Lack of uracil nucleotide– and cysteinyl leukotriene–promoted accumulation of inositol phosphates in 1321N1 or CHO cells stably expressing GPR17. UDP, UDP-glucose (UDP-Glu), UDP-galactose (UDP-Gal) (all at 100 μM), or LTC4 (100 nM) failed to promote significant accumulation of inositol phosphates in (A) 1321N1 or (B) CHO cells stably expressing GPR17 compared with cells expressing the empty vector. (C) Cell surface expression of HA-tagged GPR17 was verified by an intact cell RIA. Data shown are from a representative assay performed three times with similar results. Ab, antibody; cpm, counts per minute; WT, wild type.