Neuronal Plasma Membrane Research Articles

Effects of leptin treatment immediately after neonatal seizures on serum clusterin and VEGF levels and brain oxidative stress-related proteins and neurobehavioral phenotypes

The developing infant brain has a different response mechanism and repair potential for injury than the adult brain. There is an urgent need for new anticonvulsants to effectively control neonatal seizures while minimizing the drug's toxic damage to the developing brain. Leptin protects neuronal plasma membrane integrity, while it has clinical advantages in terms of anticonvulsant properties as well. This study aimed to evaluate the effect of immediate leptin treatment on the serum concentration of clusterin and vascular endothelial growth factor (VEGF), neuronal plasma membrane integrity-related proteins, and the neurobehavioral phenotypes following neonatal seizures. Leptin was injected i.p at a dose of 4 mg/kg 1 hour after daily 30 minutes prolonged seizures for consecutive 10 days. The serum biomarkers (clusterin and VEGF), and brain protein expression of ATF-4/GRP78/autophagy axis were measured by enzyme-linked immunosorbent assay and western blot in the acute phase (24 hours after the last seizures), respectively. Behavioral and histopathological phenotypes and seizure threshold were conducted from P23 to P34, respectively. There were rapid elevation of serum VEGF and clusterin as well as upregulated protein expression of ATF-4, GRP78, Beclin-1, and LC3 in the cerebral cortex and hippocampus following a neonatal seizure, which was restored by immediate treatment with leptin after seizures. In addition, leptin improved seizure-induced impaired neuropsychological, and cognitive functioning. Furthermore, leptin succeeded in ameliorating markers of neuronal excitability, including seizure threshold and hippocampal mossy fiber sprouting. In conclusion, this study verified that immediate treatment with leptin after neonatal seizures restored both rapid elevation of serum clusterin as well as upregulated protein expression of ATF-4/GRP78/autophagy axis in the cerebral cortex and hippocampus, which contributes to the recovery of neurological function.

Triggering of Major Brain Disorders by Protons and ATP: The Role of ASICs and P2X Receptors.

Adenosine triphosphate (ATP) is well-known as a universal source of energy in living cells. Less known is that this molecule has a variety of important signaling functions: it activates a variety of specific metabotropic (P2Y) and ionotropic (P2X) receptors in neuronal and non-neuronal cell membranes. So, a wide variety of signaling functions well fits the ubiquitous presence of ATP in the tissues. Even more ubiquitous are protons. Apart from the unspecific interaction of protons with any protein, many physiological processes are affected by protons acting on specific ionotropic receptors-acid-sensing ion channels (ASICs). Both protons (acidification) and ATP are locally elevated in various pathological states. Using these fundamentally important molecules as agonists, ASICs and P2X receptors signal a variety of major brain pathologies. Here we briefly outline the physiological roles of ASICs and P2X receptors, focusing on the brain pathologies involving these receptors.

This Week in The Journal

Kazuaki Ikeda, Masaki Kataoka, and Nobuaki K. Tanaka (see pages [8621–8628][1]) Current flowing through the plasma membrane of individual neurons causes fluctuations in the surrounding electrical field that can be detected with extracellular electrodes. Changes in the local field potential can

The roles of K+-dependent Na+/Ca2+ exchanger 2 (NCKX2) in methamphetamine-induced behavioral sensitization and conditioned place preference in mice

Drug addiction, including methamphetamine (METH) addiction, is a significant public health and social issue. Perturbations in intracellular Ca2+ homeostasis are associated with drug addiction. K+-dependent Na+/Ca2+ exchanger 2 (NCKX2) is located on neuronal cell membranes and constitutes a Ca2+ clearance mechanism, with key roles in synaptic plasticity. NCKX2 is associated with motor learning, memory, and cognitive functions. However, the role of NCKX2 in METH addiction remains unclear. In this study, we investigated the expression levels of NCKX2 in four addiction-related brain regions: the prefrontal cortex (PFc), nucleus accumbens (NAc), dorsal striatum (DS), and hippocampus (Hip) in a C57/BL6 mouse model of METH-induced conditioned place preference (CPP) and behavioral sensitization. Levels of NCKX2 were unchanged in these brain regions in mice with METH-induced CPP but were decreased in the PFc and NAc of mice with METH-induced behavioral sensitization. Adeno-associated virus (AAV)-mediated overexpression of NCKX2 in the PFc attenuated the expression phase of METH-induced behavioral sensitization in mice, whereas AAV-mediated knockdown of NCKX2 enhanced the effects of METH. Collectively, our results suggest that NCKX2 is involved in METH-induced behavioral sensitization but does not affect conditioned reward-related memory, highlighting the potential of NCKX2 as a molecular target for studying the mechanisms underscoring METH addiction.

Gender differences in cocaine-induced hyperactivity and dopamine transporter trafficking to the plasma membrane.

As well known, cocaine induces stimulant effects and dopamine transporter (DAT) trafficking to the plasma membrane of dopaminergic neurons. In the present study, we examined cocaine-induced hyperactivity along with cocaine-induced DAT trafficking and the recovery rate of the dopaminergic system in female rats in comparison with male rats, demonstrating interesting gender differences. Female rats are initially more sensitive to cocaine than male rats in terms of both the DAT trafficking and hyperactivity induced by cocaine. Particularly, intraperitoneal (i.p.) administration of 5 mg/kg cocaine induced significant hyperactivity and DAT trafficking in female rats but not in male rats. After repeated cocaine exposures (i.e., i.p. administration of 20 mg/kg cocaine every other day from Day 0 to Day 32), cocaine-induced hyperactivity in female rats gradually became a clear pattern of two phases, with the first phase of the hyperactivity lasting for only a few minutes and the second phase lasting for over an hour beginning at ~30 min, which is clearly different from that of male rats. It has also been demonstrated that the striatal DAT distribution of female rats may recover faster than that of male rats after multiple cocaine exposures. Nevertheless, despite the remarkable gender differences, our recently developed long-acting cocaine hydrolase, known as CocH5-Fc(M6), can similarly and effectively block cocaine-induced DAT trafficking and hyperactivity in both male and female rats.

Plasma membrane and brain dysfunction of the old: Do we age from our membranes?

One of the characteristics of aging is a gradual hypo-responsiveness of cells to extrinsic stimuli, mainly evident in the pathways that are under hormone control, both in the brain and in peripheral tissues. Age-related resistance, i.e., reduced response of receptors to their ligands, has been shown to Insulin and also to leptin, thyroid hormones and glucocorticoids. In addition, lower activity has been reported in aging for ß-adrenergic receptors, adenosine A2B receptor, and several other G-protein-coupled receptors. One of the mechanisms proposed to explain the loss of sensitivity to hormones and neurotransmitters with age is the loss of receptors, which has been observed in several tissues. Another mechanism that is finding more and more experimental support is related to the changes that occur with age in the lipid composition of the neuronal plasma membrane, which are responsible for changes in the receptors’ coupling efficiency to ligands, signal attenuation and pathway desensitization. In fact, recent works have shown that altered membrane composition—as occurs during neuronal aging—underlies reduced response to glutamate, to the neurotrophin BDNF, and to insulin, all these leading to cognition decay and epigenetic alterations in the old. In this review we present evidence that altered functions of membrane receptors due to altered plasma membrane properties may be a triggering factor in physiological decline, decreased brain function, and increased vulnerability to neuropathology in aging.

Molecular mechanisms of direct and indirect interplay between amyloid β42 oligomer and characteristic lipids

Accumulating evidence suggests that toxicity in patients with Alzheimer's disease originates from the deposition of Aβ42 aggregates on the neuronal cell membrane. However, the molecular mechanism underlying Aβ42 aggregation on the surface of different lipids is poorly understood. In this study, coarse-grained and all-atomic molecular dynamics (MD) simulations were used to characterize the assembly process of two Aβ42 pentameric oligomers and the perturbation “footprints” of three characteristic lipid constitute bilayer membranes: POPC, POPG, and their hybrid PcPg composed of POPG and POPC in a 1:3 ratio. Our results revealed that the Aβ decamer was first formed in the water phase prior to its contact with the lipid surface, indicating that the water phase plays an incubation role in Aβ42 oligomer aggregation. Moreover, the presence of any of the three lipids accelerated the assembly process of the two Aβ42 pentameric. The aggregation rate and aggregate conformation were strictly dependent on lipid charge, oligomer size, and degree of aggregation. In turn, the presence of oligomer impacted the surface of the lipid, generating a clear perturbation “footprint”, regardless of whether the interplay was direct or indirect, revealing for the first time that the indirect interaction is not seamless and can be detected clearly at the molecular level. Indirect interplay stands for the non-contacting interaction interfaced by the water phase, indicating a metastable state with long-range interaction under non-shaking conditions. Our results reveal the crucial role of non-contacting interactions in determining the phase status of zwitterionic membranes.

Plasma membrane phospholipid phosphatase-related proteins as pleiotropic regulators of neuron growth and excitability.

Neuronal plasma membrane proteins are essential for integrating cell extrinsic and cell intrinsic signals to orchestrate neuronal differentiation, growth and plasticity in the developing and adult nervous system. Here, we shed light on the family of plasma membrane proteins phospholipid phosphatase-related proteins (PLPPRs) (alternative name, PRGs; plasticity-related genes) that fine-tune neuronal growth and synaptic transmission in the central nervous system. Several studies uncovered essential functions of PLPPRs in filopodia formation, axon guidance and branching during nervous system development and regeneration, as well as in the control of dendritic spine number and excitability. Loss of PLPPR expression in knockout mice increases susceptibility to seizures, and results in defects in sensory information processing, development of psychiatric disorders, stress-related behaviors and abnormal social interaction. However, the exact function of PLPPRs in the context of neurological diseases is largely unclear. Although initially described as active lysophosphatidic acid (LPA) ecto-phosphatases that regulate the levels of this extracellular bioactive lipid, PLPPRs lack catalytic activity against LPA. Nevertheless, they emerge as atypical LPA modulators, by regulating LPA mediated signaling processes. In this review, we summarize the effects of this protein family on cellular morphology, generation and maintenance of cellular protrusions as well as highlight their known neuronal functions and phenotypes of KO mice. We discuss the molecular mechanisms of PLPPRs including the deployment of phospholipids, actin-cytoskeleton and small GTPase signaling pathways, with a focus on identifying gaps in our knowledge to stimulate interest in this understudied protein family.

Early stage β-amyloid-membrane interactions modulate lipid dynamics and influence structural interfaces and fibrillation

Molecular interactions between β-amyloid (Aβ) peptide and membranes contribute to the neuronal toxicity of Aβ and the pathology of Alzheimer’s disease. Neuronal plasma membranes serve as biologically relevant environments for the Aβ aggregation process as well as affect the structural polymorphisms of Aβ aggregates. However, the nature of these interactions is unknown. Here, we utilized solid-state NMR spectroscopy to explore the site-specific interactions between Aβ peptides and lipids in synaptic plasma membranes at the membrane-associated nucleation stage. The key results show that different segments in the hydrophobic sequence of Aβ initiate membrane binding and interstrand assembling. We demonstrate early stage Aβ-lipid interactions modulate lipid dynamics, leading to more rapid lipid headgroup motion and reduced lateral diffusive motion. These early events influence the structural polymorphisms of yielded membrane-associated Aβ fibrils with distinct C-terminal quaternary interface structure compared to fibrils grown in aqueous solutions. Based on our results, we propose a schematic mechanism by which Aβ-lipid interactions drive membrane-associated nucleation processes, providing molecular insights into the early events of fibrillation in biological environments.

Septin-5 and -7-IgGs: Neurologic, Serologic, and Pathophysiologic Characteristics.

We sought to determine clinical significance of neuronal septin autoimmunity and evaluate for potential IgG effects. Septin-IgGs were detected by indirect immunofluorescence assays (IFAs; mouse tissue and cell based) or Western blot. IgG binding to (and internalization of) extracellular septin epitopes were evaluated for by live rat hippocampal neuron assay. The impact of purified patient IgGs on murine cortical neuron function was determined by recording extracellular field potentials in a multielectrode array platform. Septin-IgGs were identified in 23 patients. All 8 patients with septin-5-IgG detected had cerebellar ataxia, and 7 had prominent eye movement disorders. One of 2 patients with co-existing septin-7-IgG had additional psychiatric phenotype (apathy, emotional blunting, and poor insight). Fifteen patients had septin-7 autoimmunity, without septin-5-IgG detected. Disorders included encephalopathy (11; 2 patients with accompanying myelopathy, and 2 were relapsing), myelopathy (3), and episodic ataxia (1). Psychiatric symptoms (≥1 of agitation, apathy, catatonia, disorganized thinking, and paranoia) were prominent in 6 of 11 patients with encephalopathic symptoms. Eight of 10 patients with data available (from 23 total) improved after immunotherapy, and a further 2 patients improved spontaneously. Staining of plasma membranes of live hippocampal neurons produced by patient IgGs (subclasses 1 and 2) colocalized with pre- and post-synaptic markers. Decreased spiking and bursting behavior in mixed cultures of murine glutamatergic and GABAergic cortical neurons produced by patient IgGs were attributable to neither antigenic crosslinking and internalization nor complement activation. Septin-IgGs are predictive of distinct treatment-responsive autoimmune central nervous system (CNS) disorders. Live neuron binding and induced electrophysiologic effects by patient IgGs may support septin-specific pathophysiology. ANN NEUROL 2022;92:1090-1101.

Skeletal Muscle is a Source of α-Synuclein with a Sarcolemmal Non-Lipid Raft Distribution.

Alpha synuclein (αSN) is a widely distributed protein in vertebrates whose physiological significance in many tissues remains unclear, being a key protein present in neurodegenerative disease such as Parkinson's Disease, Lewy Body Dementia, and in Sporadic-Inclusion Body Myositis. We search for αSN in skeletal muscle (SM) and neuronal plasma membrane isolated from brain (BR) from young and old rats. In isolated Sarcolemma from SM and from myelin-free neuronal plasma membrane isolated from BR, we determine by Western blot with anti-αSN (2B2D1) and anti-P-αSN (EP1536Y) the αSN membrane distribution, and the SM αSN intra and extracellular localization. In SM and BR, αSN is present in cytosol (CYT) as monomer and oligomer structures mainly tetramers (TM) and in plasma membranes as oligomers (TM and PM). All αSN oligomers were localized in non-lipid rafts and their distribution was unaffected by cholesterol-depletion with Methyl-β-Cyclodextrin. Membranes with natively high cholesterol content such as Transverse Tubules in SM and myelin in BR, reduce the presence of αSN. Under the same experimental conditions, aged SM and BR plasma membranes show ≈2 folds more αSN. In SM, αSN is extruded without cell damage in young and old rats. We conclude that oligomeric αSN are regularly present in SM and BR plasma membranes of healthy young and old rats. Interestingly, low-cholesterol content membranes promote αSN interaction. SM, the largest tissue in vertebrate body is a source of αSN and may contribute to the presence of αSN in extracellular fluids.

