Roles of protein kinase C and G proteins in activation of murine resting B lymphocytes by endotoxin-associated protein.
Endotoxin-associated protein (EP) from the outer membrane of gram-negative bacteria is a potent immunomodulator. To examine the mechanism of EP stimulation, the protein kinase C inhibitors H7 and staurosporine were used. Both DNA and RNA synthesis of EP-stimulated murine resting B cells were completely inhibited when inhibitors were added at 0 h, whereas 55 to 76% inhibition of DNA synthesis was observed when H7 was added after 12 h of stimulation. In contrast, HA 1004, which blocks protein kinase A and protein kinase G activity, was relatively ineffective even at high concentrations, suggesting that the activity of protein kinase C is a primary mechanism of EP-induced murine B-cell proliferation. To examine the role of G proteins in EP-induced DNA synthesis in B cells, the effects of pertussis toxin (PT), which inactivates certain G proteins, and the B oligomer of PT (PTB), which does not, were also examined. PT was found to inhibit EP-induced DNA synthesis in a dose-dependent manner. However, PTB also caused equivalent inhibition, suggesting that PTB may be responsible for most of the inhibitory effect seen with the holotoxin. These results serve to question whether G proteins are involved in the signal transduction that occurs during EP-induced DNA synthesis in murine B cells.
Bandekar
J R
JR
Department of Microbiology and Immunology, State University of New York, Brooklyn 11203.
Castagna
R
R
Sultzer
B M
BM
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001426:Bacterial Proteins / Q000494:pharmacology*; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000494:pharmacology*; D005260:Female; D019204:GTP-Binding Proteins / Q000276:immunology*; D007546:Isoquinolines / Q000494:pharmacology; D008050:Lipid A / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D037342:Pertussis Toxin; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000276:immunology*; D047428:Protein Kinase Inhibitors; D012313:RNA / Q000096:biosynthesis; D019311:Staurosporine; D013449:Sulfonamides; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000470:Alkaloids; D001426:Bacterial Proteins; D004731:Endotoxins; D007546:Isoquinolines; D008050:Lipid A; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D010566:Virulence Factors, Bordetella; C027315:lipid A-associated protein, Bacteria; D012313:RNA; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; C043204:N-(2-guanidinoethyl)-5-isoquinolinesulfonamide; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D019311:Staurosporine