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Chen R, Huang Z, Wang J, Chen X, Fu Y, Wang W. Silent Information Regulator 1 Negatively Regulates Atherosclerotic Angiogenesis via Mammalian Target of Rapamycin Complex 1 Signaling Pathway. Am J Med Sci 2018; 356:168-176. [PMID: 30219159 DOI: 10.1016/j.amjms.2018.04.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 04/19/2018] [Accepted: 04/20/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND This study aimed to investigate the interactions between silent information regulator 1 (SIRT1) and mammalian target of rapamycin (mTOR) in intraplaque angiogenesis and their potential mechanisms through in vivo and in vitro studies. METHODS An atherosclerosis model was established in 12 rabbits on a high-cholesterol diet. The rabbits were equally divided into 3 groups: a control group (high-lipid diet), RAP group (high-lipid diet supplemented with rapamycin) and RAP + NAM group (high-lipid diet supplemented with rapamycin and nicotinamide). At the end of 4 weeks, the area of plaques in the aorta was determined and the protein expression of CD31 and vascular endothelial growth factor (VEGF) was detected through hematoxylin and eosin staining and immunohistochemical staining, respectively. For in vitro study, a hypoxia model was established in human umbilical vein endothelial cells (HUVECs) by using the chemical method (CoCl2). The MTT assay, scratch assay and tube formation assay were performed to evaluate the proliferation and angiogenesis abilities of HUVECs. Reverse transcription polymerase chain reaction was used to examine the mRNA levels of SIRT1, hypoxia-inducible factor-1α (HIF-1α), mTOR and p70 ribosomal S6 kinase (p70S6K). Western blotting was used to examine the protein levels of SIRT1, HIF-1α, mTOR, p-mTOR, p-raptor and p-p70S6K. RESULTS The results of the in vivo study indicated a significant inhibitory effect of rapamycin on plaque size and intraplaque angiogenesis (0.05 ± 0.02mm2 versus 5.44 ± 0.50mm2, P < 0.05). This effect was attenuated by nicotinamide (0.76 ± 0.15mm2 versus 0.05 ± 0.02mm2, P < 0.05). Compared with the RAP group, CD31- and VEGF-positive vessels were abundant in the RAP + NAM group. The RAP group showed lower expression of p-mTOR, p-p70S6K and HIF-1α than did the control group (P < 0.05), whereas the RAP + NAM group showed slightly higher expression of these factors than did the RAP group (P < 0.05). Furthermore, in vitro studies revealed that the inhibitory effect of rapamycin on the angiogenic ability of HUVECs and its significant inhibitory effects on the protein level of HIF-1α and the phosphorylation of proteins involved in the mTORC1 pathway, including mTOR, raptor and p70S6K (P < 0.05), were enhanced by cotreatment with SRT1720 and rapamycin (P < 0.05). In contrast to mTOR and SIRT1, the mRNA levels of p70S6K and HIF-1α were reduced by rapamycin (P < 0.05) and further reduced by cotreatment with SRT1720 and rapamycin. CONCLUSIONS The study results indicate that SIRT1 might negatively regulate atherosclerotic angiogenesis via mTORC1 and HIF-1α signaling pathway and cointervention of SIRT1 and mTOR may serve as a crucial therapeutic strategy in cardiovascular medicine.
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Affiliation(s)
- Runtai Chen
- Department of Cardiology of the Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong Province, People's Republic of China
| | - Zhenchun Huang
- Department of Cardiology of the Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong Province, People's Republic of China
| | - Junyi Wang
- Department of Cardiology of the Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong Province, People's Republic of China
| | - Xiaoying Chen
- Department of Cardiology of the Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong Province, People's Republic of China
| | - Yucai Fu
- Laboratory of Cell Senescence, Shantou University Medical College, Shantou, Guangdong Province, People's Republic of China
| | - Wei Wang
- Department of Cardiology of the Second Affiliated Hospital, Shantou University Medical College, Shantou, Guangdong Province, People's Republic of China.
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152
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Nguyen QD, Merrill PT, Sepah YJ, Ibrahim MA, Banker A, Leonardi A, Chernock M, Mudumba S, Do DV. Intravitreal Sirolimus for the Treatment of Noninfectious Uveitis: Evolution through Preclinical and Clinical Studies. Ophthalmology 2018; 125:1984-1993. [PMID: 30060978 DOI: 10.1016/j.ophtha.2018.06.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 05/31/2018] [Accepted: 06/11/2018] [Indexed: 10/28/2022] Open
Abstract
In recent decades, the treatment paradigm for noninfectious intermediate uveitis, posterior uveitis, and panuveitis, a group of intraocular inflammatory diseases, has included systemic and local (periocular or intraocular) corticosteroids, biologics, and other steroid-sparing immunomodulatory therapy agents. Recently, an intravitreal formulation of sirolimus, an immunosuppressant that inhibits the mammalian target of rapamycin, a key regulator of cell growth in the immune system, was developed. On the basis of this mechanism and the local method of delivery, it was hypothesized that intravitreal sirolimus can improve ocular inflammation in patients with noninfectious intermediate uveitis, posterior uveitis, and panuveitis, with minimal systemic exposure and systemic adverse events (AEs). This review summarizes the pharmacokinetics, efficacy, and safety results of intravitreal sirolimus from 3 preclinical studies and 4 phase 1-3 clinical studies. Preclinical studies in rabbits showed that 22 to 220 μg intravitreal sirolimus results in sustained release of sirolimus in the vitreous for 2 months or more, with systemic concentrations below the threshold for systemic immunosuppression (approximately 8 ng/ml). Subsequently, 2 phase 1 studies (n = 50 and n = 30) established that intravitreal sirolimus improves ocular inflammation in humans. Further investigation in phase 2 and 3 studies (n = 24 and n = 347, respectively) suggested that 440 μg has the best benefit-to-risk profile. In the phase 3 study, the proportion of patients who showed complete resolution of ocular inflammation at month 5 was significantly higher in the 440-μg group than in the 44-μg group (22.8% vs. 10.3%; P = 0.025, Fisher exact test). In addition, 47 of 69 patients (68.1%) who were treated with systemic corticosteroids at baseline discontinued corticosteroid use at month 5. No sirolimus-related systemic AEs were reported in phase 1-3 studies. Collectively, these preclinical and clinical study data of intravitreal sirolimus support the therapeutic rationale of treating noninfectious uveitis with a local mammalian target of rapamycin inhibitor and suggest that 440 μg intravitreal sirolimus has the potential to be an effective and well-tolerated anti-inflammatory and corticosteroid-sparing treatment for noninfectious intermediate uveitis, posterior uveitis, and panuveitis.
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Affiliation(s)
- Quan Dong Nguyen
- Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California.
| | - Pauline T Merrill
- Department of Ophthalmology, Rush University Medical Center, Chicago, Illinois
| | - Yasir J Sepah
- Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California
| | - Mohamed A Ibrahim
- Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland; Ocular Imaging Research and Reading Center (OIRRC), Menlo Park, California
| | - Alay Banker
- Banker's Retina Clinic and Laser Center, Navrangpura, Ahmedabad, India
| | - Andrea Leonardi
- Department of Neuroscience, Ophthalmology Unit, University of Padua, Padua, Italy
| | | | | | - Diana V Do
- Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California
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153
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Abstract
Background The protein kinase Target Of Rapamycin (TOR) is a nexus for the regulation of eukaryotic cell growth. TOR assembles into one of two distinct signalling complexes, TOR complex 1 (TORC1) and TORC2 (mTORC1/2 in mammals), with a set of largely non-overlapping protein partners. (m)TORC1 activation occurs in response to a series of stimuli relevant to cell growth, including nutrient availability, growth factor signals and stress, and regulates much of the cell's biosynthetic activity, from proteins to lipids, and recycling through autophagy. mTORC1 regulation is of great therapeutic significance, since in humans many of these signalling complexes, alongside subunits of mTORC1 itself, are implicated in a wide variety of pathophysiologies, including multiple types of cancer, neurological disorders, neurodegenerative diseases and metabolic disorders including diabetes. Methodology Recent years have seen numerous structures determined of (m)TOR, which have provided mechanistic insight into (m)TORC1 activation in particular, however the integration of cellular signals occurs upstream of the kinase and remains incompletely understood. Here we have collected and analysed in detail as many as possible of the molecular and structural studies which have shed light on (m)TORC1 repression, activation and signal integration. Conclusions A molecular understanding of this signal integration pathway is required to understand how (m)TORC1 activation is reconciled with the many diverse and contradictory stimuli affecting cell growth. We discuss the current level of molecular understanding of the upstream components of the (m)TORC1 signalling pathway, recent progress on this key biochemical frontier, and the future studies necessary to establish a mechanistic understanding of this master-switch for eukaryotic cell growth.
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Affiliation(s)
- Kailash Ramlaul
- Section of Structural Biology, Department of Medicine, Imperial College London, SW7 2AZ, UK
| | - Christopher H S Aylett
- Section of Structural Biology, Department of Medicine, Imperial College London, SW7 2AZ, UK
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154
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Zhang H, Lin C, Zeng C, Wang Z, Wang H, Lu J, Liu X, Shao Y, Zhao C, Pan J, Xu S, Zhang Y, Xie D, Cai D, Bai X. Synovial macrophage M1 polarisation exacerbates experimental osteoarthritis partially through R-spondin-2. Ann Rheum Dis 2018; 77:1524-1534. [DOI: 10.1136/annrheumdis-2018-213450] [Citation(s) in RCA: 151] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/12/2018] [Accepted: 06/17/2018] [Indexed: 12/14/2022]
Abstract
ObjectivesTo investigate the roles and regulatory mechanisms of synovial macrophages and their polarisation in the development of osteoarthritis (OA).MethodsSynovial tissues from normal patients and patients with OA were collected. M1 or M2-polarised macrophages in synovial tissues of patients with OA and OA mice were analysed by immunofluorescence and immunohistochemical staining. Mice with tuberous sclerosis complex 1 (TSC1) or Rheb deletion specifically in the myeloid lineage were generated and subjected to intra-articular injection of collagenase (collagenase-induced osteoarthritis, CIOA) and destabilisation of the medial meniscus (DMM) surgery to induce OA. Cartilage damage and osteophyte size were measured by Osteoarthritis Research Society International score and micro-CT, respectively. mRNA sequencing was performed in M1 and control macrophages. Mice and ATDC5 cells were treated with R-spondin-2 (Rspo2) or anti-Rspo2 to investigate the role of Rspo2 in OA.ResultsM1 but not M2-polarised macrophages accumulated in human and mouse OA synovial tissue. TSC1 deletion in the myeloid lineage constitutively activated mechanistic target of rapamycin complex 1 (mTORC1), increased M1 polarisation in synovial macrophages and exacerbated experimental OA in both CIOA and DMM models, while Rheb deletion inhibited mTORC1, enhanced M2 polarisation and alleviated CIOA in mice. The results show that promoting the macrophage M1 polarisation leads to exacerbation of experimental OA partially through secretion of Rspo2 and activation of β-catenin signalling in chondrocytes.ConclusionsSynovial macrophage M1 polarisation exacerbates experimental CIOA partially through Rspo2. M1 macrophages and Rspo2 are potential therapeutic targets for OA treatment.
