Gleason Pattern 5 May Be a Prognostic Factor in Radium-223 Treatment.

Background/Aim: Radium-223 treatment reduces the risk of death in patients with metastatic castration-resistant prostate cancer (CRPC). This study analyzed the prognostic factors in patients treated with radium-223 dichloride. Patients and Methods: Patients who received radium-223 dichloride were retrospectively analyzed. Prostate-specific antigen (PSA) response and alkaline phosphatase (ALP) decline rates were analyzed. Overall survival (OS) was evaluated using Kaplan-Meier curves, and prognostic factors for OS were assessed using Cox proportional hazards analysis. Results: Fifty-six patients were included in the study. The five-year OS rate in patients after diagnosis of CRPC was 62.2% [95% confidence interval (CI)=27.55-112.45], while the five-year OS rate in patients at the initiation of radium-223 treatment was 21.3% (95%CI=17.20-36.79). Six patients (11.1%) had a >50% PSA decline rate, and 10 (17.9%) had a >50% ALP decline rate. Cox proportional hazards analysis showed that PSA levels at the initiation of radium-223 treatment [hazard ratio (HR)=1.00; 95%CI=1.00-1.00; p=0.0054] and Gleason Pattern (GP) 5 (HR=5.42; 95%CI=1.08-27.27; p=0.0400) were associated with OS. Patients with GP 5 had a significantly poorer prognosis compared with patients with a GP ≤4. Early administration of radium-223 as a first- or second-line treatment was not associated with OS compared with late administration of radium-223 as a third-line or later treatment. Conclusion: GP 5 and high PSA levels at radium-223 initiation were associated with worse OS. Radium-223 as first- or second-line treatment was not associated with OS. Therefore, a treatment strategy for CRPC based on GP 5 is needed.

Compartmentalization of soluble endocytic proteins in synaptic vesicle clusters by phase separation.

Synaptic vesicle (SV) clusters, which reportedly result from synapsin's capacity to undergo liquid-liquid phase separation (LLPS), constitute the structural basis for neurotransmission. Although these clusters contain various endocytic accessory proteins, how endocytic proteins accumulate in SV clusters remains unknown. Here, we report that endophilin A1 (EndoA1), the endocytic scaffold protein, undergoes LLPS under physiologically relevant concentrations at presynaptic terminals. On heterologous expression, EndoA1 facilitates the formation of synapsin condensates and accumulates in SV-like vesicle clusters via synapsin. Moreover, EndoA1 condensates recruit endocytic proteins such as dynamin 1, amphiphysin, and intersectin 1, none of which are recruited in vesicle clusters by synapsin. In cultured neurons, like synapsin, EndoA1 is compartmentalized in SV clusters through LLPS, exhibiting activity-dependent dispersion/reassembly cycles. Thus, beyond its essential function in SV endocytosis, EndoA1 serves an additional structural function by undergoing LLPS, thereby accumulating various endocytic proteins in dynamic SV clusters in concert with synapsin.

Prognostic factors in Japanese men with high-Gleason metastatic castration-resistant prostate cancer.

Background: Several therapeutic agents are available for metastatic castration-resistant prostate cancer (CRPC). However, prognosis is still not well developed. The Gleason score (GS) is a prognostic factor available for patients with metastatic CRPC. GSs ranging from 6 to 10 and GSs ≥8 are usually categorized as single prognostic factors. In this study, we evaluated the prognosis of high-GS metastatic CRPC in Japanese men. Methods: Overall, 105 patients with metastatic CRPC with a GS ≥8 were retrospectively analyzed. Multivariate analyses of patient age, GS, and Eastern Cooperative Oncology Group performance status (ECOG-PS) were performed using Cox proportional hazards analysis to predict overall survival (OS). Results: GS 8 had all Gleason patterns of 4+4. Thirty patients (28.6%) had GS of 8, and 75 (71.4%) had GS of 9 or 10. As a first-line treatment for metastatic CRPC, 42 patients (40%) received abiraterone, 35 (33.3%) received enzalutamide, and 26 (24.8%) received docetaxel. The 5-year OS in patients with GS of 8 was 65.0% [95% confidence interval (CI): 43.07-86.82%], while the 5-year OS in patients with GS of 9 or 10 was 37.0% (95% CI: 24.41-56.11%). There was a significant difference in OS between the GS 8 and GS 9-10 groups (log-rank test, P=0.038). Multivariate analysis showed that GS and ECOG-PS were significant prognostic factors for OS. Conclusions: Patients with metastatic CRPC with GS 9-10 had poor prognoses, suggesting the need for additional treatment options.

