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Nature Communications May 2024The two-pore domain potassium (K) channels TREK-1 and TREK-2 link neuronal excitability to a variety of stimuli including mechanical force, lipids, temperature and...
The two-pore domain potassium (K) channels TREK-1 and TREK-2 link neuronal excitability to a variety of stimuli including mechanical force, lipids, temperature and phosphorylation. This regulation involves the C-terminus as a polymodal stimulus sensor and the selectivity filter (SF) as channel gate. Using crystallographic up- and down-state structures of TREK-2 as a template for full atomistic molecular dynamics (MD) simulations, we reveal that the SF in down-state undergoes inactivation via conformational changes, while the up-state structure maintains a stable and conductive SF. This suggests an atomistic mechanism for the low channel activity previously assigned to the down state, but not evident from the crystal structure. Furthermore, experimentally by using (de-)phosphorylation mimics and chemically attaching lipid tethers to the proximal C-terminus (pCt), we confirm the hypothesis that moving the pCt towards the membrane induces the up-state. Based on MD simulations, we propose two gating pathways by which movement of the pCt controls the stability (i.e., conductivity) of the filter gate. Together, these findings provide atomistic insights into the SF gating mechanism and the physiological regulation of TREK channels by phosphorylation.
Topics: Potassium Channels, Tandem Pore Domain; Molecular Dynamics Simulation; Humans; Phosphorylation; Ion Channel Gating; Protein Domains; Cytosol; Animals; HEK293 Cells; Crystallography, X-Ray
PubMed: 38821927
DOI: 10.1038/s41467-024-48823-y -
Journal of Applied Biomaterials &... 2024Adhesions are fibrous tissue connections which are a common complication of surgical procedures and may be prevented by protecting tissue surfaces and reducing...
Adhesions are fibrous tissue connections which are a common complication of surgical procedures and may be prevented by protecting tissue surfaces and reducing inflammation. The combination of biodegradable polymers and nanocrystalline silver can be used to create an anti-inflammatory gel to be applied during surgery. In this study, sodium hyaluronate and sodium carboxymethyl cellulose were added in concentrations from 0.25% to 1% w/v to aqueous nanocrystalline silver solutions to create viscous gels. Gels were loaded into dialysis cassettes and placed in PBS for 3 days. pH was adjusted using potassium phosphate monobasic and sodium hydroxide. Release of silver into the PBS was measured at several time points. Polymer degradation was compared by measuring the viscosity of the gels before and after the experiment. Gels lost up to 84% of initial viscosity over 3 days and released between 24% and 41% of the added silver. Gels with higher initial viscosity did not have a greater degree of degradation, as measured by percent viscosity reduction, but still resulted in a higher final viscosity. Silver release was not significantly impacted by pH or composition, but still varied between experimental groups.
Topics: Hyaluronic Acid; Carboxymethylcellulose Sodium; Hydrogen-Ion Concentration; Silver; Viscosity; Gels; Metal Nanoparticles
PubMed: 38819121
DOI: 10.1177/22808000241257124 -
Genome Medicine May 2024KCNE1 encodes a 129-residue cardiac potassium channel (I) subunit. KCNE1 variants are associated with long QT syndrome and atrial fibrillation. However, most variants...
BACKGROUND
KCNE1 encodes a 129-residue cardiac potassium channel (I) subunit. KCNE1 variants are associated with long QT syndrome and atrial fibrillation. However, most variants have insufficient evidence of clinical consequences and thus limited clinical utility.
METHODS
In this study, we leveraged the power of variant effect mapping, which couples saturation mutagenesis with high-throughput sequencing, to ascertain the function of thousands of protein-coding KCNE1 variants.
RESULTS
We comprehensively assayed KCNE1 variant cell surface expression (2554/2709 possible single-amino-acid variants) and function (2534 variants). Our study identified 470 loss- or partial loss-of-surface expression and 574 loss- or partial loss-of-function variants. Of the 574 loss- or partial loss-of-function variants, 152 (26.5%) had reduced cell surface expression, indicating that most functionally deleterious variants affect channel gating. Nonsense variants at residues 56-104 generally had WT-like trafficking scores but decreased functional scores, indicating that the latter half of the protein is dispensable for protein trafficking but essential for channel function. 22 of the 30 KCNE1 residues (73%) highly intolerant of variation (with > 70% loss-of-function variants) were in predicted close contact with binding partners KCNQ1 or calmodulin. Our functional assay data were consistent with gold standard electrophysiological data (ρ = - 0.64), population and patient cohorts (32/38 presumed benign or pathogenic variants with consistent scores), and computational predictors (ρ = - 0.62). Our data provide moderate-strength evidence for the American College of Medical Genetics/Association of Molecular Pathology functional criteria for benign and pathogenic variants.
