Granulocyte-macrophage colony-stimulating factor is a chemoattractant cytokine for human neutrophils: involvement of the ribosomal p70 S6 kinase signaling pathway.
GM-CSF stimulates proliferation of myeloid precursors in bone marrow and primes mature leukocytes for enhanced functionality. We demonstrate that GM-CSF is a powerful chemotactic and chemokinetic agent for human neutrophils. GM-CSF-induced chemotaxis is time dependent and is specifically neutralized with Abs directed to either the ligand itself or its receptor. Maximal chemotactic response was achieved at approximately 7 nM GM-CSF, and the EC(50) was approximately 0.9 nM. Both concentrations are similar to the effective concentrations of IL-8 and less than the effective concentrations of other neutrophil chemoattractants such as neutrophil-activating peptide-78, granulocyte chemotactic protein-2, leukotriene B(4), and FMLP. GM-CSF also acts as a chemoattractant for native cells bearing the GM-CSF receptor, such as monocytes, as well as for GM-CSF receptor-bearing myeloid cell lines, HL60 (promyelomonocyte leukemic cell line) and MPD (myeloproliferative disorder cell line), following differentiation induction. GM-CSF induced a rapid, transient increase in F-actin polymerization and the formation of focal contact rings in neutrophils, which are prerequisites for cell migration. The mechanism of GM-CSF-induced chemotaxis appears to involve the cell signaling molecule, ribosomal p70 S6 kinase (p70S6K). Both p70S6K enzymatic activity and T(421)/S(424) and T(389) phosphorylation are markedly increased with GM-CSF. In addition, the p70S6K inhibitor hamartin transduced into cells as active protein, interfered with GM-CSF-dependent migration, and attenuated p70S6K phosphorylation. These data indicate that GM-CSF exhibits chemotactic functionality and suggest new avenues for the investigation of the molecular basis of chemotaxis as it relates to inflammation and tissue injury.
Gomez-Cambronero
Julian
J
Department of Physiology and Biophysics, Wright State University, Dayton, OH 45435, USA. julian.cambronero@wright.edu
Horn
Jeffrey
J
Paul
Cassandra C
CC
Baumann
Michael A
MA
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002464:Cell Migration Inhibition; D002630:Chemotactic Factors / Q000502:physiology*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000502:physiology*; D018922:HL-60 Cells; D006801:Humans; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D000199:Actins; D002630:Chemotactic Factors; D004791:Enzyme Inhibitors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D038762:Ribosomal Protein S6 Kinases, 70-kDa