Glucose-dependent Insulinotropic Polypeptide Activates the Raf-Mek1/2-ERK1/2 Module via a Cyclic AMP/cAMP-dependent Protein Kinase/Rap1-mediated Pathway

Ehses, Jan A.; Pelech, Steven; Pederson, Raymond A.; McIntosh, Christopher H.S.

doi:10.1074/jbc.m205055200

Cited by 115 publications

(73 citation statements)

References 57 publications

(56 reference statements)

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“…These findings could be of clinical significance, as GLP-1 is currently in clinical trials for the treatment of hyperglycaemia in patients with Type 2 diabetes. tosis in INS-1 cells, in association with activation of PKBα, PKBβ and MAPK [37,40,43]. However, unlike the responses to GLP-1, wortmannin does not prevent GIP-induced beta-cell growth or survival [40].…”

Section: Discussionmentioning

confidence: 99%

Glucagon-like peptide-1 regulates proliferation and apoptosis via activation of protein kinase B in pancreatic INS-1 beta cells

et al. 2004

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Aims/hypothesis. The incretin hormone glucagon-like peptide-1 augments islet cell mass in vivo by increasing proliferation and decreasing apoptosis of the beta cells. However, the signalling pathways that mediate these effects are mostly unknown. Using a clonal rat pancreatic beta cell line (INS-1), we examined the role of protein kinase B in mediating beta-cell growth and survival stimulated by glucagon-like peptide-1. Methods. Immunoblot analysis was used to detect active (phospho-) and total protein kinase B. Proliferation was assessed using 3 H-thymidine incorporation, while apoptosis was quantitated using 4′-6-diamidino-2-phenylindole staining and APO percentage apoptosis assay. Kinase-dead and wild-type protein kinase B was introduced into cells using adenoviral vectors. Results. Glucagon-like peptide-1 rapidly activated protein kinase B in INS-1 cells (by 2.7±0.7-fold, p<0.05). This effect was completely abrogated by inhibition, with wortmannin, of the upstream activator of protein kinase B, phosphatidylinositol-3-kinase. Glucagon-like peptide-1 also stimulated INS-1 cell proliferation in a dose-dependent manner (by 1.8±0.5-fold at 10 −7 mol/l, p<0.01), and inhibited staurosporine-induced apoptosis (by 69±12%, p<0.05). Both of these effects were also prevented by wortmannin treatment. Ablation of protein kinase B by adenovirus-mediated overexpression of the kinase-dead form of protein kinase Bα prevented protein kinase B phosphorylation and completely abrogated both cellular proliferation (p<0.05) and protection from drug-induced cellular death (p<0.01) induced by glucagon-like peptide-1. Conclusions/interpretation. These results identify protein kinase B as an essential mediator linking the glucagon-like peptide-1 signal to the intracellular machinery that modulates beta-cell growth and survival. [Diabetologia (2004) 47:478-487]

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Section: Discussionmentioning

confidence: 99%

Glucagon-like peptide-1 regulates proliferation and apoptosis via activation of protein kinase B in pancreatic INS-1 beta cells

et al. 2004

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“…Hence, in ␤ cells, glucagon-stimulated ERK1/2 activation is mediated by cAMP-activated PKA pathway but was independent of other cAMP molecular targets. As Rap-1 and B-Raf have been shown to be present in MIN6 cells (19,37), it is possible that glucagon stimulates ERK1/2 by influencing the B-Raf activity through PKA-mediated phosphorylation of Rap-1, as shown for others GPCRs (19,37).…”

Section: Discussionmentioning

confidence: 99%

Glucagon Promotes cAMP-response Element-binding Protein Phosphorylation via Activation of ERK1/2 in MIN6 Cell Line and Isolated Islets of Langerhans

Dalle

Longuet

Costes

et al. 2004

Journal of Biological Chemistry

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By using the MIN6 cell line and pancreatic islets, we show that in the presence of a low glucose concentration, corresponding to physiological glucagon release from ␣ cells, glucagon treatment of the ␤ cell caused a rapid, time-dependent phosphorylation and activation of p44/p42 mitogen-activated protein kinase (ERK1/2) independently from extracellular calcium influx. Inhibition of either cAMP-dependent protein kinase (PKA) or MEK completely blocked ERK1/2 activation by glucagon. However, no significant activation of several upstream activators of MEK, including Shc-p21Ras and phosphatidylinositol 3-kinase, was observed in response to glucagon treatment. Chelation of intracellular calcium (intracellular [Ca 2؉ ]) reduced glucagon-mediated ERK1/2 activation. In addition, internalization of glucagon receptors through clathrin-coated pits formation is required for ERK1/2 activation. Remarkably, glucagon promotes the nuclear translocation of ERK1/2 and induces the phosphorylation of cAMP-response elementbinding protein (CREB). Miniglucagon, produced from glucagon and released together with the mother hormone from the ␣ cells in low glucose situations, blocks the insulinotropic effect of glucagon, whereas it does not inhibit the glucagon-induced PKA/ERK1/2/CREB pathway. We conclude that glucagon-induced ERK1/2 activation is mediated by PKA and that an increase in [Ca 2؉ ] i is required for maximal ERK activation. Our results uncover a novel mechanism by which the PKA/ ERK1/2 signaling network engaged by glucagon, in situation of low glucose concentration, regulates phosphorylation of CREB, a transcription factor crucial for normal ␤ cell function and survival.

