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Neurotoxicology Mar 2024Methamphetamine (METH) - induced cognitive impairments may be related to synaptic degeneration at mossy fiber terminals, critical for spatial memory formation in...
Methamphetamine (METH) - induced cognitive impairments may be related to synaptic degeneration at mossy fiber terminals, critical for spatial memory formation in hippocampal circuits. We have previously found METH-induced neurodegeneration in the striatum by increasing the α-synuclein (α-SYN) level. However, whether and how the METH-induced mossy fiber degeneration is also blamed for the abnormal accumulation of α-SYN remains to be elucidated. Chronic METH exposure decreased mossy fiber density but upregulatedα-SYN and phosphorylated TAU (TAU-pSer396) in hippocampal CA3, associated with glial cell overactivation, axonal neuropathies, and memory impairment. Notably, the knockout of the α-SYN gene significantly alleviated the METH-induced mossy fiber degeneration and memory impairment. Meanwhile, the TAU-pSer396 accumulation and glial activation were ameliorated by α-SYN knockout. Our findings suggest an essential role of α-SYN in mediating METH-induced mossy fiber degeneration, providing promising therapeutic and prophylactic targets for METH-related neurodegenerative diseases.
Topics: Methamphetamine; alpha-Synuclein; Mossy Fibers, Hippocampal; Hippocampus
PubMed: 38311184
DOI: 10.1016/j.neuro.2024.01.005 -
Cell Reports Feb 2024Inflammation is closely associated with many neurodegenerative disorders. Yet, whether inflammation causes, exacerbates, or responds to neurodegeneration has been...
Inflammation is closely associated with many neurodegenerative disorders. Yet, whether inflammation causes, exacerbates, or responds to neurodegeneration has been challenging to define because the two processes are so closely linked. Here, we disentangle inflammation from the axon damage it causes by individually blocking cytotoxic T cell function and axon degeneration. We model inflammatory damage in mouse skin, a barrier tissue that, despite frequent inflammation, must maintain proper functioning of a dense array of axon terminals. We show that sympathetic axons modulate skin inflammation through release of norepinephrine, which suppresses activation of γδ T cells via the β2 adrenergic receptor. Strong inflammatory stimulation-modeled by application of the Toll-like receptor 7 agonist imiquimod-causes progressive γδ T cell-mediated, Sarm1-dependent loss of these immunosuppressive sympathetic axons. This removes a physiological brake on T cells, initiating a positive feedback loop of enhanced inflammation and further axon damage.
Topics: Animals; Mice; Feedback; Inflammation; Axons; Dermatitis; Presynaptic Terminals
PubMed: 38310514
DOI: 10.1016/j.celrep.2024.113721 -
Human Gene Therapy Feb 2024The enzyme choline acetyltransferase (ChAT) synthesizes acetylcholine from acetyl-CoA and choline at the neuromuscular junction and at the nerve terminals of cholinergic...
The enzyme choline acetyltransferase (ChAT) synthesizes acetylcholine from acetyl-CoA and choline at the neuromuscular junction and at the nerve terminals of cholinergic neurons. Mutations in the ChAT gene () result in a presynaptic congenital myasthenic syndrome (CMS) that often associates with life-threatening episodes of apnea. Knockout mice for die at birth. To circumvent the lethality of this model, we crossed mutant mice possessing sites flanking exons 4 and 5 with mice that expressed . Injection of tamoxifen (Tx) at postnatal (P) day 11 in these mice induced downregulation of , autonomic failure, weakness, and death. However, a proportion of mice receiving at birth an intracerebroventricular injection of 2 × 10 vg/kg adeno-associated virus type 9 (AAV9) carrying human (AAV9-) survived a subsequent Tx injection and lived to adulthood without showing signs of weakness. Likewise, injection of AA9- by intracisternal injection at P28 after the onset of weakness also resulted in survival to adulthood. The expression of Chat in spinal motor neurons of mice injected with Tx was markedly reduced, but AAV-injected mice showed a robust recovery of ChAT expression, which was mainly translated by the human RNA. The biodistribution of the viral genome was widespread but maximal in the spinal cord and brain of AAV-injected mice. No significant histopathological changes were observed in the brain, liver, and heart of AAV-injected mice after 1 year follow-up. Thus, AAV9-mediated gene therapy may provide an effective and safe treatment for patients severely affected with CMS.
Topics: Mice; Humans; Animals; Choline O-Acetyltransferase; Dependovirus; Tissue Distribution; Mice, Knockout; Genetic Therapy
PubMed: 38299967
DOI: 10.1089/hum.2023.173 -
Pharmaceutics Jan 2024The administration of therapeutics to peripheral nerve tissue is challenging due to the complexities of peripheral neuroanatomy and the limitations imposed by the...
The administration of therapeutics to peripheral nerve tissue is challenging due to the complexities of peripheral neuroanatomy and the limitations imposed by the blood-nerve barrier (BNB). Therefore, there is a pressing need to enhance delivery effectiveness and implement targeted delivery methods. Recently, erythrocyte-derived exosomes (Exos) have gained widespread attention as biocompatible vehicles for therapeutics in clinical applications. However, engineering targeted Exos for the peripheral nervous system (PNS) is still challenging. This study aims to develop a targeted Exo delivery system specifically designed for presynaptic terminals of peripheral nerve tissue. The clostridium neurotoxin, tetanus toxin-C fragment (TTC), was tethered to the surface of red blood cell (RBC)-derived Exos via a facile and efficient bio-orthogonal click chemistry method without a catalyst. Additionally, Cyanine5 (Cy5), a reactive fluorescent tag, was also conjugated to track Exo movement in both in vitro and in vivo models. Subsequently, Neuro-2a, a mouse neuronal cell line, was treated with dye-labeled Exos with/without TTC in vitro, and the results indicated that TTC-Exos exhibited more efficient accumulation along the soma and axonal circumference, compared to their unmodified counterparts. Further investigation, using a mouse model, revealed that within 72 h of intramuscular administration, engineered TTC-Exos were successfully transported into the neuromuscular junction and sciatic nerve tissues. These results indicated that TTC played a crucial role in the Exo delivery system, improving the affinity to peripheral nerves. These promising results underscore the potential of using targeted Exo carriers to deliver therapeutics for treating peripheral neuropathies.
PubMed: 38258111
DOI: 10.3390/pharmaceutics16010102 -
Neuroscience Insights 2024Loss of the gene inevitably leads to spinal muscular atrophy (SMA), one of the most common fatal neuromuscular diseases in children with FDA and EMA approved therapies....
Loss of the gene inevitably leads to spinal muscular atrophy (SMA), one of the most common fatal neuromuscular diseases in children with FDA and EMA approved therapies. However, the cellular mechanisms leading to neuromuscular junction (NMJ) dysfunction due to impaired Ca homeostasis in the presynaptic compartment remain largely unexplained. In the last decade, the so-called SMA modifiers have gained attention. The F-actin bundler Plastin 3 (PLS3) is one of them and counteracts neurotransmission defects, including altered vesicle endocytosis, in Smn-deficient NMJs. Properly bundled F-actin is the basis for the translocation and arrangement of transmembrane proteins at the cell surface. Our recently published data by Hennlein et al., J Cell Biol. (2023) clearly showed that Smn deficiency impairs the F-actin dependent translocation of the high-affinity BDNF receptor TrkB to the cell surface resulting in reduced BDNF-mediated TrkB activation in motor axon terminals. Strikingly, the overexpression of PLS3 restores TrkB availability, and significantly improves the clustering of the active zone-associated voltage-gated calcium channel Ca2.2 in growth cones of Smn-deficient motoneurons. These observations raise the question of how PLS3 mediates the proper cell surface localization and cluster-like formation of Ca2.2 in motor axon terminals.
PubMed: 38249130
DOI: 10.1177/26331055241226623 -
Cells Jan 2024Neurological diseases can lead to the denervation of brain regions caused by demyelination, traumatic injury or cell death. The molecular and structural mechanisms...
