Ribosomal Protein S6 Kinase Is a Critical Downstream Effector of the Target of Rapamycin Complex 1 for Long-term Facilitation in Aplysia*

Long-term facilitation (LTF) in Aplysia is a leading cellular model for elucidating the biochemical mechanisms of synaptic plasticity underlying learning. In Aplysia, LTF requires translational control downstream of the target of rapamycin (TOR) complex 1 (TORC1). The major known downstream targets of TORC1 are 4E binding protein (4E-BP) and S6 kinase (S6K). By removing the site within these regulators required for their interaction with TORC1, we have generated dominant negative proteins that disrupt specific pathways downstream of TORC1. Expression of dominant negative S6K, but not dominant negative 4E-BP, in Aplysia sensory neurons (SNs) blocked 24-h LTF. TORC1 is directly activated by the small GTP-binding protein, Ras homologue enriched in brain (Rheb). To determine the effects of TORC1 activation on translation in Aplysia neurons, we have examined the effects of expressing a constitutively active form of the Aplysia orthologue of Rheb, ApRheb (ApRheb(Q63L)). Expression of ApRheb(Q63L) increased 4E-BP phosphorylation and the level of general, cap-dependent translation within the SN cell soma in a rapamycin-sensitive manner. This increase in cap-dependent translation was blocked neither by dominant negative 4E-BP nor dominant negative S6K. Thus, we demonstrate that S6K is an important downstream target of TORC1 in Aplysia and that it is necessary for 24-h LTF, but not for TORC1-mediated increases in somatic cap-dependent translation.

[1]  W. Sossin,et al.  The atypical protein kinase C in Aplysia can form a protein kinase M by cleavage , 2009, Journal of neurochemistry.

[2]  N. Sonenberg,et al.  Translational Control of Long-Lasting Synaptic Plasticity and Memory , 2009, Neuron.

[3]  Richard L. Huganir,et al.  Elongation Factor 2 and Fragile X Mental Retardation Protein Control the Dynamic Translation of Arc/Arg3.1 Essential for mGluR-LTD , 2008, Neuron.

[4]  N. Sonenberg,et al.  Translational control of the innate immune response through IRF-7 , 2008, Nature.

[5]  E. Klann,et al.  mGluR-Dependent Long-Term Depression Is Associated with Increased Phosphorylation of S6 and Synthesis of Elongation Factor 1A but Remains Expressed in S6K-Deficient Mice , 2008, Molecular and Cellular Biology.

[6]  R. Carroll,et al.  Characterization of the Role of Microtubule-Associated Protein 1B in Metabotropic Glutamate Receptor-Mediated Endocytosis of AMPA Receptors in Hippocampus , 2007, The Journal of Neuroscience.

[7]  C. Proud,et al.  PRAS40 Is a Target for Mammalian Target of Rapamycin Complex 1 and Is Required for Signaling Downstream of This Complex* , 2007, Journal of Biological Chemistry.

[8]  A. Nakashima,et al.  The Proline-rich Akt Substrate of 40 kDa (PRAS40) Is a Physiological Substrate of Mammalian Target of Rapamycin Complex 1* , 2007, Journal of Biological Chemistry.

[9]  G. Thomas,et al.  mTOR Complex1-S6K1 signaling: at the crossroads of obesity, diabetes and cancer. , 2007, Trends in molecular medicine.

[10]  N. Sonenberg,et al.  Elevated sensitivity to diet-induced obesity and insulin resistance in mice lacking 4E-BP1 and 4E-BP2. , 2007, The Journal of clinical investigation.

[11]  W. Sossin,et al.  Serotonin Increases Phosphorylation of Synaptic 4EBP through TOR, but Eukaryotic Initiation Factor 4E Levels Do Not Limit Somatic Cap-Dependent Translation in Aplysia Neurons , 2006, Molecular and Cellular Biology.

[12]  W. Sossin,et al.  Mnk is a negative regulator of cap‐dependent translation in Aplysia neurons , 2006, Journal of neurochemistry.

[13]  N. Sonenberg,et al.  Regulation of Eukaryotic Initiation Factor 4E by Converging Signaling Pathways during Metabotropic Glutamate Receptor-Dependent Long-Term Depression , 2006, The Journal of Neuroscience.

