Voltage-gated Channels Research Articles

CACNA2D1 regulates the progression and influences the microenvironment of colon cancer.

Calcium voltage-gated channel auxiliary subunit alpha 2/delta 1 (CACNA2D1), a gene encoding a voltage-gated calcium channel, has been reported as an oncogene in several cancers. However, its role in colon cancer (CC) remains unclear. This study aimed to investigate the function of CACNA2D1 and its effect on the microenvironment in CC. Immunohistochemistry (IHC) analysis was performed on samples collected from 200 patients with CC who underwent curative colectomy. Knockdown experiments were performed using CACNA2D1 siRNA in the human CC cell lines HCT116 and RKO, and cell proliferation, cycle, apoptosis, and migration were then analyzed. The fibroblast cell line CCD-18Co was co-cultured with CC cell lines to determine the effect of CACNA2D1 on fibroblasts and the relationship between CACNA2D1 and the cancer microenvironment. Gene expression profiles of cells were analyzed using microarray analysis. IHC revealed that high CACNA2D1 expression was an independent poor prognostic factor in patients with CC and that CACNA2D1 expression and the stroma are correlated. CACNA2D1 depletion decreased cell proliferation and migration; CACNA2D1 knockdown increased the number of cells in the sub-G1 phase and induced apoptosis. CCD-18Co and HCT116 or RKO cell co-culture revealed that CACNA2D1 affects the cancer microenvironment via fibroblast regulation. Furthermore, microarray analysis showed that the p53 signaling pathway and epithelial-mesenchymal transition-associated pathways were enhanced in CACNA2D1-depleted HCT116 cells. CACNA2D1 plays an important role in the progression and the microenvironment of CC by regulating fibroblasts and may act as a biomarker for disease progression and a therapeutic target for CC.

Deletion of Dictyostelium tpc2 gene forms multi-tipped structures, regulates autophagy and cell-type patterning.

Two pore channels (TPCs) are voltage-gated ion channel superfamily members that release Ca2+ from acidic intracellular stores and are ubiquitously present in both animals and plants. Starvation initiates multicellular development in Dictyostelium discoideum. Increased intracellular calcium levels bias Dictyostelium cells towards the stalk pathway and thus we decided to analyze the role of TPC2 in development, differentiation, and autophagy. We showed TPC2 protein localizes in lysosome-like acidic vesicles and the in situ data showed stalk cell biasness. Deletion of tpc2 showed defective and delayed development with formation of multi-tipped structures attached to a common base, while tpc2OE cells showed faster development with numerous small-sized aggregates and wiry fruiting bodies. The tpc2OE cells showed higher intracellular cAMP levels as compared to the tpc2- cells while pinocytosis was found to be higher in the tpc2- cells. Also, TPC2 regulates cell-substrate adhesion and cellular morphology. Under nutrient starvation, deletion of tpc2 reduced autophagic flux as compared to Ax2. During chimera formation, tpc2- cells showed a bias towards the prestalk/stalk region while tpc2OE cells showed a bias towards the prespore/spore region. tpc2 deficient strain exhibits aberrant cell-type patterning and loss of distinct boundary between the prestalk/prespore regions. TPC2 is required for effective development and differentiation in Dictyostelium and supports autophagic cell death and cell-type patterning. Decreased calcium due to deletion of tpc2 inhibit autophagic flux.

Generation of KCNH2 heterozygous knockout induced pluripotent stem cell (iPSC) line (Long and Short QT Syndrome)

KCNH2 (Potassium Voltage-Gated Channel Subfamily H Member) encodes a voltage-activated potassium channel role as rapidly activating-delayed rectifier potassium channel that plays an essential role in the final repolarization of the ventricular action potential. Mutations in this gene can cause long QT syndrome and short QT syndrome. Transcript variants encoding distinct isoforms were also identified. In this study, we generated induced pluripotent stem cells (iPSC) from a healthy individual by electroporation of peripheral blood mononuclear cells and generated a KCNH2 heterozygous knockout human iPSC line via CRISPR/Cas9 gene editing. The resulting iPSCs had a normal karyotype, were free of genomically integrated epitomal plasmids, expressed pluripotency markers, and maintained trilineage differentiation potential.

