Syntaxin 1A Expression Research Articles

Striatal Syntaxin 1A Is Associated with Development of Tourette Syndrome in an Iminodipropionitrile-Induced Animal Model.

Tourette syndrome (TS) is a neurodevelopmental movement disorder characterized by multiple motor and vocal tics. In this study, we used a TS rat model induced by 3,3′-iminodipropionitrile (IDPN) and aimed to investigate the expression change of Syntaxin 1A (STX1A). Rats in the control group received intraperitoneal injection of normal saline, and TS rats were injected with IDPN (150 mg/kg/day). After 7 days of treatment, the stereotypic behaviors were assessed. Next, rats were sacrificed; brains were removed for RNA extraction and Western blotting analysis and fixed in 4% paraformaldehyde for immunofluorescence analysis. After 7 days of IDPN administration, stereotypic behaviors were successfully induced. The IDPN group exhibited more counts in biting, putting forepaws around mouth, licking, head twitching, shaking claws, body raising, and episodic utterance. The striatal STX1A mRNA, protein, and STX1A expression in striatal dopaminergic neurons were investigated. As expected, the total STX1A mRNA and protein levels were decreased in the TS model rats. In the striatal dopaminergic neurons, the IDPN group showed a slightly decreased STX1A/TH double positive area, but no statistical significance was found. Additionally, we assessed the expression of some genes closely related to STX1A, such as SNAP25, SY, and gephyrin, and no differences were found between the two groups. Together, reduced STX1A expression is associated with IDPN-induced TS development. Our findings suggested that decreased striatal STX1A expression is associated with the development of TS in the IDPN-induced rat model.

Down-regulation of miR-181a promotes microglial M1 polarization through increasing expression of NDRG2

Background: Microglia exist in two polarized states: a classical activation state (M1) and an alternative activation state (M2). Accumulating evidence has suggested an involvement of miR-181a in neuronal development, survival, function, and plasticity, but its exact functional role in microglial polarization still requires clarification. We investigated the impact of miR-181a on microglial polarization using a rat chronic social stress model of depression. Methods: N9 microglia were stimulated with lipopolysaccharide (LPS; 100 ng/mL ) or IL-4 (10 ng/mL ) for 12h. Expression of Nos2, Arg-1, miR-181a, and NDRG2 was determined using real-time PCR. NDRG2 and syntaxin-1A protein expressions were analyzed by western blotting. The cell viability of N2A neuron was measured by an MTT assay. Body weight gain and adrenal weight were also evaluated. Results: Five weeks of daily social defeat significantly increased Nos2 and NDRG2 mRNA expression and dramatically reduced miR-181a expression in the hippocampus. Microglia were also polarized into different functional phenotypes. LPS treatment significantly enhanced mRNA expression of Nos2 and dramatically inhibited the expression of miR-181a. Conversely, treatment with IL-4 markedly increased the mRNA levels of Arg-1 and the expression of miR-181a. Expression of miR-181a regulated microglia differentiation by targeting NDRG2, while inhibition of miR-181a expression in N9 microglia induced N2A neuron death, which could be reversed by NDRG2 interference. Overexpression of miR-181a overcame the impacts of chronic psychosocial stress on body weight gain, adrenal weight, and syntaxin-1A expression in the hippocampus. Conclusion: Down-regulation of miR-181a promoted microglial M1 polarization by enhancing NDRG2 expression. Keywords: miR-181a, microglial M1 polarization, NDRG2

Omega-3 modulates anxiety and improves autistic like features induced by high fat diet but not valproate

Backgroundcontinuous consumption of high-fat diet (HFD) during pregnancy and lactation could alter developmental complexity of higher brain functions and enhance appearance of social withdrawal and anxiety among offsprings. On the contrary, omega-3 fatty acids with its multi-neuro-protective effects could limit oxidative stress production and complications. We aimed to investigate the impact of HFD intake before and during pregnancy till weaning versus prenatal exposure to valproate (as a model of autism) on behavior and brain neurochemistry as well as the possible therapeutic rational of omega-3 intake. Material and methodsAfter confirmation of G0 day of pregnancy, thirty Sprague–Dawley female rats were divided into: control group fed normal chow (10 kcal% from fat), group II (HFD) mothers supplied with diet of 60 kcal% from fat and group III (HFD-Omega) supplied with 60% HFD enriched with omega-3, group IV (Valp) pregnant females received sodium valproate once i.p, and group V (Valp-Omega) rats received valproate once i.p and diet enriched with omega-3. From day 7 till end of the study, offsprings were subjected to growth, neurodevelopmental assessment and behavioral tests using elevated plus maze and social interaction in open field. Levels of serotonin, GABA, neuropeptide Y, IL-6 and relative gene expression of syntaxin1A and FoxO1 gene were measured. ResultsOffsprings born to HFD and Valp-groups demonstrated growth retardation, social withdrawal together with disturbed levels of measured neurotransmitter that were improved in HFD group supplied with omega-3. ConclusionOmega-3 exhibited to be potential modulator of behavioral changes and autistic-like features induced by HFD.

Abstract 5079: Role of syntaxin-1A, a synaptic-related protein, in HER2-enriched and luminal B breast cancer progression

Abstract Breast cancer (BC) is the most prevalent cancer in women. It can be classified into 4 subtypes according to their gene expression signature, each one characterized by its aggressiveness and treatment approach. Mortality has declined as a result of earlier diagnoses and the availability of adjuvant therapies. However, a significant number of patients do not respond to these therapies or develop resistance after an initial response. The therapies currently available fail at curing or preventing BC tumor progression and metastasis. Therefore, there is an urgent need to develop novel therapeutic tools to improve BCs patients´ survival rates. The interaction of cancer cells with the stroma has been well established and has led to exciting new therapies. However, the presence and relevance of nerve axons and their secreted neurotransmitters and neuropeptides in the tumor microenvironment has been acknowledged only very recently. We have identified 6 nervous system related genes differentially expressed in BC subtypes. Among them, Syntaxin-1A (STX1A) is up-regulated in luminal B and HER2-enriched tumors, and its expression significantly correlates with a shorter overall survival and metastasis free survival. Therefore, we hypothesized that STX1A regulates luminal B and HER2 enriched tumors progression and metastasis development. STX1A belongs to the soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins superfamily that regulate membrane fusion events, including exocytosis and neurotransmission, intracellular trafficking, and cell proliferation. To test its role in breast cancer we have characterized STX1A pathway in a panel of BC cells. Our results showed that STX1A is overexpressed in luminal B and HER2-enriched cell lines at protein and mRNA level, as we have seen in patient's database. Moreover we have analyzed STX1A expression in cell lines that were derived either from lung or brain metastases respectively and we have discovered that the cells that have migrated to the brain or to the lung have increased STX1A expression in comparison to the parentals. Moreover, downregulation of STX1A using siRNA results in inhibition of epithelial to mesenchymal markers, such as Twist-1, indicating a possible role of STX1A in tumor cell migration and metastasis. Furthermore, downregulation of STX1A also represses FGFR2 activation, suggesting that STX1A might regulate tyrosine kinase receptors membrane trafficking. In conclusion we propose STXIA and SNARE proteins as potential biomarkers and targets for novel BC therapy. Citation Format: Aleix Noguera-Castells, Leire Recalde-Percaz, Núria Moragas, Patricia Fernández-Nogueira, Gemma Fuster, Anna López-Plana, Patricia Jauregui, Pere Gascón, Paloma Bragado, Mario Mancino. Role of syntaxin-1A, a synaptic-related protein, in HER2-enriched and luminal B breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5079.

Diet‐induced β‐cell insulin resistance results in reversible loss of functional β‐cell mass

Although convincing in genetic models, the relevance of β-cell insulin resistance in diet-induced type 2 diabetes (T2DM) remains unclear. Exemplified by diabetes-prone, male, C57B1/6J mice being fed different combinations of Western-style diet, we show that β-cell insulin resistance occurs early during T2DM progression and is due to a combination of lipotoxicity and increased β-cell workload. Within 8 wk of being fed a high-fat, high-sucrose diet, mice became obese, developed impaired insulin and glucose tolerances, and displayed noncompensatory insulin release, due, at least in part, to reduced expression of syntaxin-1A. Through reporter islets transplanted to the anterior chamber of the eye, we demonstrated a concomitant loss of functional β-cell mass. When mice were changed from diabetogenic diet to normal chow diet, the diabetes phenotype was reversed, suggesting a remarkable plasticity of functional β-cell mass in the early phase of T2DM development. Our data reinforce the relevance of diet composition as an environmental factor determining different routes of diabetes progression in a given genetic background. Employing the in vivo reporter islet–monitoring approach will allow researchers to define key times in the dynamics of reversible loss of functional β-cell mass and, thus, to investigate the underlying, molecular mechanisms involved in the progression toward T2DM manifestation.—Paschen, M., Moede, T., Valladolid-Acebes, I., Leibiger, B., Moruzzi, N., Jacob, S., García-Prieto, C. F., Brismar, K., Leibiger, I. B., Berggren, P.-O. Diet-induced β-cell insulin resistance results in reversible loss of functional β-cell mass.

MiR-34a-5p mediates sevoflurane preconditioning induced inhibition of hypoxia/reoxygenation injury through STX1A in cardiomyocytes

Anesthetic preconditioning is a cellular protective approach whereby exposure to a volatile anesthetic renders cardio injury. Sevoflurane preconditioning has been shown to exhibit cardio protective effect on hypoxia/reoxygenation (H/R) injury, but the underlying mechanism is unclear. Syntaxin 1A (STX1A), an important regulator in cardio disease, was predicted to be the target gene of microRNA-34a-5p (miR-34a-5p). The current research was designed to delineate the role of miR-34a-5p in regulating sevoflurane preconditioning in cardiomyocytes injury. In this study, the results demonstrated that the expression of STX1A was significantly increased, while miR-34a-5p was dramatically decreased in sev-preconditioning H9c2 cells as compared with cells only under H/R stimulation. Moreover, miR-34a-5p regulated the protective effect of sev-preconditioning in injured H9c2 cells by mediating cell proliferation and cell apoptosis. Additionally, the luciferase report confirmed the targeting reaction between STX1A and miR-34a-5p. Taken together, our study suggested that miR-34a-5p regulated sev-preconditioning induced inhibition of hypoxia/reoxygenation injury through mediating STX1A, provided a potential therapeutic target for anesthetic protection in cardio disease.

MTORC1 Is a Local, Postsynaptic Voltage Sensor Regulated by Positive and Negative Feedback Pathways.

The mammalian/mechanistic target of rapamycin complex 1 (mTORC1) serves as a regulator of mRNA translation. Recent studies suggest that mTORC1 may also serve as a local, voltage sensor in the postsynaptic region of neurons. Considering biochemical, bioinformatics and imaging data, we hypothesize that the activity state of mTORC1 dynamically regulates local membrane potential by promoting and repressing protein synthesis of select mRNAs. Our hypothesis suggests that mTORC1 uses positive and negative feedback pathways, in a branch-specific manner, to maintain neuronal excitability within an optimal range. In some dendritic branches, mTORC1 activity oscillates between the “On” and “Off” states. We define this as negative feedback. In contrast, positive feedback is defined as the pathway that leads to a prolonged depolarized or hyperpolarized resting membrane potential, whereby mTORC1 activity is constitutively on or off, respectively. We propose that inactivation of mTORC1 increases the expression of voltage-gated potassium alpha (Kv1.1 and 1.2) and beta (Kvβ2) subunits, ensuring that the membrane resets to its resting membrane potential after experiencing increased synaptic activity. In turn, reduced mTORC1 activity increases the protein expression of syntaxin-1A and promotes the surface expression of the ionotropic glutamate receptor N-methyl-D-aspartate (NMDA)-type subunit 1 (GluN1) that facilitates increased calcium entry to turn mTORC1 back on. Under conditions such as learning and memory, mTORC1 activity is required to be high for longer periods of time. Thus, the arm of the pathway that promotes syntaxin-1A and Kv1 protein synthesis will be repressed. Moreover, dendritic branches that have low mTORC1 activity with increased Kv expression would balance dendrites with constitutively high mTORC1 activity, allowing for the neuron to maintain its overall activity level within an ideal operating range. Finally, such a model suggests that recruitment of more positive feedback dendritic branches within a neuron is likely to lead to neurodegenerative disorders.