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155
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Abstract
Target of rapamycin (TOR) is an evolutionarily conserved protein kinase that plays a central role in both plants and animals, despite their distinct developmental programs and survival strategies. Indeed, TOR integrates nutrient, energy, hormone, growth factor and environmental inputs to control proliferation, growth and metabolism in diverse multicellular organisms. Here, we compare the molecular composition, upstream regulators and downstream signaling relays of TOR complexes in plants and animals. We also explore and discuss the pivotal functions of TOR signaling in basic cellular processes, such as translation, cell division and stem/progenitor cell regulation during plant development.
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Affiliation(s)
- Lin Shi
- Department of Molecular Biology and Centre for Computational and Integrative Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Yue Wu
- Department of Molecular Biology and Centre for Computational and Integrative Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Jen Sheen
- Department of Molecular Biology and Centre for Computational and Integrative Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
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156
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Abstract
The LRRK2 gene is a major contributor to genetic risk for Parkinson's disease and understanding the biology of the leucine-rich repeat kinase 2 (LRRK2, the protein product of this gene) is an important goal in Parkinson's research. LRRK2 is a multi-domain, multi-activity enzyme and has been implicated in a wide range of signalling events within the cell. Because of the complexities of the signal transduction pathways in which LRRK2 is involved, it has been challenging to generate a clear idea as to how mutations and disease associated variants in this gene are altered in disease. Understanding the events in which LRRK2 is involved at a systems level is therefore critical to fully understand the biology and pathobiology of this protein and is the subject of this review.
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Affiliation(s)
- Alice Price
- School of Pharmacy, University of Reading, Whiteknights, Reading, RG6 6AP, UK
| | - Claudia Manzoni
- School of Pharmacy, University of Reading, Whiteknights, Reading, RG6 6AP, UK
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Mark R Cookson
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Building. 35, 35 Convent Drive, Bethesda, MD, 20892, USA
| | - Patrick A Lewis
- School of Pharmacy, University of Reading, Whiteknights, Reading, RG6 6AP, UK.
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK.
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157
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Wang H, Lo WT, Vujičić Žagar A, Gulluni F, Lehmann M, Scapozza L, Haucke V, Vadas O. Autoregulation of Class II Alpha PI3K Activity by Its Lipid-Binding PX-C2 Domain Module. Mol Cell 2018; 71:343-351.e4. [DOI: 10.1016/j.molcel.2018.06.042] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 05/14/2018] [Accepted: 06/27/2018] [Indexed: 11/30/2022]
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158
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Hill A, Niles B, Cuyegkeng A, Powers T. Redesigning TOR Kinase to Explore the Structural Basis for TORC1 and TORC2 Assembly. Biomolecules 2018; 8:biom8020036. [PMID: 29865216 PMCID: PMC6023025 DOI: 10.3390/biom8020036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 05/25/2018] [Accepted: 05/25/2018] [Indexed: 12/21/2022] Open
Abstract
TOR is a serine/threonine protein kinase that assembles into distinct TOR Complexes 1 and 2 (TORC1 or TORC2) to regulate cell growth. In mammalian cells, a single mTOR incorporates stably into mTORC1 and mTORC2. By contrast, in Saccharomyces cerevisiae, two highly similar Tor1 and Tor2 proteins exist, where Tor1 assembles exclusively into TORC1 and Tor2 assembles preferentially into TORC2. To gain insight into TOR complex assembly, we used this bifurcation in yeast to identify structural elements within Tor1 and Tor2 that govern their complex specificity. We have identified a concise region of ~500 amino acids within the N-terminus of Tor2, which we term the Major Assembly Specificity (MAS) domain, that is sufficient to confer significant TORC2 activity when placed into an otherwise Tor1 protein. Consistently, introduction of the corresponding MAS domain from Tor1 into an otherwise Tor2 is sufficient to confer stable association with TORC1-specific components. Remarkably, much like mTOR, this latter chimera also retains stable interactions with TORC2 components, indicating that determinants throughout Tor1/Tor2 contribute to complex specificity. Our findings are in excellent agreement with recent ultrastructural studies of TORC1 and TORC2, where the MAS domain is involved in quaternary interactions important for complex formation and/or stability.
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Affiliation(s)
- Andrew Hill
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
| | - Brad Niles
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
| | - Andrew Cuyegkeng
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
| | - Ted Powers
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California Davis, Davis, CA 95616, USA.
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159
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mTOR Signaling and Neural Stem Cells: The Tuberous Sclerosis Complex Model. Int J Mol Sci 2018; 19:ijms19051474. [PMID: 29772672 PMCID: PMC5983755 DOI: 10.3390/ijms19051474] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/04/2018] [Accepted: 05/11/2018] [Indexed: 12/24/2022] Open
Abstract
The mechanistic target of rapamycin (mTOR), a serine-threonine kinase, plays a pivotal role in regulating cell growth and proliferation. Notably, a great deal of evidence indicates that mTOR signaling is also crucial in controlling proliferation and differentiation of several stem cell compartments. Consequently, dysregulation of the mTOR pathway is often associated with a variety of disease, such as cancer and metabolic and genetic disorders. For instance, hyperactivation of mTORC1 in neural stem cells (NSCs) is associated with the insurgence of neurological manifestation characterizing tuberous sclerosis complex (TSC). In this review, we survey the recent contributions of TSC physiopathology studies to understand the role of mTOR signaling in both neurogenesis and tumorigenesis and discuss how these new insights can contribute to developing new therapeutic strategies for neurological diseases and cancer.
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160
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cPKCγ-Modulated Sequential Reactivation of mTOR Inhibited Autophagic Flux in Neurons Exposed to Oxygen Glucose Deprivation/Reperfusion. Int J Mol Sci 2018; 19:ijms19051380. [PMID: 29734780 PMCID: PMC5983661 DOI: 10.3390/ijms19051380] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 04/24/2018] [Accepted: 05/03/2018] [Indexed: 01/05/2023] Open
Abstract
We have reported that conventional protein kinase Cγ (cPKCγ)-modulated neuron-specific autophagy improved the neurological outcome of mice following ischemic stroke through the Akt-mechanistic target of rapamycin (mTOR) pathway. However, its detailed molecular mechanism remains unclear. In this study, primary cortical neurons from postnatal one-day-old C57BL/6J cPKCγ wild-type (cPKCγ+/+) and knockout (cPKCγ−/−) mice suffering oxygen glucose deprivation/reperfusion (OGD/R) were used to simulate ischemia/reperfusion injury in vitro. A block of autophagic flux was observed in cPKCγ+/+ neurons under OGD/R exposure, characterized by accumulation of p62. Immunofluorescent results showed a decrease in colocalization between LC3 and Atg14 or Stx17 in cPKCγ+/+ neurons when compared with cPKCγ−/− neurons after OGD/R. However, the colocalization between LC3 and Lamp2 was barely decreased, indicating the presence of autolysosomes. The larger lysotracker-positive structures were also significantly increased. These results suggest that cPKCγ-induced inhibition of autophagy occurred at the stages of autophagosome formation, Stx17 anchoring, and the degradation of autolysosomes in particular. In addition, cPKCγ-modulated phosphorylation of mTOR at Ser 2481 was dependent on the site of Ser 2448, which may have blocked autophagic flux. cPKCγ-modulated sequential reactivation of mTOR inhibited autophagic flux in neurons exposed to OGD/R, which may provide endogenous interventional strategies for stroke, especially ischemia/reperfusion injury.
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161
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Sawicka M, Aramayo R, Ayala R, Glyde R, Zhang X. Single-Particle Electron Microscopy Analysis of DNA Repair Complexes. Methods Enzymol 2018; 592:159-186. [PMID: 28668120 DOI: 10.1016/bs.mie.2017.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
DNA repair complexes play crucial roles in maintaining genome integrity, which is essential for the survival of an organism. The understanding of their modes of action is often obscure due to limited structural knowledge. Structural characterizations of these complexes are often challenging due to a poor protein production yield, a conformational flexibility, and a relatively high molecular mass. Single-particle electron microscopy (EM) has been successfully applied to study some of these complexes as it requires low amount of samples, is not limited by the high molecular mass of a protein or a complex, and can separate heterogeneous assemblies. Recently, near-atomic resolution structures have been obtained with EM owing to the advances in technology and image processing algorithms. In this chapter, we review the EM methodology of obtaining three-dimensional reconstructions of macromolecular complexes and provide a workflow that can be applied to DNA repair complex assemblies.
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Affiliation(s)
- Marta Sawicka
- Section of Structural Biology, Imperial College London, South Kensington, London, United Kingdom
| | - Ricardo Aramayo
- Section of Structural Biology, Imperial College London, South Kensington, London, United Kingdom
| | - Rafael Ayala
- Section of Structural Biology, Imperial College London, South Kensington, London, United Kingdom
| | - Robert Glyde
- Section of Structural Biology, Imperial College London, South Kensington, London, United Kingdom
| | - Xiaodong Zhang
- Section of Structural Biology, Imperial College London, South Kensington, London, United Kingdom.
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162
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Ukai H, Araki Y, Kira S, Oikawa Y, May AI, Noda T. Gtr/Ego-independent TORC1 activation is achieved through a glutamine-sensitive interaction with Pib2 on the vacuolar membrane. PLoS Genet 2018; 14:e1007334. [PMID: 29698392 PMCID: PMC5919408 DOI: 10.1371/journal.pgen.1007334] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 03/15/2018] [Indexed: 12/18/2022] Open
Abstract
TORC1 is a central regulator of cell growth in response to amino acids. The role of the evolutionarily conserved Gtr/Rag pathway in the regulation of TORC1 is well-established. Recent genetic studies suggest that an additional regulatory pathway, depending on the activity of Pib2, plays a role in TORC1 activation independently of the Gtr/Rag pathway. However, the interplay between the Pib2 pathway and the Gtr/Rag pathway remains unclear. In this study, we show that Pib2 and Gtr/Ego form distinct complexes with TORC1 in a mutually exclusive manner, implying dedicated functional relationships between TORC1 and Pib2 or Gtr/Rag in response to specific amino acids. Furthermore, simultaneous depletion of Pib2 and the Gtr/Ego system abolishes TORC1 activity and completely compromises the vacuolar localization of TORC1. Thus, the amino acid-dependent activation of TORC1 is achieved through the Pib2 and Gtr/Ego pathways alone. Finally, we show that glutamine induces a dose-dependent increase in Pib2-TORC1 complex formation, and that glutamine binds directly to the Pib2 complex. These data provide strong preliminary evidence for Pib2 functioning as a putative glutamine sensor in the regulation of TORC1. TORC1 is a central regulator of cell growth in response to amino acids. The evolutionarily conserved Gtr/Rag pathway is a well-established TORC1 regulatory pathway. In this study, we show that two molecular machineries, Pib2 and Gtr/Ego, form distinct complexes with TORC1 in a mutually exclusive manner, implying an exclusive functional relationship between TORC1 and Pib2 or Gtr/Rag in response to various amino acids. We also show that the amino acid-dependent activation of TORC1 is achieved through the Pib2 and Gtr/Ego pathways by anchoring them to the vacuolar membrane. Finally, we show that glutamine binds directly to the Pib2 complex and that glutamine enhances Pib2-TORC1 complex formation. Collectively we provide evidence supporting a role for Pib2 as an element of a putative glutamine sensor.
