Syntaxin Research Articles

Exercise facilitates the action of dietary DHA on functional recovery after brain trauma

The abilities of docosahexaenoic acid (DHA) and exercise to counteract cognitive decay after traumatic brain injury (TBI) is getting increasing recognition; however, the possibility that these actions can be complementary remains just as an intriguing possibility. Here we have examined the likelihood that the combination of diet and exercise has the added potential to facilitate functional recovery following TBI. Rats received mild fluid percussion injury (mFPI) or sham injury and then were maintained on a diet high in DHA (1.2% DHA) with or without voluntary exercise for 12days. We found that FPI reduced DHA content in the brain, which was accompanied by increased levels of lipid peroxidation assessed using 4-hydroxy-2-hexenal (4-HHE). FPI reduced the enzymes acyl-CoA oxidase 1 (Acox1) and 17β-hydroxysteroid dehydrogenase type 4 (17β-HSD4), and the calcium-independent phospholipases A2 (iPLA2), which are involved in metabolism of membrane phospholipids. FPI reduced levels of syntaxin-3 (STX-3), involved in the action of membrane DHA on synaptic membrane expansion, and also reduced brain-derived neurotrophic factor (BDNF) signaling through its tyrosine kinase B (TrkB) receptor. These effects of FPI were optimally counteracted by the combination of DHA and exercise. Our results support the possibility that the complementary action of exercise is exerted on restoring membrane homeostasis after TBI, which is necessary for supporting synaptic plasticity and cognition. It is our contention that strategies that take advantage of the combined applications of diet and exercise may have additional effects to the injured brain.

T-SNARE Syntaxin2 (STX2) Is Implicated in Intracellular Transport of Sulfoglycolipids During Meiotic Prophase in Mouse Spermatogenesis

Syntaxin2 (STX2), also known as epimorphin, is a member of the SNARE family of proteins, with expression in various types of cells. We previously identified an ENU-induced mutation, repro34, in the mouse Stx2 gene. The Stx2(repro34) mutation causes male-restricted infertility due to syncytial multinucleation of spermatogenic cells during meiotic prophase. A similar phenotype is also observed in mice with targeted inactivation of Stx2, as well as in mice lacking enzymes involved in sulfoglycolipid synthesis. Herein we analyzed expression and subcellular localization of STX2 and sulfoglycolipids in spermatogenesis. The STX2 protein localizes to the cytoplasm of germ cells at the late pachytene stage. It is found in a distinct subcellular pattern, presumably in the Golgi apparatus of pachytene/diplotene spermatocytes. Sulfoglycolipids are produced in the Golgi apparatus and transported to the plasma membrane. In Stx2(repro34) mutants, sulfoglycolipids are aberrantly localized in both pachytene/diplotene spermatocytes and in multinucleated germ cells. These results suggest that STX2 plays roles in transport and/or subcellular distribution of sulfoglycolipids. STX2 function in the Golgi apparatus and sulfoglycolipids may be essential for maintenance of the constriction between neighboring developing spermatocytes, which ensures ultimate individualization of germ cells in later stages of spermatogenesis.

Syntaxin-3 regulates newcomer insulin granule exocytosis and compound fusion in pancreatic beta cells

The molecular basis of the exocytosis of secretory insulin-containing granules (SGs) during biphasic glucose-stimulated insulin secretion (GSIS) from pancreatic beta cells remains unclear. Syntaxin (SYN)-1A and SYN-4 have been shown to mediate insulin exocytosis. The insulin-secretory function of SYN-3, which is particularly abundant in SGs, is unclear. Mouse pancreatic islets and INS-1 cells were treated with adenovirus carrying Syn-3 (also known as Stx3) or small interfering RNA targeting Syn-3 in order to examine insulin secretion by radioimmunoassay. The localisation and distribution of insulin granules were examined by confocal and electron microscopy. Dynamic single-granule fusion events were assessed using total internal reflection fluorescence microscopy (TIRFM). Depletion of endogenous SYN-3 inhibited insulin release. TIRFM showed no change in the number or fusion competence of previously docked SGs but, instead, a marked reduction in the recruitment of newcomer SGs and their subsequent exocytotic fusion during biphasic GSIS. Conversely, overexpression of Syn-3 enhanced both phases of GSIS, owing to the increase in newcomer SGs and, remarkably, to increased SG-SG fusion, which was confirmed by electron microscopy. In insulin secretion, SYN-3 plays a role in the mediation of newcomer SG exocytosis and SG-SG fusion that contributes to biphasic GSIS.

Phosphatidylinositol 4,5-biphosphate (PIP(2)) lipids regulate the phosphorylation of syntaxin N-terminus by modulating both its position and local structure.

Syntaxin (STX) is a N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein that binds to the plasma membrane and regulates ion channels and neurotransmitter transporters. Experiments have established the involvement of the N-terminal segment of STX in direct protein–protein interactions and have suggested a critical role for the phosphorylation of serine 14 (S14) by casein kinase-2 (CK2). Because the organization of STX in the plasma membrane was shown to be regulated by phosphatidylinositol 4,5-biphosphate (PIP2) lipids, we investigated the mechanistic involvement of PIP2 lipids in modulating both the membrane interaction and the phosphorylation of STX, using a computational strategy that integrates mesoscale continuum modeling of protein–membrane interactions, with all-atom molecular dynamics (MD) simulations. Iterative applications of this protocol produced quantitative evaluations of lipid-type demixing due to the protein and identified conformational differences between STX immersed in PIP2-containing and PIP2-depleted membranes. Specific sites in STX were identified to be important for the electrostatic interactions with the PIP2 lipids attracted to the protein, and the segregation of PIP2 lipids near the protein is shown to have a dramatic effect on the positioning of the STX N-terminal segment with respect to the membrane/water interface. This PIP2-dependent repositioning is shown to modulate the extent of exposure of S14 to large reagents representing the CK2 enzyme and hence the propensity for phosphorylation. The prediction of STX sites involved in such PIP2-dependent regulation of STX phosphorylation at S14 offers experimentally testable probes of the mechanisms and models presented in this study, through structural modifications that can modulate the effects.

Aberrant localization of fusion receptors involved in regulated exocytosis in salivary glands of Sjögren’s syndrome patients is linked to ectopic mucin secretion

Sjögren’s syndrome (SS) is a chronic inflammatory autoimmune disease that mainly affects tear and salivary glands, whereby SS-patients frequently complain of eye and mouth dryness. Salivary acinar cells of SS-patients display alterations in their cell polarity; which may affect the correct localization and function of proteins involved in regulated exocytosis. Here we determined whether the expression and localization of SNARE proteins (membrane fusion receptors) involved in regulated secretion, such as VAMP8, syntaxin 3 (STX3), STX4 and SNAP-23 were altered in salivary glands (SG) from SS-patients. Additionally, we investigated SNARE proteins function, by evaluating their ability to form SNARE complexes under basal conditions. In SG from SS-patients and control subjects mRNA and proteins levels of SNARE complex components were determined by real-time PCR and Western blotting, respectively. SNARE protein distribution and mucin exocytosis were determined by indirect immunofluorescence. In SS-patients, the expression levels of mRNA and protein for VAMP8, STX4 and STX3 were altered. STX4, STX3, SNAP-23 and VAMP8 relocated from the apical to the basal region of acinar cells. Increased formation of SNARE complexes in a manner independent of external stimuli for secretion was detected. Mucins were detected in the extracellular matrix (ECM). Presence of mucins in the ECM, together with the observed alterations in SNARE protein localization is indicative of ectopic exocytosis. In the context of SS, such aberrantly localized mucins are likely to favor a pro-inflammatory response, which may represent an important initial step in the pathogenesis of this disease.

Synaptobrevin Trans-Membrane Domain forms a Complex that Enhances the Rate of “Stalk” and Pore Formation in PEG-Mediated Vesicle Fusion

Synaptobrevin (SB), a membrane anchored protein in the neuronal cell membrane, complexes with syntaxin (SX) and SNAP-25 to facilitate membrane fusion in neurotransmitter release. SB and SX promote Poly(ethylene glycol) (PEG)-mediated fusion whether or not they are assembled into a SNARE complex (Dennison et al., BJ, 2006, 1661). Viral fusion protein trans-membrane domains (TMDs) enhance the fusion. Thus, we hypothesized that the SB-TMD may also affect fusion kinetics. The kinetics of PEG-mediated fusion of DOPC/DOPE/sphingomyelin/cholesterol/DOPS (32/25/15/20/8) 25 nm vesicles (SUVs) was examined in the presence and absence of SB TMD. Lipid mixing (LM), contents mixing (CM) and leakage (L) time courses were fitted globally to a 3-state sequential model (Weinreb & Lentz, BJ, 2007, 4012), from which we obtained estimates of rate constants for conversion between states as well as probabilities of LM, CM and L for each state. SB TMD enhanced the rates of “stalk” and fusion pore (FP) formation in a cooperative fashion (maximum effect at 3 peptide/vesicle). TMD ordered the bilayer interior in a similarly cooperative fashion. The effects of hexadecane and TMD on fusion kinetics were quite distinct and not mutual. SB TMD increased the probability of both LM and CM in the initial intermediate, suggesting that it promoted formation of transient pores before the final pore state. Transition state thermodynamic changes indicate that the effects on “stalk” and FP formation involved different mechanism, although both showed that in presence of TMD the change in entropy is always greater than enthalpy. Supported by NIH grant GM32707 to BRL.

SNAP-23 and syntaxin-3 are required for chemokine release by mature human mast cells

Mast cells play a key role in allergic and non-allergic disease by releasing a broad array of mediators. Soluble N-ethyl-maleimide-sensitive factor attachment protein receptors (SNAREs) are necessary for membrane fusion events during mast cell exocytosis. We have shown recently that the SNAREs SNAP-23, syntaxin (STX)-4, vesicle associated membrane protein (VAMP)-7, and VAMP-8 are required for release of pre-stored histamine by mast cells. Here we analyze the involvement of different SNARE isoforms in exocytosis of de novo synthesized chemokines in mast cells isolated from human intestine. Following IgE receptor cross-linking, mast cells released substantial amounts of the chemokines CXCL8, CCL2, CCL3, and CCL4. Measurement of SNARE mRNA expression revealed only a moderate up-regulation of mRNA for STX-4 after stimulation for 1.5h. Inhibition of SNAP-23 or STX-3 abolished IgE mediated release of the chemokines CXCL8, CCL2, CCL3, and CCL4. In contrast, blocking of STX-2, or VAMP-3 did not affect the chemokine release. Inhibition of STX-4 or VAMP-8 resulted in a reduced release of CXCL8, but not of CCL2, CCL3, or CCL4. Inhibition of STX-6 attenuated the release of CXCL8 and CCL2, inhibition of VAMP-7 that of CCL3. In summary, STX-3 and SNAP-23 are crucial for the release of all chemokines in mature human mast cells whereas other SNAREs affect only release of selected chemokines.

A role for the SNARE protein syntaxin 3 in human cytomegalovirus morphogenesis

As an enveloped virus, replication of human cytomegalovirus (HCMV) is dependent on interaction with cellular membrane systems. Its final envelopment occurs into intracellular membranes prior to its secretion. However the mechanisms underlying these processes are poorly understood. Here, we show that HCMV infection induces expression of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) syntaxin 3 (STX3), a component of the cellular machinery for membrane fusion. STX3 was located at the plasma membrane and at the assembly site where it was found associated with virus wrapping membranes by immunogold labelling. Depletion of STX3 using RNA interference reduced HCMV production, while expression of a STX3 construct resistant to RNAi inhibition enhanced virus production. Ultrastructural examination of the assembly site in HCMV-infected STX3-depleted cells showed fewer mature virions and more viruses undergoing final envelopment. In contrast, silencing of STX3 did not affect herpes simplex virus type 1 production. The mechanism through which STX3 affected HCMV morphogenesis likely involved late endosomes/lysosomes since STX3 depletion reduced the expression of lysosomal membrane glycoproteins. Our results demonstrate a function for STX3 in HCMV morphogenesis, and unravel a new role for this SNARE protein in late endosomes/lysosomes compartments.

