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Objectives: Cold snare polypectomy (CSP) is widely performed for small colorectal polyps. However, small colorectal polyps sometimes include high-grade adenomas or carcinomas that require endoscopic resection with electrocautery. This study aimed to evaluate the efficacy and safety of a novel resection technique, hot snare polypectomy with low-power pure-cut current (LPPC-HSP) for small colorectal polyps, compared with CSP and conventional endoscopic mucosal resection (EMR). Methods: Records of patients who underwent CSP, EMR, or LPPC-HSP for nonpedunculated colorectal polyps less than 10 mm between April 2021 and March 2022 were retrospectively evaluated. We analyzed and compared the treatment outcomes of CSP and EMR with those of LPPC-HSP using propensity score matching. Results: After propensity score matching of 396 pairs, an analysis of CSP and LPPC-HSP indicated that LPPC-HSP had a significantly higher R0 resection rate (84% vs. 68%; p < 0.01). Delayed bleeding was observed in only two cases treated with CSP before matching. Perforation was not observed with either treatment. After propensity score matching of 176 pairs, an analysis of EMR and LPPC-HSP indicated that their en bloc and R0 resection rates were not significantly different (99.4% vs. 100%, p = 1.00; 79% vs. 81%, p = 0.79). Delayed bleeding and perforation were not observed with either treatment. Conclusions: The safety of LPPC-HSP was comparable to that of CSP. The treatment outcomes of LPPC-HSP were comparable to those of conventional EMR for small polyps. These results suggest that this technique is a safe and effective treatment for nonpedunculated polyps less than 10 mm.
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Objectives: Delayed bleeding is the most frequent adverse event associated with endoscopic mucosal resection (EMR) and hot snare polypectomy (HSP) of colorectal polyps. However, whether the incidence of delayed bleeding differs between outpatient and inpatient treatment is unknown. Therefore, in this study, we aimed to evaluate delayed bleeding rates between outpatient and inpatient endoscopic treatments and clarify the safety of outpatient treatment. Methods: We enrolled 469 patients (1077 polyps) and 420 patients (1080 polyps) in the outpatient and inpatient groups, respectively, who underwent EMR or HSP for colorectal polyps at our institution between April 2020 and May 2023. Using propensity score matching, we evaluated the delayed bleeding rates between the two groups. Delayed bleeding was defined as a hemorrhage requiring endoscopic hemostasis occurring within 14 days of the procedure. Results: Propensity score matching created 376 (954 polyps) matched patient pairs. The median maximum diameter of polyps removed was 10 mm in both groups. Delayed bleeding rates per patients were 1.3% (5/376) in the outpatient group and 2.9% (11/376) in the inpatient group (P=0.21). In term of per polyp, early delayed bleeding (occurring within 24 hours) rates were higher in the inpatient group than outpatient group (0.2% [2/954] vs. 1.1% [10/954], respectively; P=0.04). No severe bleeding requiring a transfusion occurred in either group. Conclusions: Outpatient endoscopic treatment did not increase delayed bleeding compared with inpatient treatment. Outpatient treatment would be safe and common for the removal of colorectal polyps.
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Chlamydia trachomatis, a leading cause of bacterial sexually transmitted infections, creates a specialized intracellular replicative niche by translocation and insertion of a diverse array of effectors (Incs [inclusion membrane proteins]) into the inclusion membrane. Here, we characterize IncE, a multifunctional Inc that encodes two non-overlapping short linear motifs (SLiMs) within its short cytosolic C terminus. The proximal SLiM, by mimicking just a small portion of an R-N-ethylmaleimide-sensitive factor adaptor protein receptor (SNARE) motif, binds and recruits syntaxin (STX)7- and STX12-containing vesicles to the inclusion. The distal SLiM mimics the sorting nexin (SNX)5 and SNX6 cargo binding site to recruit SNX6-containing vesicles to the inclusion. By simultaneously binding two distinct vesicle classes, IncE brings these vesicles in close apposition with each other at the inclusion to facilitate C. trachomatis intracellular development. Our work suggests that Incs may have evolved SLiMs to enable rapid evolution in a limited protein space to disrupt host cell processes.
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Current guidelines recommend cold snare polypectomy for polyps less than 10 mm in size. Conversely, endoscopic mucosal resection is still the preferred technique for larger polyps. Concerns regarding cold snare polypectomy for larger polyps revolve around the difficulty in conducting en-bloc resection (resulting in piecemeal removal), and the potential for local residual polyp tissue and a high rate of recurrence. On the other hand, cold snare technique has the advantages of shortening procedure time, reducing delayed bleeding risks and lowering cost of treatment. Numerous ongoing and recent studies are focused on evaluating the risks and benefits of this technique for polyps larger than 10 mm, with the goal of providing clear guidelines in the near future. The aim of this editorial is to provide our readers with an overview regarding this subject and the latest developments surrounding it.
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Age-related conditions, such as sarcopenia, cause physical disabilities for an increasing section of society. At the neuromuscular junction, the postsynaptic-derived neurotrophic factors brain-derived neurotrophic factor (BDNF) and neurotrophin 4 (NT-4) have neuroprotective functions and contribute to the correct regulation of the exocytotic machinery. Similarly, presynaptic muscarinic signalling plays a fundamental modulatory function in this synapse. However, whether or not these signalling pathways are compromised in ageing neuromuscular system has not yet been analysed. The present study analyses, through Western blotting, the differences in expression and activation of the main key proteins of the BDNF/NT-4 and muscarinic pathways related to neurotransmission in young versus ageing Extensor digitorum longus (EDL) rat muscles. The main results show an imbalance in several sections of these pathways: (i) a change in the stoichiometry of BDNF/NT-4, (ii) an imbalance of Tropomyosin-related kinase B receptor (TrkB)-FL/TrkB-T1 and neurotrophic receptor p 75 (p75NTR), (iii) no changes in the cytosol/membrane distribution of phosphorylated downstream protein kinase C (PKC)ßI and PKCε, (iv) a reduction in the M2-subtype muscarinic receptor and P/Q-subtype voltage-gated calcium channel, (v) an imbalance of phosphorylated mammalian uncoordinated-18-1 (Munc18-1) (S313) and synaptosomal-associated protein 25 (SNAP-25) (S187), and (vi) normal levels of molecules related to the management of acetylcholine (Ach). Based on this descriptive analysis, we hypothesise that these pathways can be adjusted to ensure neurotransmission rather than undergoing negative alterations caused by ageing. However, further studies are needed to assess this hypothetical suggestion. Our results contribute to the understanding of some previously described neuromuscular functional age-related impairments. Strategies to promote these signalling pathways could improve the neuromuscular physiology and quality of life of older people.
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Envelhecimento , Fator Neurotrófico Derivado do Encéfalo , Junção Neuromuscular , Receptor trkB , Transdução de Sinais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Animais , Junção Neuromuscular/metabolismo , Envelhecimento/metabolismo , Ratos , Receptor trkB/metabolismo , Fatores de Crescimento Neural/metabolismo , Masculino , Receptores Muscarínicos/metabolismo , Transmissão Sináptica , Receptores de Fator de Crescimento Neural/metabolismo , Ratos WistarRESUMO
Ectopic pancreas, also known as heterotopic pancreas, is a rare condition in which the pancreatic tissue is found outside its usual location in the gastrointestinal (GI) tract. It is commonly asymptomatic and benign, and is often discovered incidentally during routine imaging, endoscopy, surgery, or autopsy. However, complications can arise, such as inflammation, bleeding, obstruction, or even malignant transformation, necessitating surgical intervention in some cases. Ectopic pancreas at the ampulla of Vater (EPAV) is an extremely rare condition and a diagnostic and therapeutic nightmare. Most cases have been diagnosed through invasive surgery due to concerns for malignancy, which carries significant morbidity and mortality. In our case, endoscopic snare papillectomy (ESP) was employed to establish a diagnosis. Thus far, only one other case has been reported in which ESP was used to diagnose and resect a pancreatic heterotopia at the ampulla.
