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B Cell-Intrinsic mTORC1 Promotes Germinal Center-Defining Transcription Factor Gene Expression, Somatic Hypermutation, and Memory B Cell Generation in Humoral Immunity.
Raybuck AL, Cho SH, Li J, Rogers MC, Lee K, Williams CL, Shlomchik M, Thomas JW, Chen J, Williams JV, Boothby MR
(2018) J Immunol 200: 2627-2639
MeSH Terms: Animals, B-Lymphocytes, Cell Differentiation, Gene Expression, Germinal Center, Immunity, Humoral, Immunoglobulin G, Immunologic Memory, Lymphocyte Activation, Mechanistic Target of Rapamycin Complex 1, Mice, Mice, Inbred C57BL, Mutation, Plasma Cells, Proto-Oncogene Proteins c-bcl-6, Signal Transduction, Transcription Factors
Show Abstract · Added March 14, 2018
B lymphocytes migrate among varied microenvironmental niches during diversification, selection, and conversion to memory or Ab-secreting plasma cells. Aspects of the nutrient milieu differ within these lymphoid microenvironments and can influence signaling molecules such as the mechanistic target of rapamycin (mTOR). However, much remains to be elucidated as to the B cell-intrinsic functions of nutrient-sensing signal transducers that modulate B cell differentiation or Ab affinity. We now show that the amino acid-sensing mTOR complex 1 (mTORC1) is vital for induction of Bcl6-a key transcriptional regulator of the germinal center (GC) fate-in activated B lymphocytes. Accordingly, disruption of mTORC1 after B cell development and activation led to reduced populations of Ag-specific memory B cells as well as plasma cells and GC B cells. In addition, induction of the germ line transcript that guides activation-induced deaminase in selection of the IgG1 H chain region during class switching required mTORC1. Expression of the somatic mutator activation-induced deaminase was reduced by a lack of mTORC1 in B cells, whereas point mutation frequencies in Ag-specific GC-phenotype B cells were only halved. These effects culminated in a B cell-intrinsic defect that impacted an antiviral Ab response and drastically impaired generation of high-affinity IgG1. Collectively, these data establish that mTORC1 governs critical B cell-intrinsic mechanisms essential for establishment of GC differentiation and effective Ab production.
Copyright © 2018 by The American Association of Immunologists, Inc.
1 Communities
2 Members
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17 MeSH Terms
Cardiac natriuretic peptides promote adipose 'browning' through mTOR complex-1.
Liu D, Ceddia RP, Collins S
(2018) Mol Metab 9: 192-198
MeSH Terms: Adipose Tissue, Brown, Animals, Atrial Natriuretic Factor, Cells, Cultured, Cyclic GMP-Dependent Protein Kinases, Female, HEK293 Cells, Humans, Male, Mechanistic Target of Rapamycin Complex 1, Mice, Mice, Inbred C57BL, Mitochondria, Signal Transduction, Uncoupling Protein 1
Show Abstract · Added September 25, 2018
OBJECTIVE - Activation of thermogenesis in brown adipose tissue (BAT) and the ability to increase uncoupling protein 1 (UCP1) levels and mitochondrial biogenesis in white fat (termed 'browning'), has great therapeutic potential to treat obesity and its comorbidities because of the net increase in energy expenditure. β-adrenergic-cAMP-PKA signaling has long been known to regulate these processes. Recently PKA-dependent activation of mammalian target of rapamycin complex 1 (mTORC1) was shown to be necessary for adipose 'browning' as well as proper development of the interscapular BAT. In addition to cAMP-PKA signaling pathways, cGMP-PKG signaling also promotes this browning process; however, it is unclear whether or not mTORC1 is also necessary for cGMP-PKG induced browning.
METHOD - Activation of mTORC1 by natriuretic peptides (NP), which bind to and activate the membrane-bound guanylyl cyclase, NP receptor A (NPRA), was assessed in mouse and human adipocytes in vitro and mouse adipose tissue in vivo.
RESULTS - Activation of mTORC1 by NP-cGMP signaling was observed in both mouse and human adipocytes. We show that NP-NPRA-PKG signaling activate mTORC1 by direct PKG phosphorylation of Raptor at Serine 791. Administration of B-type natriuretic peptide (BNP) to mice induced Ucp1 expression in inguinal adipose tissue in vivo, which was completely blocked by the mTORC1 inhibitor rapamycin.