Abstract 4705: Repetitive membrane potential oscillations enhance metformin's antiproliferative effect in glioblastoma stem cells

Abstract Glioblastoma (GB) is the most common and lethal brain tumor and there is a general agreement that GB stem cells (GSCs) are primarily responsible for its high aggressiveness and recurrence. It was recently reported that GSCs are enriched in the transmembrane form of CLIC1 protein (tmCLIC1) and its inhibition was shown to impair tumor growth both in vitro and in vivo. IAA94 hampers tmCLIC1 function but could not be used in clinics. However, tmCLIC1 is also sensitive to metformin, the most used drug to treat type-2 diabetes. Metformin has been demonstrated to have the same effect as IAA94 in in vitro experiments, resulting in an antitumoral action on cancer cells. Moreover, GB orthotopic mouse model treated with metformin shows a 50% survival compared to control animals, even if metformin concentration in the mice brain resulted in the nanomolar range. In this scenario, the main aim of this work is to enhance the effect of metformin able to reach the brain, improving its antitumoral activity in GB. The interaction between metformin and tmCLIC1 occurs only when this protein is in its open state. TmCLIC1 has the peculiarity of being a voltage-dependent ion channel that opens at depolarized voltages. Thus, our strategy is to apply electromagnetic field (EMF) stimulation to induce repetitive membrane depolarization, increasing metformin-tmCLIC1 binding. Our results show that EMF stimulation induces the close-to-open transitions of tmCLIC1, resulting in a 10-fold decrease of the operative concentration of Metformin. This was verified initially in vitro with GSC culture and spheroids model and afterward confirmed also in an in vivo model. The project’s long-term goal is to combine transcranial stimulation and metformin administration in patients as an adjuvant therapy able to target cells that are resistant to chemotherapy and drive tumor relapse. Citation Format: Ivan Verduci, Gaetano Cannavale, Guido Rey, Francesca Cianci, Alessandro Fantin, Michele Mazzanti. Repetitive membrane potential oscillations enhance metformin's antiproliferative effect in glioblastoma stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4705.

Roles of KCNA2 in Neurological Diseases: from Physiology to Pathology.

Potassium voltage-gated channel subfamily a member 2 (Kv1.2, encoded by KCNA2) is highly expressed in the central and peripheral nervous systems. Based on the patch clamp studies, gain-of function (GOF), loss-of-function (LOF), and a mixed type (GOF/LOF) variants can cause different conditions/disorders. KCNA2-related neurological diseases include epilepsy, intellectual disability (ID), attention deficit/hyperactive disorder (ADHD), autism spectrum disorder (ASD), pain as well as autoimmune and movement disorders. Currently, the molecular mechanisms for the reported variants in causing diverse disorders are unknown. Consequently, this review brings up to date the related information regarding the structure and function of Kv1.2 channel, expression patterns, neuronal localizations, and tetramerization as well as important cell and animal models. In addition, it provides updates on human genetic variants, genotype-phenotype correlations especially highlighting the deep insight into clinical prognosis of KCNA2-related developmental and epileptic encephalopathy, mechanisms, and the potential treatment targets for all KCNA2-related neurological disorders.

Bioinspired carbon nanotube-based nanofluidic ionic transistor with ultrahigh switching capabilities for logic circuits.

The voltage-gated ion channels, also known as ionic transistors, play substantial roles in biological systems and ion-ion selective separation. However, implementing the ultrafast switchable capabilities and polarity switching of ionic transistors remains a challenge. Here, we report a nanofluidic ionic transistor based on carbon nanotubes, which exhibits an on/off ratio of 104 at operational gate voltage as low as 1 V. By controlling the morphology of carbon nanotubes, both unipolar and ambipolar ionic transistors are realized, and their on/off ratio can be further improved by introducing an Al2O3 dielectric layer. Meanwhile, this ionic transistor enables the polarity switching between p-type and n-type by controlled surface properties of carbon nanotubes. The implementation of constructing ionic circuits based on ionic transistors is demonstrated, which enables the creation of NOT, NAND, and NOR logic gates. The ionic transistors are expected to have profound implications for low-energy consumption computing devices and brain-machine interfacing.

