epidermal-growth-factor and fructose-2-6-diphosphate

The use of NIH3T3 fibroblasts overexpressing different mutations of the EGF receptor shows that regulation of fructose-2,6-bisphosphate (Fru-2,6-P2) metabolism by EGF is mediated by the kinase activity of the EGF receptor and suggests a PLCgamma1-mediated mechanism. The effect of several extracellular matrix components on glucose metabolism was assessed by incubating A431 cells and NIH3T3 fibroblasts with heparin, laminin, fibronectin, collagen and PG-I and PG-II proteoglycans and measuring the levels of Fru-2,6-P2. Laminin increased the levels of Fru-2,6-P2 and heparin decreased the levels of the metabolite, whereas the other molecules did not have any effect. No effect of laminin or heparin in glucose uptake by the cell was observed. Laminin was able to modulate the effects of EGF on Fru-2,6-P2 concentration, suggesting cross-talk between these agents.

Topics: 3T3 Cells; Animals; Cell Line; Collagen; Epidermal Growth Factor; ErbB Receptors; Extracellular Matrix Proteins; Fibronectins; Fructosediphosphates; Heparin; Humans; Isoenzymes; Kinetics; Laminin; Mice; Phospholipase C gamma; Proteoglycans; Type C Phospholipases

Chick embryo hepatocytes were maintained in monolayer culture in a serum-free chemically defined medium for periods of up to 2 days. Over this time period, insulin provoked selective increases (up to 5-fold) in factors relevant to the control of glycolysis: the activities of phosphofructokinase-1 (PFK-1), phosphofructokinase-2 (PFK-2) and hexokinase isoenzymes and the content of fructose 2,6-bisphosphate (F26BP). Half-maximal effects of insulin on pFK-1 activity were in the physiological range (0.1 nM). Changes in enzyme activities and F26BP content in response to insulin were correlated with stimulation of glycolytic flux as estimated by radioisotopic flux. These data are discussed in relation to known changes which occur in hepatic glycolytic activity and PFK-1 activity in the intact chick around hatching. The effects of insulin on F26BP content, PFK-1 activity and glycolytic flux were mimicked by epidermal growth factor (EGF). In contrast, phorbol esters produced minimal actions on any of the above parameters. Our data indicate that protein kinase C is not involved in the actions of insulin or EGF in control of F26BP content or PFK-1 activity. This work indicates that the related tyrosyl kinase receptors of insulin and EGF may provoke identical responses within hepatocytes, but through the utilization of different transduction systems which merge to common control points.

Topics: Animals; Cells, Cultured; Chick Embryo; Epidermal Growth Factor; Fructosediphosphates; Glycolysis; Insulin; Liver; Phorbol Esters; Phosphofructokinase-1