Cross-desensitization among CXCR1, CXCR2, and CCR5: role of protein kinase C-epsilon.
The IL-8 (or CXCL8) chemokine receptors, CXCR1 and CXCR2, activate protein kinase C (PKC) to mediate leukocyte functions. To investigate the roles of different PKC isoforms in CXCL8 receptor activation and regulation, human mononuclear phagocytes were treated with CXCL8 or CXCL1 (melanoma growth-stimulating activity), which is specific for CXCR2. Plasma membrane association was used as a measure of PKC activation. Both receptors induced time-dependent association of PKCalpha, -beta1, and -beta2 to the membrane, but only CXCR1 activated PKCepsilon. CXCL8 also failed to activate PKCepsilon in RBL-2H3 cells stably expressing CXCR2. DeltaCXCR2, a cytoplasmic tail deletion mutant of CXCR2 that is resistant to internalization, activated PKCepsilon as well as CXCR1. Expression of the PKCepsilon inhibitor peptide epsilonV1 in RBL-2H3 cells blocked PKCepsilon translocation and inhibited receptor-mediated exocytosis, but not phosphoinositide hydrolysis or peak intracellular Ca(2+) mobilization. epsilonV1 also inhibited CXCR1-, CCR5-, and DeltaCXCR2-mediated cross-regulatory signals for GTPase activity, Ca(2+) mobilization, and internalization. Peritoneal macrophages from PKCepsilon-deficient mice (PKCepsilon(-/-)) also showed decreased CCR5-mediated cross-desensitization of G protein activation and Ca(2+) mobilization. Taken together, the results indicate that CXCR1 and CCR5 activate PKCepsilon to mediate cross-inhibitory signals. Inhibition or deletion of PKCepsilon decreases receptor-induced exocytosis and cross-regulatory signals, but not phosphoinositide hydrolysis or peak intracellular Ca(2+) mobilization, suggesting that cross-regulation is a Ca(2+)-independent process. Because DeltaCXCR2, but not CXCR2, activates PKCepsilon and cross-desensitizes CCR5, the data further suggest that signal duration leading to activation of novel PKC may modulate receptor-mediated cross-inhibitory signals.
Nasser
Mohd W
MW
Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, 27707, USA.
Marjoram
Robin J
RJ
Brown
Stephan L
SL
Richardson
Ricardo M
RM
D000818:Animals; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D004705:Endocytosis / Q000235:genetics / Q000276:immunology; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D005822:Genetic Vectors; D006801:Humans; D007527:Isoenzymes / Q000172:deficiency / Q000378:metabolism / Q000502:physiology; D017737:Macrophages, Peritoneal / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011493:Protein Kinase C / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051744:Protein Kinase C-epsilon; D051381:Rats; D019713:Receptors, CCR5 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D023062:Receptors, Interleukin-8A / Q000378:metabolism / Q000502:physiology*; D023063:Receptors, Interleukin-8B / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
D007527:Isoenzymes; D019713:Receptors, CCR5; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B; C497256:Prkce protein, mouse; C497257:Prkce protein, rat; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon