Inhibition of Granulocyte-Macrophage Colony-Stimulating Factor Signaling and Microglial Proliferation by Anti-CD45RO: Role of Hck Tyrosine Kinase and Phosphatidylinositol 3-Kinase/Akt

• Published in: The Journal of immunology (1950) Vol. 174; no. 5; pp. 2712 - 2719
• Main Authors: Suh, Hyeon-Sook, Kim, Mee-Ohk, Lee, Sunhee C
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.03.2005
• Subjects: Binding Sites, Antibody; Cell Proliferation; Cells, Cultured; Granulocyte-Macrophage Colony-Stimulating Factor - antagonists & inhibitors; Granulocyte-Macrophage Colony-Stimulating Factor - physiology; Growth Inhibitors - antagonists & inhibitors; Growth Inhibitors - pharmacology; Humans; Immune Sera - metabolism; Immune Sera - pharmacology; Leukocyte Common Antigens - immunology; Leukocyte Common Antigens - metabolism; Microglia - cytology; Microglia - enzymology; Microglia - immunology; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Phosphatidylinositol 3-Kinases - physiology; Phosphorylation; Protein Kinase Inhibitors - pharmacology; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - metabolism; Protein-Serine-Threonine Kinases - physiology; Protein-Tyrosine Kinases - antagonists & inhibitors; Protein-Tyrosine Kinases - metabolism; Protein-Tyrosine Kinases - physiology; Proto-Oncogene Proteins - antagonists & inhibitors; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins - physiology; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-hck; Signal Transduction - drug effects; Signal Transduction - immunology; Solubility; U937 Cells
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.174.5.2712

Increasing evidence suggests that CD45, a transmembrane protein tyrosine phosphatase, is an important modulator of macrophage activation. Microglia, resident brain macrophages, express CD45 and proliferate under pathologic conditions. In this study, we examined the role of CD45 in modulating GM-CSF-induced proliferation and signal transduction in primary human microglial cultures. Soluble, but not immobilized anti-CD45RO induced tyrosine phosphatase activity and inhibited GM-CSF-induced microglial proliferation. Microglial proliferation was also inhibited by PP2 (Src inhibitor), LY294002 (PI3K inhibitor), and U0126 (MEK inhibitor). GM-CSF induced phosphorylation of Jak2, Stat5, Hck (the myeloid-restricted Src kinase), Akt, Stat3, and Erk MAPKs in microglia. Of these, anti-CD45RO inhibited phosphorylation of Hck and Akt, and PP2 inhibited phosphorylation of Hck and Akt. In a macrophage cell line stably overexpressing wild-type or kinase-inactive Hck, GM-CSF increased proliferation of the control (empty vector) and wild-type but not kinase-inactive cells, and this was inhibited by anti-CD45RO. Together, these results demonstrate that, in macrophages, Hck tyrosine kinase is activated by GM-CSF, and that Hck plays a pivotal role in cell proliferation and survival by activating the PI3K/Akt pathway. Ab-mediated activation of macrophage and microglial CD45 tyrosine phosphatase may have therapeutic implications for CNS inflammatory diseases.