AMPK phosphorylation of raptor mediates a metabolic checkpoint.

doi:10.1016/J.MOLCEL.2008.03.003

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AMPK phosphorylation of raptor mediates a metabolic checkpoint.

Journal Article•DOI•

AMPK phosphorylation of raptor mediates a metabolic checkpoint.

Dana M. Gwinn¹, David B. Shackelford¹, Daniel F. Egan¹, Maria M. Mihaylova¹, Annabelle Mery¹, Debbie S. Vasquez¹, Benjamin E. Turk², Reuben J. Shaw¹ - Show less +4 more•Institutions (2)

Salk Institute for Biological Studies¹, Yale University²

25 Apr 2008-Molecular Cell (NIH Public Access)-Vol. 30, Iss: 2, pp 214-226

TL;DR: AMPK directly phosphorylates the mTOR binding partner raptor on two well-conserved serine residues, and this phosphorylation induces 14-3-3 binding to raptor, uncovering a conserved effector of AMPK that mediates its role as a metabolic checkpoint coordinating cell growth with energy status.

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About: This article is published in Molecular Cell.The article was published on 2008-04-25 and is currently open access. It has received 3328 citations till now. The article focuses on the topics: AMPK & Autophagy-Related Protein-1 Homolog.

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mTOR Signaling in Growth Control and Disease

[...]

Mathieu Laplante¹, David M. Sabatini¹•Institutions (1)

Massachusetts Institute of Technology¹

01 Apr 2012

TL;DR: The mechanistic target of rapamycin (mTOR) signaling pathway senses and integrates a variety of environmental cues to regulate organismal growth and homeostasis as mentioned in this paper, and is implicated in an increasing number of pathological conditions, including cancer, obesity, type 2 diabetes, and neurodegeneration.

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Abstract: The mechanistic target of rapamycin (mTOR) signaling pathway senses and integrates a variety of environmental cues to regulate organismal growth and homeostasis. The pathway regulates many major cellular processes and is implicated in an increasing number of pathological conditions, including cancer, obesity, type 2 diabetes, and neurodegeneration. Here, we review recent advances in our understanding of the mTOR pathway and its role in health, disease, and aging. We further discuss pharmacological approaches to treat human pathologies linked to mTOR deregulation.

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6,268 citations

Journal Article•DOI•

mTOR signaling in growth control and disease.

[...]

Mathieu Laplante¹, David M. Sabatini¹•Institutions (1)

Massachusetts Institute of Technology¹

13 Apr 2012-Cell

TL;DR: Recent advances in understanding of the mTOR pathway are reviewed and pharmacological approaches to treat human pathologies linked to mTOR deregulation are discussed.

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5,792 citations

Cites background from "AMPK phosphorylation of raptor medi..."

...Like Akt, AMPK also communicates directly with mTORC1; it phosphorylates raptor, leading to 14-3-3 binding and the allosteric inhibition of mTORC1 (Gwinn et al., 2008)....
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Journal Article•DOI•

AMPK and mTOR regulate autophagy through direct phosphorylation of Ulk1

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Joungmok Kim¹, Mondira Kundu², Benoit Viollet³, Kun-Liang Guan¹•Institutions (3)

University of California, San Diego¹, St. Jude Children's Research Hospital², Paris Descartes University³

01 Feb 2011-Nature Cell Biology

TL;DR: A molecular mechanism for regulation of the mammalian autophagy-initiating kinase Ulk1, a homologue of yeast ATG1, is demonstrated and a signalling mechanism for UlK1 regulation and autophagic induction in response to nutrient signalling is revealed.

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Abstract: Autophagy is a process by which components of the cell are degraded to maintain essential activity and viability in response to nutrient limitation. Extensive genetic studies have shown that the yeast ATG1 kinase has an essential role in autophagy induction. Furthermore, autophagy is promoted by AMP activated protein kinase (AMPK), which is a key energy sensor and regulates cellular metabolism to maintain energy homeostasis. Conversely, autophagy is inhibited by the mammalian target of rapamycin (mTOR), a central cell-growth regulator that integrates growth factor and nutrient signals. Here we demonstrate a molecular mechanism for regulation of the mammalian autophagy-initiating kinase Ulk1, a homologue of yeast ATG1. Under glucose starvation, AMPK promotes autophagy by directly activating Ulk1 through phosphorylation of Ser 317 and Ser 777. Under nutrient sufficiency, high mTOR activity prevents Ulk1 activation by phosphorylating Ulk1 Ser 757 and disrupting the interaction between Ulk1 and AMPK. This coordinated phosphorylation is important for Ulk1 in autophagy induction. Our study has revealed a signalling mechanism for Ulk1 regulation and autophagy induction in response to nutrient signalling.

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5,314 citations

Journal Article•DOI•

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

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Daniel J. Klionsky¹, Kotb Abdelmohsen², Akihisa Abe³, Joynal Abedin⁴ +2519 more•Institutions (695)

21 Jan 2016-Autophagy

TL;DR: In this paper, the authors present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macro-autophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes.

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Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular assays, we hope to encourage technical innovation in the field.

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5,187 citations

Journal Article•DOI•

mTOR Signaling in Growth, Metabolism, and Disease.

[...]

Robert A. Saxton, David M. Sabatini

09 Mar 2017-Cell

TL;DR: Recent advances in understanding of mTOR function, regulation, and importance in mammalian physiology are reviewed and how the mTOR signaling network contributes to human disease is highlighted.

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4,719 citations

Cites background from "AMPK phosphorylation of raptor medi..."

...…as during glucose deprivation, activates the stress responsive metabolic regulator AMPK, which inhibits mTORC1 both indirectly, through phosphorylation and activation of TSC2, as well as directly, through the phosphorylation of Raptor (Gwinn et al., 2008; Inoki et al., 2003b; Shaw et al., 2004)....
[...]
...A reduction in cellular energy charge, such as during glucose deprivation, activates the stress responsive metabolic regulator AMPK, which inhibits mTORC1 both indirectly, through phosphorylation and activation of TSC2, as well as directly, through the phosphorylation of Raptor (Gwinn et al., 2008; Inoki et al., 2003b; Shaw et al., 2004)....
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References

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Open Access

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Journal Article•DOI•

TOR signaling in growth and metabolism.

[...]

Stephan Wullschleger¹, Robbie Loewith², Michael N. Hall¹•Institutions (2)

University of Basel¹, University of Geneva²

10 Feb 2006-Cell

TL;DR: The physiological consequences of mammalianTORC1 dysregulation suggest that inhibitors of mammalian TOR may be useful in the treatment of cancer, cardiovascular disease, autoimmunity, and metabolic disorders.

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5,553 citations

"AMPK phosphorylation of raptor medi..." refers background in this paper

...Similarly, mTOR signaling is hyperactivated in hamartomas from LKB1heterozygous mice (Shaw et al., 2004b) and in LKB1-deficient human lung carcinomas (Carretero et al., 2007). mTOR is a highly conserved nutrient-responsive regulator of cell growth found in all eukaryotes (Wullschleger et al., 2006)....
[...]
...mTOR, like its budding yeast orthologs, is found in two biochemically and functionally distinct signaling complexes (Wullschleger et al., 2006)....
[...]
...mTOR is a highly conserved nutrient-responsive regulator of cell growth found in all eukaryotes (Wullschleger et al., 2006)....
[...]
...In higher eukaryotes, mTOR activation requires positive signals from both nutrients (glucose, amino acids) and growth factors. mTOR, like its budding yeast orthologs, is found in two biochemically and functionally distinct signaling complexes (Wullschleger et al., 2006)....
[...]

Journal Article•DOI•

TSC2 mediates cellular energy response to control cell growth and survival.

[...]

Ken Inoki¹, Tianqing Zhu¹, Kun-Liang Guan¹•Institutions (1)

University of Michigan¹

26 Nov 2003-Cell

TL;DR: It is described that TSC2 is regulated by cellular energy levels and plays an essential role in the cellular energy response pathway and its phosphorylation by AMPK protect cells from energy deprivation-induced apoptosis.

