Synaptic Vesicle Cycle Research Articles

Monitoring of activity-driven trafficking of endogenous synaptic proteins through proximity labeling.

To enable transmission of information in the brain, synaptic vesicles fuse to presynaptic membranes, liberating their content and exposing transiently a myriad of vesicular transmembrane proteins. However, versatile methods for quantifying the synaptic translocation of endogenous proteins during neuronal activity remain unavailable, as the fast dynamics of synaptic vesicle cycling difficult specific isolation of trafficking proteins during such a transient surface exposure. Here, we developed a novel approach using synaptic cleft proximity labeling to capture and quantify activity-driven trafficking of endogenous synaptic proteins at the synapse. We show that accelerating cleft biotinylation times to match the fast dynamics of vesicle exocytosis allows capturing endogenous proteins transiently exposed at the synaptic surface during neural activity, enabling for the first time the study of the translocation of nearly every endogenous synaptic protein. As proof-of-concept, we further applied this technology to obtain direct evidence of the surface translocation of noncanonical trafficking proteins, such as ATG9A and NPTX1, which had been proposed to traffic during activity but for which direct proof had not yet been shown. The technological advancement presented here will facilitate future studies dissecting the molecular identity of proteins exocytosed at the synapse during activity, helping to define the molecular machinery that sustains neurotransmission in the mammalian brain.

Synaptic vesicle endocytosis deficits underlie GBA-linked cognitive dysfunction in Parkinson's disease and Dementia with Lewy bodies.

GBA mutations are major risk factors for Parkinson's disease (PD) and Dementia with Lewy Bodies (DLB), two common α-synucleinopathies associated with cognitive impairment. Here, we investigated the role of GBA mutations in cognitive decline by utilizing Gba L444P mutant mice, SNCA transgenic (tg), and Gba-SNCA double mutant mice. Notably, Gba mutant mice showed early cognitive deficits but no PD-like motor deficits up to 12 months old. Conversely, SNCA tg mice displayed age-related motor deficits but no cognitive abnormalities. Gba-SNCA mice exhibited exacerbated motor deficits and cognitive decline. Immunohistological analysis revealed cortical phospho-α-synuclein pathology in SNCA tg mice, which was exacerbated in Gba-SNCA mice, especially in layer 5 cortical neurons. Significantly, Gba mutant mice did not show α-synuclein pathology. Single-nucleus RNA sequencing of cortices instead uncovered selective synaptic vesicle cycle defects in excitatory neurons of Gba mutant and Gba-SNCA mice, via robust downregulation in gene networks regulating synapse vesicle cycle and synapse assembly. Meanwhile SNCA tg mice displayed broader synaptic changes. Immunohistochemical and electron microscopic analyses validated these findings. Together, our results indicate that Gba mutations, while exacerbating pre-existing α-synuclein aggregation and PD-like motor deficits, contribute to cognitive deficits through α-synuclein-independent mechanisms, likely involving dysfunction in synaptic vesicle endocytosis. Additionally, Gba-SNCA mice are a valuable model for studying cognitive and motor deficits in PD and DLB.

A Novel PTPRQ c.3697del Variant Causes Autosomal Dominant Progressive Hearing Loss in Both Humans and Mice.