Bio-inspired Two-dimensional Nanofluidic Ionic Transistor for Neuromorphic Signal Processing.

Voltage-gated ion channels prevalent in neurons play important roles in generating action potential and information transmission by responding to transmembrane potential. Fabricating bio-inspired ionic transistors with ions as charge carriers will be crucial for realizing neuro-inspired devices and brain-liking computing. Here, we reported a two-dimensional nanofluidic ionic transistor based on a MXene membrane with sub-1 nm interlayer channels. By applying a gating voltage on the MXene nanofluidic, a transmembrane potential will be generated to active the ionic transistor, which is similar to the transmembrane potential of neuron cells and can be effectively regulated by changing membrane parameters, e.g., thickness, composition, and interlayer spacing. For the symmetric MXene nanofluidic, a high on/off ratio of ~2000 can be achieved by forming an ionic depletion or accumulation zone, contingent on the sign of the gating potential. An asymmetric PET/MXene-composited nanofluidic transitioned the ionic transistor from ambipolar to unipolar, resulting in a more sensitive gate voltage characteristic with a low subthreshold swing of 560 mV/decade. Furthermore, ionic logic gate circuits, including the "NOT", "NAND", and "NOR" gate, were implemented for neuromorphic signal processing successfully, which provides a promising pathway towards highly parallel, low energy consumption, and ion-based brain-like computing.

The role of lncRNAKCNQ1OT1/miR-301b/Tcf7 axis in cardiac hypertrophy.

Cardiac hypertrophy, acting as a pathologic process of chronic hypertension and coronary disease, and its underlying mechanisms still need to be explored. Long non-coding RNA (LncRNA) potassium voltage-gated channel subfamily Q member 1 Transcript 1 (KCNQ1OT1) has been implicated in myocardial infarction. However, its role in cardiac hypertrophy remains reported. To explore the regulated effect of lncRNAKCNQ1OT1 and miR-301b in cardiac hypertrophy, gain-and-lose function assays were tested. The expression of lncRNAKCNQ1OT1 and miR-301b were tested by quantitative real time polymerase chain reaction (qRT-PCR). The levels of transcription factor 7 (Tcf7), Proto-oncogene c-myc (c-myc), Brainnatriureticpeptide (BNP)and β-myosin heavy chain (β-MHC) were detected by Western blot. Additionally, luciferase analysis revealed interaction between lncRNAKCNQ1OT1, BNPβ-MHCmiR-301b, and Tcf7. LncRNAKCNQ1OT1 overexpression significantly induced cardiac hypertrophy. Furthermore, lncRNAKCNQ1OT1 acts as a sponge for microRNA-301b, which exhibited lower expression in cardiac hypertrophy model, indicating an anti-hypertrophic role. Furthermore, the BNP and β-MHC expression increased, as well as cardiomyocyte surface area, with Ang II treatment, while the effect was repealed by miR-301b. Moreover, the protein expression of Tcf7 was inversely regulated by miR-301b and Antisense miRNA oligonucleotides (AMO)-301b. Our study has shown that overexpression of lncRNAKCNQ1OT1 could promote the development of cardiac hypertrophy by regulating miR-301b and Tcf7. Therefore, inhibition of lncRNAKCNQ1OT1 might be a potential therapeutic strategy for cardiac hypertrophy.

Potential therapeutic targets for hypotension in duchenne muscular dystrophy

Duchenne Muscular Dystrophy (DMD) is marked by genetic mutations occurring in the DMD gene, which is widely expressed in the cardiovascular system. In addition to developing cardiomyopathy, patients with DMD have been reported to be susceptible to the development of symptomatic hypotension, although the mechanisms are unclear. Analysis of single-cell RNA sequencing data has identified potassium voltage-gated channel subfamily Q member 5 (KCNQ5) and possibly ryanodine receptor 2 (RyR2) as potential candidate hypotension genes whose expression is significantly upregulated in the vascular smooth muscle cells of DMD mutant mice. We hypothesize that heightened KCNQ5 and RyR2 expression contributes to decreased arterial blood pressure in patients with DMD. Exploring pharmacological approaches to inhibit the KCNQ5 and RyR2 channels holds promise in managing the systemic hypotension observed in individuals with DMD. This avenue of investigation presents new prospects for improving clinical outcomes for these patients.