Clathrin-independent endocytic retrieval of SV proteins mediated by the clathrin adaptor AP-2 at mammalian central synapses.

Neurotransmission is based on the exocytic fusion of synaptic vesicles (SVs) followed by endocytic membrane retrieval and the reformation of SVs. Conflicting models have been proposed regarding the mechanisms of SV endocytosis, most notably clathrin/adaptor protein complex 2 (AP-2)-mediated endocytosis and clathrin-independent ultrafast endocytosis. Partitioning between these pathways has been suggested to be controlled by temperature and stimulus paradigm. We report on the comprehensive survey of six major SV proteins to show that SV endocytosis in mouse hippocampal neurons at physiological temperature occurs independent of clathrin while the endocytic retrieval of a subset of SV proteins including the vesicular transporters for glutamate and GABA depend on sorting by the clathrin adaptor AP-2. Our findings highlight a clathrin-independent role of the clathrin adaptor AP-2 in the endocytic retrieval of select SV cargos from the presynaptic cell surface and suggest a revised model for the endocytosis of SV membranes at mammalian central synapses.

Disseminated intravascular coagulation induced by pazopanib following combination therapy of nivolumab plus ipilimumab in a patient with metastatic renal cell carcinoma.

Recently, combination therapy including immune checkpoint inhibition (ICI) has proven to be effective as first-line therapy for patients with metastatic renal cell carcinoma. Although the first-line combination therapies with ICI have shown clinical benefit, a number of patients require second-line treatment. We report a 60-year-old man with metastatic renal cell carcinoma who was treated with pazopanib soon after nivolumab plus ipilimumab combination therapy. He experienced Grade 3 disseminated intravascular coagulation (DIC). We suspect that this was caused by an interaction between pazopanib and nivolumab even though ICI therapy was discontinued. He was treated with thrombomodulin and platelet transfusion and recovered from DIC. Treatment with pazopanib was subsequently restarted. No evidence of DIC was observed thereafter. This severe adverse reaction may have been induced by an interaction between activated proinflammatory immune cells and cytokines from an exacerbated inflammatory state and pazopanib. This report highlights the need to perform careful monitoring of patients who receive molecular targeted therapy after ICI-based immunotherapy.

Higher neutrophil-to-lymphocyte ratio after the first cycle of the first-line chemotherapy is associated with poor cancer specific survival of upper urinary tract carcinoma patients.

BACKGROUND: Inflammatory cytokines and immature myeloid derived suppressor cells (MDSCs), which increase during cancer progression, could lead to a neutrophil increase and lymphocyte reduction. Thus, the neutrophil-lymphocyte ratio (NLR) was used to predict survival of patients suffering from urological cancers including upper urinary tract carcinoma. We further determined whether the NLR during the first cycle of first-line chemotherapy could predict cancer specific survival. METHODS: We recruited patients with locally advanced or metastatic upper urinary tract urothelial carcinoma (UTUC) who received chemotherapy between January 2014 and July 2019. We investigated the impact of various clinical variables, including age, sex, performance status, and estimated creatinine clearance (CCr), and NLR before and after the first cycle of the first-line chemotherapy on prognosis. RESULTS: A total of 41 patients were included in our study. Cancer specific survival of the patients with lower NLR was significantly better than that of the patients with higher NLR measured after the first cycle of the first-line chemotherapy (log-rank test P=0.005, median 29.2 vs. 11.9 months, respectively). Cox proportional regression analysis showed that higher NLR after the first cycle of the first-line chemotherapy was a significant predictor of cancer specific survival. CONCLUSIONS: The NLR after the first cycle of the first-line chemotherapy could be an indication for patients with locally advanced or metastatic UTUC to maintain their first-line chemotherapy treatment.

The endosomal Q-SNARE, Syntaxin 7, defines a rapidly replenishing synaptic vesicle recycling pool in hippocampal neurons.

Upon the arrival of repetitive stimulation at the presynaptic terminals of neurons, replenishment of readily releasable synaptic vesicles (SVs) with vesicles in the recycling pool is important for sustained neurotransmitter release. Kinetics of replenishment and the available pool size define synaptic performance. However, whether all SVs in the recycling pool are recruited for release with equal probability and speed is unknown. Here, based on comprehensive optical imaging of various presynaptic endosomal SNARE proteins in cultured hippocampal neurons, all of which are implicated in organellar membrane fusion in non-neuronal cells, we show that part of the recycling pool bearing the endosomal Q-SNARE, syntaxin 7 (Stx7), is preferentially mobilized for release during high-frequency repetitive stimulation. Recruitment of the SV pool marked with an Stx7-reporter requires actin polymerization, as well as activation of the Ca2+/calmodulin signaling pathway, reminiscent of rapidly replenishing SVs characterized previously in calyx of Held synapses. Furthermore, disruption of Stx7 function by overexpressing its N-terminal domain selectively abolished this pool. Thus, our data indicate that endosomal membrane fusion involving Stx7 forms rapidly replenishing vesicles essential for synaptic responses to high-frequency repetitive stimulation, and also highlight functional diversities of endosomal SNAREs in generating distinct exocytic vesicles in the presynaptic terminals.

[Gas-Producing Splenic Abscess after Spleen Metastasis of Left Renal Cell Carcinoma Spleen Metastasis Successfully Treated with Sunitinib].

A 67-year-old man underwent open radical left nephrectomy for left renal cell carcinoma [pT4N0M1 (right lower lobe of lung)] and thoracoscopic partial right lung resection for lung metastasis. The patient subsequently developed a solitary lung metastasis at 10 months and then at 26 months postoperatively. He underwent partial lung resection on each occasion. During the 28 months postoperatively, he was found to have a 12 mm middle mediastinal lymph node metastasis and a 30 mm splenic metastasis, which gradually increased in size. Three months after discovery, sunitinib was initiated at 37.5 mg 2 weeks on/1 week off. Twelve days later, the patient presented with complaints of fever. A gas-producing splenic abscess was diagnosed and he was admitted on the same day. His condition improved with antibiotics and splenic drainage. On day 35 of hospitalization, he underwent laparoscopic splenectomy. The patient's postoperative clinical course was uneventful and he was discharged 7 days after the surgery.

Hidden proteome of synaptic vesicles in the mammalian brain.

Current proteomic studies clarified canonical synaptic proteins that are common to many types of synapses. However, proteins of diversified functions in a subset of synapses are largely hidden because of their low abundance or structural similarities to abundant proteins. To overcome this limitation, we have developed an "ultra-definition" (UD) subcellular proteomic workflow. Using purified synaptic vesicle (SV) fraction from rat brain, we identified 1,466 proteins, three times more than reported previously. This refined proteome includes all canonical SV proteins, as well as numerous proteins of low abundance, many of which were hitherto undetected. Comparison of UD quantifications between SV and synaptosomal fractions has enabled us to distinguish SV-resident proteins from potential SV-visitor proteins. We found 134 SV residents, of which 86 are present in an average copy number per SV of less than one, including vesicular transporters of nonubiquitous neurotransmitters in the brain. We provide a fully annotated resource of all categorized SV-resident and potential SV-visitor proteins, which can be utilized to drive novel functional studies, as we characterized here Aak1 as a regulator of synaptic transmission. Moreover, proteins in the SV fraction are associated with more than 200 distinct brain diseases. Remarkably, a majority of these proteins was found in the low-abundance proteome range, highlighting its pathological significance. Our deep SV proteome will provide a fundamental resource for a variety of future investigations on the function of synapses in health and disease.

Association of Daily Home-Based Hot Water Bathing and Glycemic Control in Ambulatory Japanese Patients with Type 2 Diabetes Mellitus During the COVID-19 Pandemic: A Multicenter Cross-Sectional Study.

PURPOSE: To clarify the relationship between daily hot water bathing (HWB) at home and glycemic control in middle-aged and elderly ambulatory patients with type 2 diabetes mellitus (T2DM). METHODS: We defined hemoglobin A1c (HbA1c) as the main outcome. We set 7.0% based on the mean value of the dependent variable as the cut-off point for analysis. Frequency of HWB was an explanatory variable. A two-sample t-test was used to compare between groups with continuous variables. Multiple logistic regression analysis was performed for frequency, adjusted age, sex, BMI, T2DM duration (Model 1), and other confounding factors (Model 2). Odds ratio (OR) and 95% confidence interval (95% CI) were calculated. RESULTS: Among 838 patients, there was a significant difference (p<0.001) in age between males (n=528, 62.8±8.7 years) and females (n=310, 65.0±8.1 years). In Model 1, compared with participants who used HWB more than seven times a week, those with poorly controlled HbA1c were significantly associated with low frequency of HWB: four to six times a week (OR 1.32, 95% CI 0.87-1.99) and less than three times a week (OR 1.43, 95% CI 0.98-2.10); p-value for overall trend was 0.041. In Model 2, p-value for overall trend was 0.138. CONCLUSION: A higher frequency of HWB was moderately associated with a decreased risk of poor glycemic control in middle-aged and elderly ambulatory patients with T2DM.

Reactivation of latent tuberculosis infection induced by cabazitaxel in a patient with prostate cancer: A case report.

RATIONALE: Latent tuberculosis infection (LTBI) describes the dormant state of tuberculosis (TB), in which persistent immune-related interaction between TB and T-cells maintain its state. Cabazitaxel (CBZ) is reported to improve overall survival in patients with castration-resistant prostate cancer (CRPC) after progression observed in regimens including docetaxel. CBZ is known for severe myelosuppression; however there is no recommendation for the treatment of LTBI before CBZ treatment. To the authors' knowledge, this is the first report to describe reactivation of LTBI induced by CBZ. PATIENT CONCERNS: A 75-year-old Japanese male with a medical history of TB since 16 years of age had been treated for prostate cancer (PC) (initial prostate-specific antigen 532 ng/ml; cT4N1M1b; Gleason score4+4) with androgen deprivation therapy, abiraterone, and docetaxel. Calcified nodules and radiological findings of LTBI were present in the upper right lobe since the diagnosis of PC. After progression was observed during these treatments, CBZ was administered combined with pegfilgrastim, long-acting granulocyte colony-stimulating factor (G-CSF). Seven days after the third course of CBZ, he was admitted to the authors' hospital to treat febrile neutropenia (FN). High fever persisted even after myelosuppression had recovered. Computed tomography (CT) revealed distribution of small nodules in the bilateral lungs, for which miliary TB was included in the differential diagnosis. T-Spot, interferon-gamma-release assay, and bronchoscopy yielded no significant findings; however, sputum and urine culture confirmed the diagnosis of TB. DIAGNOSIS: CT, sputum and urine culture confirmed the diagnosis of miliary TB. INTERVENTIONS: The patient was treated with anti-bacterial therapy (cefepime) on hospital admission, which was not effective. After the diagnosis of miliary TB was confirmed, anti-TB drugs, including isoniazid, rifampicin, pyrazinamide and ethambutol, were administered. OUTCOMES: Despite anti-TB therapy, high fever persisted and radiological findings worsened. Fifty days after the third course of CBZ, the patient died of respiratory dysfunction caused by progression of miliary TB. LESSONS: Management of LTBI is needed in cases of radiographic findings of LTBI and medical history of TB before CBZ treatment, despite the rarity of LTBI reactivation in patients with PC.