CONCLUSIONS
Comprehensive variant effect maps of KCNE1 can both provide insight into I channel biology and help reclassify variants of uncertain significance.
Topics: Potassium Channels, Voltage-Gated; Humans; Calmodulin; Arrhythmias, Cardiac; High-Throughput Nucleotide Sequencing; Genetic Variation; Protein Transport; HEK293 Cells
PubMed: 38816749
DOI: 10.1186/s13073-024-01340-5 -
ELife May 2024Alterations in the function of K channels such as the voltage- and Ca-activated K channel of large conductance (BK) reportedly promote breast cancer (BC) development and...
Alterations in the function of K channels such as the voltage- and Ca-activated K channel of large conductance (BK) reportedly promote breast cancer (BC) development and progression. Underlying molecular mechanisms remain, however, elusive. Here, we provide electrophysiological evidence for a BK splice variant localized to the inner mitochondrial membrane of murine and human BC cells (mitoBK). Through a combination of genetic knockdown and knockout along with a cell permeable BK channel blocker, we show that mitoBK modulates overall cellular and mitochondrial energy production, and mediates the metabolic rewiring referred to as the 'Warburg effect', thereby promoting BC cell proliferation in the presence and absence of oxygen. Additionally, we detect mitoBK and BK transcripts in low or high abundance, respectively, in clinical BC specimens. Together, our results emphasize, that targeting mitoBK could represent a treatment strategy for selected BC patients in future.
Topics: Humans; Animals; Mice; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Mitochondria; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Mitochondrial Membranes; Female; Energy Metabolism
PubMed: 38808578
DOI: 10.7554/eLife.92511 -
RSC Advances May 2024Prismatic crystals of partially potassium substituted lead fluorapatite PbCaK(PO)F were grown through a solid-state reaction. The structural study conducted by...
Prismatic crystals of partially potassium substituted lead fluorapatite PbCaK(PO)F were grown through a solid-state reaction. The structural study conducted by single-crystal X-ray diffraction revealed that the compound crystallizes in the hexagonal 6/ space group, with unit cell parameters = = 9.7190(5) Å, = 7.1700(6) Å and = 587.37(7) Å( = 1), as well as final values amounting to and w of 0.0309 and 0.0546, respectively. The structural refinement demonstrated that Pb occupies both the (6 and (4) structural sites of hexagonal fluorapatite, K occupies the (6) site, and Ca is placed on the (4) site. Powder X-ray diffraction study indicated the absence of additional phases or impurities. Chemical analysis using atomic absorption spectrometry and energy-dispersive X-ray spectroscopy confirmed the expected chemical formula. The electrical conductivity measured over a wide temperature range was found to be governed by the ion mobility mechanism in the tunnel along the axis (probably attributed to the fluorine ion located there). We, therefore, could infer from the analysis of the complex impedance spectra that the electrical conductivity of our apatite depends essentially on the temperature and frequency, which produces a relaxation phenomenon and semiconductor-like behavior. Moreover, the strong absorption in the UV-Visible region was substantiated through studies of the optical properties of the developed sample. Fluorescence spectra exhibited emissions in the orange regions when excited at 375 nm. The findings of the phenomena resulting from the emission and conduction of the apatite in question suggest its potential for application in various technological fields such as photovoltaic cells, optoelectronics, photonics, LED applications, catalysis and batteries.
PubMed: 38799221
DOI: 10.1039/d4ra01014k -
BioRxiv : the Preprint Server For... May 2024Thrombosis is a major cause of myocardial infarction and ischemic stroke. The sodium/potassium ATPase (NKA), comprising α and β subunits, is crucial in maintaining...
BACKGROUND
Thrombosis is a major cause of myocardial infarction and ischemic stroke. The sodium/potassium ATPase (NKA), comprising α and β subunits, is crucial in maintaining intracellular sodium and potassium gradients. However, the role of NKA in platelet function and thrombosis remains unclear.
METHODS
We utilized wild-type (WT, α) and NKA α1 heterozygous (α) mice, aged 8 to 16 weeks, of both sexes. An intravital microscopy-based, FeCl-induced carotid artery injury thrombosis model was employed for in vivo thrombosis assessment. Platelet transfusion assays were used to evaluate platelet NKA α1 function on thrombosis. Human platelets isolated from healthy donors and heart failure patients treated with/without digoxin were used for platelet function and signaling assay. Complementary molecular approaches were used for mechanistic studies.
RESULTS
NKA α1 haplodeficiency significantly reduced its expression on platelets without affecting sodium homeostasis. It significantly inhibited 7.5% FeCl-induced thrombosis in male but not female mice without disturbing hemostasis. Transfusion of α, but not α, platelets to thrombocytopenic WT mice substantially prolonged thrombosis. Treating WT mice with low-dose ouabain or marinobufagenin, both binding NKA α1 and inhibiting its ion-transporting function, markedly inhibited thrombosis in vivo. NKA α1 formed complexes with leucine-glycine-leucine (LGL)-containing platelet receptors, including P2Y12, PAR4, and thromboxane A2 receptor. This binding was significantly attenuated by LGL>SFT mutation or LGL peptide. Haplodeficiency of NKA α1 in mice or ouabain treatment of human platelets notably inhibited ADP-induced platelet aggregation. While not affecting 10% FeCl-induced thrombosis, NKA α1 haplodeficiency significantly prolonged thrombosis time in mice treated with an ineffective dose of clopidogrel.
CONCLUSION
NKA α1 plays an essential role in enhancing platelet activation through binding to LGL-containing platelet GPCRs. NKA α1 haplodeficiency or inhibition with low-dose ouabain and marinobufagenin significantly inhibited thrombosis and sensitized clopidogrel's anti-thrombotic effect. Targeting NKA α1 emerges as a promising antiplatelet and antithrombotic therapeutic strategy.
PubMed: 38798556
DOI: 10.1101/2024.05.13.593923 -
Plants (Basel, Switzerland) May 2024Polyploid plants often exhibit enhanced stress tolerance. Switchgrass is a perennial rhizomatous bunchgrass that is considered ideal for cultivation in marginal lands,...
Polyploid plants often exhibit enhanced stress tolerance. Switchgrass is a perennial rhizomatous bunchgrass that is considered ideal for cultivation in marginal lands, including sites with saline soil. In this study, we investigated the physiological responses and transcriptome changes in the octoploid and tetraploid of switchgrass ( L. 'Alamo') under salt stress. We found that autoploid 8× switchgrass had enhanced salt tolerance compared with the amphidiploid 4× precursor, as indicated by physiological and phenotypic traits. Octoploids had increased salt tolerance by significant changes to the osmoregulatory and antioxidant systems. The salt-treated 8× Alamo plants showed greater potassium (K) accumulation and an increase in the K/Na ratio. Root transcriptome analysis for octoploid and tetraploid plants with or without salt stress revealed that 302 upregulated and 546 downregulated differentially expressed genes were enriched in genes involved in plant hormone signal transduction pathways and were specifically associated with the auxin, cytokinin, abscisic acid, and ethylene pathways. Weighted gene co-expression network analysis (WGCNA) detected four significant salt stress-related modules. This study explored the changes in the osmoregulatory system, inorganic ions, antioxidant enzyme system, and the root transcriptome in response to salt stress in 8× and 4× Alamo switchgrass. The results enhance knowledge of the salt tolerance of artificially induced homologous polyploid plants and provide experimental and sequencing data to aid research on the short-term adaptability and breeding of salt-tolerant biofuel plants.
PubMed: 38794454
DOI: 10.3390/plants13101383 -
Materials (Basel, Switzerland) May 2024This work is focused on a novel, promising low temperature phase change material (PCM), based on the eutectic Glauber's salt composition. To allow phase transition...
This work is focused on a novel, promising low temperature phase change material (PCM), based on the eutectic Glauber's salt composition. To allow phase transition within the refrigeration range of temperatures of +5 °C to +12 °C, combined with a high repeatability of melting-freezing processes, and minimized subcooling, the application of three variants of sodium carboxymethyl cellulose (Na-CMC) with distinct molecular weights (700,000, 250,000, and 90,000) is considered. The primary objective is to optimize the stabilization of this eutectic PCM formulation, while maintaining the desired enthalpy level. Preparation methods are refined to ensure repeatability in mixing components, thereby optimizing performance and stability. Additionally, the influence of Na-CMC molecular weight on stabilization is examined through differential scanning calorimetry (DSC), T-history, and rheology tests. The PCM formulation of interest builds upon prior research in which borax, ammonium chloride, and potassium chloride were used as additives to sodium sulfate decahydrate (Glauber's salt), prioritizing environmentally responsible materials. The results reveal that CMC with molecular weights of 250 kg/mol and 90 kg/mol effectively stabilize the PCM without phase separation issues, slowing crystallization kinetics. Conversely, CMC of 700 kg/mol proved ineffective due to the disruption of gel formation at its low gel point, hindering higher concentrations. Calculations of ionic concentration indicate higher Na ion content in PCM stabilized with 90 kg/mol CMC, suggesting increased ionic interactions and gel strength. A tradeoff is discovered between the faster crystallization in lower molecular weight CMC and the higher concentration required, which increases the amount of inert material that does not participate in the phase transition. After thermal cycling, the best formulation had a latent heat of 130 J/g with no supercooling, demonstrating excellent performance. This work advances PCM's reliability as a thermal energy storage solution for diverse applications and highlights the complex relationship between Na-CMC molecular weight and PCM stabilization.
