PtdIns(3,4,5)<i>P</i>3-Dependent Activation of the mTORC2 Kinase Complex

Liu, Pengda; Gan, Wenjian; Chin, Y. Rebecca; Ogura, Kohei; Guo, Jianping; Zhang, Jinfang; Wang, Bin; Blenis, John; Cantley, Lewis C.; Toker, Alex; Su, Bing

doi:10.1158/2159-8290.cd-15-0460

Cited by 330 publications

(353 citation statements)

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“…Note that, if this is so, simplistically, the PI (4,5)P 2 pool made by PI5P4Kα that we have invoked here must have a negative effect on mTORC2 activity. [Superficially, this might serve as the precursor for the PIP 3 pool suggested recently by Liu et al in mTORC2 regulation (24), although because this appears to be stimulatory to mTORC2, the relationship of the observations by Liu et al with our observations is unclear.] There are two proteins reported as inhibiting mTORC2, DEPTOR (25) and XPLN (26), the latter being mTORC2-specific and thus, potentially, an endoplasmic reticulum protein, and both of these proteins have the theoretical potential to bind PI(4,5)P 2 through their PDZ or PH domains, respectively; these considerations point to one way in which the negative influence of PI5P4Kα on mTORC2 activity might be mediated.…”

Section: Discussionmentioning

confidence: 47%

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P₂to impact mTORC2 and Akt signaling

Bulley

Droubi

Clarke

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks) are enigmatic lipid kinases with physiological functions that are incompletely understood, not the least because genetic deletion and cell transfection have led to contradictory data. Here, we used the genetic tractability of DT40 cells to create cell lines in which endogenous PI5P4Kα was removed, either stably by genetic deletion or transiently (within 1 h) by tagging the endogenous protein genomically with the auxin degron. In both cases, removal impacted Akt phosphorylation, and by leaving one PI5P4Kα allele present but mutating it to be kinase-dead or have PI4P 5-kinase activity, we show that all of the effects on Akt phosphorylation were dependent on the ability of PI5P4Kα to synthesize phosphatidylinositol (4,5)-bisphosphate [PI(4,5) P 2 ] rather than to remove PI5P. Although stable removal of PI5P4Kα resulted in a pronounced decrease in Akt phosphorylation at Thr308 and Ser473, in part because of reduced plasma membrane PIP 3 , its acute removal led to an increase in Akt phosphorylation only at Ser473. This process invokes activation primarily of mammalian target of rapamycin complex 2 (mTORC2), which was confirmed by increased phosphorylation of other mTORC2 substrates. These findings establish PI5P4Kα as a kinase that synthesizes a physiologically relevant pool of PI(4,5)P 2 and as a regulator of mTORC2, and show a phenomenon similar to the "butterfly effect" described for phosphatidylinositol 3-kinase Iα [Hart JR, et al. (2015) Proc Natl Acad Sci USA 112(4):1131-1136], whereby through apparently the same underlying mechanism, the removal of a protein's activity from a cell can have widely divergent effects depending on the time course of that removal.phosphatidylinositol 5-phosphate 4-kinase | phosphatidylinositol 5-phosphate | phosphatidylinositol (4,5)-bisphosphate | Akt | mTOR T he phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks) are an enigmatic family of three (PI5P4Kα, -β, and -γ) with cellular functions that remain poorly understood (1-3). In general, their principal activity is believed to be to remove and thus, regulate the levels of their substrate phosphatidylinositol 5-phosphate (PI5P). Phenotypes from knockout mice have highlighted that PI5P4Ks have important roles to play in physiology and pathology, including links between PI5P4Ks and the Akt signaling pathway, and other studies have pointed to roles in the generation of cancer (3). A number of key questions, however, remain unanswered. Knocking proteins out or down (by RNAi) is a long-term strategy that may lead to indirect changes, such as, for example, those highlighted in the recent study by Hart et al. (4) concerning the indirect long-term consequences of a point mutation in phosphatidylinositol 3-kinase-α (PI3Kα). Another issue still unresolved for PI5P4Ks is whether removal of PI5P is their only function or whether their ability to synthesize phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P 2 ] may also be important (5, 6).We have recently used the high homologous recombi...

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Section: Discussionmentioning

confidence: 47%

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P₂to impact mTORC2 and Akt signaling

Bulley

Droubi

Clarke

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The accessibility of the mTOR active site is governed in part by mTORassociated proteins that form two distinct complexes: mTOR complex 1 (mTORC1) and 2 (mTORC2). These complexes differ in their composition, mode of activation and rapamycin sensitivity Liu et al, 2015). Although mTOR in both complexes interacts with DEPTOR and mLST8, the other core components are distinct between them.…”

Section: Pi3k/akt/mtor Signallingmentioning

confidence: 99%

Proliferation, survival and metabolism: the role of PI3K/AKT/mTOR signalling in pluripotency and cell fate determination

2016

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Phosphatidylinositide 3 kinases (PI3Ks) and their downstream mediators AKT and mammalian target of rapamycin (mTOR) constitute the core components of the PI3K/AKT/mTOR signalling cascade, regulating cell proliferation, survival and metabolism. Although these functions are well-defined in the context of tumorigenesis, recent studies -in particular those using pluripotent stem cells -have highlighted the importance of this pathway to development and cellular differentiation. Here, we review the recent in vitro and in vivo evidence for the role PI3K/AKT/mTOR signalling plays in the control of pluripotency and differentiation, with a particular focus on the molecular mechanisms underlying these functions.

