Involvement of FAK/Src complex in the processes of Escherichia coli phagocytosis by insect hemocytes.
Recently we demonstrated that lipopolysaccharide promotes activation of the Ras/mitogen-activated protein cascade in hemocytes and that phagocytosis of Escherichia coli by insect hemocytes is mediated by an integrin-dependent process [Foukas et al. (1998) J. Biol. Chem. 273, 14813--14818]. Here we report data concerning the focal adhesion kinase (FAK) tyrosine phosphorylation status in hemocytes in response to E. coli. We demonstrate that E. coli-triggering stimulates a significant increase in tyrosine phosphorylation of FAK in hemocytes. Furthermore, immunoblotting analysis using anti-Y397 demonstrated intense FAK activity at the Y397/SH2-binding site in hemocytes treated with E. coli. In addition, antibody-mediated inhibition of FAK and Src-kinase has been shown to abolish FAK phosphorylation and E. coli phagocytosis, indicating a specific role for the FAK/Src complex in the processes of promoting cell phagocytosis. These findings expand the known signaling functions of FAK and provide insight into signal transduction events associated with hemocyte phagocytosis in response to E. coli.
Metheniti
A
A
Department of Biology, University of Patras, Patras 265 00, Greece.
Paraskevopoulou
N
N
Lambropoulou
M
M
Marmaras
V J
VJ
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002474:Cell-Free System; D002478:Cells, Cultured; D004175:Diptera; D004331:Drosophila melanogaster; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000276:immunology*; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006434:Hemocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015151:Immunoblotting; D046911:Macromolecular Substances; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains / Q000502:physiology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000906:Antibodies; D046911:Macromolecular Substances; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019061:src-Family Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases