Inhibition of interleukin 3 and colony-stimulating factor 1-stimulated marrow cell proliferation by pertussis toxin

Abstract

Pertussis toxin (PT) catalyzes the ADP-ribosylation of several guanine nucleotide-binding (G) protein that are involved in the transduction of cell surface receptor-mediated signals. Involvement of such G-proteins in regulation of hematopoiesis by two growth factors, colony-stimulating factor-1 (CSF-1) and interleukin 3 (IL 3), was investigated using pertussis toxin. Continuous or pulse exposure of murine bone marrow cells to pertussis toxin inhibited CSF-1 or IL 3-induced colony formation by ~50%. Pertussis toxin inhibition was also demonstrated against partially separated marrow from 5-fluorouracil-treated mice. The toxin effect was blocked by heating (95°C for 30 minutes), by antitoxin antibody and was not associated with increased cAMP levels in target cells. In experiments with murine marrow, toxin-mediated inhibition appeared to involve predominantly the macrophage lineage. IL 3 stimulation of proliferation of the murine marrow-derived factor-dependent cell line FDC-P1, as measured by 3H-TdR incorporation, and CSF-1 stimulation of pure populations of murine bone marrow derived macrophages, as measured by DNA content and cell number, was also inhibited. Analysis of the effects of pertussis toxin on the growth of single cells stimulated by IL 3 demonstrated that this inhibition involved a decreased growth rate rather than a toxic ablation of cells. Phorbol myristate acetate (PMA) stimulated FDC-P1 cells and was able to abrogate the PT inhibition of IL 3 stimulation of these cells, suggesting but not establishing that IL 3 may mediate its proliferative effects through activating protein kinase C.