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Ampola Hepatopancreática , Coristoma , Pâncreas , Humanos , Ampola Hepatopancreática/cirurgia , Coristoma/cirurgia , Coristoma/diagnóstico , Coristoma/patologia , Feminino , Masculino , Pessoa de Meia-Idade , Colangiopancreatografia Retrógrada EndoscópicaRESUMO
Agriculture is the main source of livelihood for most of the population across the globe. Plants are often considered life savers for humanity, having evolved complex adaptations to cope with adverse environmental conditions. Protecting agricultural produce from devastating conditions such as stress is essential for the sustainable development of the nation. Plants respond to various environmental stressors such as drought, salinity, heat, cold, etc. Abiotic stress can significantly impact crop yield and development posing a major threat to agriculture. SNARE proteins play a major role in pathological processes as they are vital proteins in the life sciences. These proteins act as key players in stress responses. Feature extraction is essential for visualizing the underlying structure of the SNARE proteins in analyzing the root cause of abiotic stress in plants. To address this issue, we developed a hybrid model to capture the hidden structures of the SNAREs. A feature fusion technique has been devised by combining the potential strengths of convolutional neural networks (CNN) with a high dimensional radial basis function (RBF) network. Additionally, we employ a bi-directional long short-term memory (Bi-LSTM) network to classify the presence of SNARE proteins. Our feature fusion model successfully identified abiotic stress in plants with an accuracy of 74.6%. When compared with various existing frameworks, our model demonstrates superior classification results.
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Background: Entrapment and fracture of the coronary guidewire are rare but major complications of percutaneous coronary intervention (PCI). The incidence of these complications is reported to be <1%. Case summary: A 52-year-old male patient with diabetes and dyslipidaemia presented with posterior wall myocardial infarction. An angiogram revealed occlusion in the left circumflex (LCX) artery. Attempts to pass a guidewire through the lesion led to its entrapment and eventual fracture. Several techniques and manoeuvres failed to retrieve the fractured guidewire, which remained lodged in the LCX. An endovascular snare catheter also proved unsuccessful. The fragment was eventually removed using the triple-wire technique, although this caused coronary perforation and dissection. The perforation was identified and stented. A subsequent stent addressed a dissection in the left main/left ascending artery area, likely caused by the coronary snare. These interventions were crucial in stabilizing the patient's condition, leading to recovery with a left ventricular ejection fraction of 50% and a viable LCX artery. The patient exhibited an uneventful progression at the 1-year follow-up. Discussion: Coronary guidewire fracture during PCI is a rare event often associated with coronary calcifications. Percutaneous removal remains the mainstay treatment for fragment removal; however, it carries risks. The triple-wire technique, a newer method that entangles and extracts the fractured guidewire without specialized equipment, was effective in removing the fragmented guidewire. If asymptomatic, leaving the wire in situ is documented as a favourable approach. This case highlights that the triple-wire technique can effectively be used for the extraction of fractured guidewire fragments from the coronary vessels.
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Autophagy is a universal degradation system in eukaryotic cells. In plants, although autophagosome biogenesis has been extensively studied, the mechanism of how autophagosomes are transported to the vacuole for degradation remains largely unexplored. In this study, we demonstrated that upon autophagy induction, Arabidopsis homotypic fusion and protein sorting (HOPS) subunit VPS41 converts first from condensates to puncta, then to ring-like structures, termed VPS41-associated phagic vacuoles (VAPVs), which enclose autophagy-related gene (ATG)8s for vacuolar degradation. This process is initiated by ADP ribosylation factor (ARF)-like GTPases ARLA1s and occurs concurrently with autophagy progression through coupling with the synaptic-soluble N-ethylmaleimide-sensitive factor attachment protein rmleceptor (SNARE) proteins. Unlike in other eukaryotes, autophagy degradation in Arabidopsis is largely independent of the RAB7 pathway. By contrast, dysfunction in the condensates-to-VAPVs conversion process impairs autophagosome structure and disrupts their vacuolar transport, leading to a significant reduction in autophagic flux and plant survival rate. Our findings suggest that the conversion pathway might be an integral part of the autophagy program unique to plants.
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BACKGROUND AND AIMS: There is growing evidence for the role of cold piecemeal endoscopic mucosal resection (C-EMR) in the treatment of colorectal lesions ≥10mm. However, it is unclear if it is equally efficacious for all histologic subtypes and sizes. This retrospective study compares the efficacy and safety of C-EMR in the resection of medium (10-19mm) and large (≥20mm) serrated and adenomatous lesions. METHODS: A retrospective analysis was performed of Paris IIa colonic lesions resected utilising a C-EMR technique over a 3.5 year period at our center. RESULTS: C-EMR was performed for 242 lesions in 151 patients. Lesion size ranged between 10mm to 50mm, with median size of 20mm. Ninety-five polyps were adenomatous, with 147 sessile serrated lesions (SSLs). At six month surveillance colonoscopy, the combined recurrence rate was 6.2%. Adenomas ≥20mm demonstrated a higher rate of recurrence (16.1%) compared to large SSLs (4.1%), medium adenomas (3.0%), and medium SSLs (1.4%). There were no adverse events reported following C-EMR. CONCLUSIONS: C-EMR seems to be less effective for the resection of large adenomas when compared to medium adenomas or large SSLs. C-EMR is equally safe for all lesion size and histology.
