Role of Src kinases and Syk in Fcγ receptor-mediated phagocytosis and phagosome-lysosome fusion

• Published in: Journal of leukocyte biology Vol. 70; no. 5; pp. 801 - 811
• Main Authors: Majeed, Meytham, Caveggion, Elena, Lowell, Clifford A., Berton, Giorgio
• Format: Journal Article
• Language: English
• Published: Society for Leukocyte Biology 01-11-2001
• Subjects: AFc receptors; Fyn; immune receptors; protein tyrosine phosphorylation; signal transduction; Src protein; Syk protein; Yes
• ISSN: 0741-5400; 1938-3673
• DOI: 10.1189/jlb.70.5.801

Phagocytosis is increased by Fcγ receptors (FcγRs), and studies with syk−/− macrophages demonstrated that Syk kinase is required for FcγR phagocytosis. Similar studies with macrophages lacking the Src family kinases Hck, Fgr, and Lyn showed that these kinases are not required for phagocytosis but that they enhance the rate of particle engulfment. In this report we show that both wild‐type and hck−/−fgr−/− macrophages expressed Fyn, Src, and Yes and that these kinases were activated on ingestion of immunoglobulin G (IgG)‐coated particles and redistributed, together with Syk, to actin‐rich phagocytic cups and the phagosomal membrane. At doses blocking IgG‐dependent phagocytosis, the tyrosine kinase inhibitors PP1 and piceatannol inhibited both Src family kinase and Syk activities, as well as their redistribution to actin‐rich phagocytic cups. Hck, Fgr, and Lyn were dispensable for lysosome‐phagosome fusion (PLF) induced by IgG‐coated particles. However, PP1 or piceatannol hampered unopsonized yeast‐induced PLF despite the fact that they did not block yeast internalization.