title: Ribosomal protein S6 kinase is a critical downstream effector of the target of rapamycin complex 1 for long-term facilitation in Aplysia.
abstract: 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.
authors.affiliation: Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Weatherill
authors.forename: John
authors.initials: J
authors.lastname: Dyer
authors.forename: Wayne S
authors.initials: WS
authors.lastname: Sossin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D055724:Electrophysiological Phenomena; D039642:Eukaryotic Initiation Factors / Q000378:metabolism; D017774:Long-Term Potentiation / Q000502:physiology*; D008959:Models, Neurological; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000502:physiology; D016296:Mutagenesis; D009479:Neuropeptides / Q000235:genetics / Q000502:physiology; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology
chemical_list: D017931:DNA Primers; D039642:Eukaryotic Initiation Factors; D009479:Neuropeptides; D011994:Recombinant Proteins; D019893:Ribosomal Protein S6 Kinases; D020559:Monomeric GTP-Binding Proteins; D020123:Sirolimus