Structural modeling of ion channels using AlphaFold2, RoseTTAFold2, and ESMFold

ABSTRACT Ion channels play key roles in human physiology and are important targets in drug discovery. The atomic-scale structures of ion channels provide invaluable insights into a fundamental understanding of the molecular mechanisms of channel gating and modulation. Recent breakthroughs in deep learning-based computational methods, such as AlphaFold, RoseTTAFold, and ESMFold have transformed research in protein structure prediction and design. We review the application of AlphaFold, RoseTTAFold, and ESMFold to structural modeling of ion channels using representative voltage-gated ion channels, including human voltage-gated sodium (NaV) channel - NaV1.8, human voltage-gated calcium (CaV) channel – CaV1.1, and human voltage-gated potassium (KV) channel – KV1.3. We compared AlphaFold, RoseTTAFold, and ESMFold structural models of NaV1.8, CaV1.1, and KV1.3 with corresponding cryo-EM structures to assess details of their similarities and differences. Our findings shed light on the strengths and limitations of the current state-of-the-art deep learning-based computational methods for modeling ion channel structures, offering valuable insights to guide their future applications for ion channel research.

In silico investigation of potential phytoconstituents against ligand- and voltage-gated ion channels as antiepileptic agents.

The online version contains supplementary material available at 10.1007/s13205-024-03948-1.

Physiological role of potassium channels in mammalian germ cell differentiation, maturation, and capacitation

Ion channels are essential for differentiation and maturation of germ cells, and even for fertilization in mammals. Different types of potassium channels have been identified, which are grouped into voltage-gated channels (Kv), ligand-gated channels (Kligand ), inwardly rectifying channels (Kir ), and tandem pore domain channels (K2P ). The present review includes recent findings on the role of potassium channels in sperm physiology of mammals. While most studies conducted thus far have been focused on the physiological role of voltage- (Kv1, Kv3, and Kv7) and calcium-gated channels (SLO1 and SLO3) during sperm capacitation, especially in humans and rodents, little data about the types of potassium channels present in the plasma membrane of differentiating germ cells exist. In spite of this, recent evidence suggests that the content and regulation mechanisms of these channels vary throughout spermatogenesis. Potassium channels are also essential for the regulation of sperm cell volume during epididymal maturation and for preventing premature membrane hyperpolarization. It is important to highlight that the nature, biochemical properties, localization, and regulation mechanisms of potassium channels are species-specific. In effect, while SLO3 is the main potassium channel involved in the K+ current during sperm capacitation in rodents, different potassium channels are implicated in the K+ outflow and, thus, plasma membrane hyperpolarization during sperm capacitation in other mammalian species, such as humans and pigs. Potassium conductance is essential for male fertility, not only during sperm capacitation but throughout the spermiogenesis and epididymal maturation.

Continuous spike-wave of slow sleep in a patient with KCNB1-related epilepsy responsive to highly purified cannabidiol: a case report and comparison with literature

ABSTRACT KCNB1-associated encephalopathy is characterized by intellectual disability (ID), autism spectrum disorder and epilepsy. Specific treatments are still lacking. We describe a 12-year-old boy with severe ID and treatment-resistant seizures due to a pathogenic KCNB1 variant. His EEG showed a CSWS pattern. Aged 11, he started treatment with highly purified cannabidiol (CBD) and has been seizure free for 18 months, with significant EEG and social skills improvements. This suggests CBD may benefit CSWS, likely due to its anti-inflammatory properties. Some preclinical studies also indicate CBDs interact with voltage-gated channels, leading us to speculate its possible role for treating KCNB1 related encephalopathy.

A synthetic flavonoid derivate in the plasma membrane transforms the voltage-clamp fluorometry signal of CiHv1.

