scholarly journals Insulin-mimetic signalling of synthetic phosphoinositolglycans in isolated rat adipocytes

1998 ◽  
Vol 336 (1) ◽  
pp. 163-181 ◽  
Author(s):  
Wendelin FRICK ◽  
Andrea BAUER ◽  
Jochen BAUER ◽  
Susanne WIED ◽  
Günter MÜLLER
Keyword(s):  
Lipid Metabolism ◽  
Protein Kinase ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Glycogen Synthase ◽  
Insulin Response ◽  
Mitogen Activated Protein Kinase ◽  
Rat Adipocytes ◽  
Insulin Mimetic ◽  
Glucose And Lipid Metabolism

A set of synthetic phosphoinositolglycan (PIG) compounds has been demonstrated to exert insulin-mimetic activity on glucose and lipid metabolism in rat adipocytes differing considerably in potency [compound 41 > 37 > 45 ≫ 7 > 1; W. Frick, A. Bauer, J. Bauer, S. Wied and G. Müller, G. (1998) Biochemistry 37, 13421–13436]. In the present study we examine whether these differences are based on the capability of the PIG compounds to stimulate signalling components which are thought to mediate metabolic insulin action. Studies using a tyrosine kinase inhibitor and introduction into adipocytes of anti-phosphotyrosine or inhibitory anti-insulin receptor β-subunit antibodies demonstrated dependence on tyrosine phosphorylation but independence of insulin receptor kinase activation of the insulin-mimetic signalling and metabolic activity of the PIG compounds. The five compounds elicited in rat adipocytes a significant increase in tyrosine phosphorylation of both insulin receptor substrate 1 (IRS-1) and IRS-3 and, to a minor degree, IRS-2, in IRS-1/3-associated phosphatidylinositol 3-kinase (PI 3-K) protein as well as activity, and in protein kinase B (PKB) activity as well as phosphorylation. This was most pronounced for compound 41, approaching 65–95% of the maximal insulin response (MIR) at 20 µM, and declined in the order of compounds 37, 45, 7 and 1. The same ranking was true for the maximal inhibition of glycogen synthase kinase 3 activity (GSK-3) (41, 75% of MIR; compound 37, 65%; compound 7, 25%; compound 1, 10%) and GSK-3 autophosphorylation. The half-maximal concentrations effective for signalling (compound 41, 2–5 µM; compound 37, 10–20 µM) corresponded well to those stimulating glucose and lipid metabolism. Interestingly, compounds 37 and 41 stimulated mitogen-activated protein kinase (MAPK) and protein synthesis in rat adipocytes to only about 20–30% (at 50 µM) of MIR. We conclude that in rat adipocytes: (i) the potency of PIG compounds to regulate glucose/lipid metabolism depends on the activation of PI 3-K and PKB and inhibition of GSK-3; (ii) initiation of tyrosine phosphorylation of IRS-1/3 is sufficient and activation of the PI 3-K cascade is required for insulin-mimetic metabolic signalling; and (iii) PIG compounds are quite selective for the PI 3-K compared to the MAPK cascade, (iv) PIG compounds seem to use the same signalling components downstream of PI 3-K (including Rab4) for stimulation of glucose transport as does insulin. Thus the early signalling step(s) used by PIG, but not by insulin, may represent a target for the treatment of insulin-resistant states.

scholarly journals Insulin-mimetic and insulin-sensitizing activities of a pentacyclic triterpenoid insulin receptor activator

2007 ◽  
Vol 403 (2) ◽  
pp. 243-250 ◽  
Author(s):  
Seung H. Jung ◽  
Yun J. Ha ◽  
Eun K. Shim ◽  
Soo Y. Choi ◽  
Jing L. Jin ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Glucose Transporter ◽  
Glycogen Synthase ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Β Subunit ◽  
Insulin Sensitizer ◽  
Insulin Mimetic ◽  
Pentacyclic Triterpenoid

Five pentacyclic triterpenoids isolated from Campsis grandiflora were tested for insulin-mimetic and insulin-sensitizing activity. The compounds enhanced the activity of insulin on tyrosine phosphorylation of the IR (insulin receptor) β-subunit in CHO/IR (Chinese-hamster ovary cells expressing human IR). Among the compounds tested, CG7 (ursolic acid) showed the greatest enhancement and CG11 (myrianthic acid) the least. We characterized the effect of CG7 further, and showed that it acted as an effective insulin-mimetic agent at doses above 50 μg/ml and as an insulin-sensitizer at doses as low as 1 μg/ml. Additional experiments showed that CG7 increased the number of IRs that were activated by insulin. This indicates that a major mechanism by which CG7 enhances total IR auto-phosphorylation is by promoting the tyrosine phosphorylation of additional IRs. CG7 not only potentiated insulin-mediated signalling (tyrosine phosphorylation of the IR β-subunit, phosphorylation of Akt and glycogen synthase kinase-3β), but also enhanced the effect of insulin on translocation of glucose transporter 4 in a classical insulin-sensitive cell line, 3T3-L1 adipocytes. The results of the present study demonstrate that a specific pentacyclic triterpenoid, CG7, exerts an insulin-sensitizing effect as an IR activator in CHO/IR cells and adipocytes. The enhancement of insulin activity by CG7 may be useful for developing a new class of specific IR activators for treatment of Type 1 and Type 2 diabetes.

