Figure 5. Constitutively active mutants of CXCR1.

(A) Basal and IL-8-stimulated inositol phosphate (IP) accumulation in COS-7 cells transiently co-transfected with WT or mutant CXCR1 and Gα₁₅. IP production was determined in detail as described under “Materials and Methods”. Data are mean ± SEM of replicate wells from a representative experiments performed in triplicate. **, P<0.01, vs. WT+ Gα₁₅ (in the absence of IL-8). (B) Calcium signaling capacity in COS-7 cells transfected with CXCR1 WT and V247N mutant. The increase in intracellular calcium concentration ([Ca²⁺]_i) in COS-7 cells transfected with Gα₁₅ and CXCR1 WT or V247N mutant was measured using BD calcium assay kit. The cells were stimulated with or without IL-8 (40 nM). Values represent the mean (± the SEM) increase of [Ca²⁺]_i (n = 4). **, P<0.01, vs. WT+ Gα₁₅ (in the absence of IL-8).