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Affiliation(s)
- Hirofumi Ukai
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Yasuhiro Araki
- Graduate School of Dentistry, Osaka University, Osaka, Japan
- * E-mail: (TN); (YA)
| | - Shintaro Kira
- Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Yu Oikawa
- Research Center of Cell Biology, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Alexander I. May
- Research Center of Cell Biology, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Takeshi Noda
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
- Graduate School of Dentistry, Osaka University, Osaka, Japan
- * E-mail: (TN); (YA)
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163
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Molecular Architecture of the Essential Yeast Histone Acetyltransferase Complex NuA4 Redefines Its Multimodularity. Mol Cell Biol 2018; 38:MCB.00570-17. [PMID: 29463645 DOI: 10.1128/mcb.00570-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 02/11/2018] [Indexed: 11/20/2022] Open
Abstract
Conserved from yeast to humans, the NuA4 histone acetyltransferase is a large multisubunit complex essential for cell viability through the regulation of gene expression, genome maintenance, metabolism, and cell fate during development and stress. How the different NuA4 subunits work in concert with one another to perform these diverse functions remains unclear, and addressing this central question requires a comprehensive understanding of NuA4's molecular architecture and subunit organization. We have determined the structure of fully assembled native yeast NuA4 by single-particle electron microscopy. Our data revealed that NuA4 adopts a trilobal overall architecture, with each of the three lobes constituted by one or two functional modules. By performing cross-linking coupled to mass spectrometry analysis and in vitro protein interaction studies, we further mapped novel intermolecular interfaces within NuA4. Finally, we combined these new data with other known structural information of NuA4 subunits and subassemblies to construct a multiscale model to illustrate how the different NuA4 subunits and modules are spatially arranged. This model shows that the multiple chromatin reader domains are clustered together around the catalytic core, suggesting that NuA4's multimodular architecture enables it to engage in multivalent interactions with its nucleosome substrate.
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164
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Imseng S, Aylett CHS, Maier T. Architecture and activation of phosphatidylinositol 3-kinase related kinases. Curr Opin Struct Biol 2018; 49:177-189. [DOI: 10.1016/j.sbi.2018.03.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 03/02/2018] [Accepted: 03/08/2018] [Indexed: 12/23/2022]
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165
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Chen X, Liu M, Tian Y, Li J, Qi Y, Zhao D, Wu Z, Huang M, Wong CCL, Wang HW, Wang J, Yang H, Xu Y. Cryo-EM structure of human mTOR complex 2. Cell Res 2018; 28:518-528. [PMID: 29567957 DOI: 10.1038/s41422-018-0029-3] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 02/02/2018] [Accepted: 02/24/2018] [Indexed: 02/07/2023] Open
Abstract
Mechanistic target of rapamycin (mTOR) complex 2 (mTORC2) plays an essential role in regulating cell proliferation through phosphorylating AGC protein kinase family members, including AKT, PKC and SGK1. The functional core complex consists of mTOR, mLST8, and two mTORC2-specific components, Rictor and mSin1. Here we investigated the intermolecular interactions within mTORC2 complex and determined its cryo-electron microscopy structure at 4.9 Å resolution. The structure reveals a hollow rhombohedral fold with a 2-fold symmetry. The dimerized mTOR serves as a scaffold for the complex assembly. The N-terminal half of Rictor is composed of helical repeat clusters and binds to mTOR through multiple contacts. mSin1 is located close to the FRB domain and catalytic cavity of mTOR. Rictor and mSin1 together generate steric hindrance to inhibit binding of FKBP12-rapamycin to mTOR, revealing the mechanism for rapamycin insensitivity of mTORC2. The mTOR dimer in mTORC2 shows more compact conformation than that of mTORC1 (rapamycin sensitive), which might result from the interaction between mTOR and Rictor-mSin1. Structural comparison shows that binding of Rictor and Raptor (mTORC1-specific component) to mTOR is mutually exclusive. Our study provides a basis for understanding the assembly of mTORC2 and a framework to further characterize the regulatory mechanism of mTORC2 pathway.
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Affiliation(s)
- Xizi Chen
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Mengjie Liu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Yuan Tian
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Jiabei Li
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Yilun Qi
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Dan Zhao
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Zihan Wu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China
| | - Min Huang
- National Center for Protein Science Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 201210, China
| | - Catherine C L Wong
- National Center for Protein Science Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 201210, China.,Center for Precision Medicine Multi-Omics Research (CPMMOR), Peking University Health Science Center, Beijing, 100871, China.,State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Science, Peking University, Beijing, 100871, China
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jiawei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Huirong Yang
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China. .,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China. .,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China.
| | - Yanhui Xu
- Fudan University Shanghai Cancer Center, Institutes of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China. .,Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China. .,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China. .,CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.
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166
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Cho C, Michailidis V, Martin LJ. Revealing brain mechanisms of mTOR-mediated translational regulation: Implications for chronic pain. NEUROBIOLOGY OF PAIN 2018; 4:27-34. [PMID: 31194026 PMCID: PMC6550104 DOI: 10.1016/j.ynpai.2018.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 03/15/2018] [Accepted: 03/16/2018] [Indexed: 12/27/2022]
Abstract
mTOR is a major regulator of protein translation. mTOR serves an important role in neural plasticity. mTOR signalling in the brain as a pathology for neurological disorder is known. mTOR signalling in the brain as a chronic pain mechanism is understudied.
In the spinal cord, altered protein transcription and translation have received a lot of recent attention for their role in neural plasticity, a major mechanism leading to the development of chronic pain. However, changes in brain plasticity are also associated with the maintenance of pain symptoms, but these cellular mechanisms remain less clear. The mechanistic/mammalian target of rapamycin (mTOR) is a master regulator of protein synthesis, and controls several neuronal functions, including neural plasticity. While aberrant changes in mTOR signaling are associated with sensitization of the pain pathway (sensory neurons and spinal cord), there are various nervous system diseases that have pain as a comorbidity and altered mTOR activity in the brain. Here, we provide a brief review of mTOR changes in the brain that are associated with some neurological disorders and focus on how these changes may be relevant to the pain of the underlying condition and chronic pain itself.
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Affiliation(s)
- Chulmin Cho
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Vassilia Michailidis
- Deptartment of Cell and Systems Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Loren J. Martin
- Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Deptartment of Cell and Systems Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Corresponding author at: Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Rd., Mississauga, ON L5L 1C6, Canada.
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167
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Architecture of the Saccharomyces cerevisiae NuA4/TIP60 complex. Nat Commun 2018; 9:1147. [PMID: 29559617 PMCID: PMC5861120 DOI: 10.1038/s41467-018-03504-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 02/19/2018] [Indexed: 01/06/2023] Open
Abstract
The NuA4/TIP60 acetyltransferase complex is required for gene regulation, DNA repair and cell cycle progression. The limited structural information impeded understanding of NuA4/TIP60 assembly and regulatory mechanism. Here, we report the 4.7 Å cryo-electron microscopy (cryo-EM) structure of a NuA4/TIP60 TEEAA assembly (Tra1, Eaf1, Eaf5, actin and Arp4) and the 7.6 Å cryo-EM structure of a TEEAA-piccolo assembly (Esa1, Epl1, Yng2 and Eaf6). The Tra1 and Eaf1 constitute the assembly scaffold. The Eaf1 SANT domain tightly binds to the LBE and FATC domains of Tra1 by ionic interactions. The actin/Arp4 peripherally associates with Eaf1 HSA domain. The Eaf5/7/3 (TINTIN) and piccolo modules largely pack against the FAT and HEAT repeats of Tra1 and their association depends on Eaf1 N-terminal and HSA regions, respectively. These structures elucidate the detailed architecture and molecular interactions between NuA4 subunits and offer exciting insights into the scaffolding and regulatory mechanisms of Tra1 pseudokinase. The NuA4 histone acetyltransferase complex is important for gene regulation, DNA repair processes and cell cycle progression. Here the authors give molecular insights into the NuA4 complex by presenting the cryo-EM structures of the NuA4 TEEAA (Tra1, Eaf1, Eaf5, actin, and Arp4) and TEEAA-piccolo NuA4 assemblies.
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168
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Wang Q, Wei LW, Zhou WT, Wang ZT, Xie XL. PCB28 and PCB52 induce hepatotoxicity by impairing the autophagic flux and stimulating cell apoptosis in vitro. Toxicol Lett 2018. [PMID: 29518472 DOI: 10.1016/j.toxlet.2018.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hepatotoxicity is one of the adverse health effects induced by polychlorinated biphenyls (PCBs). Recently, autophagy was revealed to play an important role in PCBs-induced toxicology, however, its precise role in PCBs-induced hepatotoxicity is as yet unknown. In this study, treatment of PCB28/PCB52 for 48 h dose-dependently induced hepatotoxicity at doses of 10, 20, 40 and 80 μM in homo and rattus hepatocytes. Expressions of proteins of BECN1, LC3-II and ULK1 significantly increased in PCB28/PCB52-treated cells at a dose of 40 μM, implying initiation of autophagy. Over-expression of p62 suggested deficient clearance of autophagosome. Consistently, accumulation of autophagosome was observed by transmission-electron microscopy and confocal fluorescence microscopy using adenovirus expressing mRFP-GFP-LC3, which may initiate apoptosis. Furthermore, increased reactive oxygen species levels might also induce autophagy and apoptosis. Consistently, cell apoptosis was evoked by the treatment of PCB28/PCB52 compared to the respective controls, which coincided with obvious hepatotoxicity. Subsequently, an inhibitor (3-methlyadenine) and an initiator (rapamycin) of autophagy were used. Compared to PCB28/PCB52 alone-treated cells, initiation of autophagy, blocked autophagic flux, cell apoptosis and hepatotoxicity were alleviated by 3-methlyadenine and aggravated by rapamycin, respectively. Taken together, PCB28 and PCB52 induced hepatotoxicity by impairing autophagic flux and stimulating cell apoptosis in vitro.
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Affiliation(s)
- Qi Wang
- Department of Forensic Pathology, School of Forensic Medicine, Southern Medical University, No. 1838 North Guangzhou Road, 510515 Guangzhou, China
| | - Li-Wen Wei
- Department of Toxicology, School of Public Health, Southern Medical University (Guangdong Provincial Key Laboratory of Tropical Disease Research), No. 1838 North Guangzhou Road, 510515 Guangzhou, China
| | - Wen-Tao Zhou
- Department of Toxicology, School of Public Health, Southern Medical University (Guangdong Provincial Key Laboratory of Tropical Disease Research), No. 1838 North Guangzhou Road, 510515 Guangzhou, China
| | - Zheng-Tao Wang
- The First Clinical Medical School, Southern Medical University, No. 1838 North Guangzhou Road, 510515 Guangzhou, China
| | - Xiao-Li Xie
- Department of Toxicology, School of Public Health, Southern Medical University (Guangdong Provincial Key Laboratory of Tropical Disease Research), No. 1838 North Guangzhou Road, 510515 Guangzhou, China.
