Insulin and platelet-derived growth factor acutely stimulate glucose transport in 3T3-L1 fibroblasts independently of protein kinase C.
Insulin and platelet-derived growth factor (PDGF) are mitogenic for murine 3T3-L1 fibroblasts. Both these mitogens acutely stimulate glucose transport by 2-4-fold in these cells, evident within minutes of agonist exposure. The tumour promoter and protein kinase C activator, phorbol 12-myristate 13-acetate (PMA) also stimulates glucose transport by 2-3-fold over a similar time frame, suggesting that protein kinase C may be involved in the mitogenic action of insulin and PDGF in this cell line. In an attempt to address this, we have measured intracellular sn-1,2-diacylglycerol (DAG) levels in response to insulin, PDGF and PMA. We show that PDGF and PMA induce a rapid elevation in intracellular diacylglycerol levels, but insulin was without effect. In addition, we have shown that PMA and PDGF, but not insulin, stimulate protein kinase C activity. However, depletion of protein kinase C by overnight exposure to PMA, abolished PMA-stimulated glucose transport but had no effect on insulin- and PDGF-stimulated glucose transport, suggesting that the stimulation of glucose transport by these mitogens does not involve protein kinase C. The use of the selective protein kinase C inhibitor, Roche 31-8220, which inhibited PMA-stimulated glucose transport, but was without effect on insulin- and PDGF-stimulated glucose transport further supports this conclusion. Taken together, these data argue against a role for protein kinase C in the stimulation of glucose transport in 3T3-L1 fibroblasts caused by acute exposure to insulin or PDGF.
Merrall
N W
NW
Department of Biochemistry, University of Glasgow, UK.
Wakelam
M J
MJ
Plevin
R
R
Gould
G W
GW
D016475:3T3 Cells / Q000187:drug effects; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004075:Diglycerides / Q000032:analysis; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate
C011439:1,2-diacylglycerol; D004075:Diglycerides; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D004247:DNA; D011493:Protein Kinase C; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate