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BioRxiv : the Preprint Server For... May 2024Ion channels are necessary for proper water and nutrient absorption in the intestine, which supports cellular metabolism and organismal growth. While a role for Na...
Ion channels are necessary for proper water and nutrient absorption in the intestine, which supports cellular metabolism and organismal growth. While a role for Na co-transporters and pumps in intestinal nutrient absorption is well defined, how individual K uniporters function to maintain ion homeostasis is poorly understood. Using , we show that a gain-of-function mutation in , which encodes a two-pore domain K ion channel orthologous to human KCNK3, facilitates nutrient absorption and suppresses the metabolic and developmental defects displayed by impaired intestinal MAP Kinase (MAPK) signaling. Mutations in and which encode two components of this MAPK pathway, cause severe growth defects, reduced lipid storage, and a dramatic increase in autophagic lysosomes, which mirror dietary restriction phenotypes. Additionally, these MAPK mutants display structural defects of the intestine and an impaired defecation motor program. We find that activation of TWK-26 reverses the dietary restriction-like state of the MAPK mutants by restoring intestinal nutrient absorption without correcting the intestinal bloating or defecation defects. This study provides unique insight into the mechanisms by which intestinal K ion channels support intestinal metabolic homeostasis.
PubMed: 38766028
DOI: 10.1101/2024.05.06.592787 -
ArXiv May 2024The large-conductance, calcium-activated potassium (BK) channel lacks the typical intracellular bundle-crossing gate present in most ion channels of the 6TM family. This...
The large-conductance, calcium-activated potassium (BK) channel lacks the typical intracellular bundle-crossing gate present in most ion channels of the 6TM family. This observation, initially inferred from Ca$^{2+}$-free-pore accessibility experiments and recently corroborated by a CryoEM structure of the non-conductive state, raises a puzzling question: how can gating occur in absence of steric hindrance? To answer this question, we carried out molecular simulations and accurate free energy calculations to obtain a microscopic picture of the sequence of events that, starting from a Ca$^{2+}$-free state leads to ion conduction upon Ca$^{2+}$ binding. Our results highlight an unexpected role for annular lipids, which turn out to be an integral part of the gating machinery. Due to the presence of fenestrations, the "closed" Ca$^{2+}$-free pore can be occupied by the methyl groups from the lipid alkyl chains. This dynamic occupancy triggers and stabilizes the nucleation of a vapor bubble into the inner pore cavity, thus hindering ion conduction. By contrast, Ca$^{2+}$ binding results into a displacement of these lipids outside the inner cavity, lowering the hydrophobicity of this region and thus allowing for pore hydration and conduction. This lipid-mediated hydrophobic gating rationalizes several seemingly problematic experimental observations, including the state-dependent pore accessibility of blockers.
PubMed: 38764592
DOI: No ID Found -
Gene Oct 2024Potassium ion (K) is one of the most essential nutrients for the growth and development of tobacco (Nicotiana tabacum L.), however, the molecular regulation of K...
Potassium ion (K) is one of the most essential nutrients for the growth and development of tobacco (Nicotiana tabacum L.), however, the molecular regulation of K concentration in tobacco remains unclear. In this study, a two-pore K (TPK) channel gene NtTPKa was cloned from tobacco, and NtTPKa protein contains the unique K selection motif GYGD and its transmembrane region primarily locates in the tonoplast membrane. The expression of NtTPKa gene was significantly increased under low-potassium stress conditions. The concentrations of K in tobacco were significantly increased in the NtTPKa RNA interference lines and CRISPR/Cas9 knockout mutants. In addition, the transport of K by NtTPKa was validated using patch clamp technique, and the results showed that NtTPKa channel protein exclusively transported K in a concentration-dependent manner. Together, our results strongly suggested that NtTPKa is a key gene in maintaining K homeostasis in tobacco, and it could provide a new genetic resource for increasing the concentration of K in tobacco.
Topics: Nicotiana; Potassium; Plant Proteins; Gene Expression Regulation, Plant; Potassium Channels, Tandem Pore Domain; CRISPR-Cas Systems; Potassium Channels
PubMed: 38763364
DOI: 10.1016/j.gene.2024.148576 -
Nature Communications May 2024Potassium channels of the Two-Pore Domain (K2P) subfamily, KCNK1-KCNK18, play crucial roles in controlling the electrical activity of many different cell types and...
Potassium channels of the Two-Pore Domain (K2P) subfamily, KCNK1-KCNK18, play crucial roles in controlling the electrical activity of many different cell types and represent attractive therapeutic targets. However, the identification of highly selective small molecule drugs against these channels has been challenging due to the high degree of structural and functional conservation that exists not only between K2P channels, but across the whole K channel superfamily. To address the issue of selectivity, here we generate camelid antibody fragments (nanobodies) against the TREK-2 (KCNK10) K2P K channel and identify selective binders including several that directly modulate channel activity. X-ray crystallography and CryoEM data of these nanobodies in complex with TREK-2 also reveal insights into their mechanisms of activation and inhibition via binding to the extracellular loops and Cap domain, as well as their suitability for immunodetection. These structures facilitate design of a biparatropic inhibitory nanobody with markedly improved sensitivity. Together, these results provide important insights into TREK channel gating and provide an alternative, more selective approach to modulation of K2P channel activity via their extracellular domains.
Topics: Potassium Channels, Tandem Pore Domain; Single-Domain Antibodies; Humans; Crystallography, X-Ray; Animals; Cryoelectron Microscopy; HEK293 Cells; Models, Molecular
PubMed: 38755204
DOI: 10.1038/s41467-024-48536-2 -
PloS One 2024Endophytic bacteria, recognized as eco-friendly biofertilizers, have demonstrated the potential to enhance crop growth and yield. While the plant growth-promoting...
Endophytic bacteria, recognized as eco-friendly biofertilizers, have demonstrated the potential to enhance crop growth and yield. While the plant growth-promoting effects of endophytic bacteria have been extensively studied, the impact of weed endophytes remains less explored. In this study, we aimed to isolate endophytic bacteria from native weeds and assess their plant growth-promoting abilities in rice under varying chemical fertilization. The evaluation encompassed measurements of mineral phosphate and potash solubilization, as well as indole-3-acetic acid (IAA) production activity by the selected isolates. Two promising strains, tentatively identified as Alcaligenes faecalis (BTCP01) from Eleusine indica (Goose grass) and Metabacillus indicus (BTDR03) from Cynodon dactylon (Bermuda grass) based on 16S rRNA gene phylogeny, exhibited noteworthy phosphate and potassium solubilization activity, respectively. BTCP01 demonstrated superior phosphate solubilizing activity, while BTDR03 exhibited the highest potassium (K) solubilizing activity. Both isolates synthesized IAA in the presence of L-tryptophan, with the detection of nifH and ipdC genes in their genomes. Application of isolates BTCP01 and BTDR03 through root dipping and spraying at the flowering stage significantly enhanced the agronomic performance of rice variety CV. BRRI dhan29. Notably, combining both strains with 50% of recommended N, P, and K fertilizer doses led to a substantial increase in rice grain yields compared to control plants receiving 100% of recommended doses. Taken together, our results indicate that weed endophytic bacterial strains BTCP01 and BTDR03 hold promise as biofertilizers, potentially reducing the dependency on chemical fertilizers by up to 50%, thereby fostering sustainable rice production.
Topics: Oryza; Endophytes; Alcaligenes faecalis; Plant Weeds; Fertilizers; Phosphates; Indoleacetic Acids; RNA, Ribosomal, 16S; Phylogeny; Plant Roots; Eleusine; Cynodon; Potassium
PubMed: 38753661
DOI: 10.1371/journal.pone.0296547 -
BioRxiv : the Preprint Server For... May 2024Despite the profound behavioral effects of the striatal dopamine (DA) activity and the inwardly rectifying potassium channel ( ) being a key determinant of striatal...
