The growth factor-like effects of tumor necrosis factor-alpha. Stimulation of glucose transport activity and induction of glucose transporter and immediate early gene expression in 3T3-L1 preadipocytes.
In the present study, the ability of tumor necrosis factor-alpha (TNF) to stimulate hexose transport in quiescent 3T3-L1 fibroblasts has been examined. Activation of transport occurred in a dose- and time-dependent manner, with maximal stimulation (6-8-fold) observed 16 h after exposure to 2.5 nM TNF. Early activation of hexose transport by TNF (2-fold within 30 min) was associated with increased plasma membrane immunoreactive glucose transporters. Prolonged exposure to TNF (16 h) resulted in a 2-fold increase in glucose transporter content of both plasma and inner membrane compartments. The magnitude of increased glucose transport (6-8-fold) was greater than the increased content of plasma membrane glucose transporters (2-fold), suggesting that the TNF-treatment altered the intrinsic activity of the glucose transporters. Increased transcription of the glucose transporter (GLUT-1) gene, as well as several immediate-early genes (c-fos, c-jun, jun-B, and beta-actin) was observed within 15 min of exposure to TNF. Transcriptional activation of immediate-early genes was tightly coupled to subsequent accumulation of their respective mRNAs. However, increased GLUT-1 mRNA (8 h after TNF treatment) was due to an apparent 3-fold increase in the stability of this message and not to increased transcription. The time course of TNF-induced hexose transport occurred concomitant with a 6-fold increase in total RNA synthesis which preceded a 3-fold increase in protein synthesis. Moreover, TNF induced cell-cycle progression through S-phase, as measured by aphidicolin-sensitive thymidine uptake. Phorbol myristate acetate also stimulated hexose transport as well as expression of the GLUT-1 gene and several immediate-early genes in quiescent 3T3-L1 cells. TNF-induced immediate-early gene expression was intact in PMA-pretreated cells (with the exception of GLUT-1 and beta-actin genes where the response was muted), suggesting the involvement of multiple pathways in TNF signal transduction. Our results indicate that TNF initiates mitogenic events in quiescent 3T3-L1 fibroblasts reminiscent of serum-derived growth factors.
Department of Biochemistry, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
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P
Cornelius
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M
Marlowe
M D
MD
Lee
P H
PH
Pekala
D000255:Adenosine Triphosphate / Q000378:metabolism; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D015342:DNA Probes; D003847:Deoxyglucose / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects*; D006133:Growth Substances; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014529:Uridine / Q000378:metabolism
D015342:DNA Probes; D006133:Growth Substances; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D012313:RNA; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D007930:Leucine; D013755:Tetradecanoylphorbol Acetate; D013936:Thymidine; D014529:Uridine