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169
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Perez-Alvarez MJ, Villa Gonzalez M, Benito-Cuesta I, Wandosell FG. Role of mTORC1 Controlling Proteostasis after Brain Ischemia. Front Neurosci 2018; 12:60. [PMID: 29497356 PMCID: PMC5818460 DOI: 10.3389/fnins.2018.00060] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 01/24/2018] [Indexed: 01/24/2023] Open
Abstract
Intense efforts are being undertaken to understand the pathophysiological mechanisms triggered after brain ischemia and to develop effective pharmacological treatments. However, the underlying molecular mechanisms are complex and not completely understood. One of the main problems is the fact that the ischemic damage is time-dependent and ranges from negligible to massive, involving different cell types such as neurons, astrocytes, microglia, endothelial cells, and some blood-derived cells (neutrophils, lymphocytes, etc.). Thus, approaching such a complicated cellular response generates a more complex combination of molecular mechanisms, in which cell death, cellular damage, stress and repair are intermixed. For this reason, animal and cellular model systems are needed in order to dissect and clarify which molecular mechanisms have to be promoted and/or blocked. Brain ischemia may be analyzed from two different perspectives: that of oxygen deprivation (hypoxic damage per se) and that of deprivation of glucose/serum factors. For investigations of ischemic stroke, middle cerebral artery occlusion (MCAO) is the preferred in vivo model, and uses two different approaches: transient (tMCAO), where reperfusion is permitted; or permanent (pMCAO). As a complement to this model, many laboratories expose different primary cortical neuron or neuronal cell lines to oxygen-glucose deprivation (OGD). This ex vivo model permits the analysis of the impact of hypoxic damage and the specific response of different cell types implicated in vivo, such as neurons, glia or endothelial cells. Using in vivo and neuronal OGD models, it was recently established that mTORC1 (mammalian Target of Rapamycin Complex-1), a protein complex downstream of PI3K-Akt pathway, is one of the players deregulated after ischemia and OGD. In addition, neuroprotective intervention either by estradiol or by specific AT2R agonists shows an important regulatory role for the mTORC1 activity, for instance regulating vascular endothelial growth factor (VEGF) levels. This evidence highlights the importance of understanding the role of mTORC1 in neuronal death/survival processes, as it could be a potential therapeutic target. This review summarizes the state-of-the-art of the complex kinase mTORC1 focusing in upstream and downstream pathways, their role in central nervous system and their relationship with autophagy, apoptosis and neuroprotection/neurodegeneration after ischemia/hypoxia.
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Affiliation(s)
- Maria J Perez-Alvarez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Departamento de Biología (Fisiología Animal), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas, Madrid, Spain
| | - Mario Villa Gonzalez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Departamento de Biología (Fisiología Animal), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Irene Benito-Cuesta
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas, Madrid, Spain
| | - Francisco G Wandosell
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas, Madrid, Spain
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170
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Stuttfeld E, Aylett CH, Imseng S, Boehringer D, Scaiola A, Sauer E, Hall MN, Maier T, Ban N. Architecture of the human mTORC2 core complex. eLife 2018; 7:33101. [PMID: 29424687 PMCID: PMC5837792 DOI: 10.7554/elife.33101] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 02/08/2018] [Indexed: 11/20/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is a key protein kinase controlling cellular metabolism and growth. It is part of the two structurally and functionally distinct multiprotein complexes mTORC1 and mTORC2. Dysregulation of mTOR occurs in diabetes, cancer and neurological disease. We report the architecture of human mTORC2 at intermediate resolution, revealing a conserved binding site for accessory proteins on mTOR and explaining the structural basis for the rapamycin insensitivity of the complex. To grow and multiply, a living cell must take a variety of factors into account, such as its own energy levels and the availability of nutrients. A protein called mTOR sits at the core of a signaling pathway that integrates these and other sources information. Problems with the mTOR pathway contribute to several diseases including diabetes and cancer. The mTOR protein occurs in two distinct protein complexes, called mTORC1 and mTORC2. These complexes contain a mix of other proteins – known as accessory proteins. They also sense different cues and act upon distinct targets in the cell. Recent research reported the structure of mTORC1, which provided clues about how this complex works. Yet, much less was known about the mTORC2 complex. Stuttfeld, Aylett et al. have now used a technique called cryo-electron microscopy to reveal the three-dimensional architecture of the human version of mTORC2. Comparing the new mTORC2 structure to the existing one for mTORC1 showed that they have many features in common but important differences too. The overall shape of both complexes is similar and each complex contains two copies of mTOR arranged in a similar way. Also, the main accessory proteins in each complex interact with almost the exact same parts of mTOR, but the accessory proteins in mTORC2 are organized differently from those of mTORC1. The different accessory proteins also have distinct shapes. These differences could help to explain why the complexes respond to different cues and recognize different targets. These new findings provide an entry point for further studies on how mTORC2 works in cells. The next step is to get a higher resolution image of the structure of this complex to see the finer details of all the components. This may in the future help scientists to develop drugs that inhibit mTORC2 to treat cancer and other diseases.
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Affiliation(s)
| | | | | | | | - Alain Scaiola
- Institute for Molecular Biology and Biophysics, Zürich, Switzerland
| | - Evelyn Sauer
- Biozentrum, University of Basel, Basel, Switzerland
| | | | - Timm Maier
- Biozentrum, University of Basel, Basel, Switzerland.,Institute for Molecular Biology and Biophysics, Zürich, Switzerland
| | - Nenad Ban
- Institute for Molecular Biology and Biophysics, Zürich, Switzerland
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171
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Gao X, Chen W, Li J, Shen C, Zhou P, Che X, Li X, Xie R. The protective effect of alpha-lipoic acid against brain ischemia and reperfusion injury via mTOR signaling pathway in rats. Neurosci Lett 2018; 671:108-113. [PMID: 29432779 DOI: 10.1016/j.neulet.2018.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Revised: 02/05/2018] [Accepted: 02/06/2018] [Indexed: 10/18/2022]
Abstract
Alpha-lipoic Acid(ALA), an endogenous short-chain fatty acid, has been found inducing a protective effect against ischemia and reperfusion(I/R) injury. Recently, mTOR signaling pathway has been proved to involve in the mechanism of I/R injury. In our previous study, we determined that ALA could protect cerebral endothelial cells against I/R injury via mTOR signaling pathway. However, whether ALA can protect against brain I/R injury in vivo and its mechanisms is uncertain. In this study, we try to explore if the ALA treatment can protect against brain I/R injury and confirm the relationship between ALA and mTOR signaling pathway. ALA was administrated to the animals after dMCAo and reperfusion model established with or without rapamycin pre-treatment. The results showed the infarct size was obviously reduced after ALA treatment in acute stage, neurological functions were also improved distinctly. The mTOR signaling pathway was remarkably blocked after brain I/R injury while it could be activated through ALA treatment. However, rapamycin, can abolish the protective effects induced by ALA treatment in both acute and long-term phase. In conclusion, we demonstrate the protective effects induced by ALA treatment against the brain I/R injury in rats and mTOR signaling pathway is required for the protective effects of ALA against brain I/R injury. The results might contribute to the potential clinical application of ALA and provide a potential therapeutic target on ischemic stroke.
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Affiliation(s)
- Xinjie Gao
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Wei Chen
- Department of Neurosurgery, Jingan District Center Hospital, Shanghai 200040, China
| | - Jinquan Li
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Chao Shen
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Ping Zhou
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Xiaoming Che
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Xiaomu Li
- Department of Endocrinology, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
| | - Rong Xie
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China.
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172
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Parallel PI3K, AKT and mTOR inhibition is required to control feedback loops that limit tumor therapy. PLoS One 2018; 13:e0190854. [PMID: 29357370 PMCID: PMC5777650 DOI: 10.1371/journal.pone.0190854] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 12/21/2017] [Indexed: 12/26/2022] Open
Abstract
Targeting the PI3K pathway has achieved limited success in cancer therapy. One reason for the disappointing activity of drugs that interfere with molecules that are important player in this pathway is the induction of multiple feedback loops that have been only partially understood. To understand these limitations and develop improved treatment strategies, we comprehensively characterized molecular mechanisms of PI3K pathway signaling in bladder cancer cell lines upon using small molecule inhibitors and RNAi technologies against all key molecules and protein complexes within the pathway and analyzed functional and molecular consequences. When targeting either mTORC1, mTOR, AKT or PI3K, only S6K1 phosphorylation was affected in most cell lines examined. Dephosphorylation of 4E-BP1 required combined inhibition of PI3K and mTORC1, independent from AKT, and resulted in a robust reduction in cell viability. Long-term inhibition of PI3K however resulted in a PDK1-dependent, PIP3 and mTORC2 independent rephosphorylation of AKT. AKT rephosphorylation could also be induced by mTOR or PDK1 inhibition. Combining PI3K/mTOR inhibitors with AKT or PDK1 inhibitors suppressed this rephosphorylation, induced apoptosis, decreased colony formation, cell viability and growth of tumor xenografts. Our findings reveal novel molecular mechanisms that explain the requirement for simultaneous targeting of PI3K, AKT and mTORC1 to achieve effective tumor growth inhibition.
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173
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Paquette M, El-Houjeiri L, Pause A. mTOR Pathways in Cancer and Autophagy. Cancers (Basel) 2018; 10:cancers10010018. [PMID: 29329237 PMCID: PMC5789368 DOI: 10.3390/cancers10010018] [Citation(s) in RCA: 199] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 12/22/2017] [Accepted: 01/09/2018] [Indexed: 12/11/2022] Open
Abstract
TOR (target of rapamycin), an evolutionarily-conserved serine/threonine kinase, acts as a central regulator of cell growth, proliferation and survival in response to nutritional status, growth factor, and stress signals. It plays a crucial role in coordinating the balance between cell growth and cell death, depending on cellular conditions and needs. As such, TOR has been identified as a key modulator of autophagy for more than a decade, and several deregulations of this pathway have been implicated in a variety of pathological disorders, including cancer. At the molecular level, autophagy regulates several survival or death signaling pathways that may decide the fate of cancer cells; however, the relationship between autophagy pathways and cancer are still nascent. In this review, we discuss the recent cellular signaling pathways regulated by TOR, their interconnections to autophagy, and the clinical implications of TOR inhibitors in cancer.
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Affiliation(s)
- Mathieu Paquette
- Goodman Cancer Research Center, McGill University, Montréal, QC H3A 1A3, Canada.
- Department of Biochemistry, McGill University, Montréal, QC H3G 1Y6, Canada.
| | - Leeanna El-Houjeiri
- Goodman Cancer Research Center, McGill University, Montréal, QC H3A 1A3, Canada.
- Department of Biochemistry, McGill University, Montréal, QC H3G 1Y6, Canada.
| | - Arnim Pause
- Goodman Cancer Research Center, McGill University, Montréal, QC H3A 1A3, Canada.
- Department of Biochemistry, McGill University, Montréal, QC H3G 1Y6, Canada.