PTPRQ plays an important role in the development of inner ear hair cell stereocilia. While many autosomal recessive variants in PTPRQ have been identified as the pathogenic cause for nonsyndromic hearing loss (DFNB84A), so far only one autosomal dominant PTPRQ variant, c.6881G>A (p.Trp2294*), has been reported for late-onset, mild-to-severe hearing loss (DFNA73). By using targeted next-generation sequencing, this study identified a novel PTPRQ truncating pathogenic variant, c.3697del (p.Leu1233Phefs*11), from a Chinese Han family that co-segregated with autosomal dominant, postlingual, progressive hearing loss. A Ptprq-3700del knock-in mouse model was generated by CRISPR-Cas9 and characterized for its hearing function and inner ear morphology. While the homozygous knock-in mice exhibit profound hearing loss at all frequencies at the age of 3 weeks, the heterozygous mutant mice resemble the human patients in mild, progressive hearing loss from age 3 to 12 weeks, primarily affecting high frequencies. At this stage, the homozygous knock-in mice have a normal hair cell count but disorganized stereocilia. Cochlear proteosome analysis of the homozygous mutant mice revealed differentially expressed genes and pathways involved in oxidative phosphorylation, regulation of angiogenesis and synaptic vesicle cycling. Our study provides a valuable animal model for further functional studies of the pathogenic mechanisms underlying DFNA73.

Upstream and downstream pathways of diacylglycerol kinase : Novel phosphatidylinositol turnover-independent signal transduction pathways

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DG) to produce phosphatidic acid (PA). Mammalian DGK comprise ten isozymes (α–κ) that regulate a wide variety of physiological and pathological events. Recently, we revealed that DGK isozymes use saturated fatty acid (SFA)/monosaturated fatty acid (MUFA)-containing and docosahexaenoic acid (22:6)-containing DG species, but not phosphatidylinositol (PI) turnover-derived 18:0/20:4-DG. For example, DGKδ, which is involved in the pathogenesis of type 2 diabetes, preferentially uses SFA/MUFA-containing DG species, such as 16:0/16:0- and 16:0/18:1-DG species, in high glucose-stimulated skeletal muscle cells. Moreover, DGKδ, which destabilizes the serotonin transporter (SERT) and regulates the serotonergic system in the brain, primarily generates 18:0/22:6-PA. Furthermore, 16:0/16:0-PA is produced by DGKζ in Neuro-2a cells during neuronal differentiation. We searched for SFA/MUFA-PA- and 18:0/22:6-PA-selective binding proteins (candidate downstream targets of DGKδ) and found that SFA/MUFA-PA binds to and activates the creatine kinase muscle type, an energy-metabolizing enzyme, and that 18:0/22:6-PA interacts with and activates Praja-1, an E3 ubiquitin ligase acting on SERT, and synaptojanin-1, a key player in the synaptic vesicle cycle. Next, we searched for SFA/MUFA-DG-generating enzymes upstream of DGKδ. We found that sphingomyelin synthase (SMS)1, SMS2, and SMS-related protein (SMSr) commonly act as phosphatidylcholine (PC)-phospholipase C (PLC) and phosphatidylethanolamine (PE)-PLC, generating SFA/MUFA-DG species, in addition to SMS and ceramide phosphoethanolamine synthase. Moreover, the orphan phosphatase PHOSPHO1 showed PC- and PE-PLC activities that produced SFA/MUFA-DG. Although PC- and PE-PLC activities were first described 70–35 years ago, their proteins and genes were not identified for a long time. We found that DGKδ interacts with SMSr and PHOSPHO1, and that DGKζ binds to SMS1 and SMSr. Taken together, these results strongly suggest that there are previously unrecognized signal transduction pathways that include DGK isozymes and generate and utilize SFA/MUFA-DG/PA or 18:0/22:6-DG/PA but not PI-turnover-derived 18:0/20:4-DG/PA.

Unveiling mitochondria as central components driving cognitive decline in alzheimer's disease through cross-transcriptomic analysis of hippocampus and entorhinal cortex microarray datasets

