title: A fine balance: Regulation of hippocampal Arc/Arg3.1 transcription, translation and degradation in a rat model of normal cognitive aging.
abstract: Memory decline is a common feature of aging. Expression of the immediate-early gene Arc is necessary for normal long-term memory, and although experience dependent Arc transcription is reportedly reduced in the aged rat hippocampus, it has not been clear whether this effect is an invariant consequence of growing older, or a finding linked specifically to age-related memory impairment. Here we show that experience dependent Arc mRNA expression in the hippocampus fails selectively among aged rats with spatial memory deficits. While these findings are consistent with the possibility that blunted Arc transcription contributes to cognitive aging, we also found increased basal ARC protein levels in the CA1 field of the hippocampus in aged rats with memory impairment, together with a loss of the experience dependent increase observed in young and unimpaired aged rats. Follow-up analysis revealed that increased basal translation and blunted ubiquitin mediated degradation may contribute to increased basal ARC protein levels noted in memory impaired aged rats. These findings indicate that Arc expression is regulated at multiple levels, and that several of these mechanisms are altered in cognitively impaired aged rats. Defining the influence of these alterations on the spatial and temporal fidelity of synapse specific, memory-related plasticity in the aged hippocampus is an important challenge.
authors.affiliation: Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Bonnie R
authors.initials: BR
authors.lastname: Fletcher
authors.affiliation: Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Gordon S
authors.initials: GS
authors.lastname: Hill
authors.affiliation: Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Long
authors.affiliation: Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: Michela
authors.initials: M
authors.lastname: Gallagher
authors.affiliation: Fishberg Department of Neuroscience, Mount Sinai, New York, NY 10029, USA.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Shapiro
authors.affiliation: Laboratory of Behavioral Neuroscience, Neurocognitive Aging Section, National Institute on Aging, Baltimore, MD 21224, USA. Electronic address: rappp@mail.nih.gov.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Rapp
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D003071:Cognition / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology*; D017403:In Situ Hybridization; D007858:Learning / Q000502:physiology; D008297:Male; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D014176:Protein Biosynthesis / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D003598:Cytoskeletal Proteins; D009419:Nerve Tissue Proteins; C092069:activity regulated cytoskeletal-associated protein
keywords: Immediate-early gene; Memory; Plasticity; Synapse