Search Results (60)

Neuronal synapses are the functional units of communication in the central nervous system. This review describes the molecular mechanisms regulating synaptic transmission, plasticity, and circuit refinement. At the presynaptic active zone, scaffolding proteins including bassoon, piccolo, RIMs, and munc13 organize vesicle priming and the localization of voltage-gated calcium channels. Neurotransmitter release is mediated by the SNARE complex, comprising syntaxin-1, SNAP25, and synaptobrevin, and triggered by the calcium sensor synaptotagmin-1. Following exocytosis, synaptic vesicles are recovered through clathrin-mediated, ultrafast, bulk, or kiss-and-run endocytic pathways. Postsynaptically, the postsynaptic density (PSD) serves as a protein hub where scaffolds such as PSD-95, shank, homer, and gephyrin anchor excitatory (AMPA, NMDA) and inhibitory (GABA-A, Glycine) receptors are observed. Synaptic strength is modified during long-term potentiation (LTP) and depression (LTD) through signaling cascades involving kinases like CaMKII, PKA, and PKC, or phosphatases such as PP1 and calcineurin. These pathways regulate receptor trafficking, Arc-mediated endocytosis, and actin-dependent remodeling of dendritic spines. Additionally, synapse formation and elimination are guided by cell adhesion molecules, including neurexins and neuroligins, and by microglial pruning via the complement cascade (C1q, C3) and “don’t eat me” signals like CD47. Molecular diversity is further expanded by alternative splicing and post-translational modifications. A unified model of synaptic homeostasis is required to understand the basis of neuropsychiatric and neurological disorders. Full article

Neuroinflammation and oxidative stress are key drivers of various ocular diseases. Experimental hypoxia, modeled using cobalt chloride (CoCl₂), induces hypoxia-inducible factor 1-alpha (HIF-1α) stabilization, mitochondrial dysfunction, and excessive reactive oxygen species (ROS) production, primarily via the NADPH oxidase 2 (Nox2)–voltage-gated proton channel Hv1 axis. Although Botulinum neurotoxin type A (BoNT/A) is classically recognized for SNAP-25 cleavage, recent studies suggest broader anti-inflammatory and neuroprotective effects. We evaluated BoNT/A in R28 retinal precursor cells and ex vivo retinal explants subjected to CoCl₂-induced hypoxic stress. BoNT/A pretreatment attenuated CoCl₂-induced upregulation of HIF-1α, Hv1, Nox2, NOD-like receptor protein 3 (NLRP3), COX2, and nuclear factor kappa B (NF-κB), while enhancing protective mediators including suppressor of cytokine signaling 3 (SOCS3), Growth Associated Protein 43 (Gap43), and Syntaxin12. Brn3a expression and retinal architecture were preserved, apoptotic cell death reduced, and glial activation suppressed. Moreover, BoNT/A decreased mitochondrial ROS accumulation, restored voltage-dependent anion channel 1 (VDAC1) distribution, and partially stabilized intracellular pH. These findings indicate that BoNT/A mitigates oxidative stress and inflammation in hypoxia-driven retinal injury, at least in part, via modulation of the Nox2–Hv1–ROS axis, and support its potential as a therapeutic candidate for ocular disorders associated with hypoxia and neuroinflammation. Full article

Diaphorina citri is the primary global vector of “Candidatus Liberibacter asiaticus”, the bacterium responsible for Huanglongbing. Syntaxin-1A (Syx1A), a member of the Qa-SNARE family, is essential for vesicle fusion and signal transduction, though its function in hemipteran insects remains poorly understood. This study presents the first comprehensive analysis of Syx1A expression in D. citri. Transcripts were detected across all life stages, with peak expression in the salivary glands. RNAi silencing of Syx1A reduced mRNA levels by 39.0% in nymphs and 58.0% in adults, resulting in 58.3% nmortality in nymphs within 5 days and 73.3% in adults within seven days, along with significant weight loss. Treated females showed marked declines in fecundity, ovarian degeneration, and deficient yolk deposition. RT-qPCR confirmed significant downregulation of Vg1, VgA, and VgR. These findings establish Syx1A as a regulator of growth and reproduction in citrus psyllids via modulation of yolk synthesis. RNAi targeting of Syx1A represents a promising strategy for ecologically sound pest control and may contribute to efforts in halting the transmission of the Huanglongbing pathogen CLas. Full article

As the average age of the population increases, memory impairment has become an increasingly prevalent issue. This study investigates the effects of 14 days of oral birch sap administration on memory functions in healthy rats using the Morris water maze (MWM) test and explores the underlying mechanisms. A compositional analysis revealed that birch soap is rich in polysaccharides, specifically a low-molecular weight polysaccharide (MW 1.29 kDa), and exhibits no hepatotoxicity or renal toxicity at the tested dose. The results from the MWM test demonstrated that the time and distance required to reach the platform were significantly shorter in the birch sap-treated group compared to the control group, suggesting that birch sap supports memory preservation. Moreover, rats treated with birch sap showed improved cerebral blood flow compared to the control rats. Additionally, in hippocampal nerve terminals (synaptosomes), rats treated with birch sap exhibited a significant increase in evoked glutamate release, as well as elevated levels of presynaptic proteins, including vesicular glutamate transporter 1 (VGluT1), synaptophysin, synaptobrevin, synaptotagmin, syntaxin, synapsin I, and the 25 kDa synaptosome-associated protein (SNAP-25). Transmission electron microscopy also revealed a notable increase in the number of synaptic vesicles in hippocampal synaptosomes of the birch-sap-treated rats. These findings suggest that birch sap enhances hippocampal presynaptic glutamatergic functions and cerebral blood flow, contributing to its memory-preserving effects in rats. Full article

Root growth and development are contingent upon continuous cell division and differentiation in root tips. In this study, we found that the knockdown of the syntaxin gene SYNTAXIN OF PLANTS132 (SYP132) in Arabidopsis thaliana resulted in a significant reduction in root meristem activity and disruption of root stem cell niche (SCN) identity. The SYP132 knockdown mutant exhibits a compromised SCN characterized by an increased number of quiescent center (QC) cells, abnormal columella stem cells (CSCs), reduced meristem size, and subsequent inhibition of root growth. In syp132, vesicle transport of PIN proteins is disrupted, leading to altered auxin distribution and decreased expression of the auxin-response transcription factors PLETHORA 1 (PLT1) and PLETHORA 2 (PLT2). Furthermore, the transcription level of the precursor of root meristem growth factor 1 (RGF1) is also modified in syp132. The reduction in PLT2 transcription and protein levels along with defects in the root SCN are partially rescued by the application of synthesized RGF1. This finding suggests that both the auxin-PLT and RGF-PLT pathways are interconnected through SYP132-mediated vesicle transport. Collectively, our findings indicate that SYP132 regulates the PLT pathway to maintain the root stem cell niche (SCN) in an RGF1-dependent manner. Full article

Aquaporins are transmembrane proteins that mediate the transport of water, as well as various ions and molecules. In plants, they play a critical role in numerous processes, including stress adaptation, nutrition, cellular communication, and transpiration. Therefore, understanding the function and interactions of these proteins with others—known as interactomes—is of significant agronomic and biological interest. This study aims to analyse the interactome of all aquaporins in Arabidopsis thaliana L. using two distinct databases, STRING and BioGRID. After analysing both interactomes, a wide range of interactions were identified between each aquaporin and a diverse array of proteins, including nutrient transporters for ammonium, potassium, phosphorus, sulphur, copper, and sugars; proteins related to responses to abiotic stresses; proteins mediating vesicle membrane fusion, such as synaptobrevins and syntaxins; ubiquitinases; kinases; and other transmembrane proteins. These extensive connections further underscore the critical importance of aquaporins in numerous biological processes, positioning them as central modulators and integration points for cellular and systemic responses in plants. Full article

Alzheimer’s disease is a chronic neurodegenerative disorder characterized by progressive memory loss and a significant impact on quality of life. The APOE ε4 allele is a major genetic contributor to AD pathogenesis, with synaptic dysfunction being a central hallmark in its pathophysiology. While the role of APOE4 in reducing SNARE protein levels has been established, the underlying molecular mechanisms of this interaction remain obscure. Our research employs molecular dynamics simulations to analyze interactions between APOE4 and APOE3 isoforms and the synaptic proteins VAMP2, SNAP25, and SYNTAXIN1, which play crucial roles in the presynaptic membrane. Our findings reveal that APOE4 significantly destabilizes the SNARE complex, suppresses its structural dynamics, and reduces hydrogen bonding, consequently partially hindering neurotransmitter release—a very likely discovery for elucidating synaptic dysfunction in Alzheimer’s disease. We identified that APOE4 exhibits a diminished affinity for the SNARE complex in comparison to APOE3. This observation suggests that APOE4 may play a role in modulating the stability of the SNARE complex, potentially impacting the progression and occurrence of Alzheimer’s disease through free energy analysis. This work highlights the perturbations in synaptic function mediated by APOE4, which may offer novel insights into the molecular underpinnings of AD. By elucidating the molecular interplay between APOE4 and the SNARE complex, our study not only enhances our comprehension of AD’s synaptic pathology but also paves the way for devising innovative therapeutic interventions, such as targeting the APOE4–SNARE complex interaction or to restore neurotransmitter release. Full article

Botulinum toxin (BoNT), the most potent substance known to humans, likely evolved not to kill but to serve other biological purposes. While its use in cosmetic applications is well known, its medical utility has become increasingly significant due to the intricacies of its structure and function. The toxin’s structural complexity enables it to target specific cellular processes with remarkable precision, making it an invaluable tool in both basic and applied biomedical research. BoNT’s potency stems from its unique structural features, which include domains responsible for receptor recognition, membrane binding, internalization, and enzymatic cleavage. This division of labor within the toxin’s structure allows it to specifically recognize and interact with synaptic proteins, leading to precise cleavage at targeted sites within neurons. The toxin’s mechanism of action involves a multi-step process: recognition, binding, and catalysis, ultimately blocking neurotransmitter release by cleaving proteins like SNAP-25, VAMP, and syntaxin. This disruption in synaptic vesicle fusion causes paralysis, typically in peripheral neurons. However, emerging evidence suggests that BoNT also affects the central nervous system (CNS), influencing presynaptic functions and distant neuronal systems. The evolutionary history of BoNT reveals that its neurotoxic properties likely provided a selective advantage in certain ecological contexts. Interestingly, the very features that make BoNT a potent toxin also enable its therapeutic applications, offering precision in treating neurological disorders like dystonia, spasticity, and chronic pain. In this review, we highlight the toxin’s structural, functional, and evolutionary aspects, explore its clinical uses, and identify key research gaps, such as BoNT’s central effects and its long-term cellular impact. A clear understanding of these aspects could facilitate the representation of BoNT as a unique scientific paradigm for studying neuronal processes and developing targeted therapeutic strategies. Full article

Granule secretion is an essential platelet function that contributes not only to haemostasis but also to wound healing, inflammation, and atherosclerosis. Granule secretion from platelets is facilitated, at least in part, by Soluble N-ethylmaleimide-Sensitive Factor (NSF) Attachment Protein Receptor (SNARE) complex-mediated granule fusion. Although α-synuclein is a protein known to modulate the assembly of the SNARE complex in other cells, its role in platelet function remains poorly understood. In this study, we provide evidence that α-synuclein is critical for haemostasis using α-synuclein-deficient (^−/−) mice. The genetic deletion of α-synuclein resulted in impaired platelet aggregation, secretion, and adhesion in vitro. In vivo haemostasis models showed that α-synuclein^−/− mice had prolonged bleeding times and activated partial thromboplastin times (aPTTs). Mechanistically, platelet activation induced α-synuclein serine (ser) 129 phosphorylation and re-localisation to the platelet membrane, accompanied by an increased association with VAMP 8, syntaxin 4, and syntaxin 11. This phosphorylation was calcium (Ca²⁺)- and RhoA/ROCK-dependent and was inhibited by prostacyclin (PGI₂). Our data suggest that α-synuclein regulates platelet secretion by facilitating SNARE complex formation. Full article

Syntaxin 3 is a member of a large protein family of syntaxin proteins that mediate fusion between vesicles and their target membranes. Mutations in the ubiquitously expressed syntaxin 3A splice form give rise to a serious gastrointestinal disorder in humans called microvillus inclusion disorder, while mutations that additionally involve syntaxin 3B, a splice form that is expressed primarily in retinal photoreceptors and bipolar cells, additionally give rise to an early onset severe retinal dystrophy. In this review, we discuss recent studies elucidating the roles of syntaxin 3B and the regulation of syntaxin 3B functionality in membrane fusion and neurotransmitter release in the vertebrate retina. Full article

Epinephrine influences the function of pancreatic β-cells, primarily through the α2A-adrenergic receptor (α2A-AR) on their plasma membrane. Previous studies indicate that epinephrine transiently suppresses insulin secretion, whereas prolonged exposure induces its compensatory secretion. Nonetheless, the impact of epinephrine-induced α2A-AR signaling on the survival and function of pancreatic β-cells, particularly the impact of reprogramming after their removal from sustained epinephrine stimulation, remains elusive. In the present study, we applied MIN6, a murine insulinoma cell line, with 3 days of high concentration epinephrine incubation and 2 days of standard incubation, explored cell function and activity, and analyzed relevant regulatory pathways. The results showed that chronic epinephrine incubation led to the desensitization of α2A-AR and enhanced insulin secretion. An increased number of docked insulin granules and impaired Syntaxin-2 was found after chronic epinephrine exposure. Growth curve and cell cycle analyses showed the inhibition of cell proliferation. Transcriptome analysis showed the occurrence of endoplasmic reticulum stress (ER stress) and oxidative stress, such as the presence of BiP, CHOP, IRE1, ATF4, and XBP, affecting cellular endoplasmic reticulum function and survival, along with UCP2, OPA1, PINK, and PRKN, associated with mitochondrial dysfunction. Consequently, we conclude that chronic exposure to epinephrine induces α2A-AR desensitization and leads to ER and oxidative stress, impairing protein processing and mitochondrial function, leading to modified pancreatic β-cell secretory function and cell fate. Full article

Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine that plays a critical role in insulin secretion, energy metabolism, and mitochondrial biogenesis. However, the action of serotonin in insulin production and secretion by pancreatic β cells has not yet been elucidated. Here, we investigated how exogenous nanomolar serotonin concentrations regulate insulin synthesis and secretion in rat insulinoma INS-1E cells. Nanomolar serotonin concentrations (10 and 50 nM) significantly increased insulin protein expression above the constant levels in untreated control cells and decreased insulin protein levels in the media. The reductions in insulin protein levels in the media may be associated with ubiquitin-mediated protein degradation. The levels of membrane vesicle trafficking-related proteins including Rab5, Rab3A, syntaxin6, clathrin, and EEA1 proteins were significantly decreased by serotonin treatment compared to the untreated control cells, whereas the expressions of Rab27A, GOPC, and p-caveolin-1 proteins were significantly reduced by serotonin treatment. In this condition, serotonin receptors, Gαq-coupled 5-HT2b receptor (Htr2b), and ligand-gated ion channel receptor Htr3a were significantly decreased by serotonin treatment. To confirm the serotonylation of Rab3A and Rab27A during insulin secretion, we investigated the protein levels of Rab3A and Rab27A, in which transglutaminase 2 (TGase2) serotonylated Rab3A but not Rab27A. The increases in ERK phosphorylation levels were consistent with increases in the expression of p-Akt. Also, the expression level of the Bcl-2 protein was significantly increased by 50 and 100 nM serotonin treatment compared to the untreated control cells, whereas the levels of Cu/Zn-SOD and Mn-SOD proteins decreased. These results indicate that nanomolar serotonin treatment regulates the insulin protein level but decreases this level in media through membrane vesicle trafficking-related proteins (Rab5, Rab3A, syntaxin6, clathrin, and EEA1), the Akt/ERK pathway, and Htr2b/Htr3a in INS-1E cells. Full article

The main characteristic of polycystic kidney disease is the development of multiple fluid-filled renal cysts. The discovery of mislocalized sodium-potassium pump (Na,K-ATPase) in the apical membrane of cyst-lining epithelia alluded to reversal of polarity as a possible explanation for the fluid secretion. The topic of apical Na,K-ATPase in cysts remains controversial. We investigated the localization of the Na,K-ATPase and assessed the apical-basolateral polarization of cyst-lining epithelia by means of immunohistochemistry in kidney tissue from six polycystic kidney disease patients undergoing nephrectomy. The Na,K-ATPase α1 subunit was conventionally situated in the basolateral membrane of all immunoreactive cysts. Proteins of the Crumbs and partitioning defective (Par) complexes were localized to the apical membrane domain in cyst epithelial cells. The apical targeting protein Syntaxin-3 also immunolocalized to the apical domain of cyst-lining epithelial cells. Proteins of the basolateral Scribble complex immunolocalized to the basolateral domain of cysts. Thus, no deviations from the typical epithelial distribution of basic cell polarity proteins were observed in the cysts from the six patients. Furthermore, we confirmed that cysts can originate from virtually any tubular segment with preserved polarity. In conclusion, we find no evidence of a reversal in apical-basolateral polarity in cyst-lining epithelia in polycystic kidney disease. Full article

A major consequence of insulin binding its receptor on fat and muscle cells is the stimulation of glucose transport into these tissues. This is achieved through an increase in the exocytic trafficking rate of the facilitative glucose transporter GLUT4 from intracellular stores to the cell surface. Delivery of GLUT4 to the cell surface requires the formation of functional SNARE complexes containing Syntaxin 4, SNAP23, and VAMP2. Insulin stimulates the formation of these complexes and concomitantly causes phosphorylation of Syntaxin 4. Here, we use a combination of biochemistry and cell biological approaches to provide a mechanistic link between these observations. We present data to support the hypothesis that Tyr-115 and Tyr-251 of Syntaxin 4 are direct substrates of activated insulin receptors, and that these residues modulate the protein’s conformation and thus regulate the rate at which Syntaxin 4 forms SNARE complexes that deliver GLUT4 to the cell surface. This report provides molecular details on how the cell regulates SNARE-mediated membrane traffic in response to an external stimulus. Full article

Cerebrospinal fluid (CSF) is a biochemical–clinical window into the brain. Unfortunately, its wide dynamic range, low protein concentration, and small sample quantity significantly limit the possibility of using it routinely. Extraventricular drainage (EVD) of CSF allows us to solve quantitative problems and to study the biological role of extracellular vesicles (EVs). In this study, we implemented bioinformatic analysis of our previous data of EVD of CSF and its EVs obtained from congenital hydrocephalus with the aim of identifying a comprehensive list of potential tumor and non-tumor biomarkers of central nervous system diseases. Among all proteins identified, those enriched in EVs are associated with synapses, synaptosomes, and nervous system diseases including gliomas, embryonal tumors, and epilepsy. Among these EV-enriched proteins, given the broad consensus present in the recent scientific literature, we validated syntaxin-binding protein 1 (STXBP1) as a marker of malignancy in EVD of CSF and its EVs from patients with pilocytic astrocytoma and medulloblastoma. Our results show that STXBP1 is negatively enriched in EVs compared to non-tumor diseases and its downregulation correlates with adverse outcomes. Further experiments are needed to validate this and other EV markers in the blood of pediatric patients for translational medicine applications. Full article