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Background: The wide range of R0 resection rates (R0RR) and incomplete resection rates (IRR) observed with conventional cold snare polypectomy (CCSP) emphasizes the necessity for technique enhancement. The COLDWATER study aimed to compare underwater cold snare polypectomy (UCSP) to CCSP for 5-10-mm colorectal polyps, focusing on comprehensive histopathological evaluation, efficacy, and safety. Methods: This was a randomized, single-blind, controlled trial comparing UCSP to CCSP for non-pedunculated colorectal polyps of size 5-10 mm. The primary outcome was to report differences in the muscularis mucosa resection ratio. The secondary outcomes focused on differences in depth of excision, R0-RR, IRR, en bloc resection rate, adverse events, and recurrence rate. Results: The COLDWATER study found higher muscularis mucosa resection in UCSP (81.72±62.81% vs. CCSP: 72.33±22.33%, P=0.003) with comparable submucosa presence (UCSP: 16.6%, CCSP: 12.5%, P=0.25). UCSP showed better outcomes regarding IRR (3.5% vs. 8.5%, P=0.05) and en bloc resection (98% vs. 93.5%, P=0.04). In CCSP, expert endoscopists achieved higher R0RR than non-experts, while UCSP showed no significant difference in R0RR across endoscopist's experience levels. Conclusions: UCSP achieves a more extensive excision of the muscularis mucosa compared to CCSP, even though it does not attain a deeper excision. Additionally, UCSP shows a higher en bloc resection rate, with lower rates of IRR, and emerges as a promising technique for training inexperienced endoscopists in polypectomy, given its experience-independent success in achieving R0 resection.
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Over the years, research on the pathogenesis of neurological diseases has progressed slowly worldwide. However, as the incidence rate continues to increase and the disease gradually develops, early diagnosis and treatment have become a top priority. SANP25, a protein present on the presynaptic membrane and involved in neurotransmitter release, is closely related to the loss or abnormal expression of synapses and neurons. SNAP25 deficiency can lead to synaptic disorders and inhibit neurotransmitter release. Therefore, a large amount of literature believes that SNAP25 gene mutation is a risk factor for many neurological diseases. This review used advanced search on PubMed to conduct extensive article searches for relevant literature. The search keywords included SNAP25 and Alzheimer's disease, SNAP25 and Parkinson's disease, and so on. After reading and summarizing the previous papers, the corresponding conclusions were obtained to achieve the purpose of the review. The deficiency or variation of SNAP25 might be related to the onset of schizophrenia, epilepsy, attention deficit/hypoactivity disorder, bipolar disorder effective disorder, and autism. SNAP25 has been found to be used as a neuropathological marker for neurological diseases, which could be the target of diagnosis or treatment of Alzheimer's disease and Parkinson's disease. Cerebrospinal Fluid (CSF) or blood has been found to enable more effective drug development.
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We report the case of a 22-year-old male who underwent endoluminal surgery and was implanted an Option Elite filter in the superior vena cava (SVC) while the filter retraction hook was attached to the vessel wall. The patient requested to remove the filter after 155 days. Preoperative ultrasonography and CT examination revealed that the filter retraction hook was very likely to penetrate the SVC wall and its tip was very close to the right pulmonary artery. The SVC was not obstructed, and no thrombus was observed in either upper limb. After the filter retrieval device (ZYLOX, China) failed to capture the filter hook, we introduced a pigtail catheter with its tip partly removed and a loach guidewire, used a modified loop-snare technique to cut the proliferative tissues and free the hook, and finally removed the filter successfully by direct suspension of the guidewire. During this procedure, the patient experienced discomfort, such as chest pain and palpitations, but these symptoms disappeared when procedure completed. Repeated multiangle angiography revealed no contrast medium extravasation, no complications such as pericardial tamponade, pleural effusion, SVC haematoma formation, right pulmonary artery dissecting aneurysm, or intramural haematoma. We initially presented the modified loop-snare technique used to remove a conical superior vena cava filter (SVCF), so this method can be considered a practical and novel auxiliary technique for successful filter retrieval.
