Soluble NSF Attachment Protein Research Articles

α-Synuclein is the major platelet isoform but is dispensable for activation, secretion, and thrombosis

Platelets play many roles in the vasculature ensuring proper hemostasis and maintaining integrity. These roles are facilitated, in part, by cargo molecules released from platelet granules via Soluble NSF Attachment Protein Receptor (SNARE) mediated membrane fusion, which is controlled by several protein-protein interactions. Chaperones have been characterized for t-SNAREs (i.e. Munc18b for Syntaxin-11), but none have been clearly identified for v-SNAREs. α-Synuclein has been proposed as a v-SNARE chaperone which may affect SNARE-complex assembly, fusion pore opening, and thus secretion. Despite its abundance and that it is the only isoform present, α-synuclein’s role in platelet secretion is uncharacterized. In this study, immunofluorescence showed that α-synuclein was present on punctate structures that co-stained with markers for α-granules and lysosomes and in a cytoplasmic pool. We analyzed the phenotype of α-synuclein−/− mice and their platelets. Platelets from knockout mice had a mild, agonist-dependent secretion defect but aggregation and spreading in vitro were unaffected. Consistently, thrombosis/hemostasis were unaffected in the tail-bleeding, FeCl3 carotid injury and jugular vein puncture models. None of the platelet secretory machinery examined, e.g. the v-SNAREs, were affected by α-synuclein’s loss. The results indicate that, despite its abundance, α-synuclein has only a limited role in platelet function and thrombosis.

Gβγ-SNAP25 exocytotic brake removal enhances insulin action, promotes adipocyte browning, and protects against diet-induced obesity.

Negative regulation of exocytosis from secretory cells is accomplished through inhibitory signals from Gi/o GPCRs by Gβγ subunit inhibition of 2 mechanisms: decreased calcium entry and direct interaction of Gβγ with soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) plasma membrane fusion machinery. Previously, we disabled the second mechanism with a SNAP25 truncation (SNAP25Δ3) that decreased Gβγ affinity for the SNARE complex, leaving exocytotic fusion and modulation of calcium entry intact and removing GPCR-Gβγ inhibition of SNARE-mediated exocytosis. Here, we report substantial metabolic benefit in mice carrying this mutation. Snap25Δ3/Δ3 mice exhibited enhanced insulin sensitivity and beiging of white fat. Metabolic protection was amplified in Snap25Δ3/Δ3 mice challenged with a high-fat diet. Glucose homeostasis, whole-body insulin action, and insulin-mediated glucose uptake into white adipose tissue were improved along with resistance to diet-induced obesity. Metabolic protection in Snap25Δ3/Δ3 mice occurred without compromising the physiological response to fasting or cold. All metabolic phenotypes were reversed at thermoneutrality, suggesting that basal autonomic activity was required. Direct electrode stimulation of sympathetic neuron exocytosis from Snap25Δ3/Δ3 inguinal adipose depots resulted in enhanced and prolonged norepinephrine release. Thus, the Gβγ-SNARE interaction represents a cellular mechanism that deserves further exploration as an additional avenue for combating metabolic disease.

Potential Role of Moesin in Regulating Mast Cell Secretion.

Mast cells have existed for millions of years in species that never suffer from allergic reactions. Hence, in addition to allergies, mast cells can play a critical role in homeostasis and inflammation via secretion of numerous vasoactive, pro-inflammatory and neuro-sensitizing mediators. Secretion may utilize different modes that involve the cytoskeleton, but our understanding of the molecular mechanisms regulating secretion is still not well understood. The Ezrin/Radixin/Moesin (ERM) family of proteins is involved in linking cell surface-initiated signaling to the actin cytoskeleton. However, how ERMs may regulate secretion from mast cells is still poorly understood. ERMs contain two functional domains connected through a long α-helix region, the N-terminal FERM (band 4.1 protein-ERM) domain and the C-terminal ERM association domain (C-ERMAD). The FERM domain and the C-ERMAD can bind to each other in a head-to-tail manner, leading to a closed/inactive conformation. Typically, phosphorylation on the C-terminus Thr has been associated with the activation of ERMs, including secretion from macrophages and platelets. It has previously been shown that the ability of the so-called mast cell "stabilizer" disodium cromoglycate (cromolyn) to inhibit secretion from rat mast cells closely paralleled the phosphorylation of a 78 kDa protein, which was subsequently shown to be moesin, a member of ERMs. Interestingly, the phosphorylation of moesin during the inhibition of mast cell secretion was on the N-terminal Ser56/74 and Thr66 residues. This phosphorylation pattern could lock moesin in its inactive state and render it inaccessible to binding to the Soluble NSF attachment protein receptors (SNAREs) and synaptosomal-associated proteins (SNAPs) critical for exocytosis. Using confocal microscopic imaging, we showed moesin was found to colocalize with actin and cluster around secretory granules during inhibition of secretion. In conclusion, the phosphorylation pattern and localization of moesin may be important in the regulation of mast cell secretion and could be targeted for the development of effective inhibitors of secretion of allergic and inflammatory mediators from mast cells.

Botox (onabotulinumtoxinA) mechanism of action.

Studies in the 1920s found that botulinum neurotoxin type A (BoNT/A) inhibited the activity of motor and parasympathetic nerve endings, confirmed several decades later to be due to decreased acetylcholine release. The 1970s were marked by studies of cellular mechanisms aided by use of neutralizing antibodies as pharmacologic tools: BoNT/A disappeared from accessibility to neutralizing antibodies within minutes, although it took several hours for onset of muscle weakness. The multi-step mechanism was experimentally confirmed and is now recognized to consist broadly of binding to nerve terminals, internalization, and lysis or cleavage of a protein (SNAP-25: synaptosomal associated protein-25 kDa) that is part of the SNARE (Soluble NSF Attachment protein REceptor) complex needed for synaptic vesicle docking and fusion. Clinical use of the BoNT/A product onabotulinumtoxinA was based on its ability to reduce muscle contractions via inhibition of acetylcholine from motor terminals. Sensory mechanisms of onabotulinumtoxinA have now been identified, supporting its successful treatment of chronic migraine and urgency in overactive bladder. Exploration into migraine mechanisms led to anatomical studies documenting pain fibers that send axons through sutures of the skull to outside the head-a potential route by which extracranial injections could affect intracranial processes. Several clinical studies have also identified benefits of onabotulinumtoxinA in major depression, which have been attributed to central responses induced by feedback from facial muscle and skin movement. Overall, the history of BoNT/A is distinguished by basic science studies that stimulated clinical use and, conversely, clinical observations that spurred basic research into novel mechanisms of action.

Impaired Autophagic-Lysosomal Fusion in Parkinson's Patient Midbrain Neurons Occurs through Loss of ykt6 and Is Rescued by Farnesyltransferase Inhibition.

Macroautophagy is a catabolic process that coordinates with lysosomes to degrade aggregation-prone proteins and damaged organelles. Loss of macroautophagy preferentially affects neuron viability and is associated with age-related neurodegeneration. We previously found that α-synuclein (α-syn) inhibits lysosomal function by blocking ykt6, a farnesyl-regulated soluble NSF attachment protein receptor (SNARE) protein that is essential for hydrolase trafficking in midbrain neurons. Using Parkinson's disease (PD) patient iPSC-derived midbrain cultures, we find that chronic, endogenous accumulation of α-syn directly inhibits autophagosome-lysosome fusion by impairing ykt6-SNAP-29 complexes. In wild-type (WT) cultures, ykt6 depletion caused a near-complete block of autophagic flux, highlighting its critical role for autophagy in human iPSC-derived neurons. In PD, macroautophagy impairment was associated with increased farnesyltransferase (FTase) activity, and FTase inhibitors restored macroautophagic flux through promoting active forms of ykt6 in human cultures, and male and female mice. Our findings indicate that ykt6 mediates cellular clearance by coordinating autophagic-lysosomal fusion and hydrolase trafficking, and that macroautophagy impairment in PD can be rescued by FTase inhibitors.SIGNIFICANCE STATEMENT The pathogenic mechanisms that lead to the death of neurons in Parkinson's disease (PD) and Dementia with Lewy bodies (LBD) are currently unknown. Furthermore, disease modifying treatments for these diseases do not exist. Our study indicates that a cellular clearance pathway termed autophagy is impaired in patient-derived culture models of PD and in vivo We identified a novel druggable target, a soluble NSF attachment protein receptor (SNARE) protein called ykt6, that rescues autophagy in vitro and in vivo upon blocking its farnesylation. Our work suggests that farnesyltransferase (FTase) inhibitors may be useful therapies for PD and DLB through enhancing autophagic-lysosomal clearance of aggregated proteins.

Cohen syndrome and early-onset epileptic encephalopathy in male triplets: two disease-causing mutations in VPS13B and NAPB

Cohen syndrome (CS) is a rare multisystem autosomal recessive disorder associated with mutations in VPS13B (vacuolar protein sorting homolog 13B). The NAPB-related neurodevelopmental disorder is characterized mainly by early-onset epileptic encephalopathy (EOEE) and is associated with mutations in NAPB that encodes for SNAP-beta (soluble NSF attachment protein beta). Here we describe male triplets, clinically presenting with the phenotype of subtle but distinctive facial features, intellectual disability, increased body weight, neonatal EOEE, and prominently variable abnormal behaviors of autism and sexual arousal. The EEG showed multifocal epilepsy, while the brain MRI showed no abnormalities. Diagnostic exome sequencing (ES), the applied next-generation sequencing approach, revealed the interesting finding of two novel homozygous variants in two genes: VPS13B missense variant (c.8516G > A) and NAPB splice-site loss (c.354 + 2 T > G). Sanger sequencing verified the segregation of the two recessive gene variants with the phenotype in family members. The prediction algorithms support the pathogenicity of these variants. Homozygosity mapping of ES data of this consanguineous family revealed multiple chromosomal regions of homozygosity stretches with the residing of VPS13B (chr8: 100830758G > A) and NAPB (Chr20: 23,375,774 A > C) variants within the largest homozygous blocks further supporting the disease-genes causal role. Interestingly, the functions of the two proteins; VPS13B, a transmembrane protein involved in intracellular protein transport, and SNAP-beta involved in neurotransmitters release at the neuronal synaptic complexes, have been associated with Golgi-mediated vesicular trafficking. Our ES findings provide new insights into the pathologic mechanism underlying the expansion of the neurodevelopmental spectrum in CS and further highlight the importance of Golgi and Golgi-membrane-related proteins in the development of neurodevelopmental syndromes associated with early-onset non-channelopathy epilepsy. To our knowledge, this is the first report documenting multifocal EOEE in CS patients with the association of a pathogenic NAPB variant.

The Role of Tomosyn in the Regulation of Neurotransmitter Release.

Soluble NSF attachment protein receptor (SNARE) proteins play a central role in synaptic vesicle (SV) exocytosis. These proteins include the vesicle-associated SNARE protein (v-SNARE) synaptobrevin and the target membrane-associated SNARE proteins (t-SNAREs) syntaxin and SNAP-25. Together, these proteins drive membrane fusion between synaptic vesicles (SV) and the presynaptic plasma membrane to generate SV exocytosis. In the presynaptic active zone, various proteins may either enhance or inhibit SV exocytosis by acting on the SNAREs. Among the inhibitory proteins, tomosyn, a syntaxin-binding protein, is of particular importance because it plays a critical and evolutionarily conserved role in controlling synaptic transmission. In this chapter, we describe how tomosyn was discovered, how it interacts with SNAREs and other presynaptic regulatory proteins to regulate SV exocytosis and synaptic plasticity, and how its various domains contribute to its synaptic functions.

Membrane Proteomic Profiling of Soybean Leaf and Root Tissues Uncovers Salt-Stress-Responsive Membrane Proteins.

Cultivated soybean (Glycine max (L.)), the world's most important legume crop, has high-to-moderate salt sensitivity. Being the frontier for sensing and controlling solute transport, membrane proteins could be involved in cell signaling, osmoregulation, and stress-sensing mechanisms, but their roles in abiotic stresses are still largely unknown. By analyzing salt-induced membrane proteomic changes in the roots and leaves of salt-sensitive soybean cultivar (C08) seedlings germinated under NaCl, we detected 972 membrane proteins, with those present in both leaves and roots annotated as receptor kinases, calcium-sensing proteins, abscisic acid receptors, cation and anion channel proteins, proton pumps, amide and peptide transporters, and vesicle transport-related proteins etc. Endocytosis, linoleic acid metabolism, and fatty acid biosynthesis pathway-related proteins were enriched in roots whereas phagosome, spliceosome and soluble NSF attachment protein receptor (SNARE) interaction-related proteins were enriched in leaves. Using label-free quantitation, 129 differentially expressed membrane proteins were found in both tissues upon NaCl treatment. Additionally, the 140 NaCl-induced proteins identified in roots and 57 in leaves are vesicle-, mitochondrial-, and chloroplast-associated membrane proteins and those with functions related to ion transport, protein transport, ATP hydrolysis, protein folding, and receptor kinases, etc. Our proteomic results were verified against corresponding gene expression patterns from published C08 RNA-seq data, demonstrating the importance of solute transport and sensing in salt stress responses.

Porosomes in uterine epithelial cells: Ultrastructural identification and characterization during early pregnancy.

Porosomes are plasma membrane structures in secretory cells that allow transient docking and/or partial fusion of vesicles during which they release their content then disengage. This is referred to as "kiss and run" exocytosis. During early pregnancy, at the time of receptivity, there is a high level of vesicle activity in uterine epithelial cells (UECs). One of the secretory pathways for these vesicles could be via porosomes, which have yet to be identified in UECs. This study identified porosomes in the apical plasma membrane of UECs for the first time. These structures were present on days 1, 5.5, and 6 of early pregnancy, where they likely facilitate partial secretion via "kiss and run" exocytosis. The porosomes were measured and quantified on days 1, 5.5, and 6, which showed there are significantly more porosomes on day 5.5 (receptive) compared to day 1 (nonreceptive) of pregnancy. This increase in porosome numbers may reflect major morphological and molecular changes in the apical plasma membrane at this time such as increased cholesterol and soluble NSF attachment proteinreceptorproteins, as these are structural and functional components of the porosome complex assembly. Porosomes were observed in both resting (inactive) and dilated (active) states on days 1, 5.5, and 6 of early pregnancy. Porosomes on day 5.5 are significantly more active than on day 1 as demonstrated by the dilation of their base diameter. Further two-way ANOVA analysis of base diameter in resting and dilated states found a significant increase in porosome activity in day 5.5 compared to day 1. This study therefore indicates an increase in the number and activity of porosomes at the time of uterine receptivity in the rat, revealing a mechanism by which the UECs modify the uterine luminal environment at this time.

Presynaptic mechanisms underlying GABAB-receptor-mediated inhibition of spontaneous neurotransmitter release.

SUMMARYInhibition of neurotransmitter release by neurotransmitter substances constitutes a fundamental means of neuromodulation. In contrast to well-delineated mechanisms that underlie inhibition of evoked release via suppression of voltage-gated Ca2+ channels, processes that underlie neuromodulatory inhibition of spontaneous release remain unclear. Here, we interrogated inhibition of spontaneous glutamate and GABA release by presynaptic metabotropic GABAB receptors. Our findings show that this inhibition relies on Gβγ subunit action at the membrane, and it is largely independent of presynaptic Ca2+ signaling for both forms of release. In the case of spontaneous glutamate release, inhibition requires Gβγ interaction with the C terminus of the key fusion machinery component SNAP25, and it is modulated by synaptotagmin-1. Inhibition of spontaneous GABA release, on the other hand, is independent of these pathways and likely requires alternative Gβγ targets at the presynaptic terminal.

Room for Two: The Synaptophysin/Synaptobrevin Complex.