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174
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Guduru SKR, Arya P. Synthesis and biological evaluation of rapamycin-derived, next generation small molecules. MEDCHEMCOMM 2018; 9:27-43. [PMID: 30108899 PMCID: PMC6072512 DOI: 10.1039/c7md00474e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Accepted: 11/21/2017] [Indexed: 12/20/2022]
Abstract
Over the years, rapamycin has attracted serious attention due to its remarkable biological properties and as a potent inhibitor of the mammalian target of rapamycin (mTOR) protein through its binding with FKBP-12. Several efficient strategies that utilize synthetic and biosynthetic approaches have been utilized to develop small molecule rapamycin analogs or for synthesizing hybrid compounds containing a partial rapamycin structure to improve pharmacokinetic properties. Herein, we report selected case studies related to the synthesis of rapamycin-derived compounds and hybrid molecules to explore their biological properties.
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Affiliation(s)
- Shiva Krishna Reddy Guduru
- Center for Drug Discovery , Department of Pharmacology and Chemical Biology , Baylor College of Medicine , One Baylor Plaza , Houston , Texas 77030 , USA . ; ; Tel: +1 713 798 8794
- Department of Pharmacology and Chemical Biology , Baylor College of Medicine , One Baylor Plaza , Houston , Texas 77030 , USA
| | - Prabhat Arya
- Chemistry and Chemical Biology , Dr. Reddy's Institute of Life Sciences (DRILS) , University of Hyderabad Campus , Hyderabad 500046 , India
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175
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Roustan V, Weckwerth W. Quantitative Phosphoproteomic and System-Level Analysis of TOR Inhibition Unravel Distinct Organellar Acclimation in Chlamydomonas reinhardtii. FRONTIERS IN PLANT SCIENCE 2018; 9:1590. [PMID: 30546371 PMCID: PMC6280106 DOI: 10.3389/fpls.2018.01590] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 10/15/2018] [Indexed: 05/13/2023]
Abstract
Rapamycin is an inhibitor of the evolutionary conserved Target of Rapamycin (TOR) kinase which promotes and coordinates translation with cell growth and division. In heterotrophic organisms, TOR regulation is based on intra- and extracellular stimuli such as amino acids level and insulin perception. However, how plant TOR pathways have evolved to integrate plastid endosymbiosis is a remaining question. Despite the close association of the TOR signaling with the coordination between protein turn-over and growth, proteome and phosphoproteome acclimation to a rapamycin treatment have not yet been thoroughly investigated in Chlamydomonas reinhardtii. In this study, we have used in vivo label-free phospho-proteomic analysis to profile both protein and phosphorylation changes at 0, 24, and 48 h in Chlamydomonas cells treated with rapamycin. Using multivariate statistics we highlight the impact of TOR inhibition on both the proteome and the phosphoproteome. Two-way ANOVA distinguished differential levels of proteins and phosphoproteins in response either to culture duration and rapamycin treatment or combined effects. Finally, protein-protein interaction networks and functional enrichment analysis underlined the relation between plastid and mitochondrial metabolism. Prominent changes of proteins involved in sulfur, cysteine, and methionine as well as nucleotide metabolism on the one hand, and changes in the TCA cycle on the other highlight the interplay of chloroplast and mitochondria metabolism. Furthermore, TOR inhibition revealed changes in the endomembrane trafficking system. Phosphoproteomics data, on the other hand, highlighted specific differentially regulated phosphorylation sites for calcium-regulated protein kinases as well as ATG7, S6K, and PP2C. To conclude we provide a first combined Chlamydomonas proteomics and phosphoproteomics dataset in response to TOR inhibition, which will support further investigations.
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Affiliation(s)
- Valentin Roustan
- Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
| | - Wolfram Weckwerth
- Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
- Vienna Metabolomics Center (VIME), University of Vienna, Vienna, Austria
- *Correspondence: Wolfram Weckwerth,
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176
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Cryo-EM structure of human ATR-ATRIP complex. Cell Res 2017; 28:143-156. [PMID: 29271416 DOI: 10.1038/cr.2017.158] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/01/2017] [Accepted: 12/05/2017] [Indexed: 12/18/2022] Open
Abstract
ATR (ataxia telangiectasia-mutated and Rad3-related) protein kinase and ATRIP (ATR-interacting protein) form a complex and play a critical role in response to replication stress and DNA damage. Here, we determined the cryo-electron microscopy (EM) structure of the human ATR-ATRIP complex at 4.7 Å resolution and built an atomic model of the C-terminal catalytic core of ATR (residues 1 521-2 644) at 3.9 Å resolution. The complex adopts a hollow "heart" shape, consisting of two ATR monomers in distinct conformations. The EM map for ATRIP reveals 14 HEAT repeats in an extended "S" shape. The conformational flexibility of ATR allows ATRIP to properly lock the N-termini of the two ATR monomers to favor ATR-ATRIP complex formation and functional diversity. The isolated "head-head" and "tail-tail" each adopts a pseudo 2-fold symmetry. The catalytic pockets face outward and substrate access is not restricted by inhibitory elements. Our studies provide a structural basis for understanding the assembly of the ATR-ATRIP complex and a framework for characterizing ATR-mediated DNA repair pathways.
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177
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Yang H, Jiang X, Li B, Yang HJ, Miller M, Yang A, Dhar A, Pavletich NP. Mechanisms of mTORC1 activation by RHEB and inhibition by PRAS40. Nature 2017; 552:368-373. [PMID: 29236692 PMCID: PMC5750076 DOI: 10.1038/nature25023] [Citation(s) in RCA: 330] [Impact Index Per Article: 47.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 11/08/2017] [Indexed: 12/13/2022]
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth and metabolism in response to nutrients, energy levels, and growth factors. It contains the atypical kinase mTOR and the RAPTOR subunit that binds to the Tor signalling sequence (TOS) motif of substrates and regulators. mTORC1 is activated by the small GTPase RHEB (Ras homologue enriched in brain) and inhibited by PRAS40. Here we present the 3.0 ångström cryo-electron microscopy structure of mTORC1 and the 3.4 ångström structure of activated RHEB-mTORC1. RHEB binds to mTOR distally from the kinase active site, yet causes a global conformational change that allosterically realigns active-site residues, accelerating catalysis. Cancer-associated hyperactivating mutations map to structural elements that maintain the inactive state, and we provide biochemical evidence that they mimic RHEB relieving auto-inhibition. We also present crystal structures of RAPTOR-TOS motif complexes that define the determinants of TOS recognition, of an mTOR FKBP12-rapamycin-binding (FRB) domain-substrate complex that establishes a second substrate-recruitment mechanism, and of a truncated mTOR-PRAS40 complex that reveals PRAS40 inhibits both substrate-recruitment sites. These findings help explain how mTORC1 selects its substrates, how its kinase activity is controlled, and how it is activated by cancer-associated mutations.
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Affiliation(s)
- Haijuan Yang
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Xiaolu Jiang
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Buren Li
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Hyo J Yang
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Meredith Miller
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Angela Yang
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Ankita Dhar
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Nikola P Pavletich
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.,Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
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178
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Abstract
Plasma membrane (PM) phosphoinositides play essential roles in cell physiology, serving as both markers of membrane identity and signaling molecules central to the cell's interaction with its environment. The first step in PM phosphoinositide synthesis is the conversion of phosphatidylinositol (PI) to PI4P, the precursor of PI(4,5)P2 and PI(3,4,5)P3 This conversion is catalyzed by the PI4KIIIα complex, comprising a lipid kinase, PI4KIIIα, and two regulatory subunits, TTC7 and FAM126. We here report the structure of this complex at 3.6-Å resolution, determined by cryo-electron microscopy. The proteins form an obligate ∼700-kDa superassembly with a broad surface suitable for membrane interaction, toward which the kinase active sites are oriented. The structural complexity of the assembly highlights PI4P synthesis as a major regulatory junction in PM phosphoinositide homeostasis. Our studies provide a framework for further exploring the mechanisms underlying PM phosphoinositide regulation.
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179
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Wang X, Ran T, Zhang X, Xin J, Zhang Z, Wu T, Wang W, Cai G. 3.9 Å structure of the yeast Mec1-Ddc2 complex, a homolog of human ATR-ATRIP. Science 2017; 358:1206-1209. [DOI: 10.1126/science.aan8414] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 11/01/2017] [Indexed: 12/12/2022]
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180
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Karuppasamy M, Kusmider B, Oliveira TM, Gaubitz C, Prouteau M, Loewith R, Schaffitzel C. Cryo-EM structure of Saccharomyces cerevisiae target of rapamycin complex 2. Nat Commun 2017; 8:1729. [PMID: 29170376 PMCID: PMC5700991 DOI: 10.1038/s41467-017-01862-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 10/18/2017] [Indexed: 12/11/2022] Open
Abstract
The target of rapamycin (TOR) kinase assembles into two distinct multiprotein complexes, conserved across eukaryote evolution. In contrast to TOR complex 1 (TORC1), TORC2 kinase activity is not inhibited by the macrolide rapamycin. Here, we present the structure of Saccharomyces cerevisiae TORC2 determined by electron cryo-microscopy. TORC2 contains six subunits assembling into a 1.4 MDa rhombohedron. Tor2 and Lst8 form the common core of both TOR complexes. Avo3/Rictor is unique to TORC2, but interacts with the same HEAT repeats of Tor2 that are engaged by Kog1/Raptor in mammalian TORC1, explaining the mutual exclusivity of these two proteins. Density, which we conclude is Avo3, occludes the FKBP12-rapamycin-binding site of Tor2’s FRB domain rendering TORC2 rapamycin insensitive and recessing the kinase active site. Although mobile, Avo1/hSin1 further restricts access to the active site as its conserved-region-in-the-middle (CRIM) domain is positioned along an edge of the TORC2 active-site-cleft, consistent with a role for CRIM in substrate recruitment. Target of rapamycin (TOR) kinase operates within two distinct multiprotein complexes named TORC1 and TORC2. Here the authors report a cryo-EM structure of TORC2, establish its subunit organization, providing a rationale for TORC2’s rapamycin insensitivity and the mutually exclusive inclusion of Avo3/Rictor or Raptor within their respective TOR complex.
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Affiliation(s)
- Manikandan Karuppasamy
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Beata Kusmider
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland
| | - Taiana M Oliveira
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042, Grenoble, France
| | - Christl Gaubitz
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland
| | - Manoel Prouteau
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland
| | - Robbie Loewith
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, 30 Quai Ernest Ansermet, CH1211, Geneva, Switzerland. .,Swiss National Centre for Competence in Research (NCCR) in Chemical Biology, University of Geneva, 30 Quai Ernest-Ansermet, Bristol, CH1211 Geneva, Switzerland.
| | - Christiane Schaffitzel
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042, Grenoble, France. .,School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK.
