Tumor necrosis factor-mediated biological activities involve a G-protein-dependent mechanism.
The guanine nucleotide binding protein (G-protein) dependency of several of the activities of tumor necrosis factor (TNF), including cytotoxicity, inhibition of lipoprotein lipase activity, blockade of 3T3-L1 differentiation, and receptor binding were examined. TNF induced killing of the TNF-sensitive cell line L929S (ED50 = 30 pM), but had little to no effect on the TNF-resistant cell line L929R (ED50 = 5,300 pM). TNF-induced cytotoxicity in L929S was antagonized in a dose-dependent manner by pertussis toxin (sevenfold increase in ED50). However, TNF-induced cytotoxicity in L929R cells was only minimally affected by pretreatment with a high dose (50 ng/ml) of pertussis toxin (1.5-fold increase in ED50). Parallel biochemical investigations revealed that inhibition was accompanied by toxin-induced ADP ribosylation of a Gi alpha-like subunit in L929 and 3T3-L1 cell membranes. Pertussis toxin also significantly reduced TNF-induced inhibition of lipoprotein lipase activity in 3T3-L1 adipocytes and TNF blockade of 3T3-L1 preadipocyte differentiation. However, pertussis toxin pretreatment of L929S, L929R, and 3T3-L1 cell cultures had little to no effect on TNF receptor binding. These data indicate that several TNF-induced biological activities in the L929 and 3T3-L1 cell lines are partially dependent upon a pertussis toxin-sensitive G-protein.
Earl
C Q
CQ
Department of Clinical Investigation, Smith Kline and French Laboratories, King of Prussia, Pennsylvania 19406-0939.
Stadel
J M
JM
Anzano
M A
MA
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007739:L Cells / Q000187:drug effects; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors; D037342:Pertussis Toxin; D011485:Protein Binding / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D010566:Virulence Factors, Bordetella
D011956:Receptors, Cell Surface; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D008071:Lipoprotein Lipase; D019204:GTP-Binding Proteins