Synaptic vesicle release is regulated by upwards of 30 proteins at the fusion complex alone, but disruptions in any one of these components can have devastating consequences for neuronal communication. Aberrant molecular responses to calcium signaling at the pre-synaptic terminal dramatically affect vesicle trafficking, docking, fusion, and release. At the organismal level, this is reflected in disorders such as epilepsy, depression, and neurodegeneration. Among the myriad pre-synaptic proteins, perhaps the most functionally mysterious is synaptophysin (SYP). On its own, this vesicular transmembrane protein has been proposed to function as a calcium sensor, a cholesterol-binding protein, and to form ion channels across the phospholipid bilayer. The downstream effects of these functions are largely unknown. The physiological relevance of SYP is readily apparent in its interaction with synaptobrevin (VAMP2), an integral element of the neuronal SNARE complex. SNAREs, soluble NSF attachment protein receptors, comprise a family of proteins essential for vesicle fusion. The complex formed by SYP and VAMP2 is thought to be involved in both trafficking to the pre-synaptic membrane as well as regulation of SNARE complex formation. Recent structural observations specifically implicate the SYP/VAMP2 complex in anchoring the SNARE assembly at the pre-synaptic membrane prior to vesicle fusion. Thus, the SYP/VAMP2 complex appears vital to the form and function of neuronal exocytotic machinery.

The vSNAREs VAMP2 and VAMP4 control recycling and intracellular sorting of post-synaptic receptors in neuronal dendrites.

The endosomal recycling system dynamically tunes synaptic strength, which underlies synaptic plasticity. Exocytosis is involved in the expression of long-term potentiation (LTP), as postsynaptic cleavage of the SNARE (soluble NSF-attachment protein receptor) protein VAMP2 by tetanus toxin blocks LTP. Moreover, induction of LTP increases the exocytosis of transferrin receptors (TfRs) and markers of recycling endosomes (REs), as well as post-synaptic AMPA type receptors (AMPARs). However, the interplay between AMPAR and TfR exocytosis remains unclear. Here, we identify VAMP4 as the vesicular SNARE that mediates most dendritic RE exocytosis. In contrast, VAMP2 plays a minor role in RE exocytosis. LTP induction increases the exocytosis of both VAMP2- and VAMP4-labeled organelles. Knock down (KD) of VAMP4 decreases TfR recycling but increases AMPAR recycling. Moreover, VAMP4 KD increases AMPAR-mediated synaptic transmission, which consequently occludes LTP expression. The opposing changes in AMPAR and TfR recycling upon VAMP4 KD reveal their sorting into separate endosomal populations.

BECN2 (beclin 2) Negatively Regulates Inflammasome Sensors Through ATG9A-Dependent but ATG16L1- and LC3-Independent Non-Canonical Autophagy

ABSTRACT Macroautophagy/autophagy-related proteins regulate infectious and inflammatory diseases in autophagy-dependent or -independent manner. However, the role of a newly identified mammalian-specific autophagy protein-BECN2 (beclin 2) in innate immune regulation is largely unknown. Here we showed that loss of BECN2 enhanced the activities of NLRP3, AIM2, NLRP1, and NLRC4 inflammasomes upon ligand stimulations. Mechanistically, BECN2 interacted with inflammasome sensors and mediated their degradation through a ULK1- and ATG9A-dependent, but BECN1-WIPI2-ATG16L1-LC3-independent, non-canonical autophagic pathway. BECN2 recruited inflammasome sensors on ATG9A+ vesicles to form a complex (BECN2-ATG9A-sensors) upon ULK1 activation. Three soluble NSF attachment protein receptor (SNARE) proteins (SEC22A, STX5, and STX6) were further shown to mediate the BECN2-ATG9A-dependent inflammasome sensor degradation. Loss of BECN2 promoted alum-induced peritonitis, which could be rescued by the ablation of CASP1 in Becn2-deficient mice. Hence, BECN2 negatively regulated inflammasome activation to control inflammation, serving as a potential therapeutic target for the treatment of infectious and inflammatory diseases. Abbreviations: AIM2: absent in melanoma 2; ATG: autophagy related; BECN1: beclin 1; BMDC: bone marrow-derived dendritic cells; BMDM: bone marrow-derived macrophages; CASP1: caspase 1; CQ: chloroquine; gMDSC: granulocytic myeloid-derived suppressor cells; IL: interleukin; LPS: lipopolysaccharide; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; mMDSC: monocytic myeloid-derived suppressor cells; NLRC4: NLR family CARD domain containing 4; NLRP1: NLR family pyrin domain containing 1; NLRP3: NLR family pyrin domain containing 3; PECs: peritoneal exudate cells; PYCARD/ASC: apoptosis-associated speck-like protein containing a caspase activation and recruitment domain; SNAREs: soluble NSF attachment protein receptors; STX5: syntaxin 5; STX6: syntaxin 6; ULK1: unc-51 like autophagy activating kinase 1; WIPI: WD repeat domain, phosphoinositide interacting.