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181
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Structure of the transcription activator target Tra1 within the chromatin modifying complex SAGA. Nat Commun 2017; 8:1556. [PMID: 29146944 PMCID: PMC5691046 DOI: 10.1038/s41467-017-01564-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Accepted: 09/27/2017] [Indexed: 12/21/2022] Open
Abstract
The transcription co-activator complex SAGA is recruited to gene promoters by sequence-specific transcriptional activators and by chromatin modifications to promote pre-initiation complex formation. The yeast Tra1 subunit is the major target of acidic activators such as Gal4, VP16, or Gcn4 but little is known about its structural organization. The 430 kDa Tra1 subunit and its human homolog the transformation/transcription domain-associated protein TRRAP are members of the phosphatidyl 3-kinase-related kinase (PIKK) family. Here, we present the cryo-EM structure of the entire SAGA complex where the major target of activator binding, the 430 kDa Tra1 protein, is resolved with an average resolution of 5.7 Å. The high content of alpha-helices in Tra1 enabled tracing of the majority of its main chain. Our results highlight the integration of Tra1 within the major epigenetic regulator SAGA. The transcription co-activator complex SAGA is recruited to promoters by transcriptional activators and promotes the formation of the pre-initiation complex. Here, the authors present the cryo-EM structure of the SAGA complex and resolve the major target of activator binding, the 430 kDa Tra1 protein.
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182
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Hybrid Structure of the RagA/C-Ragulator mTORC1 Activation Complex. Mol Cell 2017; 68:835-846.e3. [PMID: 29107538 DOI: 10.1016/j.molcel.2017.10.016] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 10/09/2017] [Accepted: 10/16/2017] [Indexed: 12/22/2022]
Abstract
The lysosomal membrane is the locus for sensing cellular nutrient levels, which are transduced to mTORC1 via the Rag GTPases and the Ragulator complex. The crystal structure of the five-subunit human Ragulator at 1.4 Å resolution was determined. Lamtor1 wraps around the other four subunits to stabilize the assembly. The Lamtor2:Lamtor3 dimer stacks upon Lamtor4:Lamtor5 to create a platform for Rag binding. Hydrogen-deuterium exchange was used to map the Rag binding site to the outer face of the Lamtor2:Lamtor3 dimer and to the N-terminal intrinsically disordered region of Lamtor1. EM was used to reconstruct the assembly of the full-length RagAGTP:RagCGDP dimer bound to Ragulator at 16 Å resolution, revealing that the G-domains of the Rags project away from the Ragulator core. The combined structural model shows how Ragulator functions as a platform for the presentation of active Rags for mTORC1 recruitment, and might suggest an unconventional mechanism for Rag GEF activity.
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183
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Leibovitch M, Topisirovic I. Dysregulation of mRNA translation and energy metabolism in cancer. Adv Biol Regul 2017; 67:30-39. [PMID: 29150352 DOI: 10.1016/j.jbior.2017.11.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 10/26/2017] [Accepted: 11/01/2017] [Indexed: 12/20/2022]
Abstract
Dysregulated mRNA translation and aberrant energy metabolism are frequent in cancer. Considering that mRNA translation is an energy demanding process, cancer cells must produce sufficient ATP to meet energy demand of hyperactive translational machinery. In recent years, the mammalian/mechanistic target of rapamycin (mTOR) emerged as a central regulatory node which coordinates energy consumption by the translation apparatus and ATP production in mitochondria. Aberrant mTOR signaling underpins the vast majority of cancers whereby increased mTOR activity is thought to be a major determinant of both malignant translatomes and metabolomes. Nonetheless, the role of mTOR and other related signaling nodes (e.g. AMPK) in orchestrating protein synthesis and cancer energetics is only recently being unraveled. In this review, we discuss recent findings that provide insights into the molecular underpinnings of coordination of translational and metabolic programs of cancer cells, and potential strategies to translate these findings into clinical treatments.
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Affiliation(s)
- Matthew Leibovitch
- Lady Davis Institute, SMBD JGH, McGill University, Montréal, QC, H3T 1E2, Canada.
| | - Ivan Topisirovic
- Gerald Bronfman Department of Oncology, Montréal, QC, H3A 1A3, Canada; Department of Biochemistry, Montréal, QC, H3A 1A3, Canada; Department of Experimental Medicine McGill University, Montréal, QC, H3A 1A3, Canada; Lady Davis Institute, SMBD JGH, McGill University, Montréal, QC, H3T 1E2, Canada
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184
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Evolutionary Conservation of the Components in the TOR Signaling Pathways. Biomolecules 2017; 7:biom7040077. [PMID: 29104218 PMCID: PMC5745459 DOI: 10.3390/biom7040077] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 10/26/2017] [Accepted: 10/27/2017] [Indexed: 01/08/2023] Open
Abstract
Target of rapamycin (TOR) is an evolutionarily conserved protein kinase that controls multiple cellular processes upon various intracellular and extracellular stimuli. Since its first discovery, extensive studies have been conducted both in yeast and animal species including humans. Those studies have revealed that TOR forms two structurally and physiologically distinct protein complexes; TOR complex 1 (TORC1) is ubiquitous among eukaryotes including animals, yeast, protozoa, and plants, while TOR complex 2 (TORC2) is conserved in diverse eukaryotic species other than plants. The studies have also identified two crucial regulators of mammalian TORC1 (mTORC1), Ras homolog enriched in brain (RHEB) and RAG GTPases. Of these, RAG regulates TORC1 in yeast as well and is conserved among eukaryotes with the green algae and land plants as apparent exceptions. RHEB is present in various eukaryotes but sporadically missing in multiple taxa. RHEB, in the budding yeast Saccharomyces cerevisiae, appears to be extremely divergent with concomitant loss of its function as a TORC1 regulator. In this review, we summarize the evolutionarily conserved functions of the key regulatory subunits of TORC1 and TORC2, namely RAPTOR, RICTOR, and SIN1. We also delve into the evolutionary conservation of RHEB and RAG and discuss the conserved roles of these GTPases in regulating TORC1.
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185
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Pelosse M, Crocker H, Gorda B, Lemaire P, Rauch J, Berger I. MultiBac: from protein complex structures to synthetic viral nanosystems. BMC Biol 2017; 15:99. [PMID: 29084535 PMCID: PMC5661938 DOI: 10.1186/s12915-017-0447-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The MultiBac baculovirus/insect cell expression vector system was conceived as a user-friendly, modular tool-kit for producing multiprotein complexes for structural biology applications. MultiBac has allowed the structure and function of many molecular machines to be elucidated, including previously inaccessible high-value drug targets. More recently, MultiBac developments have shifted to customized baculoviral genomes that are tailored for a range of applications, including synthesizing artificial proteins by genetic code expansion. We review some of these developments, including the ongoing rewiring of the MultiBac system for mammalian applications, notably CRISPR/Cas9-mediated gene editing.
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Affiliation(s)
- Martin Pelosse
- The School of Biochemistry and Bristol Synthetic Biology Centre BrisSynBio, University of Bristol, Tankard's Close, Bristol, BS8 1TD, UK
| | - Hannah Crocker
- The School of Biochemistry and Bristol Synthetic Biology Centre BrisSynBio, University of Bristol, Tankard's Close, Bristol, BS8 1TD, UK
| | - Barbara Gorda
- The School of Biochemistry and Bristol Synthetic Biology Centre BrisSynBio, University of Bristol, Tankard's Close, Bristol, BS8 1TD, UK
| | - Paul Lemaire
- Geneva Biotech SARL, Avenue de la Roseraie 64, 1205, Genève, Switzerland
| | - Jens Rauch
- Systems Biology Ireland, University College Dublin, Belfield Dublin 4, Republic of Ireland
| | - Imre Berger
- The School of Biochemistry and Bristol Synthetic Biology Centre BrisSynBio, University of Bristol, Tankard's Close, Bristol, BS8 1TD, UK.
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186
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TORC1 organized in inhibited domains (TOROIDs) regulate TORC1 activity. Nature 2017; 550:265-269. [PMID: 28976958 PMCID: PMC5640987 DOI: 10.1038/nature24021] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 08/21/2017] [Indexed: 12/17/2022]
Abstract
The Target of Rapamycin (TOR) is a eukaryotic serine/threonine protein kinase that functions in two distinct complexes, TORC1 and TORC2, to regulate growth and metabolism1,2. GTPases, responding to signals generated by abiotic stressors, nutrients, and, in metazoans, growth factors, play an important3, but poorly understood role in TORC1 regulation. Here, we report that, in budding yeast, glucose withdrawal, which leads to an acute loss of TORC1 kinase activity4, triggers a similarly rapid Rag GTPase-dependent redistribution of TORC1 from being semi-uniform around the vacuolar membrane to a single, vacuole-associated cylindrical structure visible by super-resolution optical microscopy. 3D reconstructions of cryo-electron micrograph images of these purified cylinders demonstrate that TORC1 oligomerizes into a higher-level hollow helical assembly which we name a TOROID (TORC1 Organised in Inhibited Domain). Fitting of the recently described mammalian TORC1 structure into our helical map revealed that oligomerisation leads to steric occlusion of the active site. Guided by the implications from our reconstruction, we present a TOR1 allele that prevents both TOROID formation and TORC1 inactivation in response to glucose withdrawal demonstrating that oligomerisation is necessary for TORC1 inactivation. Our results reveal a novel mechanism by which Rag-GTPases regulate TORC1 activity and suggest that the reversible assembly/disassembly of higher-level structure may be a new paradigm for the regulation of protein kinases.
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187
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Earl LA, Falconieri V, Milne JL, Subramaniam S. Cryo-EM: beyond the microscope. Curr Opin Struct Biol 2017; 46:71-78. [PMID: 28646653 PMCID: PMC5683925 DOI: 10.1016/j.sbi.2017.06.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 05/31/2017] [Accepted: 06/06/2017] [Indexed: 01/18/2023]
Abstract
The pace at which cryo-EM is being adopted as a mainstream tool in structural biology has continued unabated over the past year. Initial successes in obtaining near-atomic resolution structures with cryo-EM were enabled to a large extent by advances in microscope and detector technology. Here, we review some of the complementary technical improvements that are helping sustain the cryo-EM revolution. We highlight advances in image processing that permit high resolution structure determination even in the presence of structural and conformational heterogeneity. We also review selected examples where biochemical strategies for membrane protein stabilization facilitate cryo-EM structure determination, and discuss emerging approaches for further improving the preparation of reliable plunge-frozen specimens.