Voltage-clamp fluorometry (VCF) enables the study of voltage-sensitive proteins through fluorescent labeling accompanied by ionic current measurements for voltage-gated ion channels. The heterogeneity of the fluorescent signal represents a significant challenge in VCF. The VCF signal depends on where the cysteine mutation is incorporated, making it difficult to compare data among different mutations and different studies and standardize their interpretation. We have recently shown that the VCF signal originates from quenching amino acids in the vicinity of the attached fluorophores, together with the effect of the lipid microenvironment. Based on these, we performed experiments to test the hypothesis that the VCF signal could be altered by amphiphilic quenching molecules in the cell membrane. Here we show that a phenylalanine-conjugated flavonoid (4-oxo-2-phenyl-4H-chromene-7-yl)-phenylalanine, (later Oxophench) has potent effects on the VCF signals of the Ciona intestinalis HV1 (CiHv1) proton channel. Using spectrofluorimetry, we showed that Oxophench quenches TAMRA (5(6)-carboxytetramethylrhodamine-(methane thiosulfonate)) fluorescence. Moreover, Oxophench reduces the baseline fluorescence in oocytes and incorporates into the cell membrane while reducing the membrane fluidity of HEK293 cells. Our model calculations confirmed that Oxophench, a potent membrane-bound quencher, modifies the VCF signal during conformational changes. These results support our previously published model of VCF signal generation and point out that a change in the VCF signal may not necessarily indicate an altered conformational transition of the investigated protein.

Association between Single Nucleotide Polymorphisms of PRKD1 and KCNQ3 Gene and Milk Quality Traits in Gannan Yak (Bos grunniens).

Protein kinase D1 (PRKD1) functions primarily in normal mammary cells, and the potassium voltage-gated channel subfamily Q member 3 (KCNQ3) gene plays an important role in controlling membrane potential and neuronal excitability, it has been found that this particular gene is linked to the percentage of milk fat in dairy cows. The purpose of this study was to investigate the relationship between nucleotide polymorphisms (SNPs) of PRKD1 and KCNQ3 genes and the milk quality of Gannan yak and to find molecular marker sites that may be used for milk quality breeding of Gannan yak. Three new SNPs were detected in the PRKD1 (g.283,619T>C, g.283,659C>A) and KCNQ3 gene (g.133,741T>C) of 172 Gannan lactating female yaks by Illumina yak cGPS 7K liquid-phase microarray technology. Milk composition was analyzed using a MilkoScanTM milk composition analyzer. We found that the mutations of these three loci significantly improved the lactose, milk fat, casein, protein, non-fat milk solid (SNF) content and acidity of Gannan yaks. The lactose content of the TC heterozygous genotype population at g.283,619T>C locus was significantly higher than that of the TT wild-type population (p < 0.05); the milk fat content of the CA heterozygous genotype population at g.283,659C>A locus was significantly higher than that of the CC wild-type and AA mutant populations (p < 0.05); the casein, protein and acidity of the CC mutant and TC heterozygous groups at the g.133,741T>C locus were significantly higher than those of the wild type (p < 0.05), and the SNF of the TC heterozygous group was significantly higher than that of the mutant group (p < 0.05). The results showed that PRKD1 and KCNQ3 genes could be used as candidate genes affecting the milk traits of Gannan yak.

Interaction with stomatin directs human proton channels into cholesterol-dependent membrane domains

Many membrane proteins are modulated by cholesterol. Here we report profound effects of cholesterol depletion and restoration on the human voltage-gated proton channel, hHV1, in excised patches but negligible effects in the whole-cell configuration. Despite the presence of a putative cholesterol-binding site, a CARC motif in hHV1, mutation of this motif did not affect cholesterol effects. The murine HV1 lacks a CARC sequence but displays similar cholesterol effects. These results argue against a direct effect of cholesterol on the HV1 protein. However, the data are fully explainable if HV1 preferentially associates with cholesterol-dependent lipid domains, or “rafts.” The rafts would be expected to concentrate in the membrane/glass interface and to be depleted from the electrically accessible patch membrane. This idea is supported by evidence that HV1 channels can diffuse between seal and patch membranes when suction is applied. Simultaneous truncation of the large intracellular N and C termini of hHV1 greatly attenuated the cholesterol effect, but C truncation alone did not; this suggests that the N terminus is the region of attachment to lipid domains. Searching for abundant raft-associated proteins led to stomatin. Co-immunoprecipitation experiment results were consistent with hHV1 binding to stomatin. The stomatin-mediated association of HV1 with cholesterol-dependent lipid domains provides a mechanism for cells to direct HV1 to subcellular locations where it is needed, such as the phagosome in leukocytes.