A Qa-SNARE complex contributes to soybean cyst nematode resistance via regulation of mitochondria-mediated cell death.

The resistance to Heterodera glycines 1 (Rhg1) locus is widely used by soybean breeders to reduce yield loss caused by soybean cyst nematode (SCN). α-SNAP (α-soluble NSF attachment protein) within Rhg1 locus contributes to SCN resistance by modulation of cell status at the SCN feeding site; however, the underlying mechanism is largely unclear. Here, we identified an α-SNAP-interacting protein, GmSYP31A, a Qa-SNARE (soluble NSF attachment protein receptor) protein from soybean. Expression of GmSYP31A significantly induced cell death in Nicotiana benthamiana leaves, and co-expression of α-SNAP and GmSYP31A could accelerate cell death. Overexpression of GmSYP31A increased SCN resistance, while silencing or overexpression of a dominant-negative form of GmSYP31A increased SCN sensitivity. GmSYP31A expression also disrupted endoplasmic reticulum-Golgi trafficking, and the exocytosis pathway. Moreover, α-SNAP was also found to interact with GmVDAC1D (voltage-dependent anion channel). The cytotoxicity induced by the expression of GmSYP31A could be relieved either with the addition of an inhibitor of VDAC protein, or by silencing the VDAC gene. Taken together, our data not only demonstrate that α-SNAP works together with GmSYP31A to increase SCN resistance through triggering cell death, but also highlight the unexplored link between the mitochondrial apoptosis pathway and vesicle trafficking.

Extreme parsimony in ATP consumption by 20S complexes in the global disassembly of single SNARE complexes

Fueled by ATP hydrolysis in N-ethylmaleimide sensitive factor (NSF), the 20S complex disassembles rigid SNARE (soluble NSF attachment protein receptor) complexes in single unraveling step. This global disassembly distinguishes NSF from other molecular motors that make incremental and processive motions, but the molecular underpinnings of its remarkable energy efficiency remain largely unknown. Using multiple single-molecule methods, we found remarkable cooperativity in mechanical connection between NSF and the SNARE complex, which prevents dysfunctional 20S complexes that consume ATP without productive disassembly. We also constructed ATP hydrolysis cycle of the 20S complex, in which NSF largely shows randomness in ATP binding but switches to perfect ATP hydrolysis synchronization to induce global SNARE disassembly, minimizing ATP hydrolysis by non-20S complex-forming NSF molecules. These two mechanisms work in concert to concentrate ATP consumption into functional 20S complexes, suggesting evolutionary adaptations by the 20S complex to the energetically expensive mechanical task of SNARE complex disassembly.