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BACKGROUND: Delayed bleeding (DB) is a serious complication after cold snare polypectomy (CSP) for polyps in the colon. The present study aimed to investigate the incidence and risk factors of DB after CSP and to develop a risk-scoring model for predicting DB. METHODS: A retrospective study was conducted in four Chinese medical institutions. 10650 patients underwent CSP from June 2019 to May 2023. The study analyzed the rate of DB and extracted the general clinical information and polyp-related information of patients with postoperative DB. As a control, non-DB patients who received CSP at the same 4 hospitals were analyzed. A multivariate Cox regression analysis was performed to develop the prediction model. The model was further validated using a Kaplan-Meier log-rank analysis, receiver operating characteristic curve (ROC) plot and risk plot. RESULTS: In our study, we found a 0.24% rate of DB and the risk factors were history of hypertension, hyperlipidemia, antithrombotics use, antiplatelet use, anticoagulant use, abdominal operation, sigmoid colon lesion, hematoma, cold snare defect protrusion, polyp size, wound size, the grade of wound bleeding, and morphology of Ip. These factors were incorporated into the prediction model for DB after CSP. For 1, 3, and 5 days of bleeding, the AUC of the ROC curve was 0.912, 0.939, and 0.923, respectively. The Kaplan-Meier analysis indicated that the high-risk group had a significantly higher risk of DB than the low-risk group. CONCLUSIONS: This study screened the risk factors and established a prediction model of DB after CSP. The results may help preventing and reducing the DB rate after CSP of colorectal polyps.
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Pólipos do Colo , Humanos , Fatores de Risco , Estudos Retrospectivos , Masculino , Feminino , Pessoa de Meia-Idade , Pólipos do Colo/cirurgia , Hemorragia Pós-Operatória/etiologia , Hemorragia Pós-Operatória/epidemiologia , Curva ROC , Idoso , Fatores de Tempo , Adulto , Colonoscopia/efeitos adversosRESUMO
OBJECTIVES: The hemostatic mechanism of endoscopic detachable snare ligation (EDSL) for colonic diverticular hemorrhage (CDH) is similar to that of endoscopic band ligation, which is effective and safe. However, because reports on EDSL are scarce, we conducted a two-center cohort study to evaluate its effectiveness. METHODS: This study analyzed 283 patients with CDH treated with EDSL at two Japanese hospitals between July 2015 and November 2021. Patient characteristics and clinical outcomes were retrospectively evaluated. A Kaplan-Meier analysis was performed to evaluate the cumulative probability of rebleeding after EDSL. A Cox proportional hazards regression analysis was performed to compare the effects of complete and incomplete ligation on rebleeding. RESULTS: The initial hemostasis success and early rebleeding rates were 97.9% and 11.0%, respectively. The time to hemostasis after identification of the bleeding site and total procedure time were 9 min and 44 min, respectively. Red blood cell transfusion was required for 32.9% of patients. The median hospital length of stay after EDSL was 5 days. The complete ligation rate of the early rebleeding group was significantly lower than that of the group without early rebleeding (P < 0.01). The 1-year cumulative rebleeding rate with EDSL was 28.2%. Complete ligation was associated with decreased cumulative rebleeding after EDSL (P < 0.01). One patient experienced colonic diverticulitis; however, colonic perforation was not observed. CONCLUSION: Complete ligation is associated with reduced short-term and long-term rebleeding. EDSL could be valuable for CDH because of its low rebleeding rate and the absence of serious adverse events.
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BACKGROUND: Pleomorphic leiomyosarcomas make up around 8.6% of all leiomyosarcomas. They behave aggressively and often have poor prognoses. They can affect the gastrointestinal tract and retroperitoneum. To date, pleomorphic leiomyosarcoma involving the mesocolon have been reported in nine patients. CASE SUMMARY: The patient was a 44-year-old man with a history of pleomorphic leiomyosarcoma of the left maxilla with metastasis to the lung and liver. His most recent positron emission tomography-computed tomography (PET-CT) scan showed uptake in the ascending and transverse colons. A colonoscopy revealed a 5.0 cm × 3.5 cm × 3.0 cm pedunculated polyp in the ascending colon. The polyp was removed using hot snare polypectomy technique and retrieved with Rothnet. Histopathologic examination of the polyp showed a metastatic pleomorphic leiomyosarcoma. CONCLUSION: Uptake(s) on PET-CT in a patient with pleomorphic leiomyosarcoma should raise suspicion for metastasis.