[14]  S. Schacher,et al.  Two Signaling Pathways Regulate the Expression and Secretion of a Neuropeptide Required for Long-Term Facilitation in Aplysia , 2006, The Journal of Neuroscience.

[15]  N. Sonenberg,et al.  The Translation Repressor 4E-BP2 Is Critical for eIF4F Complex Formation, Synaptic Plasticity, and Memory in the Hippocampus , 2005, The Journal of Neuroscience.

[16]  Yuval Dor,et al.  Ribosomal protein S6 phosphorylation is a determinant of cell size and glucose homeostasis. , 2005, Genes & development.

[17]  A. Komar,et al.  Internal Ribosome Entry Sites in Cellular mRNAs: Mystery of Their Existence* , 2005, Journal of Biological Chemistry.

[18]  Jianping Ding,et al.  Structural Basis for the Unique Biological Function of Small GTPase RHEB* , 2005, Journal of Biological Chemistry.

[19]  Joseph Avruch,et al.  Rheb Binds and Regulates the mTOR Kinase , 2005, Current Biology.

[20]  B. Manning.  Balancing Akt with S6K , 2004, The Journal of cell biology.

[21]  Kenta Hara,et al.  Brain-Derived Neurotrophic Factor Induces Mammalian Target of Rapamycin-Dependent Local Activation of Translation Machinery and Protein Synthesis in Neuronal Dendrites , 2004, The Journal of Neuroscience.

[22]  W. Sossin,et al.  5‐HT stimulates eEF2 dephosphorylation in a rapamycin‐sensitive manner in Aplysia neurites , 2004, Journal of neurochemistry.

[23]  N. Sonenberg,et al.  Upstream and downstream of mTOR. , 2004, Genes & development.

[24]  S. Schacher,et al.  Serotonin Regulates the Secretion and Autocrine Action of a Neuropeptide to Activate MAPK Required for Long-Term Facilitation in Aplysia , 2004, Neuron.

[25]  D. W. Zimmerman.  A note on preliminary tests of equality of variances. , 2004, The British journal of mathematical and statistical psychology.

[26]  Stefano Fumagalli,et al.  S6K1−/−/S6K2−/− Mice Exhibit Perinatal Lethality and Rapamycin-Sensitive 5′-Terminal Oligopyrimidine mRNA Translation and Reveal a Mitogen-Activated Protein Kinase-Dependent S6 Kinase Pathway , 2004, Molecular and Cellular Biology.

[27]  P. Sanna,et al.  Time-restricted role for dendritic activation of the mTOR-p70S6K pathway in the induction of late-phase long-term potentiation in the CA1 , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[28]  E. Kandel,et al.  Axonal transport of eukaryotic translation elongation factor 1α mRNA couples transcription in the nucleus to long-term facilitation at the synapse , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[29]  A. F. Castro,et al.  Rheb Binds Tuberous Sclerosis Complex 2 (TSC2) and Promotes S6 Kinase Activation in a Rapamycin- and Farnesylation-dependent Manner* , 2003, Journal of Biological Chemistry.

[30]  K. Inoki,et al.  Rheb GTPase is a direct target of TSC2 GAP activity and regulates mTOR signaling. , 2003, Genes & development.

[31]  E. Hafen,et al.  Rheb is an essential regulator of S6K in controlling cell growth in Drosophila , 2003, Nature Cell Biology.

[32]  E. Hafen,et al.  Insulin activation of Rheb, a mediator of mTOR/S6K/4E-BP signaling, is inhibited by TSC1 and 2. , 2003, Molecular cell.

[33]  J. Blenis,et al.  TOS Motif-Mediated Raptor Binding Regulates 4E-BP1 Multisite Phosphorylation and Function , 2003, Current Biology.

[34]  J. Avruch,et al.  The Mammalian Target of Rapamycin (mTOR) Partner, Raptor, Binds the mTOR Substrates p70 S6 Kinase and 4E-BP1 through Their TOR Signaling (TOS) Motif* , 2003, The Journal of Biological Chemistry.

[35]  Vincent F. Castellucci,et al.  An activity-dependent switch to cap-independent translation triggered by eIF4E dephosphorylation , 2003, Nature Neuroscience.

