Studies on various forms of synaptic plasticity have demonstrated a link between mRNA translation, learning and memory. Like memory, synaptic plasticity includes an early phase which depends on modification of pre-existing proteins, and a late phase that requires transcription and synthesis of new proteins 1,2 . Activation of post-synaptic targets appears to trigger the transcription of plasticityrelated genes. The new mRNAs are either translated in the soma or transported to synapses before translation. GCN2, a key protein kinase, regulates the initiation of translation. We now report a unique feature of hippocampal slices from GCN2 -/-mice: in CA1, a single 100 Hz train induces a strong and sustained long-term potentiation (late-LTP or L-LTP), which is transcription and translation dependent. In contrast, stimulation that elicits late-LTP in wild type slices, such as four 100 Hz trains or forskolin, fails to evoke L-LTP in GCN2 -/-slices. This aberrant synaptic plasticity is mirrored in the behavior of GCN2 -/-mice in the Morris water maze: after weak training, their spatial memory is enhanced, but it is impaired after more intense training. Activated GCN2 stimulates mRNA translation of ATF4, a CREB antagonist. Accordingly, in the hippocampus of GCN2 -/-mice, the expression of ATF4 is reduced and CREB activity is increased. Our study provides genetic, physiological, behavioral and molecular evidence that GCN2 regulates synaptic plasticity, as well as learning and memory through modulation of the ATF4/CREB pathway.Translation of eukaryotic mRNAs is primarily regulated at the level of initiation 3 . Binding of the initiator tRNA, Met-tRNA i Met , to the 40S subunit is facilitated by the initiation factor 2 (eIF2) which forms a ternary complex with GTP and Met-tRNA i Met . Although phosphorylation
Neural apoptosis-regulated convertase-1/proprotein convertase subtilisin-kexin like-9 (NARC-1/PCSK9) is a proprotein convertase recently described to play a major role in cholesterol homeostasis through enhanced degradation of the lowdensity lipoprotein receptor (LDLR) and possibly in neural development. Herein, we investigated the potential involvement of this proteinase in the development of the CNS using mouse embryonal pluripotent P19 cells and the zebrafish as models. Time course quantitative RT-PCR analyses were performed following retinoic acid (RA)-induced neuroectodermal differentiation of P19 cells. Accordingly, the mRNA levels of NARC-1/PCSK9 peaked at day 2 of differentiation and fell off thereafter. In contrast, the expression of the proprotein convertases subtilisin kexin isozyme 1/site 1 protease and Furin was unaffected by RA, whereas that of PC5/6 and PC2 increased within and/or after the first 4 days of the differentiation period respectively. This pattern was not affected by the cholesterogenic transcription factor sterol regulatory elementbinding protein-2, which normally up-regulates NARC-1/ PCSK9 mRNA levels in liver. Furthermore, in P19 cells, RA treatment did not affect the protein level of the endogenous LDLR. This agrees with the unique expression pattern of NARC-1/PCSK9 in the rodent CNS, including the cerebellum, where the LDLR is not significantly expressed. Whole-mount in situ hybridization revealed that the pattern of expression of zebrafish NARC-1/PCSK9 is similar to that of mouse both in the CNS and periphery. Specific knockdown of zebrafish NARC-1/PCSK9 mRNA resulted in a general disorganization of cerebellar neurons and loss of hindbrain-midbrain boundaries, leading to embryonic death at 96 h after fertilization. These data support a novel role for NARC-1/PCSK9 in CNS development, distinct from that in cholesterogenic organs such as liver. Keywords: cholesterol, neural apoptosis-regulated convertase-1/ proprotein convertase subtilisin-kexin like-9, neurogenesis, P19 cells, proprotein convertase, zebrafish. J. Neurochem. (2006) Abbreviations used: a-MEM, modified minimum Eagle's medium; Ctrl, control; dpf, days post-fertilization; DRG, dorsal root ganglia; ECL, enhanced chemiluminescence; FBS, fetal bovine serum; GFAP, glial fibrillary acidic protein; HMG-CoA, 3-hydroxy-3-methylglutaryl co-enzyme A; HMGCR, HMG-CoA reductase; hpf, hours post-fertilization; HRP, horseradish peroxidase; ISH, in situ hybridization; LDLR, low-density lipoprotein receptor; mAb, monoclonal antibody; mm, mismatch; MO, morpholino oligonucleotide; NARC-1/PCSK9, neural apoptosis-regulated convertase-1/proprotein convertase subtilisin-kexin like-9; NeuN, neuronal nuclei; (n)SREBP, (nuclear) sterol regulatory element-binding protein; P1, day 1 after birth; PACE, paired basic amino acid cleaving enzyme; PBS, phosphate-buffered saline; PBST, PBS containing 0.1% Tween-20; PC, proprotein convertase; QPCR, quantitative RT-PCR; RA, retinoic acid; RXR, retinoid X receptor; SDS, sodium dodecyl sulfate; SG, ...
