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 G(i2) (G(ialpha2) associated with th e plasma membrane and a corresponding decrease in the amount associate d with the granule fractions. Similar results are obtained with interl eukin-8. GM-CSF has no effect on the distribution of G(ialpha3). The e ffect of GM-CSF on G(ialpha2) is time-dependent, and, although a signi ficant effect can be observed after incubation for 5 min with GM-CSF, the enhancement increases with increasing time. Genistein, a protein t yrosine kinase inhibitor, and ,2-bis-(O-aminophenoxyl)ethane-NNN'N'-te tra-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, a lthough preincubation of human neutrophils with GM-CSF increases the l evels of G(ialpha2) in the plasma membrane it does not alter the total amount of cellular G(ialpha2). In addition, the level of G(ialpha2) m RNA, unlike that of the proto-oncogene c-fos, is not increased in cell s treated with GM-CSF. This indicates that the observed increase in th e amount of G(ialpha2) associated with the plasma membrane is not due to the synthesis of new G(ialpha2). These data provide insight into th e mechanism by which GM-CSF may prime human neutrophils for increased responsiveness to subsequent stimulation by G-protein-dependent agonis ts.