PT - JOURNAL ARTICLE AU - Changchi Hsieh AU - Panayiotis Tsokas AU - Alejandro Grau-Perales AU - Edith Lesburguères AU - Joseph Bukai AU - Kunal Khanna AU - Joelle Chorny AU - Ain Chung AU - Claudia Jou AU - Nesha S. Burghardt AU - Christine A. Denny AU - Rafael E. Flores-Obando AU - Benjamin Rush Hartley AU - Laura Melissa Rodríguez Valencia AU - A. Iván Hernández AU - Peter J. Bergold AU - James E. Cottrell AU - Juan Marcos Alarcon AU - André Antonio Fenton AU - Todd Charlton Sacktor TI - Persistent increases of PKMζ in memory-activated neurons trace LTP maintenance during spatial long-term memory storage AID - 10.1101/2020.02.05.936146 DP - 2021 Jan 01 TA - bioRxiv PG - 2020.02.05.936146 4099 - http://biorxiv.org/content/early/2021/01/11/2020.02.05.936146.short 4100 - http://biorxiv.org/content/early/2021/01/11/2020.02.05.936146.full AB - PKMζ is an autonomously active PKC isoform crucial for the maintenance of synaptic long-term potentiation (LTP) and long-term memory. Unlike other protein kinases that are transiently stimulated by second messengers, PKMζ is persistently activated through sustained increases in kinase protein expression. Therefore, visualizing increases in PKMζ expression during long-term memory storage might reveal the sites of its persistent action and thus the location of memory-associated LTP maintenance in the brain. Using quantitative immunohistochemistry validated by the lack of staining in PKMζ-null mice, we examined the amount and distribution of PKMζ in subregions of the hippocampal formation of wild-type mice during LTP maintenance and spatial long-term memory storage. During LTP maintenance in hippocampal slices, PKMζ increases in the pyramidal cell body and stimulated dendritic layers of CA1 for at least 2 h. During spatial memory storage, PKMζ increases in CA1 pyramidal cells for at least 1 month, paralleling the persistence of the memory. The subset of CA1 pyramidal cells that are tagged by immediate early gene Arc-driven transcription of fluorescent proteins, whose expression increases during initial memory formation, also expresses the persistent increase of PKMζ during memory storage. In the memory-tagged cells, the increased PKMζ expression persists in dendritic compartments within stratum radiatum for 1 month, indicating the long-term storage of information in the CA3-to-CA1 pathway during remote spatial memory. We conclude that persistent increases in PKMζ trace the molecular mechanism of LTP maintenance and thus the sites of information storage within brain circuitry during long-term memory.Competing Interest StatementThe authors have declared no competing interest.AbbreviationsCA1Cornu Ammonis 1 subfieldCA3Cornu Ammonis 3 subfieldDGdentate gyrusEC3entorhinal cortex layer 3eYFPenhanced yellow fluorescent proteinfEPSPsfield excitatory postsynaptic potentialsIHCimmunohistochemistryLTPlong-term potentiationPKCprotein kinase CPKMζprotein kinase MζSEMstandard error of mean