Effects of subtoxic 3-methylmethcathinone concentrations on neuronal cell electrical properties

Synthetic cathinones are commonly abused novel psychoactive substances (NPS) that are consumed alone or in combination with other psychoactive drugs via the oral, intranasal, or intravenous routes. These substances induce physiological and subjective effects typical of psychostimulant drugs, although with a faster onset and shorter duration when compared to amphetamine derivatives. A common consequence of their short half-lives and duration of effects, is repeated administration or bingeing that results in an increase in the number of associated deaths. New synthetic cathinones, now in the fourth generation, have increasing potency and toxicity as compared to those from previous generations. NPS may interfere with the electrical activity of the catecholaminergic neuron, causing damages to neuronal function. The aim of this research is to investigate the effects of 3-methylmethcathinone (3-MMC) on excitability of neuronal cells to identify mechanisms underlying its neurotoxicity. Functional techniques detecting neuronal electrical properties including Fura-2-video imaging and current clamp electrophysiology were applied to single neurons exposed to subtoxic 3-MMC concentrations. Changes in intracellular calcium homeostasis were correlated to neuronal electrical signals during exposure. Neuronal viability was measured in cells exposed to a large range of 3-MMC concentrations by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. This assay measures metabolic cell activity by detecting the conversion of the water-soluble yellow MTT dye to an insoluble purple formazan by active mitochondrial reductases. Formazan is solubilized and its concentration determined by optical density at 570 nm. Under conditions of neuronal toxicity, a significant change in metabolic activity is identified enabling detection of cell stress from exposure to a toxic agent. 3-MMC did not affect neuronal viability at 10–300 nM concentrations. Time-lapse experiments measuring intracellular calcium concentrations ([Ca2+]i) after membrane depolarization showed that 3-MMC prevented [Ca2+]i increases elicited by high K+. At the same time current-clamp experiments revealed that 3-MMC shifts membrane potential to more depolarized values at the same range of concentrations. Collectively, before inducing neurotoxicity, 3-MMC may interfere with the electrical properties of neuronal plasma membranes, thus, dysregulating [Ca2+]i homeostasis. 3-MMC interfered with membrane depolarization at subtoxic concentrations, suggesting the ability of this synthetic cathinone to modulate an as yet unknown voltage-dependent channel(s) at the neuronal level. Due to the lack of knowledge about mechanisms underlying 3-MMC neurotoxicity, investigation of putative targets may be useful for the treatment and/or prevention of its toxic effects in humans.

Total Internal Reflection Fluorescence (TIRF) Microscopy.

Total internal reflection fluorescence (TIRF) microscopy (TIRFM) is an elegant optical technique that provides for the excitation of fluorophores in an extremely thin axial region ("optical section"). The method is based on the principle that when excitation light is completely internally reflected in a transparent solid (e.g., coverglass) at its interface with liquid, an electromagnetic field, called the evanescent wave, is generated in the liquid at the solid-liquid interface and is the same frequency as the excitation light. Since the intensity of the evanescent wave exponentially decays with distance from the surface of the solid, only fluorescent molecules within a few hundred nanometers of the solid are efficiently excited. This overview will review the history, optical theory, and hardware configurations used in TIRFM. In addition, it will provide experimental details and methodological considerations for studying receptors at the plasma membrane in neurons. © 2022 Wiley Periodicals LLC.

How Staying Negative Is Good for the (Adult) Brain: Maintaining Chloride Homeostasis and the GABA-Shift in Neurological Disorders.