Neurological diseases can lead to the denervation of brain regions caused by demyelination, traumatic injury or cell death. The molecular and structural mechanisms underlying lesion-induced reorganization of denervated brain regions, however, are a matter of ongoing investigation. In order to address this issue, we performed an entorhinal cortex lesion (ECL) in mouse organotypic entorhino-hippocampal tissue cultures of both sexes and studied denervation-induced plasticity of mossy fiber synapses, which connect dentate granule cells (dGCs) with CA3 pyramidal cells (CA3-PCs) and play important roles in learning and memory formation. Partial denervation caused a strengthening of excitatory neurotransmission in dGCs, CA3-PCs and their direct synaptic connections, as revealed by paired recordings (dGC-to-CA3-PC). These functional changes were accompanied by ultrastructural reorganization of mossy fiber synapses, which regularly contain the plasticity-regulating protein synaptopodin and the spine apparatus organelle. We demonstrate that the spine apparatus organelle and synaptopodin are related to ribosomes in close proximity to synaptic sites and reveal a synaptopodin-related transcriptome. Notably, synaptopodin-deficient tissue preparations that lack the spine apparatus organelle failed to express lesion-induced synaptic adjustments. Hence, synaptopodin and the spine apparatus organelle play a crucial role in regulating lesion-induced synaptic plasticity at hippocampal mossy fiber synapses.
Topics: Animals; Female; Male; Mice; Cell Death; Denervation; Hippocampus; Mossy Fibers, Hippocampal; Synapses; Neuronal Plasticity
PubMed: 38247806
DOI: 10.3390/cells13020114 -
Molecular Pain 2024The anterior cingulate cortex (ACC) is a key cortical area for pain perception, emotional fear and anxiety. Cortical excitation is thought to be the major mechanism for... (Review)
Review
The anterior cingulate cortex (ACC) is a key cortical area for pain perception, emotional fear and anxiety. Cortical excitation is thought to be the major mechanism for chronic pain and its related emotional disorders such as anxiety and depression. GluN2B (or called NR2B) containing NMDA receptors play critical roles for such excitation. Not only does the activation of GluN2B contributes to the induction of the postsynaptic form of LTP (post-LTP), long-term upregulation of GluN2B subunits through tyrosine phosphorylation were also detected after peripheral injury. In addition, it has been reported that presynaptic NMDA receptors may contribute to the modulation of the release of glutamate from presynaptic terminals in the ACC. It is believed that inhibiting subtypes of NMDA receptors and/or downstream signaling proteins may serve as a novel therapeutic mechanism for future treatment of chronic pain, anxiety, and depression.
Topics: Humans; Gyrus Cinguli; N-Methylaspartate; Receptors, N-Methyl-D-Aspartate; Chronic Pain; Synapses; Long-Term Potentiation
PubMed: 38246915
DOI: 10.1177/17448069241230258 -
Life Science Alliance Apr 2024The precise cell-to-cell communication relies on SNARE-catalyzed membrane fusion. Among ∼70 copies of synaptobrevin2 (syb2) in synaptic vesicles, only ∼3 copies are...
The precise cell-to-cell communication relies on SNARE-catalyzed membrane fusion. Among ∼70 copies of synaptobrevin2 (syb2) in synaptic vesicles, only ∼3 copies are sufficient to facilitate the fusion process at the presynaptic terminal. It is unclear what dictates the number of SNARE complexes that constitute the fusion pore assembly. The structure-function relation of these dynamic pores is also unknown. Here, we demonstrate that syb2 monomers and dimers differentially engage in regulating the trans-SNARE assembly during membrane fusion. The differential recruitment of two syb2 structures at the membrane fusion site has consequences in regulating individual nascent fusion pore properties. We have identified a few syb2 transmembrane domain residues that control monomer/dimer conversion. Overall, our study indicates that syb2 monomers and dimers are differentially recruited at the release sites for regulating membrane fusion events.
Topics: Membrane Fusion; SNARE Proteins; Synapses; Cell Communication; Presynaptic Terminals
PubMed: 38238088
DOI: 10.26508/lsa.202402568 -
BioRxiv : the Preprint Server For... Dec 2023To visualize the cellular and subcellular localization of neuromodulatory G-protein coupled receptors (GPCRs) in , we implement a molecular strategy recently used to...
