1. Department of Biochemistry and McGill Cancer Center,
2. Department of Pharmacology and Therapeutics,
3. Department of Psychology,
4. Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3G 1Y6, Canada
5. Département de physiologie, Centre de Recherche en Sciences Neurologiques, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada
6. Skirball Institute, Departments of Medicine, Cell Biology and Pharmacology, NYU School of Medicine, New York, New York 10016, USA
7. Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, 110 Pine Avenue, West Montreal, Quebec H2W 1R7, Canada
8. Genomic Sciences Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan

Correspondence to: Nahum Sonenberg¹ Correspondence and requests for materials should be addressed to N.S. (Email: nahum.sonenberg@mcgill.ca).

Abstract

Studies on various forms of synaptic plasticity have shown a link between messenger RNA translation, learning and memory. Like memory, synaptic plasticity includes an early phase that depends on modification of pre-existing proteins, and a late phase that requires transcription and synthesis of new proteins^{1, 2}. Activation of postsynaptic targets seems to trigger the transcription of plasticity-related genes. The new mRNAs are either translated in the soma or transported to synapses before translation. GCN2, a key protein kinase, regulates the initiation of translation. Here we report a unique feature of hippocampal slices from GCN2^-/- mice: in CA1, a single 100-Hz train induces a strong and sustained long-term potentiation (late LTP or L-LTP), which is dependent on transcription and translation. In contrast, stimulation that elicits L-LTP in wild-type slices, such as four 100-Hz trains or forskolin, fails to evoke L-LTP in GCN2^-/- slices. This aberrant synaptic plasticity is mirrored in the behaviour of GCN2^-/- mice in the Morris water maze: after weak training, their spatial memory is enhanced, but it is impaired after more intense training. Activated GCN2 stimulates mRNA translation of ATF4, an antagonist of cyclic-AMP-response-element-binding protein (CREB). Thus, in the hippocampus of GCN2^-/- mice, the expression of ATF4 is reduced and CREB activity is increased. Our study provides genetic, physiological, behavioural and molecular evidence that GCN2 regulates synaptic plasticity, as well as learning and memory, through modulation of the ATF4/CREB pathway.

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