Conformational Dynamics of SNARE Proteins during NSF‐Mediated Disassembly

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins play key roles in cellular processes involved in vesicle trafficking and neurotransmitter release of synaptic vesicles. Neuronal SNAREs are composed of syntaxin-1A, SNAP-25A and synaptobrevin-2, forming a highly stable four-helix bundle to provide the energy necessary to drive membrane fusion between the synaptic vesicle and the plasma membrane. However, the mechanistic details underlying SNARE complex disassembly is largely unknown. NSF (N-ethylmaleimide-sensitive factor), a member of AAA+ ATPase family, together with αSNAP (alpha soluble NSF attachment protein), disassembles the post-fusion SNARE complex to maintain the pool of individual SNARE proteins for recurring rounds of vesicle fusion. Using smFRET (single-molecule fluorescence resonance energy transfer), we monitored the conformational dynamics of individual SNARE proteins during the NSF-mediated disassembly process. Interestingly, all three SNARE proteins underwent order-disorder transitions during disassembly and vice versa during re-assembly into SNARE complex. In addition, we discovered a unique intermediate conformational pathway of SNAP-25A during NSF-mediated disassembly process. This notion is in line with recent findings where the N-terminus of SNAP-25A engages through the D1 pore of NSF, likely involving conformational changes. Taken together, we suggest a novel conformational pathway essential for regulating SNARE complex disassembly as well as assembly during synaptic vesicle fusion.

Role of Alpha‐Synuclein in Parkinson's Disease

While Parkinson's Disease is a multifactorial disease, influenced by both genetics and the environment, alpha-synuclein was the first genetic factor to be linked to the disease. It has henceforth become a target in therapeutic research. A-synuclein is a 140 amino acid neuronal protein that primarily regulates synaptic activity. It is considered to be intrinsically disordered as it does not have a defined structure in aqueous solutions. However, the protein forms α-helical structures when it binds to negatively charged lipids, such as phospholipids in cell membranes. Α-synuclein is a member of the synculein protein family, a group of three neuronal proteins with a highly conserved alpha-helical lipid binding domain. Synucleins have been associated with a number of neurodegenerative disorders, including Parkinson's Disease (PD) and Alzheimer's Disease (AD), as well as some cancers. A-synuclein is unique in the synuclein family for its non-amyloid component (NAC) region, which has been linked to the formation of Lewy bodies. The wild type form of α-synuclein is coded from the SNCA gene. This form has several functions, but it primarily functions as a presynaptic protein that controls neurotransmitter release by acting as a chaperone in the folding of Soluble NSF Attachment Protein Receptors (SNAREs). SNAREs mediate vesicle fusion with membranes, while α-synuclein increases local Ca2+ release from microdomains to trigger ATP-induced exocytosis. Certain mutations in SNCA cause α-synuclein to polymerize into protofibrils that eventually coalesce into fibrils, a process called α-synuclein aggregation. Aggregation of α-synuclein leads to the creation of Lewy bodies, toxic clumps in the brains of patients with PD. PD is a progressive neurodegenerative disorder that affects movement. Common symptoms include bradykinesia, muscular rigidity, and tremor. Some studies have shown that deleting the NAC region prevented aggregation of α-synuclein. Other α-synuclein therapies have used receptor blocking strategies to inhibit the spread of the protein to other parts of the brain. There are also a variety of therapies that focus on preventing aggregation by decreasing the amount of α-synuclein in the brain. While such therapies have shown positive results in fruit flies, mice, and rats, human trials have not been conducted. Medications to control symptoms are the main treatment for PD; these medications typically work by increasing or acting as a substitute for dopamine, as PD patients have low dopamine concentrations. In severe cases, surgeries like deep brain stimulations have helped to lessen tremors. Patients are encouraged to make lifestyle changes, such as uptaking aerobic exercise or physical therapy, which can improve symptoms. Further research on the relationship between α-synuclein and Parkinson's Disease is required before human trials can begin. Nonetheless, the results of therapeutic studies have been promising.