PubMed: 38793509
DOI: 10.3390/ma17102442 -
Medicina (Kaunas, Lithuania) May 2024: episodes of acute decompensation in chronic heart failure (ADHF), a common health problem for the growing elderly population, pose a significant socio-economic burden...
: episodes of acute decompensation in chronic heart failure (ADHF), a common health problem for the growing elderly population, pose a significant socio-economic burden on the public health systems. Limited knowledge is available on both the endothelial function in and the cardio-metabolic health profile of old adults hospitalized due to ADHF. This study aimed to investigate the connection between asymmetric dimethylarginine (ADMA)-a potent inhibitor of nitric oxide-and key health biomarkers in this category of high-risk patients. : this pilot study included 83 individuals with a known ADHF history who were admitted to the ICU due to acute cardiac decompensation. Selected cardiovascular, metabolic, haemogram, renal, and liver parameters were measured at admission to the ICU. Key renal function indicators (serum creatinine, sodium, and potassium) were determined again at discharge. These parameters were compared between patients stratified by median ADMA (114 ng/mL). : high ADMA patients showed a significantly higher incidence of ischemic cardiomyopathy and longer length of hospital stay compared to those with low ADMA subjects. These individuals exhibited significantly higher urea at admission and creatinine at discharge, indicating poorer renal function. Moreover, their lipid profile was less favorable, with significantly elevated levels of total cholesterol and HDL. However, no significant inter-group differences were observed for the other parameters measured. : the present findings disclose multidimensional, adverse ADMA-related changes in the health risk profile of patients with chronic heart failure hospitalized due to recurrent decompensation episodes.
Topics: Humans; Heart Failure; Arginine; Male; Female; Aged; Pilot Projects; Biomarkers; Hospitalization; Aged, 80 and over; Middle Aged
PubMed: 38792995
DOI: 10.3390/medicina60050813 -
Molecules (Basel, Switzerland) May 2024The aim of this work was to assess the chemical composition and physico-chemical, techno-functional, and in vitro antioxidant properties of flours obtained from the peel...
The aim of this work was to assess the chemical composition and physico-chemical, techno-functional, and in vitro antioxidant properties of flours obtained from the peel and flesh of pitahaya () to determine their potential for use as ingredients for food enrichment. The chemical composition, including total betalains, mineral content, and polyphenolic profile, was determined. The techno-functional properties (water holding, oil holding, and swelling capacities) were also evaluated. For the antioxidant capacity, four different methodologies, namely ferrous ion-chelating ability assay, ferric-reducing antioxidant power assay; 1,1-Diphenyl-2-picrylhydrazyl radical scavenging ability assay, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical assay, were used. Pitahaya-peel flour had higher values for protein (6.72 g/100 g), ash (11.63 g/100 g), and dietary fiber 56.56 g/100 g) than pitahaya-flesh flour, with values of 6.06, 3.63, and 8.22 g/100 g for protein, ash, and dietary fiber, respectively. In the same way, pitahaya peel showed a higher content of minerals, betalains, and polyphenolic compounds than pitahaya-flesh flour, with potassium (4.43 g/100 g), catechin (25.85 mg/g), quercetin-3-rhamnoside (11.66 mg/g) and myricetrin (12.10 mg/g) as principal compounds found in the peel. Again, pitahaya-peel flour showed better techno-functional and antioxidant properties than pitahaya-flesh flour. The results obtained suggest that the flours obtained from the peel and pulp of pitahaya () constitute a potential material to be utilized as an ingredient in the food industry due to the high content of bioactive compounds such as betalains, phenolic acids, and flavonoids, with notable antioxidant capacity.
Topics: Cactaceae; Antioxidants; Fruit; Flour; Polyphenols; Betalains; Plant Extracts
PubMed: 38792103
DOI: 10.3390/molecules29102241