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3,647 citations

"AMPK phosphorylation of raptor medi..." refers background in this paper

...224 Molecular Cell 30, 214–226, April 25, 2008 ª2008 Elsevier Inc. metics (Inoki et al., 2003; Corradetti et al., 2004; Shaw et al., 2004a, 2004b; Jones et al., 2005; Liu et al., 2006; Buzzai et al., 2007; Lee et al., 2007a)....
[...]
...…defective for AMPK activation (e.g., LKB1 deficient) or key components of the AMPK pathway (e.g., TSC2 deficient or p53 deficient) continue cycling and subsequently undergo apoptosis (Inoki et al., 2003; Corradetti et al., 2004; Shaw et al., 2004a, 2004b; Jones et al., 2005; Buzzai et al., 2007)....
[...]
...…directly phosphorylates the TSC2 tumor suppressor on conserved serine sites distinct from those targeted by other kinases, which constitutes one mechanism through which glucose and oxygen control mTORC1 activation (Inoki et al., 2003; Corradetti et al., 2004; Shaw et al., 2004b; Liu et al., 2006)....
[...]
...Upon LKB1- and AMP-dependent activation of AMPK by nutrient loss, AMPK directly phosphorylates the TSC2 tumor suppressor on conserved serine sites distinct from those targeted by other kinases, which constitutes one mechanism through which glucose and oxygen control mTORC1 activation (Inoki et al., 2003; Corradetti et al., 2004; Shaw et al., 2004b; Liu et al., 2006)....
[...]
..., TSC2 deficient or p53 deficient) continue cycling and subsequently undergo apoptosis (Inoki et al., 2003; Corradetti et al., 2004; Shaw et al., 2004a, 2004b; Jones et al., 2005; Buzzai et al., 2007)....
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Journal Article•DOI•

AMP-activated/SNF1 protein kinases: conserved guardians of cellular energy.

[...]

D. Grahame Hardie¹•Institutions (1)

University of Dundee¹

01 Oct 2007-Nature Reviews Molecular Cell Biology

TL;DR: Surprisingly, recent results indicate that the AMPK system is also important in functions that go beyond the regulation of energy homeostasis, such as the maintenance of cell polarity in epithelial cells.

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Abstract: The SNF1/AMP-activated protein kinase (AMPK) family maintains the balance between ATP production and consumption in all eukaryotic cells. The kinases are heterotrimers that comprise a catalytic subunit and regulatory subunits that sense cellular energy levels. When energy status is compromised, the system activates catabolic pathways and switches off protein, carbohydrate and lipid biosynthesis, as well as cell growth and proliferation. Surprisingly, recent results indicate that the AMPK system is also important in functions that go beyond the regulation of energy homeostasis, such as the maintenance of cell polarity in epithelial cells.

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2,095 citations

"AMPK phosphorylation of raptor medi..." refers background in this paper

...AMPK is activated under conditions of energy stress, when intracellular ATP levels decline and intracellular AMP increases, as occurs during nutrient deprivation or hypoxia (Hardie, 2007)....
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...Binding of AMP is thought to prevent dephosphorylation of the critical activation loop threonine in the a subunit (Hardie, 2007)....
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...In addition, hydrophobic residues including leucine and methionine were strongly selected in the 5 position and the +4 position consistent with previous studies of the optimal peptide substrates for AMPK based on mutagenesis and molecular modeling (Scott et al., 2002; Towler and Hardie, 2007)....
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Journal Article•DOI•

Ras, PI(3)K and mTOR signalling controls tumour cell growth.

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Reuben J. Shaw¹, Lewis C. Cantley²•Institutions (2)

Salk Institute for Biological Studies¹, Beth Israel Deaconess Medical Center²

25 May 2006-Nature

TL;DR: The preponderance of mutations in these interconnected pathways suggests that the loss of growth-control checkpoints and promotion of cell survival in nutrient-limited conditions may be an obligate event in tumorigenesis.

