Priming effects of granulocyte-macrophage colony-stimulating factor are coupled to cholera toxin-sensitive guanine nucleotide binding protein in human T lymphocytes.
In addition to the mobilization of neutrophils and monocytes, granulocyte-macrophage colony-stimulating factor (GM-CSF) also mobilizes lymphocytes into peripheral blood. We examined the ability of GM-CSF to induce the proliferation of purified human T cells (CD3+ CD4+ CD56- CD16- B1- MO2-) in two major aspects: (1) the mechanisms of GM-CSF interaction with interleukin-2 (IL-2) causing T-cell proliferation, and (2) the intracellular signals transmitted by GM-CSF in T lymphocytes. We observed that concentrations of GM-CSF between 0.01 ng/mL and 10 ng/mL had a synergistic effect with concentrations of IL-2 between 1 U/mL and 10 U/mL in stimulating T-cell proliferation. This effect of GM-CSF was maximal when it was added at the start of the culture. In situ hybridization showed the presence of mRNA for GM-CSF receptors in T cells. Further analysis showed that GM-CSF induced the expression of IL-2 receptor (IL-2R) on the surface of T lymphocytes. These events coincide with the ability of GM-CSF to increase the intracellular levels of both cyclic 3',5'-adenosine monophosphate (cAMP) and cyclic 3',5'-guanosine monophosphate (cGMP) in T cells, to increase the binding of (gamma-35S) GTP to T-cell membranes, and to enhance GTPase activity as determined by increased hydrolysis of 32P-GTP. IL-2 also induced IL-2R expression, cyclic nucleotide secretion, and G-protein activation. However, the presence of IL-2 reduced GM-CSF induction of these activities. Addition of antibodies to the alpha and beta subunits of IL-2R permitted the activation of G protein by GM-CSF even when IL-2 was present. Furthermore, GTP binding and GTPase activity induced by GM-CSF or IL-2 were inhibited by the addition of cholera toxin (CT), but not pertussis toxin (PT). Cumulatively, these results suggest that in T lymphocytes, receptors for GM-CSF or IL-2 may be coupled to the same CT-sensitive G protein, although other possibilities may exist. The role that G proteins play in mediating the intracellular signaling pathways induced by GM-CSF or IL-2 in human T cells is supported by adenosine diphosphate-ribosylation of a 44-kD or a 39-kD G protein in T-cell membranes by CT and PT, respectively.
al-Aoukaty
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Northeastern Ontario Regional Cancer Centre, Sudbury, Ontario, Canada.
Giaid
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Sinoff
C
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Ho
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AD
Maghazachi
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AA
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002772:Cholera Toxin / Q000494:pharmacology; D004357:Drug Synergism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D015870:Gene Expression; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000008:administration & dosage*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D016130:Immunophenotyping; D007376:Interleukin-2 / Q000008:administration & dosage; D008213:Lymphocyte Activation / Q000187:drug effects*; D009712:Nucleotides, Cyclic / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*
D007376:Interleukin-2; D009712:Nucleotides, Cyclic; D012333:RNA, Messenger; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D015375:Receptors, Interleukin-2; D000246:Adenosine Diphosphate Ribose; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins