The CXC chemokines growth-regulated oncogene (GRO) alpha, GRO beta, GRO gamma, neutrophil-activating peptide-2, and epithelial cell-derived neutrophil-activating peptide-78 are potent agonists for the type B, but not the type A, human interleukin-8 receptor

Interleukin-8 (IL-8), growth-related oncogene (GRO) alpha, GRO beta, GRO gamma, neutrophil-activating peptide-2 (NAP-2), epithelial cell-derived neutrophil activating peptide-78 (ENA-78), and granulocyte chemoattractant protein-2 are potent neutrophil chemoattractants 40-90% identical in amino acid sequence that comprise a subgroup of human CXC chemokines defined by the conserved sequence motif glutamic acid-leucine-arginine (ELR). Two human chemotactic receptor subtypes for IL-8, named IL-8 receptors (IL8R) A and B, have been cloned. They are 78% identical in amino acid sequence, coexpressed in neutrophils, and distinguished by their different se selectivities for GRO alpha and NAP-2. Their selectivity for other ELR(+) CXC chemokines has not been previously reported. By measuring calcium flux in human embryonic kidney 293 cells transfected with plasmids encoding IL8RA or IL8RB, we have now defined receptor selectivity for GRO beta, GRO gamma, and ENA-78. The rank order of agonist potency, based on inspection of the mean effective concentration values (EC(50)), for IL8RB was GRO gamma (1 nM) > IL-8 (4 nM) similar to GRO alpha (5 nM) similar to GRO beta (4 nM) similar to NAP-2 (7 nM) > ENA-78 (11 nM), and for IL8RA was IL-8 (4 nM) >>> ENA-78 (40 nM) similar to NAP-2 (45 nM) > GRO alpha (63 nM) similar to GRO gamma (65 nM) >> GRO beta. The maximal response of IL8RA to IL-8 was at least a-fold greater than the other five chemokines. All six agonists for IL8RB competed for high affinity I-125-IL-8, -GRO alpha NAP-2, and -ENA-78 binding sites at IL8RB. GRO alpha, GRO beta, GP gamma, NAP-2, and ENA-78 competed weakly for the high affinity IL-8 binding site at IL8RA. Thus, IL8RA and IL8RB are both highly selective for IL-8 and have similar sequences but differ dramatically in their selectivity for all other ELR(+) CXC chemokines tested. These findings have important implications for developing novel neutrophil-specific anti-inflammatory drugs directed against the CXC chemokine signaling system.