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by symptoms such as memory loss and impaired learning. This study conducted a cross-transcriptomic analysis of AD using existing microarray datasets from the hippocampus (HC) and entorhinal cortex (EC), comparing them with age-matched non-AD controls. Both of these brain regions are critical for learning and memory processing and are vulnerable areas that exhibit abnormalities in early AD. The cross-transcriptomic analysis identified 564 significantly differentially expressed genes in HC and 479 in EC. Among these, 151 genes were significantly differentially expressed in both tissues, with functions related to synaptic vesicle clustering, synaptic vesicle exocytosis/endocytosis, mitochondrial ATP synthesis, hydrogen ion transmembrane transport, and structural constituent of cytoskeleton, suggesting a potential association between cognitive decline in AD, synaptic vesicle dynamics, dysregulation of cytoskeleton organization, and mitochondrial dysfunction. Further gene ontology analysis specific to the HC revealed the gene ontology enrichment in aerobic respiration, synaptic vesicle cycle, and oxidative phosphorylation. The enrichment analysis in CA1 of HC revealed differentiation in gene expression related to mitochondrial membrane functions involved in bioenergetics, mitochondrial electron transport, and biological processes associated with microtubule-based process, while analysis in the EC region showed enrichment in synaptic vesicle dynamics which is associated with neurotransmitter release and the regulation of postsynaptic membrane potential and synaptic transmission of GABAergic and glutamatergic synapse. Protein-protein interaction analysis highlighted central hub proteins predominantly expressed in mitochondria, involved in regulation of oxidative stress and ATP synthesis. These hub proteins interact not only within the mitochondria but also with proteins in the vesicular membrane and neuronal cytoskeleton, indicating a central role of mitochondria. This finding underscores the association between clinical symptoms and mitochondrial dysregulation of synaptic vesicle dynamics, cytoskeleton organization, and mitochondrial processes in both the HC and EC of AD. Therefore, targeting these dysregulated pathways could provide promising therapeutic targets aimed at cognitive decline and memory impairment in early AD stages.

Device for detection of activity-dependent changes in neural spheroids at MHz and GHz frequencies

Intracellular processes triggered by neural activity include changes in ionic concentrations, protein release, and synaptic vesicle cycling. These processes play significant roles in neurological disorders. The beneficial effects of brain stimulation may also be mediated through intracellular changes. There is a lack of label-free techniques for monitoring activity-dependent intracellular changes. Electromagnetic (EM) waves at frequencies larger than 1x106 Hz (1 MHz) were previously used to probe intracellular contents of cells, as cell membrane becomes “invisible” at this frequency range. EM waves interact with membranes of intracellular organelles, proteins, and water in the MHz – GHz range. In this work, we developed a device for probing the interaction between active neurons’ intracellular contents and EM waves. The device used an array of grounded coplanar waveguides (GCPWs) to deliver EM waves to a three-dimensional (3D) spheroid of rat cortical neurons. Neural activity was evoked using optogenetics, with synchronous detection of propagation of EM waves. Broadband measurements were conducted in the MHz-GHz range to track changes in transmission coefficients. Neuronal activity was found to reversibly alter EM wave transmission. Pharmacological suppression of neuronal activity abolished changes in transmission. Time constants of changes in transmission were in the seconds – tens of seconds range, suggesting the presence of relatively slow, activity-dependent intracellular processes. This study provides the first evidence that EM transmission through neuronal tissue is activity-dependent in MHz – GHz range. Device developed in this work may find future applications in studies of the mechanisms of neurological disorders and the development of new therapies.

Identification of the Shared Gene Signatures Between Alzheimer's Disease and Diabetes-Associated Cognitive Dysfunction by Bioinformatics Analysis Combined with Biological Experiment.