EVALUATION OF A RADON AIR MONITOR IN THE MEASUREMENT OF RADON CONCENTRATION IN WATER IN COMPARISON WITH A LIQUID SCINTILLATION COUNTER.

The World Health Organisation (WHO) recommends that the concentration of radon in water should be no more than 100 kBq m-3 (100 BqL-1) and the Codex Alimentarius Commission states that the limit of quantification (LOQ) of a method should be no more than one-fifth of this value. In this study, a degassing method with an RAD7 device was used to measure radon concentrations in water, compared to a liquid scintillation counter (LSC) method used as the reference, to investigate whether the numerical value of the LOQ of this method was more than 1/5 (20 kBq m-3) of 100 kBq m-3. The degassing method with leak prevention was shown to reach a target value of 20 kBq m-3 or less under a relative humidity of 6% or lower in the chamber of the RAD7 device. Accordingly, the RAD7 degassing method with leak prevention can be used to accurately measure radon concentrations in water within the guidance level set out by the WHO.

Relationship of daily hot water bathing at home and hot water spa bathing with underlying diseases in middle-aged and elderly ambulatory patients: A Japanese multicenter cross-sectional study.

The purpose of this study was to clarify the relationship of daily hot water bathing at home (DHW) and hot water spa bathing (HSPA) with the number of underlying diseases in middle-aged and elderly ambulatory patients. We defined the number of underlying diseases as the main outcome and dependent (criterion) variable. The frequency and time of DHW and the frequency of HSPA were set as explanatory variables. Multiple logistic regression analysis was performed for each frequency and time, adjusted age and sex. Odds ratio (OR) and 95% confidence interval (95% CI) were calculated. Among the 1261 patients who participated, there was no significant difference in age between males (n = 508, 72.8 ± 6.8 years) and females (n = 753, 73.5 ± 6.9 years). There was also no significant age difference between males (number of diseases: 2.7 ± 2.0 pts.) and females (number of diseases: 2.7 ± 2.1 pts.) in the occurrence of underlying diseases. Frequency and time of DHW were not associated with the occurrence of underlying diseases. However, compared with participants who utilized hot water spa at least once a week, the occurrence of underlying diseases was significantly associated with bathing frequency: one to three times per month (OR 2.72, 95% CI 1.63-4.52); twice or five times a year (OR 1.92, 95% CI 1.25-2.94). In conclusion, lower frequency of HSPA was significantly associated with increased risk of the occurrence of underlying diseases in middle-aged and elderly ambulatory patients. However, the relationship between proactive use of hot water spa and patients' mental and physical support should be clarified by well-designed cohort studies. The present study was registered as UMIN000033018 by the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) in Japan (refer: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000037643).

Expression of plasma membrane calcium ATPases confers Ca2+/H+ exchange in rodent synaptic vesicles.