Protective action of B1R antagonist against cerebral ischemia-reperfusion injury through suppressing miR-200c expression of Microglia-derived microvesicles

Background and objective: Cerebral ischemia–reperfusion (I/R) injury is a common side-effect for cerebral ischemic disease and its therapeutic regimen is limited. Kinin is pro-inflammatory peptide that is released and acts at the site of injury and inflammation such as brain and it works through bradykinin 1 receptor (B1R). The present study was to examine the effect of B1R antagonist on cerebral I/R injury and the potential mechanism.Methods: Cerebral I/R injury was induced in mice by transient middle cerebral artery occlusion (MCAO). Neurological function was assessed by Bederson score. Infarct volumes were measured using planimetry. In vitro cell model was made by oxygen-glucose deprivation-Hypoxia/Reoxygenation (OGD-H/R) treatment to N9 microglia cell; and the cultured medium was collected for microvesicles (MVs) isolation and subsequent co-cultured with HT22 cell for sake of assessing their function on neural cell. Relative expression of miR-200c was determined by real time quantitative PCR. Dual luciferase reporter assay was performed to detect the regulatory function of miR-200c to syntaxin-1A.Results: R715 (B1R antagonist) treatment (500 μg/kg) improves neurologic function after cerebral I/R injury indicated by the decrease of Bederson score and infarct volume. MVs from OGD-H/R treated-N9 cell attenuated neural HT22 cell viability, treatment with LDBK (B1R agonist) accelerated the suppression of HT22 resulted from OGD-H/R; whereas this attenuation was partly weakened by B1R antagonist pretreatment (100 nmol/L). At the same time, B1R antagonist pretreatment caused downregulation of miR-200c in N9 cell and N9-derived MVs, and contributed to syntaxin-1A over expression in HT22 cell. Result of luciferase reporter assay suggested that miR-200c can regulate syntaxin-1A expression. MVs from miR-200c knockdown N9 cells medium had the same effect of B1R antagonist that caused the upregulation of syntaxin-1A and improved OGD-H/R-induced reduction of HT22 cell viability.Conclusion: Our data suggested that blockage of B1R by B1R antagonist provides neuroprotection action through suppressing signaling delivery of microglia-MVs-miR-200c to neural cell.

Abstract 5007: Differential expression of neurogenes among breast cancer subtypes identifies high risk patients

Abstract The nervous system is now recognized to be a relevant component of the tumor microenvironment. Receptors for neuropeptides and neurotransmitters have been identified in breast cancer. However, very little is known about the role of neurogenes in regulating breast cancer progression. Our purpose was to identify neurogenes associated with breast cancer tumorigenesis with a potential to be used as biomarker and/or targets for treatment. We used three databases of human genes: GeneGo, GeneCards and Eugenes to generate a list of 1266 relevant neurogenes. Then we used bioinformatics tools to interrogate two published breast cancer databases SAGE and MicMa (n = 96) and generated a list of 7 neurogenes that are differentially express among breast cancer subtypes. The clinical potential was further investigated using the GOBO database (n = 1881). We identified 6 neurogenes that are differentially expressed among breast cancer subtypes and whose expression correlates with prognosis. Histamine receptor1 (HRH1), neuropilin2 (NRP2), ephrin-B1 (EFNB1), neural growth factor receptor (NGFR) and amyloid precursor protein (APP) were differentially overexpressed in basal and HER2-enriched tumor samples and syntaxin 1A (STX1A) was overexpressed in HER2-enriched and luminal B tumors. Analysis of HRH1, NRP2, and STX1A expression using the GOBO database showed that their expression significantly correlated with a shorter overall survival (p<0.0001) and distant metastasis-free survival (p<0.0001). In contrast, elevated co-expression of NGFR, EFNB1 and APP was associated with longer overall (p<0.0001) and metastasis-free survival (p<0.0001). We propose that HRH1, NRP2, and STX1A can be used as prognostic biomarkers and therapeutic targets for basal and HER2-enriched breast cancer subtypes. Citation Format: Mario Mancino. Differential expression of neurogenes among breast cancer subtypes identifies high risk patients. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5007.

Differential expression of neurogenes among breast cancer subtypes identifies high risk patients.

