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 cloned. Previous studies of neutrophils indicated that the two C-X-C chemokines, IL-8 and NAP-2, bind to IL-8rB with high affinity but that only IL-8 binds to IL-8rA with high affinity. In this study, human kidney embryonal 293 cells were transfected to express solely IL-8rA 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 specifically. 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 binding 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 [125I]NAP-2 binding, while unlabelled NAP-2 could only partially compete for [125I]IL-8 binding. Functional assays revealed that although NAP-2 is chemotactic for both IL-8rA/293 and IL-8rB/293 cells, it is less potent than IL-8. While NAP-2 induced chemotaxis of IL-8rB/293 cells at the same optimal concentrations as IL-8 (10-100 ng/ml), the induction of optimal migratory response of IL-8rA/293 cells required much higher 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 likely that tertiary structural differences between NAP-2 and IL-8 account for their divergent abilities to bind and chemoattract 293 cells transfected with either IL-8 receptor type A or type B.
Ben-Baruch
A
A
Laboratory of Molecular Immunoregulation, SAIC Frederick, National Cancer Institute-Frederick Cancer Research and Development Center, MD 21702, USA.
Bengali
K
K
Tani
K
K
Xu
L
L
Oppenheim
J J
JJ
Wang
J M
JM
D015703:Antigens, CD / Q000378:metabolism*; D001667:Binding, Competitive; D002460:Cell Line; D002633:Chemotaxis / Q000502:physiology*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D018123:Receptors, Interleukin / Q000378:metabolism*; D023062:Receptors, Interleukin-8A; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D001620:beta-Thromboglobulin
D015703:Antigens, CD; D016209:Interleukin-8; C061615:PPBP protein, human; D010455:Peptides; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D001620:beta-Thromboglobulin; C009862:connective tissue-activating peptide