Excitatory-inhibitory (E-I) imbalance has been shown to contribute to the pathogenesis of a wide range of neurodevelopmental disorders including autism spectrum disorders, epilepsy, and schizophrenia. GABA neurotransmission, the principal inhibitory signal in the mature brain, is critically coupled to proper regulation of chloride homeostasis. During brain maturation, changes in the transport of chloride ions across neuronal cell membranes act to gradually change the majority of GABA signaling from excitatory to inhibitory for neuronal activation, and dysregulation of this GABA-shift likely contributes to multiple neurodevelopmental abnormalities that are associated with circuit dysfunction. Whilst traditionally viewed as a phenomenon which occurs during brain development, recent evidence suggests that this GABA-shift may also be involved in neuropsychiatric disorders due to the “dematuration” of affected neurons. In this review, we will discuss the cell signaling and regulatory mechanisms underlying the GABA-shift phenomenon in the context of the latest findings in the field, in particular the role of chloride cotransporters NKCC1 and KCC2, and furthermore how these regulatory processes are altered in neurodevelopmental and neuropsychiatric disorders. We will also explore the interactions between GABAergic interneurons and other cell types in the developing brain that may influence the GABA-shift. Finally, with a greater understanding of how the GABA-shift is altered in pathological conditions, we will briefly outline recent progress on targeting NKCC1 and KCC2 as a therapeutic strategy against neurodevelopmental and neuropsychiatric disorders associated with improper chloride homeostasis and GABA-shift abnormalities.

K+-Dependent Na+/Ca2+ Exchanger Isoform 2, Nckx2, Takes Part in the Neuroprotection Elicited by Ischemic Preconditioning in Brain Ischemia

Sodium/Calcium exchangers are neuronal plasma membrane antiporters which, by coupling Ca2+ and Na+ fluxes across neuronal membranes, play a relevant role in brain ischemia. The most brain-expressed isoform among the members of the K+-dependent Na+/Ca2+ exchanger family, NCKX2, is involved in the progression of the ischemic lesion, since both its knocking-down and its knocking-out worsens ischemic damage. The aim of this study was to elucidate whether NCKX2 functions as an effector in the neuroprotection evoked by ischemic preconditioning. For this purpose, we investigated: (1) brain NCKX2 expression after preconditioning and preconditioning + ischemia; (2) the contribution of AKT and calpain to modulating NCKX2 expression during preconditioning; and (3) the effect of NCKX2 knocking-out on the neuroprotection mediated by ischemic preconditioning. Our results showed that NCKX2 expression increased in those brain regions protected by ischemic preconditioning. These changes were p-AKT-mediated since its inhibition prevented NCKX2 up-regulation. More interestingly, NCKX2 knocking-out significantly prevented the protection exerted by ischemic preconditioning. Overall, our results suggest that NCKX2 plays a fundamental role in the neuroprotective effect mediated by ischemic preconditioning and support the idea that the enhancement of its expression and activity might represent a reasonable strategy to reduce infarct extension after stroke.

Transient Response and Firing Behaviors of Memristive Neuron Circuit.

The signal transmission mechanism of the Resistor-Capacitor (RC) circuit is similar to the intracellular and extracellular signal propagating mechanism of the neuron. Thus, the RC circuit can be utilized as the circuit model of the neuron cell membrane. However, resistors are electronic components with the fixed-resistance and have no memory properties. A memristor is a promising neuro-morphological electronic device with nonvolatile, switching, and nonlinear characteristics. First of all, we consider replacing the resistor in the RC neuron circuit with a memristor, which is named the Memristor-Capacitor (MC) circuit, then the MC neuron model is constructed. We compare the charging and discharging processes between the RC and MC neuron circuits. Secondly, two models are compared under the different external stimuli. Finally, the synchronous and asynchronous activities of the RC and MC neuron circuits are performed. Extensive experimental results suggest that the charging and discharging speed of the MC neuron circuit is faster than that of the RC neuron circuit. Given sufficient time and proper external stimuli, the RC and MC neuron circuits can produce the action potentials. The synchronous and asynchronous phenomena in the two neuron circuits reproduce nonlinear dynamic behaviors of the biological neurons.

Monosialotetrahexosylganglioside Promotes Early Aβ42 Oligomer Formation and Maintenance.

