Transforming G protein-coupled receptors block insulin and ras-induced adipocytic differentiation in 3T3-L1 cells: evidence for a PKC and MAP kinase independent pathway.
We have used the expression of muscarinic m1 receptors in the preadipocytic 3T3-L1 cell line for dissecting the nature of the G protein-linked pathways governing adipocytic differentiation, a complex process controlled by many stimuli and their downstream targets. 3T3-L1 cells can be differentiated by insulin or by ras oncogenes, and MAP kinase has been implicated in this process. However, m1 stimulation failed to induce differentiation of 3T3-L1 cells. Furthermore, it prevented insulin or v-ras-induced adipocytic differentiation, utilizing a protein kinase C-independent pathway. m1 stimulation did not alter the phosphorylation state of the insulin receptor substrates IRS-1 and SHC, nor the recruitment of Grb-2. Interestingly, whereas m1 receptors potently activated MAP kinase, another differentiation-inhibitor, TNF alpha, did not affect it. These results suggest that the control of adipocytic differentiation can occur utilizing a biochemical route independent of protein kinase C, and acting downstream, or independently from the Ras-MAP kinase pathway.
Crespo
P
P
Molecular Signaling Unit, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892, USA. crespop@medi.unican.es
Font de Mora
J
J
Aaronson
D S
DS
Santos
E
E
Gutkind
J S
JS
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology*; D051380:GRB2 Adaptor Protein; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006651:Histocytochemistry; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction / Q000502:physiology; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D018631:ras Proteins / Q000494:pharmacology*
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D007211:Indoles; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D008301:Maleimides; D010750:Phosphoproteins; D011506:Proteins; D011976:Receptors, Muscarinic; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014409:Tumor Necrosis Factor-alpha; D002217:Carbachol; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D018631:ras Proteins; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate