies of intracellular calcium flow of transfected HeLa cells exposed to various leukotrienes showed that also the novel BLTR-like receptor can be activated by leukotriene B(4), and it is therefore tentatively named BLTR2.