title: SynGAP regulates ERK/MAPK signaling, synaptic plasticity, and learning in the complex with postsynaptic density 95 and NMDA receptor.
abstract: At excitatory synapses, the postsynaptic scaffolding protein postsynaptic density 95 (PSD-95) couples NMDA receptors (NMDARs) to the Ras GTPase-activating protein SynGAP. The close association of SynGAP and NMDARs suggests that SynGAP may have an important role in NMDAR-dependent activation of Ras signaling pathways, such as the MAP kinase pathway, and in synaptic plasticity. To explore this issue, we examined long-term potentiation (LTP), p42 MAPK (ERK2) signaling, and spatial learning in mice with a heterozygous null mutation of the SynGAP gene (SynGAP(-/+)). In SynGAP(-/+) mutant mice, the induction of LTP in the hippocampal CA1 region was strongly reduced in the absence of any detectable alteration in basal synaptic transmission and NMDAR-mediated synaptic currents. Although basal levels of activated ERK2 were elevated in hippocampal extracts from SynGAP(-/+) mice, NMDAR stimulation still induced a robust increase in ERK activation in slices from SynGAP(-/+) mice. Thus, although SynGAP may regulate the ERK pathway, its role in LTP most likely involves additional downstream targets. Consistent with this, the amount of potentiation induced by stimulation protocols that induce an ERK-independent form of LTP were also significantly reduced in slices from SynGAP(-/+) mice. An elevation of basal phospho-ERK2 levels and LTP deficits were also observed in SynGAP(-/+)/H-Ras(-)/- double mutants, suggesting that SynGAP may normally regulate Ras isoforms other than H-Ras. A comparison of SynGAP and PSD-95 mutants suggests that PSD-95 couples NMDARs to multiple downstream signaling pathways with very different roles in LTP and learning.
authors.affiliation: Division of Neuroscience, University of Edinburgh, Edinburgh EH8-9JZ, United Kingdom.
authors.forename: Noboru H
authors.initials: NH
authors.lastname: Komiyama
authors.forename: Ayako M
authors.initials: AM
authors.lastname: Watabe
authors.forename: Holly J
authors.initials: HJ
authors.lastname: Carlisle
authors.forename: Karen
authors.initials: K
authors.lastname: Porter
authors.forename: Paul
authors.initials: P
authors.lastname: Charlesworth
authors.forename: Jennifer
authors.initials: J
authors.lastname: Monti
authors.forename: Douglas J C
authors.initials: DJ
authors.lastname: Strathdee
authors.forename: Colin M
authors.initials: CM
authors.lastname: O'Carroll
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Martin
authors.forename: Richard G M
authors.initials: RG
authors.lastname: Morris
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: O'Dell
authors.forename: Seth G N
authors.initials: SG
authors.lastname: Grant
mesh_terms: D000818:Animals; D000076122:Disks Large Homolog 4 Protein; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005328:Fetal Viability / Q000235:genetics; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D018390:Gene Targeting; D051528:Guanylate Kinases; D006579:Heterozygote; D006624:Hippocampus / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D007858:Learning / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D046911:Macromolecular Substances; D008565:Membrane Proteins; D051379:Mice; D008817:Mice, Mutant Strains; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D020690:GTPase-Activating Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016194:Receptors, N-Methyl-D-Aspartate; C033652:postsynaptic density proteins; D019950:Mitogen-Activated Protein Kinase 1; D051528:Guanylate Kinases; D018631:ras Proteins