The murine cysteinyl leukotriene 2 (CysLT₂) receptor: cDNA and genomic cloning, alternative splicing, and in vitro characterization

Two classes of cysteinyl leukotriene receptor, CysLT₁ and CysLT₂, have been identified and pharmacologically characterized in human tissues. Although the CysLT¹ receptor mediates the proinflammatory effects of leukotrienes in human asthma, the physiological roles of CysLT₂ receptor are not defined, and a suitable mouse model would be useful in delineating function. We report here the molecular cloning and characterization of the mouse CysLT₂ receptor (mCysLT2R) from heart tissue. mCysLT₂R cDNA encodes a protein of 309 amino acids, truncated at both ends compared with the human ortholog (hCysLT₂R). The gene resides on the central region of mouse chromosome 14 and is composed of 6 exons with the entire coding region located in the last exon. Two 5′-untranslated region splice variants were identified with the short form lacking exon 3 as the predominant transcript. Although the overall expression of mCysLT₂R is very low, the highest expression was detected in spleen, thymus, and adrenal gland by ribonuclease protection assay, and discrete sites of expression in heart were observed by in situ hybridization. Intracellular calcium mobilization in response to cysteinyl leukotriene administration was detected in human embryonic kidney 293T cells transfected with recombinant mCysLT2R with a rank order of potency leukotriene C₄ (LTC₄) = LTD₄ ≫ LTE₄. [ ³H]LTD₄ binding to membranes expressing mCysLT ₂R could be effectively competed by LTC₄ and LTD ₄ and only partially inhibited by LTE₄ and BAYu9773. The identification of mCysLT₂R will be useful for establishing CysLT ₂R-deficient mice and determining novel leukotriene functions.