Up-regulation of the amount of Gi alpha 2 associated with the plasma membrane in human neutrophils stimulated by granulocyte-macrophage colony-stimulating factor.
Preincubation of human neutrophils with the human cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) results in an increase in the amount of alpha-subunit of Gi2 (Gi alpha 2) associated with the plasma membrane and a corresponding decrease in the amount associated with the granule fractions. Similar results are obtained with interleukin-8. GM-CSF has no effect on the distribution of Gi alpha 3. The effect of GM-CSF on Gi alpha 2 is time-dependent, and, although a significant effect can be observed after incubation for 5 min with GM-CSF, the enhancement increases with increasing time. Genistein, a protein tyrosine kinase inhibitor, and 1,2-bis-(O-aminophenoxyl)ethane-NNN'N'-tetra-acetic acid (BAPTA), an intracellular Ca2+ chelator, decrease the stimulatory effect of GM-CSF. On the other hand, the protein-synthesis inhibitor cycloheximide does not affect the action of GM-CSF. Also, although preincubation of human neutrophils with GM-CSF increases the levels of Gi alpha 2 in the plasma membrane it does not alter the total amount of cellular Gi alpha 2. In addition, the level of Gi alpha 2 mRNA, unlike that of the proto-oncogene c-fos, is not increased in cells treated with GM-CSF. This indicates that the observed increase in the amount of Gi alpha 2 associated with the plasma membrane is not due to the synthesis of new Gi alpha 2. These data provide insight into the mechanism by which GM-CSF may prime human neutrophils for increased responsiveness to subsequent stimulation by G-protein-dependent agonists.
Department of Physiology, University of Connecticut Health Center, Farmington 06030.
M
M
Durstin
S R
SR
McColl
J
J
Gomez-Cambronero
P H
PH
Naccache
R I
RI
Sha'afi
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger / Q000378:metabolism; D015854:Up-Regulation
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019204:GTP-Binding Proteins