CONCLUSION - Our results demonstrate that NP-cGMP signaling activates mTORC1 via PKG, which is a component in the mechanism of adipose browning.
Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.
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15 MeSH Terms
Loss of mTORC2 signaling in oligodendrocyte precursor cells delays myelination.
Grier MD, West KL, Kelm ND, Fu C, Does MD, Parker B, McBrier E, Lagrange AH, Ess KC, Carson RP
(2017) PLoS One 12: e0188417
MeSH Terms: Animals, Cell Differentiation, Cell Proliferation, Central Nervous System, Gene Expression Regulation, Developmental, Mechanistic Target of Rapamycin Complex 1, Mechanistic Target of Rapamycin Complex 2, Mice, Mice, Knockout, Myelin Sheath, Oligodendrocyte Precursor Cells, Rapamycin-Insensitive Companion of mTOR Protein, Signal Transduction, White Matter
Show Abstract · Added March 14, 2018
Myelin abnormalities are increasingly being recognized as an important component of a number of neurologic developmental disorders. The integration of many signaling pathways and cell types are critical for correct myelinogenesis. The PI3-K and mechanistic target of rapamycin (mTOR) pathways have been found to play key roles. mTOR is found within two distinct complexes, mTORC1 and mTORC2. mTORC1 activity has been shown to play a major role during myelination, while the role of mTORC2 is not yet well understood. To determine the role of mTORC2 signaling in myelinogenesis, we generated a mouse lacking the critical mTORC2 component Rictor in oligodendrocyte precursors (OPCs). Targeted deletion of Rictor in these cells decreases and delays the expression of myelin related proteins and reduces the size of cerebral white matter tracts. This is developmentally manifest as a transient reduction in myelinated axon density and g-ratio. OPC cell number is reduced at birth without detectable change in proliferation with proportional reductions in mature oligodendrocyte number at P15. The total number of oligodendrocytes as well as extent of myelination, does improve over time. Adult conditional knock-out (CKO) animals do not demonstrate a behavioral phenotype likely due in part to preserved axonal conduction velocities. These data support and extend prior studies demonstrating an important but transient contribution of mTORC2 signaling to myelin development.
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14 MeSH Terms
Loss of mTORC1 signaling alters pancreatic α cell mass and impairs glucagon secretion.
Bozadjieva N, Blandino-Rosano M, Chase J, Dai XQ, Cummings K, Gimeno J, Dean D, Powers AC, Gittes GK, Rüegg MA, Hall MN, MacDonald PE, Bernal-Mizrachi E
(2017) J Clin Invest 127: 4379-4393
MeSH Terms: Animals, Glucagon, Glucagon-Secreting Cells, Hepatocyte Nuclear Factor 3-beta, Mechanistic Target of Rapamycin Complex 1, Mice, Mice, Knockout, Regulatory-Associated Protein of mTOR, Signal Transduction
Show Abstract · Added September 21, 2018
Glucagon plays a major role in the regulation of glucose homeostasis during fed and fasting states. However, the mechanisms responsible for the regulation of pancreatic α cell mass and function are not completely understood. In the current study, we identified mTOR complex 1 (mTORC1) as a major regulator of α cell mass and glucagon secretion. Using mice with tissue-specific deletion of the mTORC1 regulator Raptor in α cells (αRaptorKO), we showed that mTORC1 signaling is dispensable for α cell development, but essential for α cell maturation during the transition from a milk-based diet to a chow-based diet after weaning. Moreover, inhibition of mTORC1 signaling in αRaptorKO mice and in WT animals exposed to chronic rapamycin administration decreased glucagon content and glucagon secretion. In αRaptorKO mice, impaired glucagon secretion occurred in response to different secretagogues and was mediated by alterations in KATP channel subunit expression and activity. Additionally, our data identify the mTORC1/FoxA2 axis as a link between mTORC1 and transcriptional regulation of key genes responsible for α cell function. Thus, our results reveal a potential function of mTORC1 in nutrient-dependent regulation of glucagon secretion and identify a role for mTORC1 in controlling α cell-mass maintenance.