CLCN3 in mediating the proliferation of human ovarian cancer cells.

Chloride channel-3 (CLCN3), a crucial component of the voltage-gated chloride channel family, is implicated in numerous physiological and pathophysiological processes. This study aimed to investigate the characteristics of CLCN3 in pancancer and its influence on the immune response through the use of a range of databases. Concurrently, we assessed the impact of CLCN3 on the proliferation of ovarian cancer (OC) cells and explored its potential mechanisms. We employed the Tumor Immune Estimation Resource (TIMER) 2.0 and Clinical Proteomic Tumor Analysis Consortium (CPTAC) databases to examine the messenger RNA (mRNA) and the protein expression of CLCN3 across various cancers. The prognostic significance of CLCN3 was evaluated using the Gene Expression Profiling Interactive Analysis 2.0 (GEPIA 2.0) database. The University of Alabama at Birmingham Cancer Data Analysis Portal (UALCAN) facilitated the analysis of CLCN3 promoter methylation levels. The association between CLCN3 expression and tumor-infiltrating immune cells was investigated using various algorithms. The cBioportal database facilitated the analysis of CLCN3 mutations and mutation sites across various cancers. The Tumor-Immune System Interactions Database (TISIDB) database was employed to explore the correlation between CLCN3 expression and immune or molecular subtypes across a variety of cancer types. We collected ovarian tissue samples, encompassing both normal ovarian and OC tissues. The human OC cell lines, SKOV3 cells and OVCAR433 cells, were cultured. CLCN3 expression was determined via reverse-transcription quantitative polymerase chain reaction (RT-qPCR), while phosphatidylinositol 3-kinase/Akt kinase (PI3K/AKT) expression was detected using Western blot. We utilized small interfering RNA (siRNA) technology to suppress CLCN3 expression. The proliferative capacity of SKOV3 and OVCAR433 cells was assessed using the Cell Counting Kit 8 (CCK-8) assay. CLCN3 demonstrated an aberrant expression in a number of cancer types and was markedly reduced in OC tissues. Poor prognosis in cervical squamous cell cancer and myeloid leukemia was linked to excessive expression of CLCN3. The examination of immune cell infiltration, which included CD8+ T cells, B cells, T regulatory cells, and cancer-associated fibroblast cells, showed a strong association with aberrant CLCN3 expression. Following the use of siRNA technology, the ability of the ovarian carcinoma cell line SKOV3 and OVCAR433 to proliferate as well as the expression of PI3K/AKT both increased. CLCN3 is a possible biomarker for immune-related processes and the prognosis of cancer, and the PI3K/AKT signaling pathway may affect OC cells' ability to proliferate.

The Roles of Potassium Channels and Nitric oxide in the Modulation of Apelin induced-relaxation in Isolated Diabetic Rat Aorta

Diabetes is associated with endothelial dysfunction, which impairs blood vesselscapacity to maintain vascular tone. Apelin is an adipocyte-produced relaxing factor that has endothelium-dependent and nitric oxide (NO)-mediated vasorelaxant effects. The current study investigated how streptozotocin (STZ)-induced type one diabetes modulates the mechanisms involved in aortic vascular response to apelin, focusing on the role of potassium channels and endothelial derived relaxing factors (EDRF). In this study, precontracted rat thoracic aortic segments were pre-incubated with the NO inhibitor, cyclooxygenase (COX) inhibitor and potassium channels blockers including: non-selective calcium-activated potassium channel, big conductance calcium-activated potassium channels (BKca), intermediate conductance calcium activated potassium channels (IKca), delayed inward rectifier potassium channels (Kir), adenosine triphosphates-sensitive potassium channels (KATP) and voltage sensitive potassium channels (Kv) blockers, then cumulative concentrations of apelin were applied to each group in both non-diabetic and diabetic conditions. The statistical analysis between diabetic and non-diabetic groups revealed that endothelial impairment induced by diabetes in rat thoracic aorta remarkably attenuated the vascular responses to apelin. An important new finding in this study was that almost all potassium channels blockers noticeably P&lt;0.001 increased apelin efficacy with relatively no changes in the peptide potency. However, in diabetic aortic segments, the non-selective Kca, BKca blockers, NO inhibitor and COX inhibitor reversed vascular responses to apelin, but Kir, KATP and Kv blockers significantly reduced vascular responses to apelin in comparison to control rats. It is worth noting that diabetes did not only alter the peptide potency in these experimental groups but also significantly increased the maximum responses when Kca and BKca blockers preincubated. In conclusion, our findings shed light on the mechanisms behind diabetes-induced aortic artery hypo-reactivity to apelin which involve the inhibition of endothelial NO synthase activities and decreased contribution of Kca, BKca, IKca, Kv, Kir and KATP channels.

