Stress and mTORture signaling

Reiling, Jan H.; Sabatini, David M.

doi:10.1038/sj.onc.1209889

Cited by 315 publications

(307 citation statements)

References 180 publications

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“…The role of mTORC1 in the control of cap-dependent translation has been extensively studied [29][30][31] . When mTORC1 is active, it phosphorylates (activates) p70S6 kinase (S6K) and the eIF4e binding protein (4E-BP) (FIG.…”

Section: Mtor Kinase Complexes and Their Activitiesmentioning

confidence: 99%

The TORrid affairs of viruses: effects of mammalian DNA viruses on the PI3K–Akt–mTOR signalling pathway

et al. 2008

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The successful replication of mammalian DNA viruses requires that they gain control of key cellular signalling pathways that affect broad aspects of cellular macromolecular synthesis, metabolism, growth and survival. The phosphatidylinositol 3′-kinase-Akt-mammalian target of rapamycin (PI3K-Akt-mTOR) pathway is one such pathway. Mammalian DNA viruses have evolved various mechanisms to activate this pathway to obtain the benefits of Akt activation, including the maintenance of translation through the activation of mTOR. In addition, viruses must overcome the inhibition of this pathway that results from the activation of cellular stress responses during viral infection. This Review will discuss the range of mechanisms that mammalian DNA viruses use to activate this pathway, as well as the multiple mechanisms these viruses have evolved to circumvent inhibitory stress signalling.The successful replication of mammalian DNA viruses, such as polyomaviruses (also called papovaviruses), adenoviruses, herpesviruses and poxviruses, requires viral adaptation of the host cell to establish an environment that can accommodate the increased demands for nutrients, energy and macromolecular synthesis that accompany viral infection. All DNA viruses must gain control of key cellular signalling pathways that affect broad aspects of cellular macromolecular synthesis, metabolism, growth and survival. The phosphatidylinositol 3′-kinase-Akt-mammalian target of rapamycin (PI3K-Akt-mTOR) pathway is one such pathway. Virtually all mammalian viruses, both DNA and RNA, must regulate this pathway, either by activating or inactivating some aspect of it 1 . In general, mammalian DNA viruses activate this pathway at some point in their life cycle to benefit from the growth, metabolic, anti-apoptotic and translational functions that the pathway controls. However, a viral mechanism for activating this pathway is not enough; to maintain control, viruses must also overcome the many controls that are used to inhibit this pathway when cellular stress responses are activated during viral infection.Correspondence to J.C.A., e-mail: alwine@mail.med.upenn.edu. * These authors contributed equally to this work. DATABASES NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptThe substantial alterations in cellular physiology that are induced by a viral lytic infectionas a result of nutrient depletion, energy depletion, hypoxia and endoplasmic reticulum stress -activate cellular stress responses that alert the cell to problems with metabolic and synthetic processes. The resulting stress signalling activates mechanisms that either alleviate the problems or, if this is not possible, induce apoptosis. Stress signalling has many effects that can be either beneficial or detrimental to viral growth. One example of a detrimental effect is inhibition of translation, which is among the most common consequences of cellular stress responses 2-6 . Although the inhibition of this energy-intensive process permits the cell to recover from stress,...

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Section: Mtor Kinase Complexes and Their Activitiesmentioning

confidence: 99%

The TORrid affairs of viruses: effects of mammalian DNA viruses on the PI3K–Akt–mTOR signalling pathway

et al. 2008

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“…The natural occurrence of autophagy in photoreceptors might prevent degeneration, but during starvation, oxidative stress and protein accumulation autophagy increases and cells start to degenerate. The mammalian target of rapamycin (mTOR) controls a balance between protein synthesis and degradation, and the dysregulation of mTOR has been linked to neurodegenerative disorders (Reiling and Sabatini, 2006). Regulation of mTOR (Sarkar, 2013) and the autophagy marker microtubule-associated protein light chain 3B (LC3B) (Tanida et al, 2005) has been shown to be important during starvation.…”

Section: Introductionmentioning

confidence: 99%

Autophagy and ER-stress contribute to photoreceptor degeneration in cultured adult porcine retina

et al. 2014

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Abbreviations: AMD, age-related macular degeneration; BSA, bovine serum albumin; CHOP, C/EBP homology protein; CtBP2, C-terminal binding protein 2; ER, endoplasmic reticulum; GRP78/BiP, glucoseregulated protein 78kDa/Binding immunoglobulin protein, INL, inner nuclear layer; IPL, inner plexiform layer; LC3B, microtubule-associated protein light chain 3B; mTOR, mammalian target of rapamycin; ONL, outer nuclear layer; OPL, outer nuclear layer; PBS, phosphate buffered saline; PNA, peanut agglutinin; p62/SQSTM1; nucleoporin p62/sequestosom 1; PSD-95, postsynaptic density protein 95; rd1, retinal degeneration 1; RPE, retinal pigment epithelium; UPS, ubiquitin-proteasome system; 2 AbstractThe aim of this study was to investigate rod and cone photoreceptor degeneration in organotypic cultures of adult porcine retina. Our hypothesis was that the photoreceptors accumulate opsins, which, together with exposure to cyclic dim light illumination, induce autophagy and endoplasmic reticulum stress (ER-stress) to overcome damaging protein overload. For this purpose, retinas were cultured for 48 h and 72 h during which they were illuminated with dim light for 8 h/day; specimens were analyzed by means of immunohistochemistry, western blot and transmission electron microscopy. ER-stress and photoreceptor degeneration was observed in conventionally cultured retinas. The additional stress in the form of dim light illumination for 8 h/day resulted in increased levels of the ER-stress markers GRP78/BiP and CHOP, as well as increased level of active caspase-12. Increased autophagic processes in cone and rod photoreceptors were detected by LC3B-II increases and occurrence of autophagosomes at the ultrastructural level. Illumination also resulted in altered protein expression for autophagy inducers such as p62 and Beclin-1. Moreover, there was a decrease in phosphorylated mammalian target of rapamycin (mTOR), which further indicate an increase of autophagy. Rod and cone photoreceptors in retinas from a diurnal animal that were exposed to dim light illumination in vitro displayed autophagy and ER-stress processes. In particular, these processes resulted in decreased protein levels for rhodopsin.3

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“…Two of the best characterized targets of mammalian TOR, the ribosomal S6 protein kinases (S6K) and the eukaryotic initiation factor 4E binding proteins, are regulators of protein synthesis [1][2][3]. TOR-dependent activation of mammalian S6K increases protein synthesis by promoting assembly of the eukaryotic translation preinitiation complex [4].…”

Section: Introductionmentioning

confidence: 99%

Functional analysis of the PP2A subfamily of protein phosphatases in regulating Drosophila S6 kinase

Bielinski¹,

Mumby²

2007

Experimental Cell Research

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Phosphorylation and activation of ribosomal S6 protein kinase is an important link in the regulation of cell size by the target of rapamycin (TOR) protein kinase. A combination of selective inhibition and RNA interference were used to test the roles of members of the PP2A subfamily of protein phosphatases in dephosphorylation of Drosophila S6 kinase (dS6K). Treatment of Drosophila Schneider 2 cells with calyculin A, a selective inhibitor of PP2A-like phosphatases, resulted in a 7-fold increase in the basal level of dS6K phosphorylation at the TOR phosphorylation site (Thr398) and blocked dephosphorylation following inactivation of TOR by amino acid starvation or rapamycin treatment. Knockdown of the PP2A catalytic subunit increased basal dS6K phosphorylation and inhibited dephosphorylation induced by amino acid withdrawal. In contrast, depletion of the catalytic subunits of the other two members of the subfamily did not enhance dS6K phosphorylation. Knockdown of PP4 caused a 20% decrease in dS6K phosphorylation and knockdown of PP6 had no effect. Knockdown of the Drosophila B56-2 subunit resulted in enhanced dephosphorylation of dS6K following removal of amino acids. In contrast, knockdown of the homologs of the other PP2A regulatory subunits had no effects. Knockdown of the Drosophila homolog of the PP2A/PP4/PP6 interaction protein α4/Tap42 did not affect S6K phosphorylation, but did induce apoptosis. These results indicate that PP2A, but not other members of this subfamily, is likely to be a major S6K phosphatase in intact cells and is consistent with an important role for this phosphatase in the TOR pathway.

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Stress and mTORture signaling

Cited by 315 publications

References 180 publications

The TORrid affairs of viruses: effects of mammalian DNA viruses on the PI3K–Akt–mTOR signalling pathway

The TORrid affairs of viruses: effects of mammalian DNA viruses on the PI3K–Akt–mTOR signalling pathway

Autophagy and ER-stress contribute to photoreceptor degeneration in cultured adult porcine retina

Functional analysis of the PP2A subfamily of protein phosphatases in regulating Drosophila S6 kinase

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