title: GM-CSF and phorbol esters modulate GM-CSF receptor expression by independent mechanisms.
abstract: Human granulocyte-macrophage colony-stimulating factor (GM-CSF) (0.1 nM) down-modulates its receptor in IL-3/GM-CSF dependent M-07e cells, in KG-1 cells and normal granulocytes, whereas phorbol esters 12-O-tetradecanoylphorbol-13-acetate (TPA) (2 nM) down-modulates the GM-CSF receptor in M-07e cells and granulocytes but not in KG-1 cells. As data analysis shows by nonlinear regression, the decreased binding ability depends on a reduction of the binding sites with no significant change of their dissociation constant. To gain insight into the mechanisms involved in the GM-CSF receptor regulation, we investigated the role of protein kinase C (PKC). GM-CSF, unlike TPA, was unable to activate PKC in all the cells studied. Moreover, unlike TPA, GM-CSF was still able to down-modulate its receptor in cells where PKC was inhibited by 1-(5-isoquinolonesulphonyl)-2-methylpiperazine (H7) and staurosporine or in cells where PKC was exhausted by prolonged incubation with 1 microM TPA. Finally, the receptor re-expression rate was accelerated by protein kinases inhibitors. These results, taken together, indicate the presence of a PKC-dependent and -independent down-modulation mechanism and a negative role of the endogeneous protein kinases in GM-CSF receptor re-expression.
authors.affiliation: Dipartimento di Scienze Biomediche e Oncologia Umana, Universitá di Torino, Italy.
authors.forename: M F
authors.initials: MF
authors.lastname: Brizzi
authors.forename: C
authors.initials: C
authors.lastname: Arduino
authors.forename: G C
authors.initials: GC
authors.lastname: Avanzi
authors.forename: F
authors.initials: F
authors.lastname: Bussolino
authors.forename: L
authors.initials: L
authors.lastname: Pegoraro
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D007546:Isoquinolines; D010703:Phorbol Esters; D010879:Piperazines; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate