Protein phosphatase 1 is a molecular constraint on learning and memory.
Repetition in learning is a prerequisite for the formation of accurate and long-lasting memory. Practice is most effective when widely distributed over time, rather than when closely spaced or massed. But even after efficient learning, most memories dissipate with time unless frequently used. The molecular mechanisms of these time-dependent constraints on learning and memory are unknown. Here we show that protein phosphatase 1 (PP1) determines the efficacy of learning and memory by limiting acquisition and favouring memory decline. When PP1 is genetically inhibited during learning, short intervals between training episodes are sufficient for optimal performance. The enhanced learning correlates with increased phosphorylation of cyclic AMP-dependent response element binding (CREB) protein, of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and of the GluR1 subunit of the AMPA receptor; it also correlates with CREB-dependent gene expression that, in control mice, occurs only with widely distributed training. Inhibition of PP1 prolongs memory when induced after learning, suggesting that PP1 also promotes forgetting. This property may account for ageing-related cognitive decay, as old mutant animals had preserved memory. Our findings emphasize the physiological importance of PP1 as a suppressor of learning and memory, and as a potential mediator of cognitive decline during ageing.
Genoux
David
D
Institute of Cell Biology, Swiss Federal Institute of Technology, Department of Biology, ETH Hönggerberg, CH-8093 Zürich, Switzerland.
Haditsch
Ursula
U
Knobloch
Marlen
M
Michalon
Aubin
A
Storm
Daniel
D
Mansuy
Isabelle M
IM
D000375:Aging / Q000235:genetics / Q000502:physiology; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D003071:Cognition / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004192:Discrimination, Psychological / Q000502:physiology; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000201:enzymology* / Q000502:physiology*; D007858:Learning / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D021122:Protein Subunits; D018091:Receptors, AMPA / Q000378:metabolism; D013028:Space Perception / Q000502:physiology; D013997:Time Factors
D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017362:Cyclic AMP Response Element-Binding Protein; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D021122:Protein Subunits; D018091:Receptors, AMPA