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Affiliation(s)
- Lesley A Earl
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Veronica Falconieri
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jacqueline Ls Milne
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sriram Subramaniam
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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188
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The TORC2-Dependent Signaling Network in the Yeast Saccharomyces cerevisiae. Biomolecules 2017; 7:biom7030066. [PMID: 28872598 PMCID: PMC5618247 DOI: 10.3390/biom7030066] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 12/21/2022] Open
Abstract
To grow, eukaryotic cells must expand by inserting glycerolipids, sphingolipids, sterols, and proteins into their plasma membrane, and maintain the proper levels and bilayer distribution. A fungal cell must coordinate growth with enlargement of its cell wall. In Saccharomyces cerevisiae, a plasma membrane-localized protein kinase complex, Target of Rapamicin (TOR) complex-2 (TORC2) (mammalian ortholog is mTORC2), serves as a sensor and master regulator of these plasma membrane- and cell wall-associated events by directly phosphorylating and thereby stimulating the activity of two types of effector protein kinases: Ypk1 (mammalian ortholog is SGK1), along with a paralog (Ypk2); and, Pkc1 (mammalian ortholog is PKN2/PRK2). Ypk1 is a central regulator of pathways and processes required for plasma membrane lipid and protein homeostasis, and requires phosphorylation on its T-loop by eisosome-associated protein kinase Pkh1 (mammalian ortholog is PDK1) and a paralog (Pkh2). For cell survival under various stresses, Ypk1 function requires TORC2-mediated phosphorylation at multiple sites near its C terminus. Pkc1 controls diverse processes, especially cell wall synthesis and integrity. Pkc1 is also regulated by Pkh1- and TORC2-dependent phosphorylation, but, in addition, by interaction with Rho1-GTP and lipids phosphatidylserine (PtdSer) and diacylglycerol (DAG). We also describe here what is currently known about the downstream substrates modulated by Ypk1-mediated and Pkc1-mediated phosphorylation.
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189
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Romero R, Erez O, Hüttemann M, Maymon E, Panaitescu B, Conde-Agudelo A, Pacora P, Yoon BH, Grossman LI. Metformin, the aspirin of the 21st century: its role in gestational diabetes mellitus, prevention of preeclampsia and cancer, and the promotion of longevity. Am J Obstet Gynecol 2017; 217:282-302. [PMID: 28619690 DOI: 10.1016/j.ajog.2017.06.003] [Citation(s) in RCA: 152] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 05/30/2017] [Accepted: 06/05/2017] [Indexed: 12/16/2022]
Abstract
Metformin is everywhere. Originally introduced in clinical practice as an antidiabetic agent, its role as a therapeutic agent is expanding to include treatment of prediabetes mellitus, gestational diabetes mellitus, and polycystic ovarian disease; more recently, experimental studies and observations in randomized clinical trials suggest that metformin could have a place in the treatment or prevention of preeclampsia. This article provides a brief overview of the history of metformin in the treatment of diabetes mellitus and reviews the results of metaanalyses of metformin in gestational diabetes mellitus as well as the treatment of obese, non-diabetic, pregnant women to prevent macrosomia. We highlight the results of a randomized clinical trial in which metformin administration in early pregnancy did not reduce the frequency of large-for-gestational-age infants (the primary endpoint) but did decrease the frequency of preeclampsia (a secondary endpoint). The mechanisms by which metformin may prevent preeclampsia include a reduction in the production of antiangiogenic factors (soluble vascular endothelial growth factor receptor-1 and soluble endoglin) and the improvement of endothelial dysfunction, probably through an effect on the mitochondria. Another potential mechanism whereby metformin may play a role in the prevention of preeclampsia is its ability to modify cellular homeostasis and energy disposition, mediated by rapamycin, a mechanistic target. Metformin has a molecular weight of 129 Daltons and therefore readily crosses the placenta. There is considerable evidence to suggest that this agent is safe during pregnancy. New literature on the role of metformin as a chemotherapeutic adjuvant in the prevention of cancer and in prolonging life and protecting against aging is reviewed briefly. Herein, we discuss the mechanisms of action and potential benefits of metformin.
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190
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Dual abrogation of MNK and mTOR: a novel therapeutic approach for the treatment of aggressive cancers. Future Med Chem 2017; 9:1539-1555. [PMID: 28841037 DOI: 10.4155/fmc-2017-0062] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Targeting the translational machinery has emerged as a promising therapeutic option for cancer treatment. Cancer cells require elevated protein synthesis and exhibit augmented activity to meet the increased metabolic demand. Eukaryotic translation initiation factor 4E is necessary for mRNA translation, its availability and phosphorylation are regulated by the PI3K/AKT/mTOR and MNK1/2 pathways. The phosphorylated form of eIF4E drives the expression of oncogenic proteins including those involved in metastasis. In this article, we will review the role of eIF4E in cancer, its regulation and discuss the benefit of dual inhibition of upstream pathways. The discernible interplay between the MNK and mTOR signaling pathways provides a novel therapeutic opportunity to target aggressive migratory cancers through the development of hybrid molecules.
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191
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Vivoli M, Renou J, Chevalier A, Norville IH, Diaz S, Juli C, Atkins H, Holzgrabe U, Renard PY, Sarkar-Tyson M, Harmer NJ. A miniaturized peptidyl-prolyl isomerase enzyme assay. Anal Biochem 2017; 536:59-68. [PMID: 28803887 DOI: 10.1016/j.ab.2017.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 08/04/2017] [Accepted: 08/09/2017] [Indexed: 01/15/2023]
Abstract
Prolyl-peptidyl isomerases (PPIases) are enzymes that are found in all living organisms. They form an essential part of the cellular protein folding homeostasis machinery. PPIases are associated with many important human diseases, e.g. cardiovascular disease, cancer and Alzheimer's. The development of novel PPIase inhibitors has been limited by the lack of a rapid, laboratory-based assay for these enzymes, as their substrates and products are challenging to distinguish. A well described continuous assay, coupled with the hydrolysis of a peptide by chymotrypsin is highly effective, but comparatively slow. To address this, we developed an improved version of the traditional assay using a temperature controlled plate reader. This assay allows semi-automated medium throughput assays in an academic laboratory for 84 samples per day. The assay shows lower errors, with an average Z' of 0.72. We further developed the assay using a fluorogenic peptide-based FRET probe. This provides an extremely sensitive PPIase assay using substrate at 200 nM, which approaches single turnover conditions. The fluorescent probe achieves an excellent quenching efficiency of 98.6%, and initial experiments showed acceptable Z' of 0.31 and 0.30 for cyclophilin A and hFKBP12 respectively. The assays provide an improved toolset for the quantitative, biochemical analysis of PPIases.
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Affiliation(s)
- Mirella Vivoli
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Julien Renou
- Normandie Univ, UNIROUEN, CNRS, INSAREOUEN, COBRA, UMR 6014 & FR 3038, 1 rue Tesnière 76000 Rouen, France
| | - Arnaud Chevalier
- Normandie Univ, UNIROUEN, CNRS, INSAREOUEN, COBRA, UMR 6014 & FR 3038, 1 rue Tesnière 76000 Rouen, France
| | - Isobel H Norville
- Defence Science and Technology Laboratory, Porton Down SP4 0JQ, United Kingdom
| | - Suraya Diaz
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Christina Juli
- Institute of Pharmacy, University of Würzburg, Am Hubland, 970074 Würzburg, Germany
| | - Helen Atkins
- Defence Science and Technology Laboratory, Porton Down SP4 0JQ, United Kingdom
| | - Ulrike Holzgrabe
- Institute of Pharmacy, University of Würzburg, Am Hubland, 970074 Würzburg, Germany
| | - Pierre-Yves Renard
- Normandie Univ, UNIROUEN, CNRS, INSAREOUEN, COBRA, UMR 6014 & FR 3038, 1 rue Tesnière 76000 Rouen, France
| | - Mitali Sarkar-Tyson
- Defence Science and Technology Laboratory, Porton Down SP4 0JQ, United Kingdom; Marshall Centre for Infectious Diseases, School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, WA 6009, Australia
| | - Nicholas J Harmer
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom.
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192
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Signalling assemblies: the odds of symmetry. Biochem Soc Trans 2017; 45:599-611. [PMID: 28620024 DOI: 10.1042/bst20170009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 02/06/2023]
Abstract
The assembly of proteins into complexes is fundamental to nearly all biological signalling processes. Symmetry is a dominant feature of the structures of experimentally determined protein complexes, observed in the vast majority of homomers and many heteromers. However, some asymmetric structures exist, and asymmetry also often forms transiently, intractable to traditional structure determination methods. Here, we explore the role of protein complex symmetry and asymmetry in cellular signalling, focusing on receptors, transcription factors and transmembrane channels, among other signalling assemblies. We highlight a recurrent tendency for asymmetry to be crucial for signalling function, often being associated with activated states. We conclude with a discussion of how consideration of protein complex symmetry and asymmetry has significant potential implications and applications for pharmacology and human disease.
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193
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Díaz-Santín LM, Lukoyanova N, Aciyan E, Cheung AC. Cryo-EM structure of the SAGA and NuA4 coactivator subunit Tra1 at 3.7 angstrom resolution. eLife 2017; 6:28384. [PMID: 28767037 PMCID: PMC5576489 DOI: 10.7554/elife.28384] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 07/31/2017] [Indexed: 01/30/2023] Open
Abstract
Coactivator complexes SAGA and NuA4 stimulate transcription by post-translationally modifying chromatin. Both complexes contain the Tra1 subunit, a highly conserved 3744-residue protein from the Phosphoinositide 3-Kinase-related kinase (PIKK) family and a direct target for multiple sequence-specific activators. We present the Cryo-EM structure of Saccharomyces cerevsisae Tra1 to 3.7 Å resolution, revealing an extensive network of alpha-helical solenoids organized into a diamond ring conformation and is strikingly reminiscent of DNA-PKcs, suggesting a direct role for Tra1 in DNA repair. The structure was fitted into an existing SAGA EM reconstruction and reveals limited contact surfaces to Tra1, hence it does not act as a molecular scaffold within SAGA. Mutations that affect activator targeting are distributed across the Tra1 structure, but also cluster within the N-terminal Finger region, indicating the presence of an activator interaction site. The structure of Tra1 is a key milestone in deciphering the mechanism of multiple coactivator complexes. Inside our cells, histone proteins package and condense DNA so that it can fit into the cell nucleus. However, this also switches off the genes, since the machines that read and interpret them can no longer access the underlying DNA. Turning genes on requires specific enzymes that chemically modify the histone proteins to regain access to the DNA. This must be carefully controlled, otherwise the ‘wrong’ genes can be activated, causing undesired effects and endangering the cell. Histone modifying enzymes often reside in large protein complexes. Two well-known examples are the SAGA and NuA4 complexes. Both have different roles during gene activation, but share a protein called Tra1. This protein enables SAGA and NuA4 to act on specific genes by binding to ‘activator proteins’ that are found on the DNA. Tra1 is one of the biggest proteins in the cell, but its size makes it difficult to study and until now, its structure was unknown. To determine the structure of Tra1, Díaz-Santín et al. extracted the protein from baker’s yeast, and examined it using electron microscopy. The structure of Tra1 resembled a diamond ring with multiple protein domains that correspond to a band, setting and a centre stone. The structure was detailed enough so that Díaz-Santín et al. could locate various mutations that affect the role of Tra1. These locations are likely to be direct interfaces to the ‘activator proteins’. Moreover, the study showed that Tra1 was similar to another protein that repairs damaged DNA. These results suggest that Tra1 not only works as an activator target, but may also have a role in repairing damaged DNA, and might even connect these two processes. Yeast Tra1 is also very similar to its human counterpart, which has been shown to stimulate cells to become cancerous. Further studies based on these results may help us understand how cancer begins.
