Evidence of two mechanisms for the activation of the glucose transporter GLUT1 by anisomycin: p38(MAP kinase) activation and protein synthesis inhibition in mammalian cells

Abstract

Inhibitors of protein synthesis stimulate sugar transport in mammalian cells through activation of plasma membrane GLUT1, the housekeeping isoform of the glucose transporter. However, it has been reported that some of these compounds, in addition to their effect on protein synthesis, also activate protein kinases. In the present study we have explored the role of these two effects on GLUT1 activation. In 3T3‐L1 adipocytes and Clone 9 cells, stimulation of sugar transport by puromycin, a translational inhibitor that does not activate kinases, was not detectable until 90 min after exposure. In contrast, stimulation by anisomycin, a potent Jun‐NH2‐terminal kinase (JNK) agonist, exhibited no lag phase. An intermediate response was observed to emetine and cycloheximide, weak activators of JNK. The potency of anisomycin to stimulate transport acutely (30 min of exposure) was 5‐ to 10‐fold greater than for its chronic stimulation of transport, measured after 4 h of exposure. The stimulation of transport by a low concentration of anisomycin (0.3 μm) was transient, peaked at 30–60 min and it was inhibited (IC50 < 1 μm) by SB203580, which indicates that its mediator is not JNK, but the homologous p38(MAP kinase) (p38(MAPK)). In contrast, the responses to 4 h exposure to 300 μm anisomycin or puromycin were refractory to SB203580. Exposure to anisomycin resulted in rapid activation of p38(MAPK). Activation of both p38(MAPK) and GLUT1 by 0.3 μm anisomycin was cancelled by puromycin. We conclude that the activation of GLUT1 in response to anisomycin includes two components: a delayed component involving translational inhibition and a fast, puromycin‐inhibitable component that is secondary to activation of p38(MAPK).

ACTIONS OF THE PRO-INFLAMMATORY CYTOKINE IL-1[beta] ON CENTRAL SYNAPTIC TRANSMISSION

“…p38 MAP kinase activation leads to expression of a number of factors, including IL_1 and TNF (Lee et al 1994), IL-6, prostaglandin E2 via induction of cyclo-oxygenase (COX-2), colleganase and stromolysin-1 (Ridley et al 1997). p38 activation also upregulates glucose transport (Barros et al 1997). The p38 MAP kinase has also been shown to be activated by other stimuli, including bradykinin, which leads to an inhibition of N-type voltage-dependent Ca¥ currents (VDCCs; Wilk-Blaszczak et al 1998), thrombin, which leads to activation of cPLA2 (Kramer et al 1996), â_amyloid fibrils (McDonald et al 1998) and glutamate in cerebellar neurones, which leads to apoptosis (Kawasaki et al 1997).…”

Preconditioning Enhanced Glucose Uptake Is Mediated by p38 MAP Kinase Not by Phosphatidylinositol 3-Kinase

“…In addition to PI3K-independent pathways leading to increased glucose transporter translocation, there are PI3K-independent mechanisms that enhance activity of glucose transporters present in the plasma membrane (23,24). A recent study suggests that insulin-stimulated glucose transport is regulated not only by translocation of transporters, which in the case of insulin is mediated by PI3K, but also by activation of transporters after they are inserted into the plasma membrane, which requires p38 MAP kinase (23).…”

“…A recent study suggests that insulin-stimulated glucose transport is regulated not only by translocation of transporters, which in the case of insulin is mediated by PI3K, but also by activation of transporters after they are inserted into the plasma membrane, which requires p38 MAP kinase (23). Anisomycin, an activator of c-Jun NH 2 -terminal kinase and p38 MAP kinase, stimulates glucose transport by a mechanism that does not involve enhanced translocation of glucose transporters to the plasma membrane but rather stimulates transporters already in the plasma membrane (24).…”

The translation inhibitor anisomycin induces Elk-1-mediated transcriptional activation of egr-1 through multiple mitogen-activated protein kinase pathways

“…According to this model, protein synthesis inhibitors block this short-lived repressor, causing hyper-induction of immediateearly response genes (Greenberg et al, 1986;Morello et al, 1990). Given that ANX stimulates c-fos gene expression through activation of MAPK signaling pathways independently of its ability to inhibit protein synthesis (Zinck et al, 1995;Barros et al, 1997), we tested whether these pathways are involved in the transcriptional activation of egr-1 by protein synthesis inhibitors in U87MG glioma cells.…”

“…The translation inhibitor anisomycin (ANX) induces c-fos gene expression by stimulating MAPK signaling (Zinck et al, 1995;Barros et al, 1997), suggesting that ANX is able to modulate intracellular signaling pathways, independently of a block to translation. However, the signaling process whereby de novo inhibition of translation stimulates egr-1 transcription has not been fully elucidated.…”