[36]  C. Proud,et al.  Regulation of peptide-chain elongation in mammalian cells. , 2002, European journal of biochemistry.

[37]  P. Worley,et al.  Rheb is in a high activation state and inhibits B-Raf kinase in mammalian cells , 2002, Oncogene.

[38]  J. Blenis,et al.  Identification of a Conserved Motif Required for mTOR Signaling , 2002, Current Biology.

[39]  E. Kandel.  The Molecular Biology of Memory Storage: A Dialogue Between Genes and Synapses , 2001, Science.

[40]  C. Proud,et al.  Regulation of elongation factor 2 kinase by p90RSK1 and p70 S6 kinase , 2001, The EMBO journal.

[41]  W. Sossin,et al.  Ca2+-Independent Protein Kinase C Apl II Mediates the Serotonin-Induced Facilitation at Depressed AplysiaSensorimotor Synapses , 2001, The Journal of Neuroscience.

[42]  W. Sossin,et al.  Serotonin Activates S6 Kinase in a Rapamycin-Sensitive Manner inAplysia Synaptosomes , 2001, The Journal of Neuroscience.

[43]  J. Urano,et al.  The Saccharomyces cerevisiae Rheb G-protein Is Involved in Regulating Canavanine Resistance and Arginine Uptake* , 2000, The Journal of Biological Chemistry.

[44]  E. Kandel,et al.  A Transient, Neuron-Wide Form of CREB-Mediated Long-Term Facilitation Can Be Stabilized at Specific Synapses by Local Protein Synthesis , 1999, Cell.

[45]  Stefano Fumagalli,et al.  Disruption of the p70s6k/p85s6k gene reveals a small mouse phenotype and a new functional S6 kinase , 1998, The EMBO journal.

[46]  W. Sossin,et al.  Biochemical Pathways by Which Serotonin Regulates Translation in the Nervous System of Aplysia , 1998, Journal of neurochemistry.

[47]  R. Pearson,et al.  Rapamycin suppresses 5′TOP mRNA translation through inhibition of p70s6k , 1997, The EMBO journal.

[48]  C. Der,et al.  The Ras-related Protein Rheb Is Farnesylated and Antagonizes Ras Signaling and Transformation* , 1997, The Journal of Biological Chemistry.

[49]  A. Nairn,et al.  Rapamycin selectively inhibits translation of mRNAs encoding elongation factors and ribosomal proteins. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[50]  A. Gingras,et al.  Insulin-dependent stimulation of protein synthesis by phosphorylation of a regulator of 5'-cap function , 1994, Nature.

[51]  J. Blankenship,et al.  Localization of immunoreactive alpha‐bag‐cell peptide in the central nervous system of Aplysia , 1989, The Journal of comparative neurology.

[52]  E. Kandel,et al.  5-HT modulates protein synthesis and the expression of specific proteins during long-term facilitation in aplysia sensory neurons , 1989, Neuron.

[53]  E R Kandel,et al.  A critical period for macromolecular synthesis in long-term heterosynaptic facilitation in Aplysia. , 1986, Science.

[54]  C. Der,et al.  Biological and biochemical properties of human ras H genes mutated at codon 61 , 1986, Cell.

[55]  J. Sarvey,et al.  Blockade of long-term potentiation in rat hippocampal CA1 region by inhibitors of protein synthesis , 1984, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[56]  S. Schacher,et al.  Neurite regeneration by Aplysia neurons in dissociated cell culture: modulation by Aplysia hemolymph and the presence of the initial axonal segment , 1983, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[57]  E. Klann,et al.  Cap-dependent translation initiation and memory. , 2008, Progress in brain research.

[58]  E. Klann,et al.  Removal of S6K1 and S6K2 leads to divergent alterations in learning, memory, and synaptic plasticity. , 2008, Learning & memory.

[59]  N. Sonenberg,et al.  Overexpression of initiation factor eIF-4E does not relieve the translational repression of ribosomal protein mRNAs in quiescent cells. , 1995, Gene expression.

[60]  E. Kandel,et al.  Structural changes accompanying memory storage. , 1993, Annual review of physiology.

[61]  E R Kandel,et al.  Inhibitor of protein synthesis blocks long-term behavioral sensitization in the isolated gill-withdrawal reflex of Aplysia. , 1989, Journal of neurobiology.