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“…The INS 832/13 cells exhibit markedly enhanced and stable responses to glucose and several of its known potentiators (21) and have been used extensively as a model system for mammalian ␤-cells (22)(23)(24)(25)(26). We first studied the effects of NE on the membrane potential.…”

Section: Discussionmentioning

confidence: 99%

Both Gi and Go Heterotrimeric G Proteins Are Required to Exert the Full Effect of Norepinephrine on the β-Cell KATP Channel

Zhao

Fang

Straub

et al. 2008

Journal of Biological Chemistry

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The effects of norepinephrine (NE), an inhibitor of insulin secretion, were examined on membrane potential and the ATPsensitive K ؉ channel (K ATP ) in INS 832/13 cells. Membrane potential was monitored under the whole cell current clamp mode. NE hyperpolarized the cell membrane, an effect that was abolished by tolbutamide. The effect of NE on K ATP channels was investigated in parallel using outside-out single channel recording. This revealed that NE enhanced the open activities of the K ATP channels ϳ2-fold without changing the single channel conductance, demonstrating that NE-induced hyperpolarization was mediated by activation of the K ATP channels. The NE effect was abolished in cells preincubated with pertussis toxin, indicating coupling to heterotrimeric G i /G o proteins. To identify the G proteins involved, antisera raised against ␣ and ␤ subunits (anti-G␣ common , anti-G␤, anti-G␣ i1/2/3 , and anti-G␣ o ) were used. Anti-G␣ common totally blocked the effects of NE on membrane potential and K ATP channels. Individually, anti-G␣ i1/2/3 and anti-G␣ o only partially inhibited the action of NE on K ATP channels. However, the combination of both completely eliminated the action. Antibodies against G ␤ had no effects. To confirm these results and to further identify the G protein subunits involved, the blocking effects of peptides containing the sequence of 11 amino acids at the C termini of the ␣ subunits were used. The data obtained were similar to those derived from the antibody work with the additional information that G␣ i3 and G␣ o1 were not involved. In conclusion, both G i and G o proteins are required for the full effect of norepinephrine to activate the K ATP channel.Insulin secretion is inhibited by ␣ 2 -adrenergic receptor activation (1, 2). The ␣ 2 -adrenergic receptors at the plasma membrane are linked to pertussis toxin (PTX) 2 -sensitive G i and G o proteins. Upon interacting with the ␣ 2 -adrenergic receptors, catecholamines (i.e. epinephrine and norepinephrine (NE)), two important physiological inhibitors of insulin secretion, activate G i and/or G o proteins and inhibit the exocytosis of insulin-containing granules (2). Four mechanisms have been suggested to account for their inhibitory effect: 1) activation of ATP-sensitive K ϩ channels (K ATP ) and repolarization of the ␤-cells; 2) inhibition of L-type Ca 2ϩ channels; 3) decreased activity of adenylyl cyclase; and 4) inhibition of exocytosis at a "distal" site in stimulus-secretion coupling, which is beyond the elevation of intracellular Ca 2ϩ and beyond the potentiating actions of cAMP and diacyglycerol (2). Although it is generally accepted that the "distal" inhibitory effect is the most dominant, the relative contribution of each of these four mechanisms to the overall inhibition of insulin release is not clear.Considering the effects of catecholamines on the membrane potential in the insulin-secreting cells, it is clear that catecholamines can repolarize the cell membrane in a PTX-sensitive manner. However, the explanations for this p...

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Glucose-dependent Insulinotropic Polypeptide Activates the Raf-Mek1/2-ERK1/2 Module via a Cyclic AMP/cAMP-dependent Protein Kinase/Rap1-mediated Pathway

Cited by 115 publications

References 57 publications

Glucagon-like peptide-1 regulates proliferation and apoptosis via activation of protein kinase B in pancreatic INS-1 beta cells

Glucagon-like peptide-1 regulates proliferation and apoptosis via activation of protein kinase B in pancreatic INS-1 beta cells

Glucagon Promotes cAMP-response Element-binding Protein Phosphorylation via Activation of ERK1/2 in MIN6 Cell Line and Isolated Islets of Langerhans

Both Gi and Go Heterotrimeric G Proteins Are Required to Exert the Full Effect of Norepinephrine on the β-Cell KATP Channel

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