UNLABELLED
To visualize the cellular and subcellular localization of neuromodulatory G-protein coupled receptors (GPCRs) in , we implement a molecular strategy recently used to add epitope tags to ionotropic receptors at their endogenous loci. Leveraging evolutionary conservation to identify sites more likely to permit insertion of a tag, we generated constitutive and conditional tagged alleles for 5-HT1A, 5-HT2A, 5-HT2B, Octβ1R, Octβ2R, two isoforms of OAMB, and mGluR. The conditional alleles allow for the restricted expression of tagged receptor in specific cell types, an option not available for any previous reagents to label these proteins. We show that 5-HT1A and 5-HT2B localize to the mushroom bodies and central complex respectively, as predicted by their roles in sleep. By contrast, the unexpected enrichment of Octβ1R in the central complex and of 5-HT1A and 5-HT2A to nerve terminals in lobular columnar cells in the visual system suggest new hypotheses about their function at these sites. Using an additional tagged allele of the serotonin transporter, a marker of serotonergic tracts, we demonstrate diverse spatial relationships between postsynaptic 5-HT receptors and presynaptic 5-HT neurons, consistent with the importance of both synaptic and volume transmission. Finally, we use the conditional allele of 5-HT1A to show that it localizes to distinct sites within the mushroom bodies as both a postsynaptic receptor in Kenyon cells and a presynaptic autoreceptor.
SIGNIFICANCE STATEMENT
In , despite remarkable advances in both connectomic and genomic studies, antibodies to many aminergic GPCRs are not available. We have overcome this obstacle using evolutionary conservation to identify loci in GPCRs amenable to epitope-tagging, and CRISPR/Cas9 genome editing to generated eight novel lines. This method also may be applied to other GPCRs and allows cell-specific expression of the tagged locus. We have used the tagged alleles we generated to address several questions that remain poorly understood. These include the relationship between pre- and post-synaptic sites that express the same receptor, and the use of relatively distant targets by pre-synaptic release sites that may employ volume transmission as well as standard synaptic signaling.
PubMed: 38234787
DOI: 10.1101/2023.12.27.573472 -
Molecular Biology Reports Jan 2024ARF (ADP-ribosylation factor) GTPases are major regulators of intracellular trafficking, and classified into 3 groups (Type I - III), among which the type I group...
BACKGROUND
ARF (ADP-ribosylation factor) GTPases are major regulators of intracellular trafficking, and classified into 3 groups (Type I - III), among which the type I group members, ARF1 and 3, are responsible genes for neurodevelopmental disorders.
METHODS
In this study, we analysed the expression of Type I ARFs ARF1-3 during mouse brain development using biochemical and morphological methods.
RESULTS
Western blotting analyses revealed that ARF1-3 are weakly expressed in the mouse brain at embryonic day 13 and gradually increase until postnatal day 30. ARF1-3 appear to be abundantly expressed in various telencephalon regions. Biochemical fractionation studies detected ARF1-3 in the synaptosome fraction of cortical neurons containing both pre- and post-synapses, however ARF1-3 were not observed in post-synaptic compartments. In immunohistochemical analyses, ARF1-3 appeared to be distributed in the cytoplasm and dendrites of cortical and hippocampal neurons as well as in the cerebellar molecular layer including dendrites of Purkinje cells and granule cell axons. Immunofluorescence in primary cultured hippocampal neurons revealed that ARF1-3 are diffusely distributed in the cytoplasm and dendrites with partial colocalization with a pre-synaptic marker, synaptophysin.
CONCLUSIONS
Overall, our results support the notion that ARF1-3 could participate in vesicle trafficking both in the dendritic shaft (excluding spines) and axon terminals (pre-synaptic compartments).
Topics: Animals; Mice; Monomeric GTP-Binding Proteins; ADP-Ribosylation Factors; Neurons; Axons; Cerebellum
PubMed: 38227057
DOI: 10.1007/s11033-023-09142-5