FcgammaR-mediated phagocytosis by human macrophages involves Hck, Syk, and Pyk2 and is augmented by GM-CSF.
The receptors for the constant region of immunoglobulin G (FcgammaR) are widely expressed on cells of hemopoietic lineage and plays an important role in host defense. We investigated the signaling pathways during FcgammaR-mediated phagocytosis in human monocyte-derived macrophages (MDMs) and examined the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on these events. FcgammaR-mediated phagocytosis resulted in enhanced tyrosine phosphorylation of a wide range of cellular proteins and activation of tyrosine kinases Hck, Syk, and Pyk2, as well as the multidomain adapter protein paxillin. Stimulation of MDMs with GM-CSF augmented FcgammaR-mediated phagocytosis and increased the levels of tyrosine phosphorylation in phagocytosing MDM cultures, indicating tyrosine kinase-mediated activation. GM-CSF treatment of MDMs without a phagocytic stimulus did not activate Syk, suggesting that GM-CSF may act either distally to Syk in the FcgammaR-mediated signaling cascade or on a parallel pathway activated by the FcgammaR. This study shows that early signaling events during FcgammaR-mediated phagocytosis in human MDMs involve activation of Syk, Hck, and paxillin. It also provides the first evidence for Pyk2 activation during phagocytosis and a baseline for further studies on the effect of GM-CSF on FcgammaR-mediated phagocytosis.
Kedzierska
K
K
AIDS Pathogenesis Research Unit, Macfarlane Burnet Centre for Medical Research, and National Centre for HIV Virology Research, Fairfield, Australia.
Vardaxis
N J
NJ
Jaworowski
A
A
Crowe
S M
SM
D018929:Cell Culture Techniques; D004792:Enzyme Precursors / Q000378:metabolism / Q000502:physiology; D051418:Focal Adhesion Kinase 2; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008264:Macrophages / Q000166:cytology / Q000276:immunology*; D009000:Monocytes / Q000166:cytology; D010587:Phagocytosis / Q000187:drug effects*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology; D051572:Proto-Oncogene Proteins c-hck; D017452:Receptors, IgG / Q000502:physiology*; D000072377:Syk Kinase
D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D017452:Receptors, IgG; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; C496631:HCK protein, human; D051572:Proto-Oncogene Proteins c-hck; C000606896:SYK protein, human; D000072377:Syk Kinase