RGS14 is a natural suppressor of both synaptic plasticity in CA2 neurons and hippocampal-based learning and memory

• Authors: Sarah Emerson Lee, Emory University; Stephen B. Simons, Emory University; Scott A. Heldt, Emory University; Meilan Zhao, Emory University; Jason P Schroeder, Emory University; Christopher P. Vellano, Emory University; D. Patrick Cowan, Emory University; Suneela Ramineni, Emory University; Cindee K. Yates, Emory University; Yue Feng, Emory University; Yoland Smith, Emory University; J. David Sweatt, University of Alabama, Birmingham; David Weinshenker, Emory University; Kerry Ressler, Emory University; Serena M. Dudek, Emory University; John R Hepler, Emory University
• Journal Title: Proceedings of the National Academy of Sciences
• Volume: Volume 107, Number 39
• Publisher: National Academy of Sciences | 2010-09-28, Pages 16994-16998
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1073/pnas.1005362107
• Subjects: Biology, Genetics; Health Sciences, Pharmacology; Biology, Neuroscience
• Keywords: long-term potentiation; hippocampus; G protein signaling; RGS proteins; ERK

Abstract

Learning and memory have been closely linked to strengthening of synaptic connections between neurons (i.e., synaptic plasticity) within the dentate gyrus (DG)–CA3–CA1 trisynaptic circuit of the hippocampus. Conspicuously absent from this circuit is area CA2, an intervening hippocampal region that is poorly understood. Schaffer collateral synapses on CA2 neurons are distinct from those on other hippocampal neurons in that they exhibit a perplexing lack of synaptic long-term potentiation (LTP). Here we demonstrate that the signaling protein RGS14 is highly enriched in CA2 pyramidal neurons and plays a role in suppression of both synaptic plasticity at these synapses and hippocampal-based learning and memory. RGS14 is a scaffolding protein that integrates G protein and H-Ras/ERK/MAP kinase signaling pathways, thereby making it well positioned to suppress plasticity in CA2 neurons. Supporting this idea, deletion of exons 2–7 of the RGS14 gene yields mice that lack RGS14 (RGS14-KO) and now express robust LTP at glutamatergic synapses in CA2 neurons with no impact on synaptic plasticity in CA1 neurons. Treatment of RGS14-deficient CA2 neurons with a specific MEK inhibitor blocked this LTP, suggesting a role for ERK/MAP kinase signaling pathways in this process. When tested behaviorally, RGS14-KO mice exhibited marked enhancement in spatial learning and in object recognition memory compared with their wild-type littermates, but showed no differences in their performance on tests of nonhippocampal-dependent behaviors. These results demonstrate that RGS14 is a key regulator of signaling pathways linking synaptic plasticity in CA2 pyramidal neurons to hippocampal-based learning and memory but distinct from the canonical DG–CA3–CA1 circuit.