Proteasome localization and activity in pig brain and in vivo small molecule screening for activators.

Loss of proteasome function, proteinopathy, and proteotoxicity may cause neurodegeneration across the human lifespan in several forms of brain injury and disease. Drugs that activate brain proteasomes in vivo could thus have a broad therapeutic impact in neurology. Using pigs, a clinically relevant large animal with a functionally compartmental gyrencephalic cerebral cortex, we evaluated the localization and biochemical activity of brain proteasomes and tested the ability of small molecules to activate brain proteasomes. By Western blotting, proteasome protein subunit PSMB5 and PSMA3 levels were similar in different pig brain regions. Immunohistochemistry for PSMB5 showed localization in the cytoplasm (diffuse and particulate) and nucleus (cytoplasm < nucleus). Some PSMB5 immunoreactivity was colocalized with mitochondrial (voltage-gated anion channel and cyclophilin D) and cell death (Aven) proteins in the neuronal soma and neuropil in the neocortex of pig and human brains. In the nucleus, PSMB5 immunoreactivity was diffuse, particulate, and clustered, including perinucleolar decorations. By fluorogenic assay, proteasome chymotrypsin-like activities (CTL) in crude tissue soluble fractions were generally similar within eight different pig brain regions. Proteasome CTL activity in the hippocampus was correlated with activity in nasal mucosa biopsies. In pilot analyses of subcellular fractions of pig cerebral cortex, proteasome CTL activity was highest in the cytosol and then ~50% lower in nuclear fractions; ~15-20% of total CTL activity was in pure mitochondrial fractions. With in-gel activity assay, 26S-singly and -doubly capped proteasomes were the dominant forms in the pig cerebral cortex. With a novel in situ histochemical activity assay, MG132-inhibitable proteasome CTL activity was localized to the neuropil, as a mosaic, and to cell bodies, nuclei, and centrosome-like perinuclear satellites. In piglets treated intravenously with pyrazolone derivative and chlorpromazine over 24 h, brain proteasome CTL activity was modestly increased. This study shows that the proteasome in the pig brain has relative regional uniformity, prominent nuclear and perinuclear presence with catalytic activity, a mitochondrial association with activity, 26S-single cap dominance, and indications from small molecule systemic administration of pyrazolone derivative and chlorpromazine that brain proteasome function appears safely activable.

Differential Proteomic Analysis of Low-Dose Chronic Paralytic Shellfish Poisoning.

Shellfish poisoning is a common food poisoning. To comprehensively characterize proteome changes in the whole brain due to shellfish poisoning, Tandem mass tag (TMT)-based differential proteomic analysis was performed with a low-dose chronic shellfish poisoning model in mice. A total of 6798 proteins were confidently identified, among which 123 proteins showed significant changes (fold changes of >1.2 or <0.83, p < 0.05). In positive regulation of synaptic transmission, proteins assigned to a presynaptic membrane (e.g., Grik2) and synaptic transmission (e.g., Fmr1) changed. In addition, altered proteins in nervous system development were observed, suggesting that mice suffered nerve damage due to the nervous system being activated. Ion transport in model mice was demonstrated by a decrease in key enzymes (e.g., Kcnj11) in voltage-gated ion channel activity and solute carrier family (e.g., Slc38a3). Meanwhile, alterations in transferase activity proteins were observed. In conclusion, these modifications observed in brain proteins between the model and control mice provide valuable insights into understanding the functional mechanisms underlying shellfish poisoning.