scholarly journals The Drosophila insulin receptor activates multiple signaling pathways but requires insulin receptor substrate proteins for DNA synthesis.

1996 ◽  
Vol 16 (5) ◽  
pp. 2509-2517 ◽  
Author(s):  
L Yenush ◽  
R Fernandez ◽  
M G Myers ◽  
T C Grammer ◽  
X J Sun ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Human Insulin ◽  
Mammalian Cells ◽  
Insulin Response ◽  
Mitogen Activated Protein Kinase ◽  
Insulin Receptor Substrate ◽  
Human Insulin Receptor ◽  
Irs Proteins ◽  
Drosophila Insulin Receptor

The Drosophila insulin receptor (DIR) contains a 368-amino-acid COOH-terminal extension that contains several tyrosine phosphorylation sites in YXXM motifs. This extension is absent from the human insulin receptor but resembles a region in insulin receptor substrate (IRS) proteins which binds to the phosphatidylinositol (PI) 3-kinase and mediates mitogenesis. The function of a chimeric DIR containing the human insulin receptor binding domain (hDIR) was investigated in 32D cells, which contain few insulin receptors and no IRS proteins. Insulin stimulated tyrosine autophosphorylation of the human insulin receptor and hDIR, and both receptors mediated tyrosine phosphorylation of Shc and activated mitogen-activated protein kinase. IRS-1 was required by the human insulin receptor to activate PI 3-kinase and p70s6k, whereas hDIR associated with PI 3-kinase and activated p70s6k without IRS-1. However, both receptors required IRS-1 to mediate insulin-stimulated mitogenesis. These data demonstrate that the DIR possesses additional signaling capabilities compared with its mammalian counterpart but still requires IRS-1 for the complete insulin response in mammalian cells.

scholarly journals Tyrosine Phosphorylation of Phosphoinositide-Dependent Kinase 1 by the Insulin Receptor IsNecessary for Insulin Metabolic Signaling

2005 ◽  
Vol 25 (24) ◽  
pp. 10803-10814 ◽  
Author(s):  
Francesca Fiory ◽  
Anna Teresa Alberobello ◽  
Claudia Miele ◽  
Francesco Oriente ◽  
Iolanda Esposito ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Insulin Receptor ◽  
Glucose Uptake ◽  
Tyrosine Phosphorylation ◽  
Glycogen Synthase ◽  
Metabolic Effects ◽  
Insulin Effect ◽  
L6 Cells ◽  
Pkb Phosphorylation

ABSTRACT In L6 myoblasts, insulin receptors with deletion of the C-terminal 43 amino acids (IRΔ43) exhibited normal autophosphorylation and IRS-1/2 tyrosine phosphorylation. The L6 cells expressing IRΔ43 (L6IRΔ43) also showed no insulin effect on glucose uptake and glycogen synthase, accompanied by a >80% decrease in insulin induction of 3-phosphoinositide-dependent protein kinase 1 (PDK-1) activity and tyrosine phosphorylation and of protein kinase B (PKB) phosphorylation at Thr308. Insulin induced the phosphatidylinositol 3 kinase-dependent coprecipitation of PDK-1 with wild-type IR (IRWT), but not IRΔ43. Based on overlay blotting, PDK-1 directly bound IRWT, but not IRΔ43. Insulin-activated IRWT, and not IRΔ43, phosphorylated PDK-1 at tyrosines 9, 373, and 376. The IR C-terminal 43-amino-acid peptide (C-terminal peptide) inhibited in vitro PDK-1 tyrosine phosphorylation by the IR. Tyr→Phe substitution prevented this inhibitory action. In the L6hIR cells, the C-terminal peptide coprecipitated with PDK-1 in an insulin-stimulated fashion. This peptide simultaneously impaired the insulin effect on PDK-1 coprecipitation with IRWT, on PDK-1 tyrosine phosphorylation, on PKB phosphorylation at Thr308, and on glucose uptake. Upon insulin exposure, PDK-1 membrane persistence was significantly reduced in L6IRΔ43 compared to control cells. In L6 cells expressing IRWT, the C-terminal peptide also impaired insulin-dependent PDK-1 membrane persistence. Thus, PDK-1 directly binds to the insulin receptor, followed by PDK-1 activation and insulin metabolic effects.

