Diverging Signal Transduction Pathways Activated by Interleukin 8 (IL-8) and Related Chemokines in Human Neutrophils: IL-8 AND Gro-α DIFFERENTIALLY STIMULATE CALCIUM INFLUX THROUGH IL-8 RECEPTORS A AND B

Bassam B Damaj,Shaun R Mccoll,Kuldeep Neote,Caroline A Hébert,Paul H Naccache

doi:10.1074/jbc.271.34.20540

Bassam B Damaj, Shaun R Mccoll + Show 3 more

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https://doi.org/10.1074/jbc.271.34.20540

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Abstract

Interleukin 8 (IL-8) and Gro-alpha are members of the CXC branch of a family of cytokines recently designated the "chemokine" superfamily. Recent evidence indicates that, contrary to previously held beliefs, IL-8 and Gro-alpha may not be perceived equivalently by neutrophils. In this study, we have evaluated the effects of IL-8 and Gro-alpha on the rate of calcium influx in human neutrophils and in 293 cells transfected with type A or type B IL-8 receptors. Of these two chemokines, only Gro-alpha induced an influx of calcium in neutrophils as judged by the sensitivity of the mobilization of calcium to the extracellular calcium chelator EGTA and to the nonselective divalent cation channel inhibitor SK&F 96365, as well as by manganese quenching experiments. IL-8 was similarly without effect on the rate of Mn2+ influx in 293 cells transfected with IL-8 receptor A (IL-8RA) or IL-8RB. On the other hand, Gro-alpha induced an SK&F 96365-sensitive increase of the rate of Mn+2 influx in IL-8RB-, but not in IL-8RA-transfected 293 cells. These results indicate not only that neutrophils respond differently to IL-8 than they do to Gro-alpha but, furthermore, that the consequences of the binding of IL-8 and Gro-alpha to IL-8RB are distinct.

Highlights

Interleukin 8 (IL-8) and Gro-␣ are members of the CXC branch of a family of cytokines recently designated the “chemokine” superfamily
No significant qualitative or quantitative differences were seen in the calcium signals induced by IL-8 at concentrations ranging from 10Ϫ7 to 10Ϫ5 M or by IL-8 added first or after the Gro-␣ signal had returned to base line, i.e. at a time when most, if not all, IL-8RB was still occupied by Gro-␣ (as evidenced by a lack of response to a second addition of Gro-␣)
The present study was undertaken to examine the signal transduction pathways activated in human neutrophils and IL-8R-transfected 293 cells upon the activation of each of the two IL-8 receptor subtypes

Summary

Introduction

Interleukin 8 (IL-8) and Gro-␣ are members of the CXC branch of a family of cytokines recently designated the “chemokine” superfamily. We have evaluated the effects of IL-8 and Gro-␣ on the rate of calcium influx in human neutrophils and in 293 cells transfected with type A or type B IL-8 receptors. Of these two chemokines, only Gro-␣ induced an influx of calcium in neutrophils as judged by the sensitivity of the mobilization of calcium to the extracellular calcium chelator EGTA and to the nonselective divalent cation channel inhibitor SK&F 96365, as well as by manganese quenching experiments. Gro-␣ induced an SK&F 96365sensitive increase of the rate of Mn؉2 influx in IL-8RB-, but not in IL-8RA-transfected 293 cells These results indicate that neutrophils respond differently to IL-8 than they do to Gro-␣ but, that the consequences of the binding of IL-8 and Gro-␣ to IL-8RB are distinct. A functional linkage between IL-8R and phospholipase C has been observed upon the co-transfection of the receptors and the ␣-subunit of Gq-like G proteins [11], and most, if not all, IL-8-induced neutrophil responses are sensitive to inhibition by pertussis toxin [13]

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