Despite the profound behavioral effects of the striatal dopamine (DA) activity and the inwardly rectifying potassium channel ( ) being a key determinant of striatal medium spiny neuron (MSN) activity that also profoundly affects behavior, previously reported DA regulations of Kir are conflicting and incompatible with MSN function in behavior. Here we show that in normal mice with an intact striatal DA system, the predominant effect of DA activation of D1Rs in D1-MSNs is to cause a modest depolarization and increase in input resistance by inhibiting Kir, thus moderately increasing the spike outputs from behavior-promoting D1-MSNs. In parkinsonian (DA-depleted) striatum, DA increases D1-MSN intrinsic excitability more strongly than in normal striatum, consequently strongly increasing D1-MSN spike firing that is behavior-promoting; this DA excitation of D1-MSNs is stronger when the DA depletion is more severe. The DA inhibition of Kir is occluded by the Kir blocker barium chloride (BaCl ). In behaving parkinsonian mice, BaCl microinjection into the dorsal striatum stimulates movement but occludes the motor stimulation of D1R agonism. Taken together, our results resolve the long-standing question about what D1R agonism does to D1-MSN excitability in normal and parkinsonian striatum and strongly indicate that D1R inhibition of Kir is a key ion channel mechanism that mediates D1R agonistic behavioral stimulation in normal and parkinsonian animals.
PubMed: 38746264
DOI: 10.1101/2024.04.29.590632 -
NPJ Science of Food May 2024Finger millet, a cereal grain widely consumed in India and Africa, has gained more attention in recent years due to its high dietary fibre (arabinoxylan) and trace...
Finger millet, a cereal grain widely consumed in India and Africa, has gained more attention in recent years due to its high dietary fibre (arabinoxylan) and trace mineral content, and its climate resilience. The aim of this study was to understand the interactions between potassium (K), calcium (Ca) and zinc (Zn) ions and the arabinoxylan structure and determine its ion-binding capacity. Three variations of a proposed model of the arabinoxylan structure were constructed and first principles Density Functional Theory calculations were carried out to determine the cation-binding capacity of the arabinoxylan complexes. Zn-arabinoxylan complexes were highly unstable and thermodynamically unfavourable in all three models. Ca and K ions, however, form thermodynamically stable complexes, particularly involving two glucuronic acid residues as a binding pocket. Glucuronic acid residues are found to play a key role in stabilising the cation-arabinoxylan complex, and steric effects are more important to the stability than charge density. Our results highlight the most important structural features of the millet fibre regarding ion-storage capacity, and provide valuable preliminary data for confirmatory experimental studies and for the planning of clinical trials where the bioavailability of bound ions following digestion may be tested.
PubMed: 38744951
DOI: 10.1038/s41538-024-00270-1 -
Heliyon May 2024, commonly known as chayote is known for its low glycemic index, high fiber content, and rich nutritional profile, which suggests it may be beneficial for individuals...