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Affiliation(s)
- Luis Miguel Díaz-Santín
- Department of Structural and Molecular Biology, Institute of Structural and Molecular Biology, University College London, London, United Kingdom
| | - Natasha Lukoyanova
- Institute of Structural and Molecular Biology, Biological Sciences, Birkbeck College, London, United Kingdom
| | - Emir Aciyan
- Institute of Structural and Molecular Biology, Biological Sciences, Birkbeck College, London, United Kingdom
| | - Alan Cm Cheung
- Department of Structural and Molecular Biology, Institute of Structural and Molecular Biology, University College London, London, United Kingdom.,Institute of Structural and Molecular Biology, Biological Sciences, Birkbeck College, London, United Kingdom
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194
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The Stress-Sensing TORC2 Complex Activates Yeast AGC-Family Protein Kinase Ypk1 at Multiple Novel Sites. Genetics 2017; 207:179-195. [PMID: 28739659 PMCID: PMC5586371 DOI: 10.1534/genetics.117.1124] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 07/16/2017] [Indexed: 01/18/2023] Open
Abstract
Yeast (Saccharomyces cerevisiae) target of rapamycin (TOR) complex 2 (TORC2) is a multi-subunit plasma membrane-associated protein kinase and vital growth regulator. Its essential functions are exerted via phosphorylation and stimulation of downstream protein kinase Ypk1 (and its paralog Ypk2). Ypk1 phosphorylates multiple substrates to regulate plasma membrane lipid and protein composition. Ypk1 function requires phosphorylation of Thr504 in its activation loop by eisosome-associated Pkh1 (and its paralog Pkh2). For cell survival under certain stresses, however, Ypk1 activity requires further stimulation by TORC2-mediated phosphorylation at C-terminal sites, dubbed the “turn” (Ser644) and “hydrophobic” (Thr662) motifs. Here we show that four additional C-terminal sites are phosphorylated in a TORC2-dependent manner, collectively defining a minimal consensus. We found that the newly identified sites are as important for Ypk1 activity, stability, and biological function as Ser644 and Thr662. Ala substitutions at the four new sites abrogated the ability of Ypk1 to rescue the phenotypes of Ypk1 deficiency, whereas Glu substitutions had no ill effect. Combining the Ala substitutions with an N-terminal mutation (D242A), which has been demonstrated to bypass the need for TORC2-mediated phosphorylation, restored the ability to complement a Ypk1-deficient cell. These findings provide new insights about the molecular basis for TORC2-dependent activation of Ypk1.
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195
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The TOR Signaling Network in the Model Unicellular Green Alga Chlamydomonas reinhardtii. Biomolecules 2017; 7:biom7030054. [PMID: 28704927 PMCID: PMC5618235 DOI: 10.3390/biom7030054] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 07/06/2017] [Accepted: 07/07/2017] [Indexed: 12/18/2022] Open
Abstract
Cell growth is tightly coupled to nutrient availability. The target of rapamycin (TOR) kinase transmits nutritional and environmental cues to the cellular growth machinery. TOR functions in two distinct multiprotein complexes, termed TOR complex 1 (TORC1) and TOR complex 2 (TORC2). While the structure and functions of TORC1 are highly conserved in all eukaryotes, including algae and plants, TORC2 core proteins seem to be missing in photosynthetic organisms. TORC1 controls cell growth by promoting anabolic processes, including protein synthesis and ribosome biogenesis, and inhibiting catabolic processes such as autophagy. Recent studies identified rapamycin-sensitive TORC1 signaling regulating cell growth, autophagy, lipid metabolism, and central metabolic pathways in the model unicellular green alga Chlamydomonas reinhardtii. The central role that microalgae play in global biomass production, together with the high biotechnological potential of these organisms in biofuel production, has drawn attention to the study of proteins that regulate cell growth such as the TOR kinase. In this review we discuss the recent progress on TOR signaling in algae.
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196
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Abstract
Mechanistic target of rapamycin controls cell growth, metabolism, and aging in response to nutrients, cellular energy stage, and growth factors. In cancers including breast cancer, mechanistic target of rapamycin is frequently upregulated. Blocking mechanistic target of rapamycin with rapamycin, first-generation and second-generation mechanistic target of rapamycin inhibitors, called rapalogs, have shown potent reduction of breast cancer tumor growth in preclinical models and clinical trials. In this review, we summarize the fundamental role of the mechanistic target of rapamycin pathway in driving breast tumors. Moreover, we also review key molecules involved with aberrant mechanistic target of rapamycin pathway activation in breast cancer and current efforts to target these components for therapeutic gain. Further development of predictive biomarkers will be useful in the selection of patients who will benefit from inhibition of the mechanistic target of rapamycin pathway.
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Affiliation(s)
- Jia Liu
- Maternal and Child Health Hospital of Qinhuangdao, Qinhuangdao, P.R. China
| | - Hui-Qing Li
- Maternal and Child Health Hospital of Qinhuangdao, Qinhuangdao, P.R. China
| | - Fu-Xia Zhou
- Maternal and Child Health Hospital of Qinhuangdao, Qinhuangdao, P.R. China
| | - Jie-Wen Yu
- Maternal and Child Health Hospital of Qinhuangdao, Qinhuangdao, P.R. China
| | - Ling Sun
- Maternal and Child Health Hospital of Qinhuangdao, Qinhuangdao, P.R. China
| | - Zhong-Hou Han
- Maternal and Child Health Hospital of Qinhuangdao, Qinhuangdao, P.R. China
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197
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Fan QW, Nicolaides TP, Weiss WA. Inhibiting 4EBP1 in Glioblastoma. Clin Cancer Res 2017; 24:14-21. [PMID: 28696243 DOI: 10.1158/1078-0432.ccr-17-0042] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 06/07/2017] [Accepted: 06/30/2017] [Indexed: 12/20/2022]
Abstract
Glioblastoma is the most common and aggressive adult brain cancer. Tumors show frequent dysregulation of the PI3K-mTOR pathway. Although a number of small molecules target the PI3K-AKT-mTOR axis, their preclinical and clinical efficacy has been limited. Reasons for treatment failure include poor penetration of agents into the brain and observations that blockade of PI3K or AKT minimally affects downstream mTOR activity in glioma. Clinical trials using allosteric mTOR inhibitors (rapamycin and rapalogs) to treat patients with glioblastoma have also been unsuccessful or uncertain, in part, because rapamycin inefficiently blocks the mTORC1 target 4EBP1 and feeds back to activate PI3K-AKT signaling. Inhibitors of the mTOR kinase (TORKi) such as TAK-228/MLN0128 interact orthosterically with the ATP- and substrate-binding pocket of mTOR kinase, efficiently block 4EBP1 in vitro, and are currently being investigated in the clinical trials. Preclinical studies suggest that TORKi have poor residence times of mTOR kinase, and our data suggest that this poor pharmacology translates into disappointing efficacy in glioblastoma xenografts. RapaLink-1, a TORKi linked to rapamycin, represents a drug with improved pharmacology against 4EBP1. In this review, we clarify the importance of 4EBP1 as a biomarker for the efficacy of PI3K-AKT-mTOR inhibitors in glioblastoma. We also review mechanistic data by which RapaLink-1 blocks p-4EBP1 and discuss future clinical strategies for 4EBP1 inhibition in glioblastoma. Clin Cancer Res; 24(1); 14-21. ©2017 AACR.
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Affiliation(s)
- Qi Wen Fan
- Department of Neurology, University of California, San Francisco, California.,Helen Diller Family Comprehensive Cancer Center, San Francisco, California
| | - Theodore P Nicolaides
- Helen Diller Family Comprehensive Cancer Center, San Francisco, California.,Department of Pediatrics, University of California, San Francisco, California.,Department of Neurological Surgery, University of California, San Francisco, California
| | - William A Weiss
- Department of Neurology, University of California, San Francisco, California. .,Helen Diller Family Comprehensive Cancer Center, San Francisco, California.,Department of Pediatrics, University of California, San Francisco, California.,Department of Neurological Surgery, University of California, San Francisco, California
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198
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Yao Y, Jones E, Inoki K. Lysosomal Regulation of mTORC1 by Amino Acids in Mammalian Cells. Biomolecules 2017; 7:biom7030051. [PMID: 28686218 PMCID: PMC5618232 DOI: 10.3390/biom7030051] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/03/2017] [Accepted: 07/04/2017] [Indexed: 12/15/2022] Open
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth in eukaryotic cells. The active mTORC1 promotes cellular anabolic processes including protein, pyrimidine, and lipid biosynthesis, and inhibits catabolic processes such as autophagy. Consistent with its growth-promoting functions, hyper-activation of mTORC1 signaling is one of the important pathomechanisms underlying major human health problems including diabetes, neurodegenerative disorders, and cancer. The mTORC1 receives multiple upstream signals such as an abundance of amino acids and growth factors, thus it regulates a wide range of downstream events relevant to cell growth and proliferation control. The regulation of mTORC1 by amino acids is a fast-evolving field with its detailed mechanisms currently being revealed as the precise picture emerges. In this review, we summarize recent progress with respect to biochemical and biological findings in the regulation of mTORC1 signaling on the lysosomal membrane by amino acids.
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Affiliation(s)
- Yao Yao
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109, USA.
| | - Edith Jones
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109, USA.
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, 1137 East Catherine Street, Ann Arbor, MI 48109, USA.
| | - Ken Inoki
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109, USA.
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, 1137 East Catherine Street, Ann Arbor, MI 48109, USA.
- Department of Internal Medicine, University of Michigan Medical School, 1500 East Medical enter Drive, Ann Arbor, MI 48109, USA.
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199
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TORC1-Dependent Phosphorylation Targets in Fission Yeast. Biomolecules 2017; 7:biom7030050. [PMID: 28671615 PMCID: PMC5618231 DOI: 10.3390/biom7030050] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 06/27/2017] [Accepted: 06/28/2017] [Indexed: 12/11/2022] Open
Abstract
Target of rapamycin (TOR) kinase controls cell metabolism and growth in response to environmental cues such as nutrients, growth factors, and stress. TOR kinase is widely conserved across eukaryotes. As in other organisms, the fission yeast Schizosaccharomyces pombe has two types of TOR complex, namely TOR complex 1 (TORC1) and TORC2. It is interesting that the two TOR complexes in S. pombe have opposite roles in sexual differentiation, which is induced by nutrient starvation. TORC1, which contains Tor2 as a catalytic subunit, promotes vegetative growth and represses sexual differentiation in nutrient-rich conditions, while TORC2 is required for the initiation of sexual differentiation. Multiple targets of TORC1 have been identified. Some of these, such as S6 kinase and an autophagy regulator Atg13, are known targets in other organisms. In addition, there is a novel group of TORC1 targets involved in the regulation of sexual differentiation. Here, we review recent findings on phosphorylation targets of TORC1 in S. pombe. Furthermore, we briefly report a novel S. pombe target of TORC1.
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200
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Gong FH, Ye YN, Li JM, Zhao HY, Li XK. Rapamycin-ameliorated diabetic symptoms involved in increasing adiponectin expression in diabetic mice on a high-fat diet. Kaohsiung J Med Sci 2017; 33:321-326. [DOI: 10.1016/j.kjms.2017.05.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 05/01/2017] [Accepted: 05/02/2017] [Indexed: 12/21/2022] Open
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