The aggregation of the amyloid beta (Aβ) peptide is associated with Alzheimer's disease (AD) pathogenesis. Cell membrane composition, especially monosialotetrahexosylganglioside (GM1), is known to promote the formation of Aβ fibrils, yet little is known about the roles of GM1 in the early steps of Aβ oligomer formation. Here, by using GM1-contained liposomes as a mimic of the neuronal cell membrane, we demonstrate that GM1 is a critical trigger of Aβ oligomerization and aggregation. We find that GM1 not only promotes the formation of Aβ fibrils but also facilitates the maintenance of Aβ42 oligomers on liposome membranes. We structurally characterize the Aβ42 oligomers formed on the membrane and find that GM1 captures Aβ by binding to its arginine-5 residue. To interrogate the mechanism of Aβ42 oligomer toxicity, we design a new liposome-based Ca2+-encapsulation assay and provide new evidence for the Aβ42 ion channel hypothesis. Finally, we determine the toxicity of Aβ42 oligomers formed on membranes. Overall, by uncovering the roles of GM1 in mediating early Aβ oligomer formation and maintenance, our work provides a novel direction for pharmaceutical research for AD.

Competitive inhibition of the classical complement pathway using exogenous single-chain C1q recognition proteins

Complement component C1q is a protein complex of the innate immune system with well-characterized binding partners that constitutes part of the classical complement pathway. In addition, C1q was recently described in the central nervous system as having a role in synapse elimination both in the healthy brain and in neurodegenerative diseases. However, the molecular mechanism of C1q-associated synapse phagocytosis is still unclear. Here, we designed monomer and multimer protein constructs, which comprised the globular interaction recognition parts of mouse C1q (globular part of C1q [gC1q]) as single-chain molecules (sc-gC1q proteins) lacking the collagen-like effector region. These molecules, which can competitively inhibit the function of C1q, were expressed in an Escherichia coli expression system, and their structure and capabilities to bind known complement pathway activators were validated by mass spectrometry, analytical size-exclusion chromatography, analytical ultracentrifugation, CD spectroscopy, and ELISA. We further characterized the interactions between these molecules and immunoglobulins and neuronal pentraxins using surface plasmon resonance spectroscopy. We demonstrated that sc-gC1qs potently inhibited the function of C1q. Furthermore, these sc-gC1qs competed with C1q in binding to the embryonal neuronal cell membrane. We conclude that the application of sc-gC1qs can reveal neuronal localization and functions of C1q in assays in vivo and might serve as a basis for engineering inhibitors for therapeutic purposes.

GM1 asymmetry in the membrane stabilizes pores

Cell membranes are highly asymmetric and their stability against poration is crucial for survival. We investigated the influence of membrane asymmetry on electroporation of giant unilamellar vesicles with membranes doped with GM1, a ganglioside asymmetrically enriched in the outer leaflet of neuronal cell membranes. Compared with symmetric membranes, the lifetimes of micronsized pores are about an order of magnitude longer suggesting that pores are stabilized by GM1. Internal membrane nanotubes caused by the GM1 asymmetry, obstruct and additionally slow down pore closure, effectively reducing pore edge tension and leading to leaky membranes. Our results point to the drastic effects this ganglioside can have on pore resealing in biotechnology applications based on poration as well as on membrane repair processes.

Clinical Case of a 36-Year-Old Man with Treatment-Resistant Paranoid Schizophrenia: Personalized Therapy Selection

Schizophrenia is a common and socially significant mental disorder that requires longterm use of antipsychotics (APs). Long-term use of APs increases the risk of developing adverse drug reactions (ADRs) and/or therapeutic resistance in some patients. This may be due to a genetically determined impairment of APs metabolism by cytochrome P450 enzymes and of Aps transport across the blood-brain barrier (BBB) and the cell membrane of APs target neurons in the brain. Pharmacogenetic testing (PGx) is a method to identify a group of patients with a high risk of developing AP-induced ADRs. The aim of the case report is to present the experience of using PGx in a 36-year-old patient with treatment-resistant schizophrenia and a medical history of AP-induced ADRs.