IFN-gamma enhances expression of formyl peptide receptors and guanine nucleotide-binding proteins by HL-60 granulocytes.
Exposure to IFN-gamma increases the respiratory burst of polymorphonuclear leukocytes stimulated by the chemoattractant FMLP. However, the mechanism by which IFN-gamma alters the response to FMLP is unclear. We addressed the hypothesis that IFN-gamma enhances the response to FMLP by regulating the expression of elements of the formyl peptide receptor transmembrane-signaling pathway. HL-60 granulocytes were used as a model of FMLP transmembrane signaling. Formyl peptide receptor number and affinity were studied in isolated plasma membranes prepared from control HL-60 cells (CM) and cells exposed to IFN-gamma 100 U/ml for 24 h (IFN-M). Formyl peptide receptors were significantly increased on IFN-M compared with CM (1473 +/- 300 vs 3209 +/- 924). FMLP stimulates increased guanine nucleotide-binding protein (G protein) activation in IFN-M as evidenced by enhanced guanosine 5'-[gamma-thio]triphosphate binding and GTPase activity. Gi sub-unit content was increased in IFN-M as measured by pertussis toxin-catalyzed ADP-ribosylation and immunoblotting with antibodies against alpha i2 and alpha i3 G protein subunits. Guanosine 5'-[gamma-thio]triphosphate equilibrium binding demonstrated an increased number of G proteins coupled to formyl peptide receptors on IFN-M. We conclude that IFN-gamma increases expression of both formyl peptide receptors and G proteins coupled to these receptors, thereby enhancing FMLP-stimulated transmembrane signaling. Regulation of transmembrane signaling element expression may be a significant mechanism by which IFN-gamma regulates cellular functions.
Klein
J B
JB
Department of Medicine, University of Louisville Health Sciences Center, KY 40292.
Scherzer
J A
JA
McLeish
K R
KR
D002454:Cell Differentiation; D019204:GTP-Binding Proteins / Q000032:analysis*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism / Q000473:pathology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism* / Q000494:pharmacology; D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic / Q000032:analysis*; D014407:Tumor Cells, Cultured
D044042:Receptors, Formyl Peptide; D011971:Receptors, Immunologic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009240:N-Formylmethionine Leucyl-Phenylalanine; D007371:Interferon-gamma; D019204:GTP-Binding Proteins