Snare-Mediated Fusion Between Highly Curved and Un-Curved Membranes

During neurotransmitter release, curved synaptic vesicles fuse with the un-curved pre-synaptic plasma membrane, leading to the merger of two lipid bilayers and the release of neurotransmitters, a process that requires SNARE proteins in both membranes. Our previous modeling of this system employed two populations of highly curved vesicles (SUV), while others have used two populations of vesicles having ill-defined but likely not high curvature. In our studies, the v-SNARE synaptobrevin (SB), the t-SNARE syntaxin (SX), and SNAP-25 linked vesicles via a SNARE complex, but were unable to promote fusion without poly ethylene glycol (PEG) to force close membrane contact. We hypothesized that the geometry of the membranes may contribute to native synaptic vesicle fusion. Here we reconstitute SB into SUVs and SX into relatively uncurved (LUV) vesicles, whose composition, DOPC/DOPE/sphingomeylin/DOPS/cholesterol (32/25/15/8/20), models that of the native membranes. Lipid mixing (LM), contents mixing (CM) and leakage (L) time courses were fitted globally to 3- or 4-state sequential models, from which we obtained estimates of rate constants for conversion between states as well as probabilities of LM, CM and L for each state (Biophys. J., 2007, 92; 4012). In the absence of SNAREs, the mismatched curvature of the LUV-SUV system promotes more efficient and productive fusion events than fusion between SUVs (Biophys. J., 2010, 98, S1; 674a). LUVs containing SX (1:2250 P/L) and SUVs containing SB (1:950 P/L) still did not fuse in the absence of PEG. However with 6% PEG, the probability of CM was greatly shifted to the first step in the fusion process. The results suggest that with mismatched curvature, SNAREs may enhance rapid transient pore formation that precedes fully LM and final pore formation. Supported by NIGMS grants GM000678 to UNC and GM32707 to BRL.

The Trans-Membrane Domain of the SNARE Fusion Protein Syntaxin (SX) Enhances the Rate of Intermediate Formation

During neurotransmitter release, synaptic vesicles fuse with the pre-synaptic plasma membrane, leading to the merger of two lipid bilayers and the release of neurotransmitters. This process requires formation of a complex between SNARE proteins in both membranes. One of the SNARE proteins required for membrane fusion is Syntaxin (SX), a membrane anchored protein in the pre-synaptic membrane. Since viral fusion peptides and trans-membrane domains (TMDs), which also insert into membranes, can affect rates of fusion, we hypothesized that the SX TMD may also affect fusion kinetics. Polyethylene glycol (PEG)-triggered fusion of highly curved 25 nm vesicles (SUVs) was examined in the presence of the TMD of SX (1:900 protein:lipid ratio) at temperatures between 17°C and 42°C. These SUVs were composed of a mixture of DOPC/DOPE/sphingomeylin/DOPS/cholesterol (32/25/15/8/20), which closely models the lipid composition of the natural membranes. Lipid mixing (LM), contents mixing (CM) and leakage (L) time courses were fitted globally to a 3 state sequential model (Weinreb, Biophys. J., 2007), from which we obtained estimates of rate constants for conversion between states as well as probabilities of LM, CM and L for each state. Results show that the SX TMD enhanced somewhat the rate of initial intermediate formation but had an even effect on the rate of pore formation. In addition, the probability of pore formation increased in the initial intermediate relative to the final fusion pore state. Since we have shown that uncomplexed SNARE proteins enhance PEG-mediated fusion roughly as effectively as does the complex, it may be that the SX TMD helps lower the activation barrier for fusion of closely juxtaposed bilayers in vivo. Supported by GM32707 to BRL and NIGMS grants GM000678 to UNC.

Effect of Genetic Variations in Syntaxin-Binding Protein-5 and Syntaxin-2 on von Willebrand Factor Concentration and Cardiovascular Risk

Elevated von Willebrand factor (VWF) plasma levels are associated with an increased risk of cardiovascular disease. A meta-analysis of genomewide association studies on VWF identified novel candidate genes, that is, syntaxin-binding protein 5 (STXBP5) and syntaxin 2 (STX2), which are possibly involved in the secretion of VWF. We investigated whether VWF antigen levels (VWF:Ag), VWF collagen-binding activity (VWF:CB) and the risk of arterial thrombosis are affected by common genetic variations in these genes. In 463 young white subjects (men ≤45 years of age and women ≤55 years of age), who were included 1 to 3 months after a first event of arterial thrombosis, and 406 control subjects, we measured VWF:Ag and VWF:CB. Nine haplotype tagging single-nucleotide polymorphisms of STXBP5 and STX2 were selected and subsequently analyzed using linear regression with additive genetic models adjusted for age, sex, and ABO blood group. The minor alleles of rs9399599 and rs1039084 in STXBP5 were associated with lower VWF plasma levels and activity, whereas the minor allele of rs7978987 in STX2 was associated with higher VWF plasma levels and activity. The minor alleles of the single-nucleotide polymorphisms in STX2 were associated with a reduced risk of arterial thrombosis (rs1236: odds ratio, 0.73 [95% confidence interval, 0.59, 0.89]; rs7978987: odds ratio, 0.81 [95% confidence interval, 0.65, 1.00]; rs11061158: odds ratio, 0.69 [95% confidence interval, 0.55, 0.88]). Genetic variability in STXBP5 and STX2 affects both VWF concentration and activity in young individuals with premature arterial thrombosis. Furthermore, in our study, genetic variability in STX2 is associated with the risk of arterial thrombosis. However, at this point, the underlying mechanism remains unclear.

Syntaxin 1 is expressed in the trout saccular hair cells: RT-PCR and immunocytochemical observations

Syntaxin is one of several proteins that may be involved in the docking of synaptic vesicles, synaptic vesicle recycling, and non-synaptic membrane trafficking. Presence of syntaxin has been reported in rat auditory and vestibular end organs. In the current study, we have examined the expression of message for syntaxin 1 in hair cells of the sacculus of the rainbow trout, Oncorhynchus mykiss, with RT-PCR using degenerate primers based on the sequence of zebrafish syntaxin. A PCR product of predicted size, 540 bp, yielded sequence with 94% amino acid identity to mouse, rat and human syntaxin and 96% identity to zebrafish syntaxin. An anti-syntaxin 1 primary antibody (S1172 Sigma) recognized a protein of 37 kDa, from the trout brain extract and the saccular hair cell homogenate in western blots. At the light microscopic level, immunoreactivity for anti-syntaxin 1 was observed within the sensory epithelium, in efferent fibers below the hair cells running parallel to the longitudinal axis of the saccule. In addition, sub- and supranuclear immunostaining was observed within select hair cells and immunoreactivity was concentrated at the base of stereocilliary arrays throughout. Immunogold electron microscopy further revealed that immunoreactivity was associated with the synaptic bodies and the basolateral and supranuclear regions of hair cells along with that present in the cuticular plate/stereocilliary regions of hair cells and efferent endings. These results suggest that syntaxin 1, expressed in the trout saccule, is associated not only with the docking of synaptic vesicles, but may be involved in vesicle recycling and in recycling of membrane.

Syntaxin 16 Binds to Cystic Fibrosis Transmembrane Conductance Regulator and Regulates Its Membrane Trafficking in Epithelial Cells

The cystic fibrosis transmembrane conductance regulator (CFTR) is a key membrane protein in the complex network of epithelial ion transporters regulating epithelial permeability. Syntaxins are one of the major determinants in the intracellular trafficking and membrane targeting of secretory proteins. In the present study we demonstrate the biochemical and functional association between CFTR and syntaxin 16 (STX16) that mediates vesicle transport within the early/late endosomes and trans-Golgi network. Immunoprecipitation experiments in rat colon and T84 human colonic epithelial cells indicate that STX16 associates with CFTR. Further analyses using the domain-specific pulldown assay reveal that the helix domain of STX16 directly interacts with the N-terminal region of CFTR. Immunostainings in rat colon and T84 cells show that CFTR and STX16 highly co-localize at the apical and subapical regions of epithelial cells. Interestingly, CFTR-associated chloride current was reduced by the knockdown of STX16 expression in T84 cells. Surface biotinylation and recycling assays indicate that the reduction in CFTR chloride current is due to decreased CFTR expression on the plasma membrane. These results suggest that STX16 mediates recycling of CFTR and constitutes an important component of CFTR trafficking machinery in intestinal epithelial cells.

Screening of proteins binding to mouse cytomegalovirus M122 protein from mouse brain cDNA library by yeast two-hybrid system

Objective To investigate the biological function of M122 in pathogenesis of MCMV in developmental brain disorders and brain damage, screening for mouse brain cDNA library interacting with M122 was performed by a yeast two-hybrid system. Methods The reconstructed bait plasmid pGBKT7-M122 was transformed into yeast cells AH109 and screened on the nutrient deficiency medium SD/-Trp. After express of the bait protein in AH109 yeast strains was detected by Western blot analysis, yeast-two hybrid screening was performed by mating AH109 with Y187 containing mouse brain cDNA library plasmid. The diploid yeast cells were plated on the nutrient deficiency medium SD/-Trp/-Leu/-His/-Ade. The second screening was performed with SD/-Trp/-Leu/-His/-Ade containing X-α-gal. The plasmids in positive colonies were extracted and transformed into E. coli JM109 cells. After plasmid DNA in JM109 cells were extracted form positive colonies and sequenced, the results were analyzed by bioinformatic methods. The interactions between M122 protein and the protein obtained from positive colonies were further confirmed by repeating yeast-two hybrid. Then, autoactivations of the proteins obtained from positive colonies were detected.Results The reconstructed bait plasmid was transformed into yeast cells AH109 successfully. The bait protein expressed in the yeast cells AH109 stably. 24 proteins interacting with MCMV M122 were screened, including syntaxin 8 ( Stx8 ), phosphoglucomutase 2 ( Pgm2 ), potassium voltage-gated channel, shaker-related subfamily, beta member 1 ( Kcnab1 ), collagen, type ⅪⅩ, alpha 1 ( Col19a1 ), archain 1 ( Arcn1 ), cytidylate kinase( Cmpk), DnaJ(Hsp40) homolog, subfamily A, member 1 (Dnaja1), ATPase, Na+/K + transporting, beta 3 polypeptide( Atp1b3 ), SH3-domain GRB2-like ( endophilin ) interacting protein 1 ( Sgip1 ),ankyrin repeat domain 17 (Ankrd17), Smg-7 homolog, nonsense mediated mRNA decay factor(Smg7),sperm associated antigen 9 ( Spag9 ), FK506 binding protein 1a ( Fkbp1a), MYST histone acetyltransferase monocytic leukemia 4 ( Myst4), hyaluronan and proteoglycan link protein 1 ( Hapln1), autophagy-related 3 (Atg3), splicing factor, arginine/serine-rich 5 ( Sfrs5 ), zinc finger, C3HC-type containing 1 ( Zc3hc1 ),thioredoxin-related transmembrane protein 1 ( Txndc1 ), adaptor protein complex AP-1, gamma 1 subunit (Ap1g1), Cullin 1 ( Cul1 ), and so on. Three of them were formerly unknown proteins. M122 protein could interact with the proteins obtained from positive colonies in the yeast cells AH109. Ap1g1 and Cul1 were proved to have autoactivation. Conclusion A class of proteins in brain interacting with M122 has been obtained. It is presumed that these proteins are correlated with neuropathogenesis of the brain disorders caused by CMV, but the candidates still need further confirmation for the interaction. Key words: Cytomegalovirus; M122 protein; Yeast two-hybrid system; Protein-protein interaction

Alterations in brain antioxidant enzymes and redox proteomic identification of oxidized brain proteins induced by the anti-cancer drug adriamycin: implications for oxidative stress-mediated chemobrain

Adriamycin (ADR) is a chemotherapeutic for the treatment of solid tumors. This quinone-containing anthracycline is well known to produce large amounts of reactive oxygen species (ROS) in vivo. A common complaint of patients undergoing long-term treatment with ADR is somnolence, often referred to as “chemobrain.” While ADR itself does not cross the blood brain barrier (BBB), we recently showed that ADR administration causes a peripheral increase in tumor necrosis factor α (TNF-α), which migrates across the BBB and leads to inflammation and oxidative stress in brain, most likely contributing to the observed decline in cognition. In the current study, we measured levels of the antioxidant glutathione (GSH) in brains of mice injected intraparitoneally (i.p.) with ADR, as well as the levels and activities of several enzymes involved in brain GSH metabolism. We observed significantly decreased GSH levels, as well as altered GSH/GSSG ratio in brains of ADR treated mice relative to saline-treated controls. Also observed in brains of ADR treated mice were increased levels of glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GR). We also observed increased activity of GPx, but a significant reduction in GST and GR activity in mice brain, 72 h post i.p. injection of ADR (20 mg/kg body weight). Furthermore, we used redox proteomics to identify specific proteins that are oxidized and/or have differential levels in mice brains as a result of a single i.p. injection of ADR. Visinin like protein 1 (VLP1), peptidyl prolyl isomerase 1 (Pin1), and syntaxin 1 (SYNT1) showed differential levels in ADR treated mice relative to saline-treated controls. Triose phosphate isomerase (TPI), enolase, and peroxiredoxin 1 (PRX-1) showed significantly increased specific carbonylation in ADR treated mice brain. These results further support the notion ADR induces oxidative stress in brain despite not crossing the BBB, and that antioxidant intervention may prevent ADR-induced cognitive dysfunction.

Heterogeneity of glutamatergic and GABAergic release machinery in cerebral cortex: analysis of synaptogyrin, vesicle-associated membrane protein, and syntaxin

To define whether cortical glutamatergic and GABAergic release machineries can be differentiated on the basis of the nature and amount of proteins they express, we studied the degree of co-localization of synaptogyrin (SGYR) 1 and 3, vesicle-associated membrane protein (VAMP) 1 and 2, syntaxin (STX) 1A and 1B in vesicular glutamate transporter (VGLUT)1-, VGLUT2- and vesicular GABA transporter (VGAT)-positive (+) puncta and synaptic vesicles in the rat cerebral cortex. Co-localization studies showed that SGYR1 and 3 were expressed in about 90% of VGLUT1+, 70% of VGLUT2+ and 80% of VGAT+ puncta; VAMP1 was expressed in approximately 45% of VGLUT1+, 55% of VGLUT2+, and 80% of VGAT+ puncta; VAMP2 in about 95% of VGLUT1+, 75% of VGLUT2+, and 80% of VGAT+ puncta; STX1A in about 65% of VGLUT1+, 30% of VGLUT2+, and 3% of VGAT+ puncta, and STX1B in approximately 45% of VGLUT1+, 35% of VGLUT2+, and 70% of VGAT+ puncta. Immunoisolation studies showed that while STX1A was completely segregated and virtually absent from VGAT synaptic vesicles, STX1B, VAMP1/VAMP2, SGYR1/SGYR3 showed a similar pattern with the highest expression in VGLUT1 immunoisolated vesicles and the lowest in VGAT immunoisolated vesicles. Moreover, we studied the localization of STX1B at the electron microscope and found that a population of axon terminals forming symmetric synapses were STX1B-positive.These results extend our previous observations on the differential expression of presynaptic proteins involved in neurotransmitter release in GABAergic and glutamatergic terminals and indicate that heterogeneity of glutamatergic and GABAergic release machinery can be contributed by both the presence or absence of a given protein in a nerve terminal and the amount of protein expressed by synaptic vesicles.

Exercise contributes to the effects of DHA dietary supplementation by acting on membrane-related synaptic systems

Dietary omega-3 fatty acid (i.e. docosohexaenoic acid (DHA)) and exercise are gaining recognition for supporting brain function under normal and challenging conditions. Here we evaluate the possibility that the interaction of DHA and exercise can involve specific elements of the synaptic plasma membrane. We found that voluntary exercise potentiated the effects of a 12-day DHA dietary supplementation regimen on increasing the levels of syntaxin 3 (STX-3) and the growth-associated protein (GAP-43) in the adult rat hippocampus region. STX-3 is a synaptic membrane-bound protein involved in the effects of DHA on membrane expansion. The DHA diet and exercise also elevated levels of the NMDA receptor subunit NR2B, which is important for synaptic function underlying learning and memory. The actions of exercise and DHA dietary supplementation reflected on enhanced learning performance in the Morris water maze as learning ability was associated with higher levels of STX-3 and NR2B. The overall findings reveal a mechanism by which exercise can interact with the function of DHA dietary enrichment to elevate the capacity of the adult brain for axonal growth, synaptic plasticity, and cognitive function.

PCR-Based Analysis of Differentially Methylated Regions of GNAS Enables Convenient Diagnostic Testing of Pseudohypoparathyroidism Type Ib