Using a yeast two-hybrid system, we screened a human brain cDNA library for possible interacting proteins with the C-terminal cytosolic tail of the b-secretase b-amyloid protein converting enzyme (BACE)1. This identified seven potential candidates, including the brain-specific type II membrane protein BRI 3 . Co-localization and co-immunoprecipitation experiments confirmed that BACE1 and BRI 3 co-localize and interact with each other via the cytosolic tail of BACE1.Furthermore, pulse and pulse-chase analyses revealed that the pro-protein convertases furin, and to a lesser extent PC7 and PC5A, process BRI 3 into a C-terminal secreted 4-kDa product. Thus, furin efficiently processes both pro-BACE1 and its novel interacting protein pro-BRI 3 .
There are three mammalian Golgi ␣1,2-mannosidases, encoded by different genes, that form Man 5 GlcNAc 2 from Man 8-9 GlcNAc 2 for the biosynthesis of hybrid and complex N-glycans. Northern blot analysis and in situ hybridization indicate that the three paralogs display distinct developmental and tissue-specific expression. The physiological role of Golgi ␣1,2-mannosidase IB was investigated by targeted gene ablation. The null mice have normal gross appearance at birth, but they display respiratory distress and die within a few hours. Histology of fetal lungs the day before birth indicate some delay in development, whereas neonatal lungs show extensive pulmonary hemorrhage in the alveolar region. No significant histopathological changes occur in other tissues. No remarkable ultrastructural differences are detected between wild type and null lungs. The membranes of a subset of bronchiolar epithelial cells are stained with lectins from Phaseolus vulgaris (leukoagglutinin and erythroagglutinin) and Datura stramonium in wild type lungs, but this staining disappears in lungs from null mice. Mass spectrometry of N-glycans from different tissues shows no significant changes in global N-glycans of null mice. Therefore, only a few glycoproteins required for normal lung function depend on ␣1,2-mannosidase IB for maturation. There are no apparent differences in the expression of several lung epithelial cell and endothelial cell markers between null and wild type mice. The ␣1,2-mannosidase IB null phenotype differs from phenotypes caused by ablation of other enzymes in N-glycan biosynthesis and from other mouse gene disruptions that affect pulmonary development and function.
The role of estrogens in Alzheimer's disease (AD) involving β-amyloid (Aβ) generation and plaque formation was mostly tested in ovariectomized mice with or without APP mutations. The aim of the present study was to explore the abnormalities of neural cells in a novel mouse model of AD with chronic estrogen deficiency. These chimeric mice exhibit a total FSH-R knockout (FORKO) and carry two transgenes, one expressing the β-amyloid precursor protein (APPsw, Swedish mutation) and the other expressing presenilin-1 lacking exon 9 (PS1Δ9). The most prominent changes in the cerebral cortex and hippocampus of these hypoestrogenic mice were marked hypertrophy of both cortical neurons and astrocytes and an increased number of activated microglia. There were no significant differences in the number of Aβ plaques although they appeared less compacted and larger than those in APPsw/PS1Δ9 control mice. Similar glia abnormalities were obtained in wild-type primary cortical neural cultures treated with letrozole, an aromatase inhibitor. The concordance of results from APPsw/PS1Δ9 mice with or without FSH-R deletion and those with letrozole treatment in vitro (with and without Aβ treatment) of primary cortical/hippocampal cultures suggests the usefulness of these models to explore molecular mechanisms involved in microglia and astrocyte activation in hypoestrogenic states in the central nervous system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.