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“…Production of this phospholipid provides binding sites for protein kinase B (PKB) and phosphoinositide-dependent kinase-1 (PDK1) that migrate to the plasma membrane where PDK1 can phosphorylate PKB review in [19] . Also the protein kinase mTORC2 (mTOR in complex with rictor) is recruited to the plasma membrane to phosphorylate PKB [20] (Fig. 2).…”

Section: Insulin Signalling In Adipocytesmentioning

confidence: 99%

“…When the PH domain of PKB is bound to PIP3 a conformational change is induced, which gives PDK1 access to phosphorylate PKB. It has been suggested that also mTORC2 is recruited to the plasma membrane via the PH domain of the subunit mSIN1, thus releasing an autoinhibition of mTORC2 and thereby promoting the phosphorylation of PKB by mTORC2 [20].…”

Section: Phosphorylation Of Pkbmentioning

confidence: 99%

“…mTORC2 is mainly activated by insulin in a PI3K dependent way, but also lipids can regulate the mTORC2 activity [77]. How PI3K activates mTORC2 is not fully understood, but PI3K has been found to promote association of ribosomes with mTORC2 for activation of the kinase and PIP3 generated from PI3K induces mSIN1 to release its inhibitory effect on mTORC2 [20,78].…”

Section: Mtorc1 and Mtorc2mentioning

confidence: 99%

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Insulin Signalling in Human Adipocytes and its Interplay with beta-Adrenergic Control of Lipolysis

Karlsson¹

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Cover: Fluorescence microscopic image demonstrating the association of caveolin-1 and IQGAP1 (paper II). In a proximity ligation assay each red dot represents a single IQGAP1 -caveolin-1 complex stained with Hoechst, nucleus is stained with DAPI. © Cecilia Jönsson 2018Published articles in this thesis have been reprinted with the permission of respective copyright holders. Printed by LiU-Tryck, Linköping 2018 During the course of the research underlying this thesis, Cecilia Jönsson was enrolled in Forum Scientium, a multidisciplinary doctoral program at Linköping University, Sweden AbstractThe prevalence of obesity has over the last 40 years nearly tripled and obesity is one of the major risk factors of developing type 2 diabetes. Type 2 diabetes was formerly called adultonset diabetes but today, probably due to the rise in childhood obesity, it is also seen in children and adolescents. Type 2 diabetes is diagnosed when the body no longer can control the glucose levels in the blood. This is due to an insulin resistant state in the insulin responding tissues, liver, adipose and muscle and insufficient production of insulin in the pancreas. However, in spite of extensive research the mechanisms behind insulin resistance is still not known.The adipose tissue is believed to play a major role in the development of whole body insulin resistance. Adipocytes are the most important sites for storage of the high energy containing triacylglycerols. Insulin stimulation causes the adipocyte to increase the uptake of glucose and to reduce lipolysis: the hydrolysis of triacylglycerol and release of glycerol and fatty acids. The insulin signalling network is complex with numerous proteins involved. These signalling proteins not only transmit the insulin signal but also create negative and positive feedbackloops and induce cross talk between different parts of the network and with the signalling of other hormones. One important positive feedback in insulin signalling is the mTORC1 mediated feedback to phosphorylation of IRS1 at serine 307. In paper I we found that in human adipocytes this feedback is not likely catalysed by the assumed kinase S6K1. However we find an immunoprecipitate of mTOR to contain a ser307 phosphorylating kinase.Scaffolding proteins serve as docking sites for several proteins to promote protein-protein interactions that facilitate signal transduction. In paper II we demonstrate the existence of the scaffolding protein IQGAP1 in human adipocytes and that the expression of IQGAP1 is downregulated in type 2 diabetes. We reveal that IQGAP1 co-localises with caveolae, invaginations of the plasma membrane where the insulin receptor is situated, and that this interaction is increased upon insulin stimulation.In paper III we focus on the control of lipolysis, and sought to understand the interplay between insulin and beta-adrenergic stimulation. We demonstrated that the re-esterification of fatty acids is downregulated in type 2 diabetes causing an increased release of fatty acids from the cells. We showed th...

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PtdIns(3,4,5)P3-Dependent Activation of the mTORC2 Kinase Complex

Cited by 330 publications

References 53 publications

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P₂to impact mTORC2 and Akt signaling

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P₂to impact mTORC2 and Akt signaling

Proliferation, survival and metabolism: the role of PI3K/AKT/mTOR signalling in pluripotency and cell fate determination

Insulin Signalling in Human Adipocytes and its Interplay with beta-Adrenergic Control of Lipolysis

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PtdIns(3,4,5)P3-Dependent Activation of the mTORC2 Kinase Complex

Cited by 330 publications

References 53 publications

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P2to impact mTORC2 and Akt signaling

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P2to impact mTORC2 and Akt signaling

Proliferation, survival and metabolism: the role of PI3K/AKT/mTOR signalling in pluripotency and cell fate determination

Insulin Signalling in Human Adipocytes and its Interplay with beta-Adrenergic Control of Lipolysis

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Product

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In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P₂to impact mTORC2 and Akt signaling

In B cells, phosphatidylinositol 5-phosphate 4-kinase–α synthesizes PI(4,5)P₂to impact mTORC2 and Akt signaling