The connection between diabetes-associated cognitive dysfunction (DACD) and Alzheimer's disease (AD) has been shown in several observational studies. However, it remains controversial as to how the two related. To explore shared genes and pathways between DACD and AD using bioinformatics analysis combined with biological experiment. We analyzed GEO microarray data to identify DEGs in AD and type 2 diabetes mellitus (T2DM) induced-DACD datasets. Weighted gene co-expression network analysis was used to find modules, while R packages identified overlapping genes. A robust protein-protein interaction network was constructed, and hub genes were identified with Gene ontology enrichment and Kyoto Encyclopedia of Genome and Genome pathway analyses. HT22 cells were cultured under high glucose and amyloid-β 25-35 (Aβ25-35) conditions to establish DACD and AD models. Quantitative polymerase chain reaction with reverse transcription verification analysis was then performed on intersection genes. Three modules each in AD and T2DM induced-DACD were identified as the most relevant and 10 hub genes were screened, with analysis revealing enrichment in pathways such as synaptic vesicle cycle and GABAergic synapse. Through biological experimentation verification, 6 key genes were identified. This study is the first to use bioinformatics tools to uncover the genetic link between AD and DACD. GAD1, UCHL1, GAP43, CARNS1, TAGLN3, and SH3GL2 were identified as key genes connecting AD and DACD. These findings offer new insights into the diseases' pathogenesis and potential diagnostic and therapeutic targets.

A transcriptomics-based analysis of mechanisms involved in the sex-dependent effects of diazepam on zebrafish

Diazepam (DZP) is a universally detected emerging pollutant in aquatic ecosystems. Although the sex-dependent effects of DZP on fish have been properly established, the underlying mechanisms remain unclear. In this study, zebrafish of both sexes were separately exposed to DZP (8 μg/L) for 21 days, and the alteration of the behaviors, brain amino acid neurotransmitter contents, and transcriptomic profiles were investigated. Although DZP exposure showed a sedative effect on both sexes, significantly reduced cumulative duration of high mobility and willingness to encounter the opposite sex were only observed in females. However, DZP significantly enhanced the brain levels of glutamate and glutamine in males but not in females. Transcriptome analysis identified more different expression genes (DEGs) in females (322 up-regulated and 311 down-regulated) than in males (138 up-regulated genes and 38 down-regulated). The DEGs in both sexes were significantly enriched in the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway of the synaptic vesicle cycle, indicating a possible pathway for the sedative effects of DZP on zebrafish. DZP exhibited different or even opposing regulatory patterns on gene expression in the brains of females and males, providing some insights into its sex-dependent impacts on the behaviors and brain neurotransmitter contents in zebrafish. Moreover, enrichment analysis also suggested that DZP exposure may affect the oocyte maturation in female zebrafish, which highlights the need to study its reproductive and transgenerational toxicity to fish species.

Exploring Intrinsic Disorder in Human Synucleins and Associated Proteins.

In this work, we explored the intrinsic disorder status of the three members of the synuclein family of proteins-α-, β-, and γ-synucleins-and showed that although all three human synucleins are highly disordered, the highest levels of disorder are observed in γ-synuclein. Our analysis of the peculiarities of the amino acid sequences and modeled 3D structures of the human synuclein family members revealed that the pathological mutations A30P, E46K, H50Q, A53T, and A53E associated with the early onset of Parkinson's disease caused some increase in the local disorder propensity of human α-synuclein. A comparative sequence-based analysis of the synuclein proteins from various evolutionary distant species and evaluation of their levels of intrinsic disorder using a set of commonly used bioinformatics tools revealed that, irrespective of their origin, all members of the synuclein family analyzed in this study were predicted to be highly disordered proteins, indicating that their intrinsically disordered nature represents an evolutionary conserved and therefore functionally important feature. A detailed functional disorder analysis of the proteins in the interactomes of the human synuclein family members utilizing a set of commonly used disorder analysis tools showed that the human α-synuclein interactome has relatively higher levels of intrinsic disorder as compared with the interactomes of human β- and γ- synucleins and revealed that, relative to the β- and γ-synuclein interactomes, α-synuclein interactors are involved in a much broader spectrum of highly diversified functional pathways. Although proteins interacting with three human synucleins were characterized by highly diversified functionalities, this analysis also revealed that the interactors of three human synucleins were involved in three common functional pathways, such as the synaptic vesicle cycle, serotonergic synapse, and retrograde endocannabinoid signaling. Taken together, these observations highlight the critical importance of the intrinsic disorder of human synucleins and their interactors in various neuronal processes.

Neurotoxic Methamphetamine Doses Alter CDCel-1 Levels and Its Interaction with Vesicular Monoamine Transporter-2 in Rat Striatum.

In recent years, methamphetamine METH misuse in the US has been rapidly increasing and there is no FDA-approved pharmacotherapy for METH use disorder (MUD). In addition to being dependent on the drug, people with MUD develop a variety of neurological problems related to the toxicity of this drug. A variety of molecular mechanisms underlying METH neurotoxicity has been identified, including dysfunction of the neuroprotective protein parkin. However, it is not known whether parkin loss of function within striatal dopaminergic (DAergic) terminals translates into a decrease in DA storage capacity. This study examined the relationship between parkin, its substrate cell division cycle related-1 (CDCrel-1), and vesicular monoamine transporter-2 (VMAT2) in METH neurotoxicity in male Sprague Dawley rats. To also assess individual differences in response to METH's neurotoxic effects, a large group of rats was treated with binge METH or saline and sacrificed 1h or 24h later. This study is the first to show that binge METH alters the levels and subcellular localization of CDCrel-1 and that CDCrel-1 interacts with VMAT2 and increases its levels at the plasma membrane. Furthermore, we found wide individual differences in the responses of measured indices to METH. Proteomic analysis of VMAT-2-associated proteins revealed upregulation of several proteins involved in the exocytosis/endocytosis cycle. The results suggest that at 1h after METH binge, DAergic neurons are engaged in counteracting METH-induced toxic effects, including oxidative stress- and hyperthermia-induced inhibition of synaptic vesicle cycling, with the responses varying between individual rats. Studying CDCrel-1, VMAT2, and other proteins in large groups of outbred rats can help define individual genetic and molecular differences in responses to METH neurotoxicity which, in turn, will aid treating humans suffering from METH use disorder and its neurological consequences.

Unraveling the molecular landscape of lead-induced cochlear synaptopathy: a quantitative proteomics analysis.

Exposure to heavy metal lead can cause serious health effects such as developmental neurotoxicity in infants, cognitive impairment in children, and cardiovascular and nephrotoxic effects in adults. Hearing loss is one of the toxic effects induced by exposure to lead. Previous studies demonstrated that exposure to lead causes oxidative stress in the cochlea and disrupts ribbon synapses in the inner hair cells. This study investigated the underlying mechanism by evaluating the changes in the abundance of cochlear synaptosomal proteins that accompany lead-induced cochlear synaptopathy and hearing loss in mice. Young-adult CBA/J mice were given lead acetate in drinking water for 28 days. Lead exposure significantly increased the hearing thresholds, particularly at the higher frequencies in both male and female mice, but it did not affect the activity of outer hair cells or induce hair cell loss. However, lead exposure decreased wave-I amplitude, suggesting lead-induced cochlear synaptopathy. In agreement, colocalization of pre- and post-synaptic markers indicated that lead exposure decreased the number of paired synapses in the basal turn of the cochlea. Proteomics analysis indicated that lead exposure increased the abundance of 352 synaptic proteins and decreased the abundance of 394 synaptic proteins in the cochlea. Bioinformatics analysis indicated that proteins that change in abundance are highly enriched in the synaptic vesicle cycle pathway. Together, these results suggest that outer hair cells are not the primary target in lead-induced ototoxicity, that lead-induced cochlear synaptopathy is more pronounced in the basal turn of the cochlea, and that synaptic vesicle cycle signaling potentially plays a critical role in lead-induced cochlear synaptopathy.

Role of adaptor protein complexes in generating functionally distinct synaptic vesicle pools.

The synaptic vesicle (SV) cycle ensures the release of neurotransmitters and the replenishment of SVs to sustain neuronal activity. Multiple endocytosis and sorting pathways contribute to the recapture of the SV membrane and proteins after fusion. Adaptor protein (AP) complexes are among the critical components of the SV retrieval machinery. The canonical clathrin adaptor AP2 ensures the replenishment of most SVs across many neuronal populations. An alternative AP1/AP3-dependent process mediates the formation of a subset of SVs that differ from AP2 vesicles in molecular composition and respond preferentially during higher frequency firing. Furthermore, recent studies show that vesicular transporters for different neurotransmitters depend to a different extent on the AP3 pathway and this affects the release properties of the respective neurotransmitters. This review focuses on the current understanding of the AP-dependent molecular and functional diversity among SVs. We also discuss the contribution of these pathways to the regulation of neurotransmitter release across neuronal populations.

Interplay between Copper, Phosphatidylserine, and α-Synuclein Suggests a Link between Copper Homeostasis and Synaptic Vesicle Cycling.

Copper homeostasis is critical to the functioning of the brain, and its breakdown is linked with many brain diseases. Copper is also known to interact with the negatively charged lipid, phosphatidylserine (PS), as well as α-synuclein, an aggregation-prone protein enriched in the synapse, which plays a role in synaptic vesicle docking and fusion. However, the interplay between copper, PS lipid, and α-synuclein is not known. Herein, we report a detailed and predominantly kinetic study of the interactions among these three components pertinent to copper homeostasis and neurotransmission. We found that synaptic vesicle-mimicking small unilamellar vesicles (SUVs) can sequester any excess free Cu2+ within milliseconds, and bound Cu2+ on SUVs can be reduced to Cu+ by GSH at a nearly constant rate under physiological conditions. Moreover, we revealed that SUV-bound Cu2+ does not affect the binding between wild-type α-synuclein and SUVs but affect that between N-terminal acetylated α-synuclein and SUVs. In contrast, Cu2+ can effectively displace both types of α-synuclein from the vesicles. Our results suggest that synaptic vesicles may mediate copper transfer in the brain, while copper could participate in synaptic vesicle docking to the plasma membrane via its regulation of the interaction between α-synuclein and synaptic vesicle.

Synaptic Vesicle-Related Proteins and Ubiquilin 2 in Cortical Synaptosomes Mediate Cognitive Impairment in Vascular Dementia Rats.

Synaptic dysfunction is considered the best neuropathological correlate of cognitive decline in vascular dementia (VaD). However, the alterations of synaptic proteins at the synaptosomal level in VaD remain unclear. In this study, a VaD model was established in male rats using bilateral common carotid artery occlusion (2VO). We performed a novel object recognition task to evaluate cognitive impairment. Immunohistochemistry was used to assess the expression of neuron-specific nuclear binding protein (NeuN). Brain synaptosomes were isolated and subjected to label-free proteomic analysis to quantify and identify the synaptic features of differentially expressed proteins (DEPs). Synaptic and hub protein expression was detected in synaptosomes using western blotting. We found that male rats with VaD presented impaired memory and decreased NeuN protein expression in the cortex. Synaptosome proteomic analysis revealed 604 DEPs, with 493 and 111 markedly downregulated and upregulated proteins, respectively. KEGG analysis and SynGO annotation revealed that the synaptic vesicle (SV) cycle may be a key signaling pathway in VaD. Hub protein analysis of the main nodes in the protein network identified UBQLN2 and SV-related proteins, including CLTC, SNAP91, AP2S1, CLTA, VAMP2, EPN1, UBQLN2, AP2B1, AP2A2, and AP2M1. Western blotting showed that the levels of SV2A, CLTC, AP2S1, and VAMP2 decreased in the synaptosomes of 2VO rats, while UBQLN2 expression significantly increased. Our results suggest that the disruption in the presynaptic SV cycle is a key event in male rats with VaD, which could be characterized by the aberrant SV2A expression. SV-related proteins and UBQLN2 may be essential in synaptopathy. Thus, targeting the specific molecular markers in synaptosomes may be critical for the development of mechanism-directed therapies against VaD.

A Transdermal Prion-Bionics Supermolecule as a RAB3A Antagonist for Enhancing Facial Youthfulness.

The mechanism research of skin wrinkles, conducted on volunteers underwent high-intensity desk work and mice subjected to partial sleep deprivation, revealed a significant reduction in dermal thickness associated with the presence of wrinkles. This can be attributed to the activation of facial nerves in a state of hysteria due to an abnormally elevated interaction between SNAP25 and RAB3A proteins involved in the synaptic vesicle cycle (SVC). Facilitated by AI-assisted structural design, a refined peptide called RSIpep is developed to modulate this interaction and normalize SVC. Drawing inspiration from prions, which possess the ability to protect themselves against proteolysis and invade neighboring nerve cells through macropinocytosis, RSIpep is engineered to demonstrate a GSH-responsive reversible self-assembly into a prion-like supermolecule (RSIprion). RSIprion showcases protease resistance, micropinocytosis-dependent cellular internalization, and low adhesion with constituent molecules in the cuticle, thereby endowing it with the transdermic absorption and subsequent biofunction in redressing the frenzied SVC. As a facial mud mask, it effectively reduces periorbital and perinasal wrinkles in the human face. Collectively, RSIprion not only presents a clinical potential as an anti-wrinkle prion-like supermolecule, but also exemplifies a reproducible instance of bionic strategy-guided drug development that bestows transdermal ability upon the pharmaceutical molecule.

Metabonomics analysis of aqueous humor samples from cataract patients with branch retinal vein occlusion.

Cataract (CAT) has a very high incidence rate among the middle-aged and elderly, with most patients complicated by branch retinal vein occlusion (BRVO), a key cause of blindness. In this study, through metabolomic analysis of aqueous humor samples from CAT patients with BRVO, a total of 319 different metabolites were found, most of which belonged to the categories of carboxylic acids and derivatives, fatty acyls, and organooxygen compounds. The most typical metabolites were 3-methylhistidine and biliverdin, which were up-regulated, as well as the down-regulated beta-glycerophosphoric acid. Tricosanoic acid showed the most significant correlation with CAT+BRVO. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the most commonly related keywords for differentially expressed metabolites were biosynthesis of unsaturated fatty acids and synaptic vesicle cycle. These results can not only help to further understand the pathogenesis of CAT complicated by BRVO in clinical practice, but also provide some new therapeutic research directions.

Exposure to an enriched environment modulates the synaptic vesicle cycle in a mouse spinal cord injury model

Spinal cord injury (SCI) leads to motor and sensory impairment below the site of injury, thereby necessitating rehabilitation. An enriched environment (EE) increases social interaction and locomotor activity in a mouse model, similar to human rehabilitation. However, the impact of EE on presynaptic plasticity in gene expression levels remains unclear. Hence, this study aimed to investigate the therapeutic potential of EE in an SCI mouse model. Mice with spinal cord contusion were divided into two groups: those housed in standard cages (control) and those in EE conditions (EE). Each group was housed separately for either 2- or 8-weeks post-injury, after which RNA sequencing was performed and compared to a sham group (receiving only a dorsal laminectomy). The synaptic vesicle cycle (SVC) pathway and related genes showed significant downregulation after SCI at both time points. Subsequently, we investigated whether exposure to EE for 2- and 8-weeks post-SCI could modulate the SVC pathway and its related genes. Notably, exposure to EE for 8 weeks resulted in a marked reversal effect of SVC-related gene expression, along with stimulation of axon regeneration and mitigation of locomotor activity loss. Thus, prolonged exposure to EE increased presynaptic activity, fostering axon regeneration and functional improvement by modulating the SVC in the SCI mouse model. These findings suggest that EE exposure proves effective in inducing activity-dependent plasticity, offering a promising therapeutic approach akin to rehabilitation training in patients with SCI.

