IL-8 AND NAP-2 DIFFER IN THEIR CAPACITIES TO BIND AND CHEMOATTRACT 293 CELLS TRANSFECTED WITH EITHER IL-8 RECEPTOR TYPE-A OR TYPE-B

Two receptors for interleukin 8 (IL-8), IL-8rA and IL-8rB, have been c loned, Previous studies of neutrophils indicated that the two C-X-C ch emokines; IL-8 and NAP-2, bind to IL-8rB with high affinity but that o nly IL-8 binds to IL-8rA with high affinity, In this study, human kidn ey embryonal 293 cells were transfected to express solely IL8rA or IL- 8rB (the cells are designated IL-8rA/293 and IL-8rB/293, respectively) , The authors show that NAP-2 bound both IL-8rA and IL-9rB specificall y, While NAP-2 and IL-8 bound IL-8rB with comparable high affinity (2. 9 +/- 0.5 and 2.8 +/- 0.8 nM, respectively), NAP-2 showed a lower bind ing affinity to IL-8rA (9 +/- 2 nM) compared with IL-8 (1.3 +/- 0.5 nM ), A lower number of binding sites was detected for NAP-2 than for IL- 8 on IL-8rA/293 cells as well on IL-8rB/293 cells, On both cell types (IL-8rA/293 and IL-8rb/293), NAP-2 and IL-8 could completely inhibit [ I-125]NAP-2 binding, while unlabelled NAP-2 could only partially compe te for [I-125]IL-8 binding. Functional assays revealed that although N AP-2 is chemotactic for both IL-8rA/293 and IL-8rB/293 cells, it is le ss potent than IL-8. While NAP-2 induced chemotaxis of IL-8rB/293 cell s at the same optimal concentrations as IL-8 (10-100 ng/ml), the induc tion of optimal migratory response of IL-8rA/293 cells required much h igher concentrations of NAP-2 than IL-8 (1000-3000 ng/ml and 10-100 ng /ml, respectively). The dose-response curve of the IL-8rB/293 cells to IL-8 was bell shaped, while the response to NAP-2 was sustained at a plateau level even at concentrations as high as 3000 ng/ml, It is like ly that tertiary structural differences bet,peen NAP-2 and IL-8 accoun t for their divergent abilities to bind and chemoattract 293 cells tra nsfected with either IL-8 receptor type A or type B. (C) 1997 Academic Press Limited.