The nervous system is now recognized to be a relevant component of the tumor microenvironment. Receptors for neuropeptides and neurotransmitters have been identified in breast cancer. However, very little is known about the role of neurogenes in regulating breast cancer progression. Our purpose was to identify neurogenes associated with breast cancer tumorigenesis with a potential to be used as biomarker and/or targets for treatment. We used three databases of human genes: GeneGo, GeneCards and Eugenes to generate a list of 1266 relevant neurogenes. Then we used bioinformatics tools to interrogate two published breast cancer databases SAGE and MicMa (n=96) and generated a list of 7 neurogenes that are differentially express among breast cancer subtypes. The clinical potential was further investigated using the GOBO database (n=1881). We identified 6 neurogenes that are differentially expressed among breast cancer subtypes and whose expression correlates with prognosis. Histamine receptor1 (HRH1), neuropilin2 (NRP2), ephrin-B1 (EFNB1), neural growth factor receptor (NGFR) and amyloid precursor protein (APP) were differentially overexpressed in basal and HER2-enriched tumor samples and syntaxin 1A (STX1A) was overexpressed in HER2-enriched and luminal B tumors. Analysis of HRH1, NRP2, and STX1A expression using the GOBO database showed that their expression significantly correlated with a shorter overall survival (p < 0.0001) and distant metastasis-free survival (p < 0.0001). In contrast, elevated co-expression of NGFR, EFNB1 and APP was associated with longer overall (p < 0.0001) and metastasis-free survival (p < 0.0001). We propose that HRH1, NRP2, and STX1A can be used as prognostic biomarkers and therapeutic targets for basal and HER2-enriched breast cancer subtypes.

NDRG2 promoted secreted miR-375 in microvesicles shed from M1 microglia, which induced neuron damage

BackgroundMicroglia microvesicles (MVs) has shown to have significant biological functions under normal conditions. A diversity of miRNAs is involved in neuronal development, survival, function, and plasticity, but the exact functional role of NDRG2 and secreted miR-375 in MVs in neuron damage is poorly understood. We investigated the effect of NDRG2 and secreted miR-375 in MVs shed from M1 microglia on neuron damage. MethodsExpression of Nos2, Arg-1, miR-375, syntaxin-1A, NDRG2 and Pdk 1 were evaluated using RT-PCR or western blotting. Cell viability of N2A neuron was quantified by a MTT assay. ResultsMicroglia can be polarized into different functional phenotypes. Expression of NDRG2 and Nos2 were significantly increased by LPS treatment on N9 cells, whereas treatment with IL-4 dramatically suppressed the expression of NDRG2 and remarkably elevated expression of Arg-1. Besides, MVs shed from LPS-treated N9 microglia significantly inhibited cell viability of N2A neurons and expression of syntaxin-1A, and NDRG2 interference reversed the up-regulated miR-375 in LPS-treated N9 microglia and MVs shed from LPS-treated N9 cells. Furthermore, NDRG2 could modulate miR-375 expression in N9 microglia and MVs. And miR-375 inhibitor remarkably elevated Pdk1 expression in N2A neurons. Finally, miR-375 inhibitor could reverse suppression effect of NDRG2 overexpression on cell viability of N2A neurons and expression of syntaxin-1A. ConclusionOur results demonstrated that NDRG2 promoted secreted miR-375 in microvesicles shed from M1 microglia, which induced neuron damage. The suppression of NDRG2 and secreted miR-375 in MVs shed from M1 microglia may be potential targets for alleviation of neuron damage.

Long-term disruption of maternal glucose homeostasis induced by prenatal glucocorticoid treatment correlates with miR-29 upregulation

Excess of glucocorticoids (GCs) during pregnancy is strongly associated with the programming of glucose intolerance in the offspring. However, the impact of high GC levels on maternal metabolism is not clearly documented. This study aimed to test the hypothesis that mothers exposed to elevated levels of GCs might also display long-term disturbances in glucose homeostasis. Dexamethasone (DEX) was administered noninvasively to the mothers via drinking water between the 14th and the 19th days of pregnancy. Mothers were subjected to glucose and insulin tolerance tests at 1, 2, 3, 6, and 12 mo postweaning. Pregnant rats not treated with DEX and age-matched virgin rats were used as controls. Pancreatic islets were isolated at the 20th day of pregnancy and 12 mo postweaning in order to evaluate glucose-stimulated insulin secretion. The expression of the miR-29 family was also studied due to its responsiveness to GCs and its well-documented role in the regulation of pancreatic β-cell function. Rats treated with DEX during pregnancy presented long-term glucose intolerance and impaired insulin secretion. These changes correlated with 1) increased expression of miR-29 and its regulator p53, 2) reduced expression of syntaxin-1a, a direct target of miR-29, and 3) altered expression of genes related to cellular senescence. Our data demonstrate that the use of DEX during pregnancy results in deleterious outcomes to the maternal metabolism, hallmarked by reduced insulin secretion and glucose intolerance. This maternal metabolic programming might be a consequence of time-sustained upregulation of miR-29s in maternal pancreatic islets.

Functional Plasticity of the Human Infant β-Cell Exocytotic Phenotype

Our understanding of adult human β-cells is advancing, but we know little about the function and plasticity of β-cells from infants. We therefore characterized islets and single islet cells from human infants after isolation and culture. Although islet morphology in pancreas biopsies was similar to that in adults, infant islets after isolation and 24-48 hours of culture had less insulin staining, content, and secretion. The cultured infant islets expressed pancreatic and duodenal homeobox 1 and several (Glut1, Cav1.3, Kir6.2) but not all (syntaxin 1A and synaptosomal-associated protein 25) markers of functional islets, suggesting a loss of secretory phenotype in culture. The activity of key ion channels was maintained in isolated infant β-cells, whereas exocytosis was much lower than in adults. We examined whether a functional exocytotic phenotype could be reestablished under conditions thought to promote β-cell differentiation. After a 24- to 28-day expansion and maturation protocol, we found preservation of endocrine markers and hormone expression, an increased proportion of insulin-positive cells, elevated expression of syntaxin 1A and synaptosomal-associated protein 25, and restoration of exocytosis to levels comparable with that in adult β-cells. Thus, human infant islets are prone to loss of their exocytotic phenotype in culture but amenable to experimental approaches aimed at promoting expansion and functional maturation. Control of exocytotic protein expression may be an important mechanism underlying the plasticity of the secretory machinery, an increased understanding of which may lead to improved regenerative approaches to treat diabetes.

SNAREpin Assembly by Munc18-1 Requires Previous Vesicle Docking by Synaptotagmin 1

Regulated exocytosis requires the general membrane fusion machinery-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) and Sec1/Munc18 (SM) proteins. Using reconstituted giant unilamellar vesicles containing preassembled t-SNARE proteins (syntaxin 1·SNAP-25), we determined how Munc18-1 controls the docking, priming, and fusion of small unilamellar vesicles containing the v-SNARE VAMP2 and the Ca(2+) sensor synaptotagmin 1. In vitro assays allowed us to position Munc18-1 in the center of a sequential reaction cascade; vesicle docking by synaptotagmin 1 is a prerequisite for Munc18-1 to accelerate trans-SNARE complex (SNAREpin) assembly and membrane fusion. Complexin II stalls SNAREpin zippering at a late stage and, hence, contributes to synchronize membrane fusion in a Ca(2+)- and synaptotagmin 1-dependent manner. Thus, at the neuronal synapse, the priming factor Munc18-1 may accelerate the conversion of docked synaptic vesicles into a readily releasable pool by activating SNAREs for efficient membrane fusion.

Replication study of Japanese cohorts supports the role of STX1A in autism susceptibility

Autism is a pervasive developmental disorder diagnosed in early childhood. Abnormalities of serotonergic neurotransmission have been reported in autism. Serotonin transporter (5-HTT), which modulates serotonin levels, is a major therapeutic target in autism. Therefore, factors that regulate 5-HTT expression might be implicated in autism. One candidate 5-HTT-regulatory protein is the presynaptic protein, syntaxin 1A (STX1A). We examined the association of STX1A with autism in a trio association study using DNA samples from Japanese trios with autistic probands. In TDT analysis, rs69510130 (p=0.027) showed nominal associations with autism; modest haplotype association was also observed. We further compared STX1A mRNA expression between the autistic and control groups in the postmortem brain. In the anterior cingulate gyrus region, STX1A expression in the autism group was found to be significantly lower than that of the control group. Thus, we suggest a possible role of STX1A in the pathogenesis of autism.

Deletion of Fas in the pancreatic β-cells leads to enhanced insulin secretion

Fas/Fas ligand belongs to the tumor necrosis factor superfamily of receptors/ligands and is best known for its role in apoptosis. However, recent evidence supports its role in other cellular responses, including proliferation and survival. Although Fas has been implicated as an essential mediator of beta-cell death in the pathogenesis of type 1 diabetes, the essential role of Fas specifically in pancreatic beta-cells has been found to be controversial. Moreover, the role of Fas on beta-cell homeostasis and function is not clear. The objective of this study is to determine the role of Fas specifically in beta-cells under both physiological and diabetes models. Mice with Fas deletion specifically in the beta-cells were generated using the Cre-loxP system. Cre-mediated Fas deletion was under the control of the rat insulin promoter. Absence of Fas in beta-cells leads to complete protection against FasL-induced cell death. However, Fas is not essential in determining beta-cell mass or susceptibility to streptozotocin- or HFD-induced diabetes. Importantly, Fas deletion in beta-cells leads to increased p65 expression, enhanced glucose tolerance, and glucose-stimulated insulin secretion, with increased exocytosis as manifested by increased changes in membrane capacitance and increased expression of Syntaxin1A, VAMP2, and munc18a. Together, our study shows that Fas in the beta-cells indeed plays an essential role in the canonical death receptor-mediated apoptosis but is not essential in regulating beta-cell mass or diabetes development. However, beta-cell Fas is critical in the regulation of glucose homeostasis through regulation of the exocytosis machinery.

Genetic and expression analyses reveal elevated expression of syntaxin 1A ( STX1A) in high functioning autism

Autism is a pervasive developmental disorder diagnosed in early childhood. Abnormalities of serotonergic neurotransmission have been reported in autism. Serotonin transporter (5-HTT), which modulates serotonin levels, is a major therapeutic target in autism. Therefore, factors that regulate 5-HTT expression might be implicated in autism. One candidate 5-HTT-regulatory protein is the presynaptic protein, syntaxin 1A (STX1A). We examined the association of STX1A with autism in a trio association study using DNA samples from 249 AGRE trios with autistic probands. Only male probands were selected, since autism is more prevalent among males. The probands of 102 trios had IQ>70, and were considered as high functioning autism (HFA). In transmission disequilibrium test (TDT) analysis, rs2293485 (p=0.034) and rs4717806 (p=0.033) showed nominal associations with HFA; modest haplotype association was also observed. The SNPs that showed associations were related to early developmental abnormalities (ADI-R_D). We further compared STX1A mRNA expression in the lymphocytes of drug-naive HFA patients (n=12) and age- and sex-matched controls (n=13). STX1A expression in the HFA group was significantly higher (p=0.001) than that of controls. Thus, we suggest a possible role of STX1A in the pathogenesis of HFA. During early childhood, there is a period of high brain serotonin synthesis that is disrupted in autistic children; STX1A might influence the serotonergic system during this stage of neurodevelopment, as implied by the association with ADI-R_D.

Sepsis affects the expression of Syntaxin1A and Norepinephrine transporter in the myocardium

Activation of the sympathetic nervous system leads to an increase release of norepinephrine (NE) during sepsis. Re‐uptake of NE by the NET (NE Transporter) protein is the primary mechanism by which the biological effects of NE in the synapse are terminated. A SNARE protein, Syntaxin 1A plays a major role in presynaptic regulatory mechanism linking neurotransmitter secretion to neurotransmitter reuptake activity. However the role of Syntaxin 1A in the regulation of NE in septic heart is not known. Therefore, in the present study the effect of increased duration of sepsis on the expression of syntaxin1A and NET in heart was elucidated. Male Sprague‐Dawley rats (300–350g) were randomized into sham, 1‐, 3‐ and 7‐day sepsis groups. Sepsis and sham‐sepsis was induced using 200mg/kg cecal inoculum and 5% dextrose water i.p., respectively. Hearts were isolated to perform the RT‐PCR and immunoblot analyses for Syntaxin 1A and NET levels. Syntaxin 1A mRNA as well as protein expression increased significantly at 1‐day, while reduced at 3‐ and 7‐day post‐sepsis. NET gene expression was not altered significantly in septic animals but NET protein expression was decreased (61%) in 3‐day post‐sepsis group. We also observed increased NE levels (50% compared to sham) at 1‐day post‐sepsis. The data suggest that the elevation of Syntaxin 1A could be responsible for an increased level of myocardial NE at 1‐day post‐sepsis. Disruption of the transporter function at 3‐day post‐sepsis may lead to an extraneuronal accumulation of the previously released NE in the heart. (This work was supported by NHLBI # 66016).