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Abstract: All eukaryotic cells coordinate cell growth with the availability of nutrients in their environment. The mTOR protein kinase has emerged as a critical growth-control node, receiving stimulatory signals from Ras and phosphatidylinositol-3-OH kinase (PI(3)K) downstream from growth factors, as well as nutrient inputs in the form of amino-acid, glucose and oxygen availability. Notably, components of the Ras and PI(3)K signalling pathways are mutated in most human cancers. The preponderance of mutations in these interconnected pathways suggests that the loss of growth-control checkpoints and promotion of cell survival in nutrient-limited conditions may be an obligate event in tumorigenesis.

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1,937 citations

"AMPK phosphorylation of raptor medi..." refers background in this paper

...Withdrawal of glucose, amino acids, or oxygen leads to rapid suppression of mTORC1 activity (Shaw and Cantley, 2006)....
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Journal Article•DOI•

The Kinase LKB1 Mediates Glucose Homeostasis in Liver and Therapeutic Effects of Metformin

[...]

Reuben J. Shaw¹, Reuben J. Shaw², Katja A. Lamia¹, Debbie S. Vasquez¹, Seung Hoi Koo², Seung Hoi Koo³, Nabeel Bardeesy¹, Ronald A. DePinho¹, Marc Montminy², Lewis C. Cantley¹ - Show less +6 more•Institutions (3)

Harvard University¹, Salk Institute for Biological Studies², Sungkyunkwan University³

09 Dec 2005-Science

TL;DR: It is shown that metformin, one of the most widely prescribed type 2 diabetes therapeutics, requires LKB1 in the liver to lower blood glucose levels, and TORC2 is a critical target of L KB1/AMPK signals in the regulation of gluconeogenesis.

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Abstract: The Peutz-Jegher syndrome tumor-suppressor gene encodes a protein-threonine kinase, LKB1, which phosphorylates and activates AMPK [adenosine monophosphate (AMP)–activated protein kinase]. The deletion of LKB1 in the liver of adult mice resulted in a nearly complete loss of AMPK activity. Loss of LKB1 function resulted in hyperglycemia with increased gluconeogenic and lipogenic gene expression. In LKB1-deficient livers, TORC2, a transcriptional coactivator of CREB (cAMP response element–binding protein), was dephosphorylated and entered the nucleus, driving the expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), which in turn drives gluconeogenesis. Adenoviral small hairpin RNA (shRNA) for TORC2 reduced PGC-1α expression and normalized blood glucose levels in mice with deleted liver LKB1, indicating that TORC2 is a critical target of LKB1/AMPK signals in the regulation of gluconeogenesis. Finally, we show that metformin, one of the most widely prescribed type 2 diabetes therapeutics, requires LKB1 in the liver to lower blood glucose levels.

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1,850 citations

"AMPK phosphorylation of raptor medi..." refers background in this paper

...We have previously shown that metformin rapidly activates AMPK in murine liver in a manner completely dependent on LKB1 (Shaw et al., 2005)....
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...Biochemical and genetic analyses in worms, flies, and mice have revealed that the serine/threonine kinase LKB1 represents the major kinase phosphorylating the AMPK activation loop under conditions of energy stress across metazoans (Apfeld et al., 2004; Shaw et al., 2005; Sakamoto et al., 2005; Mirouse et al., 2007; Lee et al., 2007b)....
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...…flies, and mice have revealed that the serine/threonine kinase LKB1 represents the major kinase phosphorylating the AMPK activation loop under conditions of energy stress across metazoans (Apfeld et al., 2004; Shaw et al., 2005; Sakamoto et al., 2005; Mirouse et al., 2007; Lee et al., 2007b)....
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...However, while classic PI3K/Akt signaling is not elevated in LKB1-deficient cells, mammalian target of rapamycin (mTOR) signaling is uniquely hyperactivated in LKB1-deficient murine embryonic fibroblasts (MEFs) and liver (Corradetti et al., 2004; Shaw et al., 2004b, 2005)....
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