Localization of G-proteins in macrophages and E. coli during phagocytosis.
Heterotrimeric GTP-binding proteins (G-proteins) have been shown to play an important role in cellular signalling. However, G-protein involvement in the intracellular spreading of bacterial pathogens is still poorly understood. In this study, antibodies, that recognize G-protein alpha-subunits (anti-G alpha), were used to investigate the localization of G-proteins in the macrophage-like cell line P388D1 and E. coli, also in their L-forms, during phagocytosis. In E. coli, anti-G alpha-binding sites were detected preferably in the cell wall and septa of the whole bacterial forms as well as in the cytoplasm of L-forms. Western blotting of bacterial lysates demonstrated protein bands with positive immunoreaction to antibodies against Gs alpha, Gi alpha, and Gcommon alpha with a higher affinity to the antibody against Gs alpha. Immunoreaction with the anti-Gs alpha-antibody was markedly higher in pathogenic strains of E. coli. Because of the conserved structure in all GTP-binding proteins which seem to derive from a single primordial protein involved in signal transduction mechanisms, it is reasonable to assume that some anti-Ga-positive proteins in E. coli might be related to G-proteins of higher organisms. A putative candidate for bacterial G-proteins seems to be a 36 kDa protein. Enhancement in G-protein immunostaining in the cytoplasm of macrophages around the internalized bacteria testifies to the involvement of G-proteins in mediation of endocytosis responses of phagocytes.
Didenko
L W
LW
Gamaleya Institute for Epidemiology and Microbiology, Moscow, Russia.
Buchwalow
I B
IB
Schulze
W
W
Augsten
K
K
Susa
M
M
Unger
E
E
D000818:Animals; D000906:Antibodies / Q000032:analysis; D015153:Blotting, Western; D004926:Escherichia coli / Q000276:immunology / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000032:analysis* / Q000648:ultrastructure; D008264:Macrophages / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D010587:Phagocytosis / Q000502:physiology*; D015398:Signal Transduction
D000906:Antibodies; D019204:GTP-Binding Proteins