Therapeutic repair of myelin disorders may be limited by the relatively slow rate of human oligodendrocyte differentiation. To identify appropriate pharmacological targets with which to accelerate differentiation of human oligodendrocyte progenitors (hOPCs) directly, we used CD140a/O4-based FACS of human forebrain and microarray to hOPC-specific receptors. Among these, we identified CHRM3, a M 3 R muscarinic acetylcholine receptor, as being restricted to oligodendrocyte-biased CD140a

Inflammation and endoplasmic reticulum (ER) stress are associated with many neurological diseases. ER stress is brought on by the accumulation of misfolded proteins in the ER, which leads to activation of the unfolded protein response (UPR), a conserved pathway that transmits signals to restore homeostasis or eliminate the irreparably damaged cell. We provide evidence that inhibition or genetic haploinsufficiency of protein kinase R-like endoplasmic reticulum kinase (PERK) can selectively control inflammation brought on by ER stress without impinging on UPR-dependent survival and adaptive responses or normal immune responses. Using astrocytes lacking one or both alleles of PERK or the PERK inhibitor GSK2606414, we demonstrate that PERK haploinsufficiency or partial inhibition led to reduced ER stress-induced inflammation (IL-6, CCL2, and CCL20 expression) without compromising prosurvival responses. In contrast, complete loss of PERK blocked canonical PERKdependent UPR genes and promoted apoptosis. Reversal of eIF2␣-mediated translational repression using ISRIB potently suppressed PERK-dependent inflammatory gene expression, indicating that the selective modulation of inflammatory gene expression by PERK inhibition may be linked to attenuation of eIF2␣ phosphorylation and reveals a previously unknown link between translational repression and transcription of inflammatory genes. Additionally, ER-stressed astrocytes can drive an inflammatory M1-like phenotype in microglia, and this can be attenuated with inhibition of PERK. Importantly, targeting PERK neither disrupted normal cytokine signaling in astrocytes or microglia nor impaired macrophage phagocytosis or T cell polarization. Collectively, this work suggests that targeting PERK may provide a means for selective immunoregulation in the context of ER stress without disrupting normal immune function.

No abstract

SUMMARY AMPAR (AMPAR) complexes contain auxiliary subunits that modulate receptor trafficking and gating. In addition to the transmembrane AMPAR regulatory proteins (TARPs) and cornichons (CNIH-2/3), recent proteomic studies identified a diverse array of additional AMPAR-associated transmembrane and secreted partners. We systematically surveyed these and found that PORCN and ABHD6 increase GluA1 levels in transfected cells. Knockdown of PORCN in rat hippocampal neurons, which express it in high amounts, selectively reduces levels of all tested AMPAR complex components. Regulation of AMPARs is independent of PORCN’s membrane-associated O-acyl transferase activity. PORCN knockdown in hippocampal neurons decreases AMPAR currents and accelerates desensitization, and leads to depletion of TARP γ-8 from AMPAR complexes. Conditional PORCN knockout mice also exhibit specific changes in AMPAR expression and gating that reduce basal synaptic transmission, but leave long-term potentiation intact. These studies define additional roles for PORCN in controlling synaptic transmission by regulating the level and composition of hippocampal AMPAR complexes.

O-GlcNAcylation, a post-translational modification involving O-linkage of β-N-acetylglucosamine to Ser/Thr residues on target proteins, is increasingly recognized as a critical regulator of synaptic function. Enzymes that catalyze O-GlcNAcylation are found at both presynaptic and postsynaptic sites, and O-GlcNAcylated proteins localize to synaptosomes. An acute increase in O-GlcNAcylation can affect neuronal communication by inducing long-term depression (LTD) of excitatory transmission at hippocampal CA3-CA1 synapses, as well as suppressing hyperexcitable circuits in vitro and in vivo. Despite these findings, to date, no studies have directly examined how O-GlcNAcylation modulates the efficacy of inhibitory neurotransmission. Here we show an acute increase in O-GlcNAc dampens GABAergic currents onto principal cells in rodent hippocampus likely through a postsynaptic mechanism, and has a variable effect on the excitation/inhibition balance. The overall effect of increased O-GlcNAc is reduced synaptically-driven spike probability via synaptic depression and decreased intrinsic excitability. Our results position O-GlcNAcylation as a novel regulator of the overall excitation/inhibition balance and neuronal output. Synaptic integration and spike initiation in neurons is controlled by synaptic inhibition, which strongly influences neuronal output and information processing 1. Importantly, the balance of excitation to inhibition (E/I) is crucial to the proper functioning of circuits, and E/I imbalances have been implicated in a number of neurodevelopmental disorders and neurodegenerative diseases including schizophrenia, autism spectrum disorders, and Alzheimer's disease 2-5. Thus, understanding the mechanisms that modulate the strength of inhibitory transmission is fundamental to unraveling how neuronal circuits function in normal and disease states. Fast inhibitory transmission in the central nervous system is mediated by GABA A receptors (GABA A Rs), which are pentameric ligand-gated ion channels. The strength of this inhibition can be rapidly up-or down-regulated by post-translational modifications including ubiquitination 6 , palmitoylation 7,8 , and phosphorylation 9 of GABA A R subunits and/or associated proteins, which can alter channel function, trafficking, or stability at the membrane. While there is a vast body of literature on these post-translational modifications, O-GlcNAcylation, involving the O-linkage of β-N-acetylglucosamine (O-GlcNAc) to Ser/Thr residues on target proteins, remains severely understudied, with no examination to date of the effect of protein O-GlcNAcylation on inhibitory synapse physiology. Addition and removal of O-GlcNAc are catalyzed by the single pair of enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). O-GlcNAcylation is essential, as genetic deletion of OGT and OGA are lethal 10,11. O-GlcNAcylation is metabolically-regulated and highly dynamic; global changes reversibly occur within minutes, and are dictated by availability of UDP-GlcNAc, which is synthesized from glucos...