PRRT2 gene and protein in human: characteristics, evolution and function

BackgroundThis study was designed to characterize human PRRT2 gene and protein, in order to provide theoretical reference for research on regulation of PRRT2 expression and its involvement in the pathogenesis of paroxysmal kinesigenic dyskinesia and other related diseases.MethodBiological softwares Protparam, Protscale, MHMM, SignalP 5.0, NetPhos 3.1, Swiss-Model, Promoter 2.0, AliBaba2.1 and EMBOSS were used to analyze the sequence characteristics, transcription factors of human PRRT2 and their binding sites in the promoter region of the gene, as well as the physicochemical properties, signal peptides, hydrophobicity property, transmembrane regions, protein structure, interacting proteins and functions of PRRT2 protein.Results(1) Evolutionary analysis of PRRT2 protein showed that the human PRRT2 had closest genetic distance from Pongo abelii. (2) The human PRRT2 protein was an unstable hydrophilic protein located on the plasma membrane. (3) The forms of random coil (67.65%) and alpha helix (23.24%) constituted the main secondary structure elements of PRRT2 protein. There were also multiple potential phosphorylation sites in the protein. (4) The results of ontology analysis showed that the cellular component of PRRT2 protein was located in the plasma membrane; the molecular function of PRRT2 included syntaxin-1 binding and SH3 domain binding; the PRRT2 protein is involved in biological processes of negative regulation of soluble NSF attachment protein receptor (SNARE) complex assembly and calcium-dependent activation of synaptic vesicle fusion. (5) String database analysis revealed 10 proteins with close interactions with the human PRRT2 protein. (6) There were at least two promoter regions in the PRRT2 gene within 2000 bp upstream the 5' flank, a 304-bp CpG island in the promoter region and four GC boxes in the 5' regulatory region of PRRT2 gene and we found 13 transcription factors that could bind the promoter region of the PRRT2 gene.ConclusionThese results provide important information for further studies on the role of PRRT2 gene and identify their functions.

The canonical α-SNAP is essential for gametophytic development in Arabidopsis.

The development of male and female gametophytes is a pre-requisite for successful reproduction of angiosperms. Factors mediating vesicular trafficking are among the key regulators controlling gametophytic development. Fusion between vesicles and target membranes requires the assembly of a fusogenic soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) complex, whose disassembly in turn ensures the recycle of individual SNARE components. The disassembly of post-fusion SNARE complexes is controlled by the AAA+ ATPase N-ethylmaleimide-sensitive factor (Sec18/NSF) and soluble NSF attachment protein (Sec17/α-SNAP) in yeast and metazoans. Although non-canonical α-SNAPs have been functionally characterized in soybeans, the biological function of canonical α-SNAPs has yet to be demonstrated in plants. We report here that the canonical α-SNAP in Arabidopsis is essential for male and female gametophytic development. Functional loss of the canonical α-SNAP in Arabidopsis results in gametophytic lethality by arresting the first mitosis during gametogenesis. We further show that Arabidopsis α-SNAP encodes two isoforms due to alternative splicing. Both isoforms interact with the Arabidopsis homolog of NSF whereas have distinct subcellular localizations. The presence of similar alternative splicing of human α-SNAP indicates that functional distinction of two α-SNAP isoforms is evolutionarily conserved.

Rapid removal of phagosomal ferroportin in macrophages contributes to nutritional immunity

AbstractNutrient sequestration is an essential facet of host innate immunity. Macrophages play a critical role in controlling iron availability through expression of the iron transport protein ferroportin (FPN), which extrudes iron from the cytoplasm to the extracellular milieu. During phagocytosis, the limiting phagosomal membrane, which derives from the plasmalemma, can be decorated with FPN and, if functional, will move iron from the cytosol into the phagosome lumen. This serves to feed iron to phagocytosed microbes and would be counterproductive to the many other known host mechanisms working to starve microbes of this essential metal. To understand how FPN is regulated during phagocytosis, we expressed FPN as a green fluorescent protein–fusion protein in macrophages and monitored its localization during uptake of various phagocytic targets, including Staphylococcus aureus, Salmonella enterica serovar Typhimurium, human erythrocytes, and immunoglobulin G opsonized latex beads. We find that FPN is rapidly removed, independently of Vps34 and PI(3)P, from early phagosomes and does not follow recycling pathways that regulate transferrin receptor recycling. Live-cell video microscopy showed that FPN movement on the phagosome is dynamic, with punctate and tubular structures forming before FPN is trafficked back to the plasmalemma. N-ethylmaleimide–sensitive factor, which disrupts soluble NSF attachment protein receptor (SNARE)–mediated membrane fusion and trafficking, prevented FPN removal from the phagosome. Our data support the hypothesis that removal of FPN from the limiting phagosomal membrane will, at the cellular level, ensure that iron cannot be pumped into phagosomes. We propose this as yet another mechanism of host nutritional immunity to subvert microbial growth.