scholarly journals Mechanisms of inhibition of lipolysis by insulin, vanadate and peroxovanadate in rat adipocytes

1999 ◽  
Vol 339 (2) ◽  
pp. 281-289 ◽  
Author(s):  
Isabelle CASTAN ◽  
Jonny WIJKANDER ◽  
Vincent MANGANIELLO ◽  
Eva DEGERMAN
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Regulatory Subunit ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Rat Adipocytes ◽  
Lipolytic Action ◽  
Dependent Protein ◽  
Phosphodiesterase Type ◽  
Phosphoinositide 3 Kinase

Vanadate and peroxovanadate (pV), potent inhibitors of tyrosine phosphatases, mimic several of the metabolic actions of insulin. Here we compare the mechanisms for the anti-lipolytic action of insulin, vanadate and pV in rat adipocytes. Vanadate (5 mM) and pV (0.01 mM) inhibited lipolysis induced by 0.01–1 µM isoprenaline, vanadate being more and pV less efficient than insulin (1 nM). A loss of anti-lipolytic effect of pV was observed by increasing the concentration of isoprenaline and/or pV. pV induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 to a greater extent than insulin, whereas vanadate affected these components little if at all. In addition, only a higher concentration (0.1 mM) of pV induced the tyrosine phosphorylation of p85, the 85 kDa regulatory subunit of phosphoinositide 3-kinase (PI-3K). Vanadate activated PI-3K-independent (in the presence of 10 nM isoprenaline) and PI-3K-dependent (in the presence of 100 nM isoprenaline) anti-lipolytic pathways, both of which were found to be independent of phosphodiesterase type 3B (PDE3B). pV (0.01 mM), like insulin, activated PI-3K- and PDE3B-dependent pathways. However, the anti-lipolytic pathway of 0.1 mM pV did not seem to require insulin receptor substrate-1-associated PI-3K and was found to be partly independent of PDE3B. Vanadate and pV (only at 0.01 mM), like insulin, decreased the isoprenaline-induced activation of cAMP-dependent protein kinase. Overall, these results underline the complexity and the diversity in the mechanisms that regulate lipolysis.

scholarly journals Mechanism of feedback regulation of insulin receptor substrate-1 phosphorylation in primary adipocytes

2005 ◽  
Vol 388 (2) ◽  
pp. 713-720 ◽  
Author(s):  
Ingeborg HERS ◽  
Jeremy M. TAVARÉ
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Mammalian Target Of Rapamycin ◽  
Feedback Regulation ◽  
Serine Phosphorylation ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
P70s6 Kinase ◽  
Mitogen Activated Protein ◽  
Phosphoinositide 3 Kinase

Serine and threonine phosphorylation of IRS-1 (insulin receptor substrate-1) has been reported to decrease its ability to be tyrosine-phosphorylated by the insulin receptor. Insulin itself may negatively regulate tyrosine phosphorylation of IRS-1 through a PI3K (phosphoinositide 3-kinase)-dependent feedback pathway. In the present study, we examined the regulation and role of IRS-1 serine phosphorylation in the modulation of IRS-1 tyrosine phosphorylation in physiologically relevant cells, namely freshly isolated primary adipocytes. We show that insulin-stimulated phosphorylation of Ser312 and Ser616 in IRS-1 was relatively slow, with maximal phosphorylation achieved after 20 and 5 min respectively. The effect of insulin on phosphorylation of both these sites required the activation of PI3K and the MAPKs (mitogen-activated protein kinases) ERK1/2 (extracellular-signal-regulated kinase 1 and 2), but not the activation of mTOR (mammalian target of rapamycin)/p70S6 kinase, JNK (c-Jun N-terminal kinase) or p38MAPK. Although inhibition of PI3K and ERK1/2 both substantially decreased insulin-stimulated phosphorylation of Ser312 and Ser616, only wortmannin enhanced insulin-stimulated tyrosine phosphorylation of IRS-1. Furthermore, inhibition of mTOR/p70S6 kinase, JNK or p38MAPK had no effect on insulin-stimulated IRS-1 tyrosine phosphorylation. The differential effect of inhibition of ERK1/2 on insulin-stimulated IRS-1 phosphorylation of Ser312/Ser616 and tyrosine indicates that these events are independent of each other and that phosphorylation of Ser312/Ser616 is not responsible for the negative regulation of IRS-1 tyrosine phosphorylation mediated by PI3K in primary adipocytes.

scholarly journals Insulin receptor substrate 1 rescues insulin action in CHO cells expressing mutant insulin receptors that lack a juxtamembrane NPXY motif.

1995 ◽  
Vol 15 (9) ◽  
pp. 4711-4717 ◽  
Author(s):  
D Chen ◽  
D J Van Horn ◽  
M F White ◽  
J M Backer
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Cho Cells ◽  
Glycogen Synthesis ◽  
Insulin Receptors ◽  
Insulin Receptor Substrate ◽  
Insulin Stimulation ◽  
Insulin Receptor Substrate 1 ◽  
Npxy Motif ◽  
Stimulation Of