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1 Members
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9 MeSH Terms
Second messenger signaling mechanisms of the brown adipocyte thermogenic program: an integrative perspective.
Shi F, Collins S
(2017) Horm Mol Biol Clin Investig 31:
MeSH Terms: Adipocytes, Beige, Adipocytes, Brown, Animals, Cyclic AMP-Dependent Protein Kinases, Cyclic GMP-Dependent Protein Kinases, Energy Metabolism, Gene Expression Regulation, Humans, Intracellular Space, Mechanistic Target of Rapamycin Complex 1, MicroRNAs, Natriuretic Agents, RNA, Long Noncoding, Receptors, Adrenergic, beta, Second Messenger Systems, Signal Transduction, Thermogenesis, Uncoupling Protein 1
Show Abstract · Added September 26, 2018
β-adrenergic receptors (βARs) are well established for conveying the signal from catecholamines to adipocytes. Acting through the second messenger cyclic adenosine monophosphate (cAMP) they stimulate lipolysis and also increase the activity of brown adipocytes and the 'browning' of adipocytes within white fat depots (so-called 'brite' or 'beige' adipocytes). Brown adipose tissue mitochondria are enriched with uncoupling protein 1 (UCP1), which is a regulated proton channel that allows the dissipation of chemical energy in the form of heat. The discovery of functional brown adipocytes in humans and inducible brown-like ('beige' or 'brite') adipocytes in rodents have suggested that recruitment and activation of these thermogenic adipocytes could be a promising strategy to increase energy expenditure for obesity therapy. More recently, the cardiac natriuretic peptides and their second messenger cyclic guanosine monophosphate (cGMP) have gained attention as a parallel signaling pathway in adipocytes, with some unique features. In this review, we begin with some important historical work that touches upon the regulation of brown adipocyte development and physiology. We then provide a synopsis of some recent advances in the signaling cascades from β-adrenergic agonists and natriuretic peptides to drive thermogenic gene expression in the adipocytes and how these two pathways converge at a number of unexpected points. Finally, moving from the physiologic hormonal signaling, we discuss yet another level of control downstream of these signals: the growing appreciation of the emerging roles of non-coding RNAs as important regulators of brown adipocyte formation and function. In this review, we discuss new developments in our understanding of the signaling mechanisms and factors including new secreted proteins and novel non-coding RNAs that control the function as well as the plasticity of the brown/beige adipose tissue as it responds to the energy needs and environmental conditions of the organism.
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MeSH Terms
Distinct roles for the mTOR pathway in postnatal morphogenesis, maturation and function of pancreatic islets.
Sinagoga KL, Stone WJ, Schiesser JV, Schweitzer JI, Sampson L, Zheng Y, Wells JM
(2017) Development 144: 2402-2414
MeSH Terms: Animals, Animals, Newborn, Cell Aggregation, Islets of Langerhans, Mechanistic Target of Rapamycin Complex 1, Mechanistic Target of Rapamycin Complex 2, Mice, Models, Biological, Morphogenesis, Multiprotein Complexes, Mutation, Signal Transduction, TOR Serine-Threonine Kinases
Show Abstract · Added February 6, 2018
While much is known about the molecular pathways that regulate embryonic development and adult homeostasis of the endocrine pancreas, little is known about what regulates early postnatal development and maturation of islets. Given that birth marks the first exposure to enteral nutrition, we investigated how nutrient-regulated signaling pathways influence postnatal islet development in mice. We performed loss-of-function studies of mechanistic target of rapamycin (mTOR), a highly conserved kinase within a nutrient-sensing pathway known to regulate cellular growth, morphogenesis and metabolism. Deletion of Mtor in pancreatic endocrine cells had no significant effect on their embryonic development. However, within the first 2 weeks after birth, mTOR-deficient islets became dysmorphic, β-cell maturation and function were impaired, and animals lost islet mass. Moreover, we discovered that these distinct functions of mTOR are mediated by separate downstream branches of the pathway, in that mTORC1 (with adaptor protein Raptor) is the main complex mediating the maturation and function of islets, whereas mTORC2 (with adaptor protein Rictor) impacts islet mass and architecture. Taken together, these findings suggest that nutrient sensing may be an essential trigger for postnatal β-cell maturation and islet development.