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BACKGROUND: The guidelines recommend conventional cold snare polypectomy (C-CSP) for diminutive and small colorectal polyps (≤ 10 mm). However, it remains unclear whether CSP with sub-mucosal injection (SI-CSP) achieves comparable efficacy to C-CSP for managing these lesions. This study compares SI-CSP with C-CSP for patients with diminutive and small colorectal polyps. METHODS: An electronic literature search was conducted to retrieve articles comparing resection outcomes between SI-CSP and C-CSP in diminutive and small colorectal polyps (registration number INPLASY2023100096). Our primary outcomes of interest were the complete resection rate (CRR), complications (namely immediate bleeding, delayed bleeding and perforation) and polypectomy time. Mean differences with 95% confidence intervals (CI) were employed for continuous variables, while odds ratios (OR) with 95% CI were calculated for categorical variables. Data was analyzed using a random effects model and the I2 test was utilized to assess heterogeneity. RESULTS: Eight studies involving 1470 patients with 2223 polyps were included in our analysis. The CRR was not significantly higher in the SI-CSP group, with an OR of 95% CI 0.50 (0.22, 1.15). The incidences of immediate bleeding (OR 95% CI 0.60 [0.26-1.40]) and delayed bleeding (OR 95% CI 0.88 [0.32-2.42]) did not differ significantly between the two groups. On average, the mean polypectomy time was 64.75 seconds shorter in the C-CSP group (95% CI, - 102.96 to - 26.53). Notably, no perforation events were reported in the included studies. CONCLUSIONS: The use of SI-CSP was not superior to C-CSP in managing diminutive and small colorectal polyps and the procedure required significantly more time.
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Various cell types release neurotransmitters, hormones and many other compounds that are stored in secretory vesicles by exocytosis via the formation of a fusion pore traversing the vesicular membrane and the plasma membrane. This process of membrane fusion is mediated by the Soluble N-ethylmaleimide-Sensitive Factor Attachment Proteins REceptor (SNARE) protein complex, which in neurons and neuroendocrine cells is composed of the vesicular SNARE protein Synaptobrevin and the plasma membrane proteins Syntaxin and SNAP25 (Synaptosomal-Associated Protein of 25â kDa). Before a vesicle can undergo fusion and release of its contents, it must dock at the plasma membrane and undergo a process named 'priming', which makes it ready for release. The primed vesicles form the readily releasable pool, from which they can be rapidly released in response to stimulation. The stimulus is an increase in Ca2+ concentration near the fusion site, which is sensed primarily by the vesicular Ca2+ sensor Synaptotagmin. Vesicle priming involves at least the SNARE proteins as well as Synaptotagmin and the accessory proteins Munc18, Munc13, and Complexin but additional proteins may also participate in this process. This review discusses the current views of the interactions and the structural changes that occur among the proteins of the vesicle priming machinery.
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Neuronal exocytosis requires the assembly of three SNARE proteins, syntaxin and SNAP25 on the plasma membrane and synaptobrevin on the vesicle membrane. However, the precise steps in this process and the points at which assembly and fusion are controlled by regulatory proteins are unclear. In the present work, we examine the kinetics and intermediate states during SNARE assembly in vitro using a combination of time resolved fluorescence and EPR spectroscopy. We show that syntaxin rapidly forms a dimer prior to forming the kinetically stable 2:1 syntaxin:SNAP25 complex and that the 2:1 complex is not diminished by the presence of excess SNAP25. Moreover, the 2:1 complex is temperature-dependent with a reduced concentration at 37 °C. The two segments of SNAP25 behave differently. The N-terminal SN1 segment of SNAP25 exhibits a pronounced increase in backbone ordering from the N- to the C-terminus that is not seen in the C-terminal SNAP25 segment SN2. Both the SN1 and SN2 segments of SNAP25 will assemble with syntaxin; however, while the association of the SN1 segment with syntaxin produces a stable 2:2 (SN1:syntaxin) complex, the complex formed between SN2 and syntaxin is largely disordered. Synaptobrevin fails to bind syntaxin alone but will associate with syntaxin in the presence of either the SN1 or SN2 segments; however, the synaptobrevin:syntaxin:SN2 complex remains disordered. Taken together, these data suggest that synaptobrevin and syntaxin do not assemble in the absence of SNAP25 and that the SN2 segment of SNAP25 is the last to enter the SNARE complex.