scholarly journals Redistribution of Glycolipid Raft Domain Components Induces Insulin-Mimetic Signaling in Rat Adipocytes

2001 ◽  
Vol 21 (14) ◽  
pp. 4553-4567 ◽  
Author(s):  
Günter Müller ◽  
Christian Jung ◽  
Susanne Wied ◽  
Stefan Welte ◽  
Holger Jordan ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Kinases ◽  
Rat Adipocytes ◽  
Insulin Mimetic ◽  
Substrate Protein ◽  
Nonreceptor Tyrosine Kinases ◽  
Signaling Components

ABSTRACT Caveolae and caveolin-containing detergent-insoluble glycolipid-enriched rafts (DIG) have been implicated to function as plasma membrane microcompartments or domains for the preassembly of signaling complexes, keeping them in the basal inactive state. So far, only limited in vivo evidence is available for the regulation of the interaction between caveolae-DIG and signaling components in response to extracellular stimuli. Here, we demonstrate that in isolated rat adipocytes, synthetic intracellular caveolin binding domain (CBD) peptide derived from caveolin-associated pp59Lyn (10 to 100 μM) or exogenous phosphoinositolglycan derived from glycosyl-phosphatidylinositol (GPI) membrane protein anchor (PIG; 1 to 10 μM) triggers the concentration-dependent release of caveolar components and the GPI-anchored protein Gce1, as well as the nonreceptor tyrosine kinases pp59Lyn and pp125Fak, from interaction with caveolin (up to 45 to 85%). This dissociation, which parallels redistribution of the components from DIG to non-DIG areas of the adipocyte plasma membrane (up to 30 to 75%), is accompanied by tyrosine phosphorylation and activation of pp59Lyn and pp125Fak (up to 8- and 11-fold) but not of the insulin receptor. This correlates well to increased tyrosine phosphorylation of caveolin and the insulin receptor substrate protein 1 (up to 6- and 15-fold), as well as elevated phosphatidylinositol-3′ kinase activity and glucose transport (to up to 7- and 13-fold). Insulin-mimetic signaling by both CBD peptide and PIG as well as redistribution induced by CBD peptide, but not by PIG, was blocked by synthetic intracellular caveolin scaffolding domain (CSD) peptide. These data suggest that in adipocytes a subset of signaling components is concentrated at caveolae-DIG via the interaction between their CBD and the CSD of caveolin. These inhibitory interactions are relieved by PIG. Thus, caveolae-DIG may operate as signalosomes for insulin-independent positive cross talk to metabolic insulin signaling downstream of the insulin receptor based on redistribution and accompanying activation of nonreceptor tyrosine kinases.

Neural network dysfunction in bipolar depression: clues from the efficacy of lamotrigine

2009 ◽  
Vol 37 (5) ◽  
pp. 1080-1084 ◽  
Author(s):  
Charles H. Large ◽  
Elena Di Daniel ◽  
Xingbao Li ◽  
Mark S. George
Keyword(s):  
Bipolar Disorder ◽  
Valproic Acid ◽  
Protein Kinase ◽  
Glycogen Synthase ◽  
Bipolar Depression ◽  
Inhibitory Effect ◽  
Mood Stabilizers ◽  
Mitogen Activated Protein Kinase ◽  
Facilitatory Effect

One strategy to understand bipolar disorder is to study the mechanism of action of mood-stabilizing drugs, such as valproic acid and lithium. This approach has implicated a number of intracellular signalling elements, such as GSK3β (glycogen synthase kinase 3β), ERK (extracellular-signal-regulated kinase)/MAPK (mitogen-activated protein kinase) or protein kinase C. However, lamotrigine does not seem to modulate any of these targets, which is intriguing given that its profile in the clinic differs from that of valproic acid or lithium, with greater efficacy to prevent episodes of depression than mania. The primary target of lamotrigine is the voltage-gated sodium channel, but it is unclear why inhibition of these channels might confer antidepressant efficacy. In healthy volunteers, we found that lamotrigine had a facilitatory effect on the BOLD (blood-oxygen-level-dependent) response to TMS (transcranial magnetic stimulation) of the prefrontal cortex. This effect was in contrast with an inhibitory effect of lamotrigine when TMS was applied over the motor cortex. In a follow-up study, a similar prefrontal specific facilitatory effect was observed in a larger cohort of healthy subjects, whereas valproic acid inhibited motor and prefrontal cortical TMS-induced BOLD response. In vitro, we found that lamotrigine (3–10 μM) enhanced the power of gamma frequency network oscillations induced by kainic acid in the rat hippocampus, an effect that was not observed with valproic acid (100 μM). These data suggest that lamotrigine has a positive effect on corticolimbic network function that may differentiate it from other mood stabilizers. The results are also consistent with the notion of corticolimbic network dysfunction in bipolar disorder.