Ca2+ transport into synaptic vesicles (SVs) at the presynaptic terminals has been proposed to be an important process for regulating presynaptic [Ca2+] during stimulation as well as at rest. However, the molecular identity of the transport system remains elusive. Previous studies have demonstrated that isolated SVs exhibit two distinct Ca2+ transport systems depending on extra-vesicular (cytosolic) pH; one is mediated by a high affinity Ca2+ transporter which is active at neutral pH and the other is mediated by a low affinity Ca2+/H+ antiporter which is maximally active at alkaline pH of 8.5. In addition, synaptic vesicle glycoprotein 2 s (SV2s), a major SV component, have been proposed to contribute to Ca2+ clearance from the presynaptic cytoplasm. Here, we show that at physiological pH, the plasma membrane Ca2+ ATPases (PMCAs) are responsible for both the Ca2+/H+ exchange activity and Ca2+ uptake into SVs. The Ca2+/H+ exchange activity monitored by acidification assay exhibited high affinity for Ca2+ (Km ~ 400 nM) and characteristic divalent cation selectivity for the PMCAs. Both activities were remarkably reduced by PMCA blockers, but not by a blocker of the ATPase that transfers Ca2+ from the cytosol to the lumen of sarcoplasmic endoplasmic reticulum (SERCA) at physiological pH. Furthermore, we rule out the contribution of SV2s, putative Ca2+ transporters on SVs, since both Ca2+/H+ exchange activity and Ca2+ transport were unaffected in isolated vesicles derived from SV2-deficient brains. Finally, using a PMCA1-pHluorin construct that enabled us to monitor cellular distribution and recycling properties in living neurons, we demonstrated that PMCA1-pHluorin localized to intracellular acidic compartments and recycled at presynaptic terminals in an activity-dependent manner. Collectively, our results imply that vesicular PMCAs may play pivotal roles in both presynaptic Ca2+ homeostasis and the modulation of H+ gradient in SVs.

Development of lentiviral vectors for efficient glutamatergic-selective gene expression in cultured hippocampal neurons.

Targeting gene expression to a particular subset of neurons helps study the cellular function of the nervous system. Although neuron-specific promoters, such as the synapsin I promoter and the α-CaMKII promoter, are known to exhibit selectivity for excitatory glutamatergic neurons in vivo, the cell type-specificity of these promoters has not been thoroughly tested in culture preparations. Here, by using hippocampal culture preparation from the VGAT-Venus transgenic mice, we examined the ability of five putative promoter sequences of glutamatergic-selective markers including synapsin I, α-CaMKII, the vesicular glutamate transporter 1 (VGLUT1), Dock10 and Prox1. Among these, a genomic fragment containing a 2.1 kb segment upstream of the translation start site (TSS) of the VGLUT1 implemented in a lentiviral vector with the Tet-Off inducible system achieved the highest preferential gene expression in glutamatergic neurons. Analysis of various lengths of the VGLUT1 promoter regions identified a segment between -2.1 kb and -1.4 kb from the TSS as a responsible element for the glutamatergic selectivity. Consistently, expression of channelrhodopsin under this promoter sequence allowed for selective light-evoked activation of excitatory neurons. Thus, the lentiviral system carrying the VGLUT1 promoter fragment can be used to effectively target exogenous gene expression to excitatory glutamatergic neurons in cultures.

The Change in Neutrophil Lymphocyte Ratio from the First to the Last Repeat Prostate Biopsy Proposed as a Marker of Carcinogenesis.

INTRODUCTION: We investigated whether the change in the neutrophil lymphocyte ratio (NLR) from the first to the last repeat prostate biopsy (ΔNLR) could be the diagnostic tool or not for prostate cancer (PCa) detection. MATERIALS AND METHODS: We retrospectively evaluated medical records of men who had undergone repeat prostate biopsy. The investigated parameters were white blood cell, neutrophil, lymphocyte counts, NLR at the last prostate biopsy, ΔNLR, prostate-specific antigen (PSA), PSA density (PSAD), and PSA velocity. Exclusion criteria were the presence of cancers other than prostate origin, medication, and diseases which induce the change of NLR. RESULTS: A total of 301 men who had undergone repeat prostate biopsy were selected for this study. After applying exclusion criteria, 223 patients were included. Of these patients, 94 were diagnosed with PCa (Group I) and 129 with no malignancy (Group II). Only a single patient had metastasis. On evaluating the area under the receiver operating characteristic curve of all study parameters, ΔNLR was the most accurate marker, followed by PSAD and then NLR measured at the last biopsy. CONCLUSIONS: ΔNLR was the most accurate marker to improve the total predictive value in repeat prostate biopsy for diagnosing PCa.