Interaction of Syntaxin 1A with the N-Terminus of Kv4.2 Modulates Channel Surface Expression and Gating

Kv4.2 channels are responsible in the heart for the Ca2+-independent transient outward currents and are important in regulating myocardial excitability and Ca2+ homeostasis. We have identified previously the expression of syntaxin 1A (STX1A) on the cardiac ventricular myocyte plasma membranes, and its modulation of cardiac ATP-sensitive K+ channels. We speculated that STX1A interacts with other cardiac ion channels, thus we examined the interaction of STX1A with Kv4.2 channels. Co-immunoprecipitation and GST pulldown assays demonstrated a direct interaction of STX1A with the Kv4.2 N-terminus. We next investigated the functional alterations of Kv4.2 gating by STX1A in Xenopus oocytes. Coexpression of Kv4.2 with STX1A (1) resulted in a reduction of Kv4.2 current amplitude; (2) caused a depolarizing shift of the steady-state inactivation curve; (3) enhanced the rate of current decay; and (4) accelerated the rate of recovery from inactivation. Additional coexpression of botulinum neurotoxin C, which cleaves STX1A, reversed the effects of STX1A on Kv4.2. STX1A inhibited partially the gating changes by KChIP2, suggesting a competitive interaction of these proteins for an overlapping binding region on the N-terminus of Kv4.2. Indeed, the N-terminal truncation mutants of Kv4.2 (Kv4.2Delta2-40 and Kv4.2Delta7-11), which form part of the KChIP2 binding site, displayed reduced sensitivity to STX1A modulation. Our study suggests that STX1A directly modulates Kv4.2 current amplitude and gating through its interaction with an overlapping region of the KChIP binding motif domain on the Kv4.2 N-terminus.

Endocytotic Function for Syntaxin 1A

Syntaxin 1A is a plasma membrane protein of the SNARE (soluble N -ethylmaleimide-sensitive factor attachment protein receptor) family, well known for its essential roles in neuronal signaling in which it regulates trafficking, docking, and fusion of synaptic vesicles with the plasma membrane. Experiments from Yu et al . show that syntaxin 1A also has a role in internalization of vesicles containing a transporter for the neurotransmitter glutamate. Transport of glutamate is important to prevent excessive stimulation of glutamate receptors and to maintain the supply of glutamate for conversion to the inhibitory neurotransmitter GABA (γ-aminobutyric acid). Yu et al . showed that in rat C6 glioma cells, expression of transfected syntaxin 1A decreased glutamate transport and the abundance of the glutamate transporter EAAC1 (excitatory amino acid carrier 1) at the cell surface. Depletion of syntaxin 1A with small interference RNA increased the abundance of EEAC1 at the cell surface and increased glutamate transport. Excessive stimulation of cells with the glutamatergic agonist kainic acid (KA) reproduces effects seen in epilepsy. The authors tracked biotinylated EAAC1 in KA-treated cells and found that suppression of syntaxin 1A expression reduced KA-stimulated internalization of EAAC1 into an endosomal or lysosomal compartment. The results suggest, as the authors put it, that syntaxin 1A must now be considered to regulate "both the ‘ins’ and the ‘outs’ of synaptic neurotransmission." Y.-X. Yu, L. Shen, P. Xia, Y.-W. Tang, L. Bao, G. Pei, Syntaxin 1A promotes the endocytic sorting of EAAC1 leading to inhibition of glutamate transport. J. Cell Sci. 119 , 3776-3787 (2006). [Abstract] [Full Text]