© 2017. Published by The Company of Biologists Ltd.
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1 Members
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13 MeSH Terms
mTORC1 and mTORC2 in cancer and the tumor microenvironment.
Kim LC, Cook RS, Chen J
(2017) Oncogene 36: 2191-2201
MeSH Terms: Animals, Humans, Mechanistic Target of Rapamycin Complex 1, Mechanistic Target of Rapamycin Complex 2, Multiprotein Complexes, Neoplasms, TOR Serine-Threonine Kinases, Tumor Microenvironment
Show Abstract · Added March 29, 2017
The mammalian target of rapamycin (mTOR) is a crucial signaling node that integrates environmental cues to regulate cell survival, proliferation and metabolism, and is often deregulated in human cancer. mTOR kinase acts in two functionally distinct complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2), whose activities and substrate specificities are regulated by complex co-factors. Deregulation of this centralized signaling pathway has been associated with a variety of human diseases including diabetes, neurodegeneration and cancer. Although mTORC1 signaling has been extensively studied in cancer, recent discoveries indicate a subset of human cancers harboring amplifications in mTORC2-specific genes as the only actionable genomic alterations, suggesting a distinct role for mTORC2 in cancer as well. This review will summarize recent advances in dissecting the relative contributions of mTORC1 versus mTORC2 in cancer, their role in tumor-associated blood vessels and tumor immunity, and provide an update on mTOR inhibitors.
1 Communities
2 Members
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8 MeSH Terms
Germinal centre hypoxia and regulation of antibody qualities by a hypoxia response system.
Cho SH, Raybuck AL, Stengel K, Wei M, Beck TC, Volanakis E, Thomas JW, Hiebert S, Haase VH, Boothby MR
(2016) Nature 537: 234-238
MeSH Terms: Animals, Antibodies, B-Lymphocytes, Cell Hypoxia, Cell Proliferation, Cell Survival, Cytosine Deaminase, Germinal Center, Hypoxia, Immunoglobulin Class Switching, Mechanistic Target of Rapamycin Complex 1, Mice, Mice, Inbred C57BL, Multiprotein Complexes, TOR Serine-Threonine Kinases
Show Abstract · Added August 9, 2016
Germinal centres (GCs) promote humoral immunity and vaccine efficacy. In GCs, antigen-activated B cells proliferate, express high-affinity antibodies, promote antibody class switching, and yield B cell memory. Whereas the cytokine milieu has long been known to regulate effector functions that include the choice of immunoglobulin class, both cell-autonomous and extrinsic metabolic programming have emerged as modulators of T-cell-mediated immunity. Here we show in mice that GC light zones are hypoxic, and that low oxygen tension () alters B cell physiology and function. In addition to reduced proliferation and increased B cell death, low impairs antibody class switching to the pro-inflammatory IgG2c antibody isotype by limiting the expression of activation-induced cytosine deaminase (AID). Hypoxia induces HIF transcription factors by restricting the activity of prolyl hydroxyl dioxygenase enzymes, which hydroxylate HIF-1α and HIF-2α to destabilize HIF by binding the von Hippel-Landau tumour suppressor protein (pVHL). B-cell-specific depletion of pVHL leads to constitutive HIF stabilization, decreases antigen-specific GC B cells and undermines the generation of high-affinity IgG, switching to IgG2c, early memory B cells, and recall antibody responses. HIF induction can reprogram metabolic and growth factor gene expression. Sustained hypoxia or HIF induction by pVHL deficiency inhibits mTOR complex 1 (mTORC1) activity in B lymphoblasts, and mTORC1-haploinsufficient B cells have reduced clonal expansion, AID expression, and capacities to yield IgG2c and high-affinity antibodies. Thus, the normal physiology of GCs involves regional variegation of hypoxia, and HIF-dependent oxygen sensing regulates vital functions of B cells. We propose that the restriction of oxygen in lymphoid organs, which can be altered in pathophysiological states, modulates humoral immunity.