scholarly journals The Insulin Receptor: A Potential Target of Amarogentin Isolated from Gentiana rigescens Franch That Induces Neurogenesis in PC12 Cells

Biomedicines ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 581
Author(s):  
Lihong Cheng ◽  
Hiroyuki Osada ◽  
Tianyan Xing ◽  
Minoru Yoshida ◽  
Lan Xiang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Insulin Receptor ◽  
Signaling Pathways ◽  
Neurite Outgrowth ◽  
Pc12 Cells ◽  
Mitogen Activated Protein Kinase ◽  
Potential Target ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Gentiana Rigescens

Amarogentin (AMA) is a secoiridoid glycoside isolated from the traditional Chinese medicine, Gentiana rigescens Franch. AMA exhibits nerve growth factor (NGF)-mimicking and NGF-enhancing activities in PC12 cells and in primary cortical neuron cells. In this study, a possible mechanism was found showing the remarkable induction of phosphorylation of the insulin receptor (INSR) and protein kinase B (AKT). The potential target of AMA was predicted by using a small-interfering RNA (siRNA) and the cellular thermal shift assay (CETSA). The AMA-induced neurite outgrowth was reduced by the siRNA against the INSR and the results of the CETSA suggested that the INSR showed a significant thermal stability-shifted effect upon AMA treatment. Other neurotrophic signaling pathways in PC12 cells were investigated using specific inhibitors, Western blotting and PC12(rasN17) and PC12(mtGAP) mutants. The inhibitors of the glucocorticoid receptor (GR), phospholipase C (PLC) and protein kinase C (PKC), Ras, Raf and mitogen-activated protein kinase (MEK) significantly reduced the neurite outgrowth induced by AMA in PC12 cells. Furthermore, the phosphorylation reactions of GR, PLC, PKC and an extracellular signal-regulated kinase (ERK) were significantly increased after inducing AMA and markedly decreased after treatment with the corresponding inhibitors. Collectively, these results suggested that AMA-induced neuritogenic activity in PC12 cells potentially depended on targeting the INSR and activating the downstream Ras/Raf/ERK and PI3K/AKT signaling pathways. In addition, the GR/PLC/PKC signaling pathway was found to be involved in the neurogenesis effect of AMA.

scholarly journals Cell cycle tyrosine phosphorylation of p34cdc2 and a microtubule-associated protein kinase homolog in Xenopus oocytes and eggs.

1991 ◽  
Vol 11 (4) ◽  
pp. 1965-1971 ◽  
Author(s):  
J E Ferrell ◽  
M Wu ◽  
J C Gerhart ◽  
G S Martin
Keyword(s):  
Molecular Weight ◽  
Protein Kinase ◽  
Map Kinase ◽  
Tyrosine Phosphorylation ◽  
Time Course ◽  
Mitotic Cell ◽  
Mitogen Activated Protein Kinase ◽  
Xenopus Laevis Oocytes ◽  
Cell Cycles ◽  
M Phase

We have examined the time course of protein tyrosine phosphorylation in the meiotic cell cycles of Xenopus laevis oocytes and the mitotic cell cycles of Xenopus eggs. We have identified two proteins that undergo marked changes in tyrosine phosphorylation during these processes: a 42-kDa protein related to mitogen-activated protein kinase or microtubule-associated protein-2 kinase (MAP kinase) and a 34-kDa protein identical or related to p34cdc2. p42 undergoes an abrupt increase in its tyrosine phosphorylation at the onset of meiosis 1 and remains tyrosine phosphorylated until 30 min after fertilization, at which point it is dephosphorylated. p42 also becomes tyrosine phosphorylated after microinjection of oocytes with partially purified M-phase-promoting factor, even in the presence of cycloheximide. These findings suggest that MAP kinase, previously implicated in the early responses of somatic cells to mitogens, is also activated at the onset of meiotic M phase and that MAP kinase can become tyrosine phosphorylated downstream from M-phase-promoting factor activation. We have also found that p34 goes through a cycle of tyrosine phosphorylation and dephosphorylation prior to meiosis 1 and mitosis 1 but is not detectable as a phosphotyrosyl protein during the 2nd through 12th mitotic cell cycles. It may be that the delay between assembly and activation of the cyclin-p34cdc2 complex that p34cdc2 tyrosine phosphorylation provides is not needed in cell cycles that lack G2 phases. Finally, an unidentified protein or group of proteins migrating at 100 to 116 kDa increase in tyrosine phosphorylation throughout maturation, are dephosphorylated or degraded within 10 min of fertilization, and appear to cycle between low-molecular-weight forms and high-molecular-weight forms during early embryogenesis.

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