Regulation of the expression of IL-8 receptor A/B by IL-8: possible functions of each receptor.
We investigated the regulatory mechanism of the expression of IL-8R, IL-8R type A (IL-8RA), and IL-8R type B (IL-8RB) on human neutrophils by IL-8. The expression of IL-8RA/B was analyzed by flow cytometry using mAb specific for each receptor. IL-8 down-modulated > 90% of IL-8RA and IL-8RB expression within 5 min. A related C-X-C chemokine, melamona growth stimulatory activity, down-modulated IL-8RB but not IL-8RA. It required 7 to 13 times more IL-8 to down-modulate IL-8RA than IL-8RB, as determined by the half-maximal effective concentration of IL-8. Scatchard analysis showed that the affinity of IL-8RA for IL-8 was lower than that of IL-8RB. The possible functions of each IL-8R were explored by comparing 1) the expression levels of IL-8RA/B on migrated neutrophils during in vitro chemotaxis assay and 2) the recovery rate of IL-8RA/B expression after down-modulation by IL-8. Results obtained from the in vitro chemotaxis show that the expression level of IL-8RB, but not IL-8RA, on neutrophils that migrated into the chamber containing low concentrations (< 1 nM) of IL-8 was significantly reduced compared with the control level. This suggests that IL-8RB may play as active role in the initiation of neutrophil migration distant from the site of inflammation, where the concentration of IL-8 is at the picomolar level. After down-modulation by 119 nM IL-8, the expression of IL-8RA fully recovered within 1.5 h, while the recovery rate of IL-8RB expression was slow and never reached more than 40% of the control level during a 3-h culture period. The rapid reexpression of IL-8RA suggests that the low affinity IL-8RA may play a more active role in mediating IL-8 signal at the site of inflammation, where the concentration of IL-8 is high.
Chuntharapai
A
A
Department of Bioanalytical Technology, Genentech, Inc., South San Francisco, CA 94080, USA.
Kim
K J
KJ
D000911:Antibodies, Monoclonal / Q000276:immunology; D054360:Chemokine CXCL1; D019743:Chemokines, CXC; D002630:Chemotactic Factors / Q000378:metabolism / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D005434:Flow Cytometry; D006133:Growth Substances / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8 / Q000378:metabolism / Q000494:pharmacology*; D009504:Neutrophils / Q000378:metabolism; D011485:Protein Binding; D018123:Receptors, Interleukin / Q000096:biosynthesis* / Q000187:drug effects* / Q000502:physiology; D023062:Receptors, Interleukin-8A
D000911:Antibodies, Monoclonal; C475829:CXCL1 protein, human; D054360:Chemokine CXCL1; D019743:Chemokines, CXC; D002630:Chemotactic Factors; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A