SUMMARY Metabolic production of acetyl-CoA is linked to histone acetylation and gene regulation, yet the precise mechanisms are largely unknown. Here we show that the metabolic enzyme acetyl-CoA synthetase 2 (ACSS2) is a direct regulator of histone acetylation in neurons and of spatial memory in mammals. In a neuronal cell culture model, ACSS2 increases in nuclei of differentiating neurons and localizes to upregulated neuronal genes near elevated histone acetylation. Reduction of ACSS2 lowers nuclear acetyl-CoA levels, histone acetylation, and responsive expression of the cohort of neuronal genes. In adult mice, attenuation of hippocampal ACSS2 expression impairs long-term spatial memory, a cognitive process reliant on histone acetylation. ACSS2 reduction in hippocampus also leads to defective upregulation of memory-related neuronal genes that are pre-bound by ACSS2. These results reveal a unique connection between cellular metabolism, gene regulation, and neural plasticity, establishing a link between acetyl-CoA generation “on-site” at chromatin for histone acetylation and the transcription of critical neuronal genes.

Brief periods of sleep loss have long-lasting consequences such as impaired memory consolidation. Structural changes in synaptic connectivity have been proposed as a substrate of memory storage. Here, we examine the impact of brief periods of sleep deprivation on dendritic structure. In mice, we find that five hours of sleep deprivation decreases dendritic spine numbers selectively in hippocampal area CA1 and increased activity of the filamentous actin severing protein cofilin. Recovery sleep normalizes these structural alterations. Suppression of cofilin function prevents spine loss, deficits in hippocampal synaptic plasticity, and impairments in long-term memory caused by sleep deprivation. The elevated cofilin activity is caused by cAMP-degrading phosphodiesterase-4A5 (PDE4A5), which hampers cAMP-PKA-LIMK signaling. Attenuating PDE4A5 function prevents changes in cAMP-PKA-LIMK-cofilin signaling and cognitive deficits associated with sleep deprivation. Our work demonstrates the necessity of an intact cAMP-PDE4-PKA-LIMK-cofilin activation-signaling pathway for sleep deprivation-induced memory disruption and reduction in hippocampal spine density.DOI: http://dx.doi.org/10.7554/eLife.13424.001

A kinase-anchoring proteins (AKAPs) organize compartmentalized pools of Protein Kinase A (PKA) to enable localized signaling events within neurons. However, it is unclear which of the many expressed AKAPs in neurons target PKA to signaling complexes important for long-lasting forms of synaptic plasticity and memory storage. In the forebrain, the anchoring protein gravin recruits a signaling complex containing PKA, PKC, calmodulin, and PDE4D to the β2-adrenergic receptor. Here, we show that mice lacking the α-isoform of gravin have deficits in PKA-dependent long-lasting forms of hippocampal synaptic plasticity including β2-adrenergic receptor-mediated plasticity, and selective impairments of long-term memory storage. Further, both hippocampal β2-adrenergic receptor phosphorylation by PKA, and learning-induced activation of ERK, are attenuated in the CA1 region of the hippocampus in mice lacking gravin-α. We conclude that gravin compartmentalizes a significant pool of PKA that regulates learning-induced β2-adrenergic receptor signaling and ERK activation in the hippocampus in vivo, organizing molecular interactions between glutamatergic and noradrenergic signaling pathways for long-lasting synaptic plasticity, and memory storage.

Summary Centromere protein CENP-E is a dimeric kinesin (Kinesin-7 family) with critical roles in mitosis including establishment of microtubule (MT)-chromosome linkage and movement of monooriented chromosomes on kinetochore microtubules (kMTs) for proper alignment at metaphase [1-9]. We performed studies to test the hypothesis that CENP-E promotes MT elongation at the MT plus-ends. A human CENP-E construct was engineered, expressed, and purified which yielded the CENP-E-6His dimeric motor protein. The results show that CENP-E promotes MT plus-end directed MT gliding at 11 nm/s. The results from real-time microscopy assays indicate that 60.3% of polarity marked MTs exhibited CENP-E promoted MT plus-end elongation. The MT extension required ATP turnover, and MT plus-end elongation occurred at 1.48 μm/30 min. Immunolocalization studies revealed that 80.8% of plus-end elongated MTs showed CENP-E at the MT plus-end. The time dependence of CENP-E promoted MT elongation in solution best fit a single exponential function (kobs = 5.1 s−1), which is indicative of a mechanism in which α,β-tubulin subunit addition is tightly coupled to ATP turnover. Based on these results, we propose that CENP-E as part of its function in chromosome kinetochore-MT linkage plays a direct role in MT elongation.

Long-lasting forms of long-term potentiation (LTP) represent one of the major cellular mechanisms underlying learning and memory. One of the fundamental questions in the field of LTP is why different molecules are critical for long-lasting forms of LTP induced by diverse experimental protocols. Further complexity stems from spatial aspects of signaling networks, such that some molecules function in the dendrite and some are critical in the spine. We investigated whether the diverse experimental evidence can be unified by creating a spatial, mechanistic model of multiple signaling pathways in hippocampal CA1 neurons. Our results show that the combination of activity of several key kinases can predict the occurrence of long-lasting forms of LTP for multiple experimental protocols. Specifically Ca2+/calmodulin activated kinase II, protein kinase A and exchange protein activated by cAMP (Epac) together predict the occurrence of LTP in response to strong stimulation (multiple trains of 100 Hz) or weak stimulation augmented by isoproterenol. Furthermore, our analysis suggests that activation of the β-adrenergic receptor either via canonical (Gs-coupled) or non-canonical (Gi-coupled) pathways underpins most forms of long-lasting LTP. Simulations make the experimentally testable prediction that a complete antagonist of the β-adrenergic receptor will likely block long-lasting LTP in response to strong stimulation. Collectively these results suggest that converging molecular mechanisms allow CA1 neurons to flexibly utilize signaling mechanisms best tuned to temporal pattern of synaptic input to achieve long-lasting LTP and memory storage.