Insulin signals are mediated through tyrosine phosphorylation of specific proteins such as insulin receptor substrate 1 (IRS-1) and Shc by the activated insulin receptor (IR). Phosphorylation of both proteins is nearly abolished by an alanine substitution at Tyr-960 (A960) in the beta-subunit of the receptor. However, overexpression of IRS-1 in CHO cells expressing the mutant receptor (A960 cells) restored sufficient tyrosine phosphorylation of IRS-1 to rescue IRS-1/Grb-2 binding and phosphatidylinositol 3' kinase activation during insulin stimulation. Shc tyrosine phosphorylation and its binding to Grb-2 were impaired in the A960 cells and were unaffected by overexpression of IRS-1. Although overexpression of IRS-1 increased IRS-1 binding to Grb-2, ERK-1/ERK-2 activation was not rescued. These data suggest that signaling molecules other than IRS-1, perhaps including Shc, are critical for insulin stimulation of p21ras. Interestingly, overexpression of IRS-1 in the A960 cells restored insulin-stimulated mitogenesis and partially restored insulin stimulation of glycogen synthesis. Thus, IRS-1 tyrosine phosphorylation is sufficient to increase the mitogenic response to insulin, whereas insulin stimulation of glycogen synthesis appears to involve other factors. Moreover, IRS-1 phosphorylation is either not sufficient or not involved in insulin stimulation of ERK.

scholarly journals Angiotensin II induces tyrosine phosphorylation of insulin receptor substrate 1 and its association with phosphatidylinositol 3-kinase in rat heart

1995 ◽  
Vol 310 (3) ◽  
pp. 741-744 ◽  
Author(s):  
M J A Saad ◽  
L A Velloso ◽  
C R O Carvalho
Keyword(s):  
Angiotensin Ii ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Rat Heart ◽  
Fold Increase ◽  
At1 Receptor ◽  
Insulin Receptor Substrate ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Receptor Substrate 1

We have investigated whether angiotensin II (AII) is able to induce insulin receptor substrate 1 (IRS-1) phosphorylation and its association with phosphatidylinositol 3-kinase (PI 3-kinase) in the rat heart in vivo. The phosphorylation state of IRS-1 following infusion of insulin or AII via the vena cava was assessed after immunoprecipitation with an anti-peptide antibody to IRS-1 followed by immunoblotting with an anti-phosphotyrosine antibody and an anti-PI 3-kinase antibody. Densitometry indicated a 5.6 +/- 1.3-fold increase in IRS-1 phosphorylation after stimulation with AII and a 12.8 +/- 3.1-fold increase after insulin. The effect was maximal at an AII concentration of 10(-8) M and occurred 1 min after infusion. There was also a 6.1 +/- 1.2-fold increase in IRS-1-associated PI 3-kinase in response to AII. In the isolated perfused heart the result was similar, showing a direct effect of AII on this pathway. When the animals were pretreated for 1 h with DuP 753, a non-peptide AII-receptor 1 (AT1 receptor) antagonist, there was a marked reduction in the AII-induced tyrosine phosphorylation of IRS-1, suggesting that phosphorylation is initially mediated by the AT1 receptor. We conclude that AII stimulates tyrosine phosphorylation of IRS-1 and its association with PI 3-kinase. This pathway thus represents an additional signalling mechanism stimulated by AII in the rat heart in vivo.

scholarly journals Insulin receptor substrate 1 binds two novel splice variants of the regulatory subunit of phosphatidylinositol 3-kinase in muscle and brain.

1996 ◽  
Vol 16 (5) ◽  
pp. 2195-2203 ◽  
Author(s):  
D A Antonetti ◽  
P Algenstaedt ◽  
C R Kahn
Keyword(s):  
Skeletal Muscle ◽  
Insulin Receptor ◽  
Tissue Distribution ◽  
Cardiac Muscle ◽  
Splice Variants ◽  
Regulatory Subunit ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Tissue Specific ◽  
Sh2 Domains

We have identified two novel alternatively spliced forms of the p85alpha regulatory subunit of phosphatidylinositol (PI) 3-kinase by expression screening of a human skeletal muscle library with phosphorylated baculovirus- produced human insulin receptor substrate 1. One form is identical to p85alpha throughout the region which encodes both Src homology 2 (SH2) domains and the inter-SH2 domain/p110 binding region but diverges in sequence from p85alpha on the 5' side of nucleotide 953, where the entire break point cluster gene and SH3 regions are replaced by a unique 34-amino-acid N terminus. This form has an estimated molecular mass of approximately 53 kDa and has been termed p85/AS53. The second form is identical to p85 and p85/AS53 except for a 24-nucleotide insert between the SH2 domains that results in a replacement of aspartic acid 605 with nine amino acids, adding two potential serine phosphorylation sites in the vicinity of the known serine autophosphorylation site (Ser-608). Northern (RNA) analyses reveal a wide tissue distribution of p85alpha, whereas p85/AS53 is dominant in skeletal muscle and brain, and the insert isoforms are restricted to cardiac muscle and skeletal muscle. Western blot (immunoblot) analyses using an anti-p85 polyclonal antibody and a specific anti-p85/AS53 antibody confirmed the tissue distribution of p85/AS53 protein and indicate a approximately 7-fold higher expression of p85/AS53 protein than of p85 in skeletal muscle. Both p85 and p85/AS53 bind to p110 in coprecipitation experiments, but p85alpha itself appears to have preferential binding to insulin receptor substrate 1 following insulin stimulation. These data indicate that the gene for the p85alpha regulatory subunit of PI 3-kinase can undergo tissue-specific alternative splicing. Two novel splice variants of the regulatory subunit of PI 3-kinase are present in skeletal muscle, cardiac muscle, and brain; these variants may have important functional differences in activity and may play a role in tissue-specific signals such as insulin-stimulated glucose transport or control of neurotransmitter secretion or action.

Sign in / Sign up

Export Citation Format

Share Document