1 Communities
4 Members
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15 MeSH Terms
AMPK Is Essential to Balance Glycolysis and Mitochondrial Metabolism to Control T-ALL Cell Stress and Survival.
Kishton RJ, Barnes CE, Nichols AG, Cohen S, Gerriets VA, Siska PJ, Macintyre AN, Goraksha-Hicks P, de Cubas AA, Liu T, Warmoes MO, Abel ED, Yeoh AE, Gershon TR, Rathmell WK, Richards KL, Locasale JW, Rathmell JC
(2016) Cell Metab 23: 649-62
MeSH Terms: AMP-Activated Protein Kinases, Animals, Cell Line, Tumor, Cell Survival, Glycolysis, Humans, Mechanistic Target of Rapamycin Complex 1, Mice, Inbred C57BL, Mitochondria, Multiprotein Complexes, Precursor Cell Lymphoblastic Leukemia-Lymphoma, Receptors, Notch, Signal Transduction, Stress, Physiological, T-Lymphocytes, TOR Serine-Threonine Kinases
Show Abstract · Added August 8, 2016
T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy associated with Notch pathway mutations. While both normal activated and leukemic T cells can utilize aerobic glycolysis to support proliferation, it is unclear to what extent these cell populations are metabolically similar and if differences reveal T-ALL vulnerabilities. Here we show that aerobic glycolysis is surprisingly less active in T-ALL cells than proliferating normal T cells and that T-ALL cells are metabolically distinct. Oncogenic Notch promoted glycolysis but also induced metabolic stress that activated 5' AMP-activated kinase (AMPK). Unlike stimulated T cells, AMPK actively restrained aerobic glycolysis in T-ALL cells through inhibition of mTORC1 while promoting oxidative metabolism and mitochondrial Complex I activity. Importantly, AMPK deficiency or inhibition of Complex I led to T-ALL cell death and reduced disease burden. Thus, AMPK simultaneously inhibits anabolic growth signaling and is essential to promote mitochondrial pathways that mitigate metabolic stress and apoptosis in T-ALL.
Copyright © 2016 Elsevier Inc. All rights reserved.
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16 MeSH Terms
Ubiquilin-mediated Small Molecule Inhibition of Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling.
Coffey RT, Shi Y, Long MJ, Marr MT, Hedstrom L
(2016) J Biol Chem 291: 5221-33
MeSH Terms: Adaptor Proteins, Signal Transducing, Arginine, Carbamates, Cell Line, Tumor, Cell Proliferation, Enzyme Inhibitors, HEK293 Cells, Humans, Mechanistic Target of Rapamycin Complex 1, Multiprotein Complexes, Phosphoproteins, Phosphorylation, Protein Binding, Protein Biosynthesis, Protein Processing, Post-Translational, Ribosomal Protein S6 Kinases, Signal Transduction, TOR Serine-Threonine Kinases, Ubiquitins
Show Abstract · Added May 9, 2016
Mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cellular metabolism, growth, and proliferation. mTORC1 has been implicated in many diseases such as cancer, diabetes, and neurodegeneration, and is a target to prolong lifespan. Here we report a small molecule inhibitor (Cbz-B3A) of mTORC1 signaling. Cbz-B3A inhibits the phosphorylation of eIF4E-binding protein 1 (4EBP1) and blocks 68% of translation. In contrast, rapamycin preferentially inhibits the phosphorylation of p70(S6k) and blocks 35% of translation. Cbz-B3A does not appear to bind directly to mTORC1, but instead binds to ubiquilins 1, 2, and 4. Knockdown of ubiquilin 2, but not ubiquilins 1 and 4, decreases the phosphorylation of 4EBP1, suggesting that ubiquilin 2 activates mTORC1. The knockdown of ubiquilins 2 and 4 decreases the effect of Cbz-B3A on 4EBP1 phosphorylation. Cbz-B3A slows cellular growth of some human leukemia cell lines, but is not cytotoxic. Thus Cbz-B3A exemplifies a novel strategy to inhibit mTORC1 signaling that might be exploited for treating many human diseases. We propose that Cbz-B3A reveals a previously unappreciated regulatory pathway coordinating cytosolic protein quality control and mTORC1 signaling.
© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
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19 MeSH Terms