A stem cell-based assay platform demonstrates alpha-synuclein dependent synaptic dysfunction in patient-derived cortical neurons

Alpha-synuclein (αS)-rich Lewy bodies and neurites in the cerebral cortex correlate with the presence of dementia in Parkinson disease (PD) and Dementia with Lewy bodies (DLB), but whether αS influences synaptic vesicle dynamics in human cortical neurons is unknown. Using a new iPSC-based assay platform for measuring synaptic vesicle cycling, we found that in human cortical glutamatergic neurons, increased αS from either transgenic expression or triplication of the endogenous locus in patient-derived neurons reduced synaptic vesicle cycling under both stimulated and spontaneous conditions. Thus, using a robust, easily adopted assay platform, we show for the first time αS-induced synaptic dysfunction in human cortical neurons, a key cellular substrate for PD dementia and DLB.

Identification of mRNA expression profiles and their characterization in age-related hearing loss.

Age-related hearing loss (ARHL), is a pervasive health problem worldwide. ARHL seriously affects the quality of life and reportedly leads to social isolation and dementia in the elderly. ARHL is caused by the degeneration or disorders of cochlear hair cells and auditory neurons. Numerous studies have verified that genetic factors contributed to this impairment, however, the mechanism behind remains unclear. In this study, we analyzed an mRNA expression dataset (GSE49543) from the GEO database. Differentially expressed genes (DEGs) between young control mice and presbycusis mice were analyzed using limma in R and weighted gene co-expression network analysis (WGCNA) methods. Functional enrichment analyses of the DEGs were conducted with the clusterProfiler R package and the results were visualized using ggplot2 R package. The STRING database was used for the construction of the protein-protein interaction (PPI) network of the screened DEGs. Two machine learning algorithms LASSO and SVM-RFE were used to screen the hub genes. We identified 54 DEGs in presbycusis using limma and WGCNA. DEGs were associated with the synaptic vesicle cycle, distal axon, neurotransmitter transmembrane transporter activity in GO analysis, and alcoholic liver disease, pertussis, lysosome pathway according to KEGG analyses. PPI network analysis identified three significant modules. Five hub genes (CLEC4D, MS4A7, CTSS, LAPTM5, ALOX5AP) were screened by LASSO and SVM-RFE. These hub genes were highly expressed in presbycusis mice compared with young control mice. We screened DEGs and identified hub genes involved in ARHL development, which might provide novel clues to understanding the molecular basis of ARHL.

Phospholipids Differentially Regulate Ca2+ Binding to Synaptotagmin-1.

Synaptotagmin-1 (Syt-1) is a calcium sensing protein that is resident in synaptic vesicles. It is well established that Syt-1 is essential for fast and synchronous neurotransmitter release. However, the role of Ca2+ and phospholipid binding in the function of Syt-1, and ultimately in neurotransmitter release, is unclear. Here, we investigate the binding of Ca2+ to Syt-1, first in the absence of lipids, using native mass spectrometry to evaluate individual binding affinities. Syt-1 binds to one Ca2+ with a KD ∼ 45 μM. Each subsequent binding affinity (n ≥ 2) is successively unfavorable. Given that Syt-1 has been reported to bind anionic phospholipids to modulate the Ca2+ binding affinity, we explored the extent that Ca2+ binding was mediated by selected anionic phospholipid binding. We found that phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and dioleoylphosphatidylserine (DOPS) positively modulated Ca2+ binding. However, the extent of Syt-1 binding to phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) was reduced with increasing [Ca2+]. Overall, we find that specific lipids differentially modulate Ca2+ binding. Given that these lipids are enriched in different subcellular compartments and therefore may interact with Syt-1 at different stages of the synaptic vesicle cycle, we propose a regulatory mechanism involving Syt-1, Ca2+, and anionic phospholipids that may also control some aspects of vesicular exocytosis.