Identification, molecular cloning, expression, and characterization of a cysteinyl leukotriene receptor

The cysteinyl leukotrienes (CysLTs) have been implicated in the;pathophysio logy of inflammatory disorders, in particular asthma, for which the CysLT r eceptor antagonists pranlukast, zafirlukast, and montelukast, have been int roduced recently as novel therapeutics. Here we report on the molecular clo ning, expression, localization, and pharmacological characterization of a C ysLT receptor (CysLTR), which was identified by ligand fishing of orphan se ven-transmembrane-spanning, G protein-coupled receptors. This receptor, exp ressed in human embryonic kidney(HEK)-293 cells responded selectively to th e individual CysLTs, LTC4, LTD4, or LTE4, with a calcium mobilization respo nse; the lank order potency was LTD, (EC50 = 2.5 nM) > LTC, (EC50 = 24 nM) > LTE4 (EC50 = 240 nM). Evidence was provided that LTE, is a partial agonis t at this receptor. [H-3]LTD, binding acid LTD4-induced calcium mobilizatio n in HEK-293 cells expressing the CysLT receptor were potently inhibited by the-structurally distinct CysLTR antagonists pranlukast, montelukast, zafi rlukast, and pobilukast; the rank order potency was: pranlukast = zafirluka st > montelukast > pobilukast. LTD4-induced calcium mobilization in HEK-293 cells expressing the CysLT receptor was not affected by pertussis toxin, a nd the signal appears to be the result of the release from intracellular st ores. Localization studies indicate the expression of this receptor in Seve ral tissues, including human lung, human bronchus, and human peripheral blo od leukocytes. The discovery of this receptor, which has characteristics of the purported CysLT(1) receptor subtype, should assist in the elucidation of the pathophysiological roles of the CysLTs and in the identification of additional receptor subtypes.