Molecular Signatures Underlying Synaptic Vesicle Cargo Retrieval.

Efficient retrieval of the synaptic vesicle (SV) membrane from the presynaptic plasma membrane, a process called endocytosis, is crucial for the fidelity of neurotransmission, particularly during sustained neural activity. Although multiple modes of endocytosis have been identified, it is clear that the efficient retrieval of the major SV cargos into newly formed SVs during any of these modes is fundamental for synaptic transmission. It is currently believed that SVs are eventually reformed via a clathrin-dependent pathway. Various adaptor proteins recognize SV cargos and link them to clathrin, ensuring the efficient retrieval of the cargos into newly formed SVs. Here, we summarize our current knowledge of the molecular signatures within individual SV cargos that underlie efficient retrieval into SV membranes, as well as discuss possible contributions of the mechanisms under physiological conditions.

Assay of Rab17 and its guanine nucleotide exchange factor Rabex-5 in the dendrites of hippocampal neurons.

Neurons are functionally and morphologically compartmentalized into axons and dendrites, and the localization of specific proteins within these compartments is critical to the proper formation of neuronal networks, which includes neurite morphogenesis and synapse formation. The small GTPase Rab17 is specifically localized in dendrites and is not found in axons, and it regulates the dendrite morphogenesis and postsynaptic development of mouse hippocampal neurons. However, the spatiotemporal regulation of Rab17 is poorly understood. We recently identified Rabex-5, originally described as a Rab5-guanine nucleotide exchange factor (GEF), as a physiological Rab17-GEF that promotes translocation of Rab17 from the cell body to the dendrites of developing hippocampal neurons. Knockdown of Rab17 in mouse hippocampal neurons resulted in reductions in dendrite growth, branch numbers, filopodium density, and active synapse numbers. Knockdown of Rab17-GEF Rabex-5 in hippocampal neurons resulted in decreased targeting of Rab17 to the dendrites, which led to a reduction in dendrite growth. In this chapter we describe the assay procedures for analyzing Rab17 and Rabex-5 in cultured mouse hippocampal neurons, and we particularly focus on the measurement of total dendrite (or axon) length and total dendrite (or axon) branch numbers, filopodium density, number of active synapses, and dendritic Rab17 signals.

Small GTPase Rab17 regulates the surface expression of kainate receptors but not α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in hippocampal neurons via dendritic trafficking of Syntaxin-4 protein.

Glutamate receptors are fundamental for control synaptic transmission, synaptic plasticity, and neuronal excitability. However, many of the molecular mechanisms underlying their trafficking remain elusive. We previously demonstrated that the small GTPase Rab17 regulates dendritic trafficking in hippocampal neurons. Here, we investigated the role(s) of Rab17 in AMPA receptor (AMPAR) and kainate receptor (KAR) trafficking. Although Rab17 knockdown did not affect surface expression of the AMPAR subunit GluA1 under basal or chemically induced long term potentiation conditions, it significantly reduced surface expression of the KAR subunit GluK2. Rab17 co-localizes with Syntaxin-4 in the soma, dendritic shaft, the tips of developing hippocampal neurons, and in spines. Rab17 knockdown caused Syntaxin-4 redistribution away from dendrites and into axons in developing hippocampal neurons. Syntaxin-4 knockdown reduced GluK2 but had no effect on GluA1 surface expression. Moreover, overexpression of constitutively active Rab17 promoted dendritic surface expression of GluK2 by enhancing Syntaxin-4 translocation to dendrites. These data suggest that Rab17 mediates the dendritic trafficking of Syntaxin-4 to selectively regulate dendritic surface insertion of GluK2-containing KARs in rat hippocampal neurons.