Pseudohypoparathyroidism type Ib (PHPIb) is characterized by parathyroid hormone (PTH) resistance, which can lead to hypocalcemia, hyperphosphatemia, and increased serum PTH. The disorder is caused by mutations in regulatory regions of the GNAS gene (GNAS complex locus) that lead to interferences in the methylation status of alternative GNAS promoters, such as exon A/B, NESP55, and XL alpha-s. PHPIb comprises disorders that show distinctive changes in methylation status but share the same clinical phenotype: (a) loss of methylation only at exon A/B of the GNAS gene and involving no other obvious epigenetic abnormalities [e.g., those caused by heterozygous microdeletions in the STX16 (syntaxin 16) region and found in many patients with autosomal dominant (AD) PHPIb]; (b) methylation abnormalities at several differentially methylated regions (DMRs), which are observed in most patients with sporadic PHPIb and some families with AD PHPIb. To permit early and reliable diagnosis of suspected PHPIb, we designed methylation-sensitive restriction enzyme-based and bisulfite deamination-based PCR tests for exon A/B and NESP55 DMRs. Both PCR strategies permit proper methylation testing of GNAS and NESP55 DMRs and elucidate different disease subtypes. We have identified a novel microsatellite repeat polymorphism within GNAS exon A/B, and pedigree analyses have shown its presence to be conclusive evidence for familial disease. We provide a simple diagnostic test for PHPIb, an imprinting disorder caused by different molecular changes within the GNAS complex locus. PHPIb, a complex and diagnostically challenging clinical phenotype, can be treated successfully by taking steps before the manifestation of symptoms to avoid clinical complications in affected patients or asymptomatic members of affected families who show positive results in genetic tests.

Vesicle associated membrane protein (VAMP)‐7 and VAMP‐8, but not VAMP‐2 or VAMP‐3, are required for activation‐induced degranulation of mature human mast cells

Mediator release from mast cells (MC) is a crucial step in allergic and non-allergic inflammatory disorders. However, the final events in response to activation leading to membrane fusion and thereby facilitating degranulation have hitherto not been analyzed in human MC. Soluble N-ethyl-maleimide-sensitive factor attachment protein receptors (SNARE) represent a highly conserved family of proteins that have been shown to mediate intracellular membrane fusion events. Here, we show that mature MC isolated from human intestinal tissue express soluble N-ethylmaleide sensitive factor attachment protein (SNAP)-23, Syntaxin (STX)-1B, STX-2, STX-3, STX-4, and STX-6 but not SNAP-25. Furthermore, we found that primary human MC express substantial amounts of vesicle associated membrane protein (VAMP)-3, VAMP-7 and VAMP-8 and, in contrast to previous reports about rodent MC, only low levels of VAMP-2. Furthermore, VAMP-7 and VAMP-8 were found to translocate to the plasma membrane and interact with SNAP-23 and STX-4 upon activation. Inhibition of SNAP-23, STX-4, VAMP-7 or VAMP-8, but not VAMP-2 or VAMP-3, resulted in a markedly reduced high-affinity IgE receptor-mediated histamine release. In summary, our data show that mature human MC express a specific pattern of SNARE and that VAMP-7 and VAMP-8, but not VAMP-2, are required for rapid degranulation.

Lack of Gnas Epigenetic Changes and Pseudohypoparathyroidism Type Ib in Mice with Targeted Disruption of Syntaxin-16

Pseudohypoparathyroidism type Ib (PHP-Ib) is characterized by hypocalcemia and hyperphosphatemia due to proximal renal tubular resistance to PTH but without evidence for Albright's hereditary osteodystrophy. The disorder is paternally imprinted and affected individuals, but not unaffected carriers, show loss of GNAS exon A/B methylation, a differentially methylated region upstream of the exons encoding Gsalpha. Affected individuals of numerous unrelated kindreds with an autosomal dominant form of PHP-Ib (AD-PHP-Ib) have an identical 3-kb microdeletion removing exons 4-6 of syntaxin-16 (STX16) (STX16del4-6), which is thought to disrupt a cis-acting element required for exon A/B methylation. To explore the mechanisms underlying the regulation of exon A/B methylation, we generated mice genetically altered to carry the equivalent of STX16del4-6 (Stx16(Delta4-6)). Although the human GNAS locus shows a similar organization as the murine Gnas ortholog and although the human and mouse STX16/Stx16 regions show no major structural differences, no phenotypic or epigenotypic abnormalities were detected in mice with Stx16(Delta4-6) on one or both parental alleles. Furthermore, calcium and PTH levels in Stx16(Delta4-6) mice were indistinguishable from those in wild-type animals, indicating that ablation of the murine equivalent of human STX16del4-6 does not contribute to the development of PTH resistance. The identification of a novel intragenic transcript from within the STX16/Stx16 locus in total RNA from kidneys of Stx16(Delta4-6) mice and lymphoblastoid cell-derived RNA of a patient with AD-PHP-Ib raises the question whether this transcript contributes, if deleted or altered, to the development of AD-PHP-Ib in humans.