, commonly known as chayote is known for its low glycemic index, high fiber content, and rich nutritional profile, which suggests it may be beneficial for individuals with diabetes. While research specifically examining the impact of chayote on diabetes is limited, this study screened its biological impacts by using different biomarkers on streptozotocin-induced diabetic (STZ-ID) rats. The ethanolic extract of the fruits was assessed for different phytochemical, biochemical, and anti-diabetic properties. In the results, chayote extract had high phenolic and flavonoid contents respectively (39.25 ± 0.65 mg/mL and 12.16 ± 0.50 mg/mL). These high phenolic and flavonoid contents showed high implications on STZ-ID rats. Altogether 200 and 400 mg/kg of the extract considerably reduced the blood sugar level and enhanced the lipid profile of the STZ-ID rats. Additionally, they have decreased blood urea and serum creatinine levels. Besides, the levels of SGOT, SGPT, LDH, sodium, and potassium ions were significantly lowered after the administration period. More importantly, the electrocardiogram (ECG) parameters such as QT, RR, and QTc which were prolonged in the diabetic rats were downregulated after 35 days of administration of extract (400 mg/kg). And, the histological examination of the pancreas and kidney showed marked improvement in structural features of 200 and 400 mg/kg groups when compared to the diabetic control group. Where the increase in the glucose levels was positively correlated with QT, RR, and QTc (r = 0.76, r = 0.76, and r = 0.43) which means that ECG could significantly reflect the diabetes glucose levels. In conclusion, our findings showed that the fruit extract exerts a high potential to reduce artifacts secondary to diabetes which can be strongly suggested for diabetic candidates. However, there is a need to study the molecular mechanisms of the extract in combating artifacts secondary to diabetes in experimental animals.
PubMed: 38742087
DOI: 10.1016/j.heliyon.2024.e30440 -
RSC Advances May 2024Iron-based electrochemical catalysts used to modify electrodes for biosensing have received more attention from biosensor manufacturers because of their excellent...
Iron-based electrochemical catalysts used to modify electrodes for biosensing have received more attention from biosensor manufacturers because of their excellent biocompatibility and low cost. In this work, a fast-ion conductor potassium ferrite (KFeO) modified glassy carbon electrode (GCE) was prepared for detecting epinephrine (EP) by electrochemical techniques. The obtained KFeO/GCE electrode exhibited not only a wide linear range over EP concentration from 2 μM to 260 μM with a detection limit of 0.27 μM (S/N = 3) but also high selectivity toward EP in the presence of common interferents ascorbic acid (AA) and uric acid (UA), as well as good reproducibility and stability.
PubMed: 38741971
DOI: 10.1039/d4ra00242c -
Inorganic Chemistry May 2024Judicious design of ligand scaffolds to highly anisotropic lanthanide ions led to substantial advances in molecular spintronics and single-molecule magnetism....
Judicious design of ligand scaffolds to highly anisotropic lanthanide ions led to substantial advances in molecular spintronics and single-molecule magnetism. Erbium-based single-molecule magnets (SMMs) are rare, which is attributed to the prolate-shaped Er ion requiring an equatorial ligand field for enhancing its single-ion magnetic anisotropy. Here, we present an electron-rich mononuclear Er SMM, [K(crypt-222)][Er(dbCOT)], (where dbCOT = dibenzocyclooctatetraene), that was obtained from a salt metathesis reaction of ErCl and KdbCOT. The dipotassium salt, KdbCOT, was generated through a two-electron reduction of the bare dbCOT ligand employing potassium graphite and was crystallized from DME to give the new solvated complex, [K(DME)][dbCOT], . was analyzed through crystallography, electrochemistry, spectroscopy, magnetometry, and CASSCF calculations. The structure of consists of an anionic metallocene complex featuring a linear (180.0°) geometry with an Er ion sandwiched between dianionic dbCOT ligands and an outer-sphere K ion encapsulated in 2.2.2-cryptand. Two pronounced redox events at negative potentials allude to the formation of a trianionic erbocene complex, [Er(dbCOT)], on the electrochemical time scale. shows slow magnetic relaxation with an effective spin-reversal barrier of = 114(2) cm, which is close in magnitude to the calculated energies of the first and second excited states of 96.9 and 109.13 cm, respectively. exhibits waist-constricted hysteresis loops below 4 K and constitutes the first example of an erbocene-SMM bearing fused aromatic rings to the central COT ligand. Notably, comprises the largest COT scaffold implemented in erbocene SMMs, yielding the most electron-rich homoleptic erbium metallocene SMM.
PubMed: 38738864
DOI: 10.1021/acs.inorgchem.4c00731