Piezo proteins are evolutionarily conserved and functionally diverse mechanosensitive cation channels. However, the overall structural architecture and gating mechanisms of Piezo channels have ...remained unknown. Here we determine the cryo-electron microscopy structure of the full-length (2,547 amino acids) mouse Piezo1 (Piezo1) at a resolution of 4.8 Å. Piezo1 forms a trimeric propeller-like structure (about 900 kilodalton), with the extracellular domains resembling three distal blades and a central cap. The transmembrane region has 14 apparently resolved segments per subunit. These segments form three peripheral wings and a central pore module that encloses a potential ion-conducting pore. The rather flexible extracellular blade domains are connected to the central intracellular domain by three long beam-like structures. This trimeric architecture suggests that Piezo1 may use its peripheral regions as force sensors to gate the central ion-conducting pore.
Ribosome associated complex (RAC), an obligate heterodimer of HSP40 and HSP70 (Zuo1 and Ssz1 in yeast), is conserved in eukaryotes and functions as co-chaperone for another HSP70 (Ssb1/2 in yeast) to ...facilitate co-translational folding of nascent polypeptides. Many mechanistic details, such as the coordination of one HSP40 with two HSP70s and the dynamic interplay between RAC-Ssb and growing nascent chains, remain unclear. Here, we report three sets of structures of RAC-containing ribosomal complexes isolated from Saccharomyces cerevisiae. Structural analyses indicate that RAC on the nascent-chain-free ribosome is in an autoinhibited conformation, and in the presence of a nascent chain at the peptide tunnel exit (PTE), RAC undergoes large-scale structural remodeling to make Zuo1 J-Domain more accessible to Ssb. Our data also suggest a role of Zuo1 in orienting Ssb-SBD proximal to the PTE for easy capture of the substrate. Altogether, in accordance with previous data, our work suggests a sequence of structural remodeling events for RAC-Ssb during co-translational folding, triggered by the binding and passage of growing nascent chain from one to another.
ATP-sensitive potassium channels (KATP) couple intracellular ATP levels with membrane excitability. These channels play crucial roles in many essential physiological processes and have been ...implicated extensively in a spectrum of metabolic diseases and disorders. To gain insight into the mechanism of KATP, we elucidated the structure of a hetero-octameric pancreatic KATP channel in complex with a non-competitive inhibitor glibenclamide by single-particle cryoelectron microscopy to 5.6-Å resolution. The structure shows that four SUR1 regulatory subunits locate peripherally and dock onto the central Kir6.2 channel tetramer through the SUR1 TMD0-L0 fragment. Glibenclamide-bound SUR1 uses TMD0-L0 fragment to stabilize Kir6.2 channel in a closed conformation. In another structural population, a putative co-purified phosphatidylinositol 4,5-bisphosphate (PIP2) molecule uncouples Kir6.2 from glibenclamide-bound SUR1. These structural observations suggest a molecular mechanism for KATP regulation by anti-diabetic sulfonylurea drugs, intracellular adenosine nucleotide concentrations, and PIP2 lipid.
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•Pancreatic KATP channel structure is determined at 5.6-Å resolution by cryo-EM•TMD0-L0 fragment mediates the interactions between Kir6.2 and SUR1•An allosteric inhibitor bound to SUR1 stabilizes Kir6.2 in a closed conformation•PIP2 uncouples Kir6.2 from glibenclamide-bound SUR1
The structure of a pancreatic ATP-sensitive potassium channel provides insights into channel assembly and regulation.
DNA replication in eukaryotes is strictly regulated by several mechanisms. A central step in this replication is the assembly of the heterohexameric minichromosome maintenance (MCM2-7) helicase ...complex at replication origins during G1 phase as an inactive double hexamer. Here, using cryo-electron microscopy, we report a near-atomic structure of the MCM2-7 double hexamer purified from yeast G1 chromatin. Our structure shows that two single hexamers, arranged in a tilted and twisted fashion through interdigitated amino-terminal domain interactions, form a kinked central channel. Four constricted rings consisting of conserved interior β-hairpins from the two single hexamers create a narrow passageway that tightly fits duplex DNA. This narrow passageway, reinforced by the offset of the two single hexamers at the double hexamer interface, is flanked by two pairs of gate-forming subunits, MCM2 and MCM5. These unusual features of the twisted and tilted single hexamers suggest a concerted mechanism for the melting of origin DNA that requires structural deformation of the intervening DNA.
Now the occurrence of delirium is more concerning to clinicians and psychiatrists. It has been reported that vitamin D deficiency may be a relevant factor in the development of delirium in ...hospitalized patients.
To investigate the association between vitamin D concentration and delirium in hospitalized patients.
Meta-analysis.
A systematic literature search was conducted using PubMed, EMBASE, and the Cochrane Library. The primary outcome was the occurrence of delirium in the inpatient setting. Odds ratios (OR) were calculated with random or fixed effects models.
In this article, we define the normal range of vitamin D concentrations as greater than 75 nmol / L, 50-75 nmol / L as vitamin D insufficiency, 25-50 nmol / L as vitamin D deficiency, and less than 25 nmol / L as vitamin D severe deficiency. The Results showed that severe vitamin D deficiency (OR: 1.98 1.41-2.79, P<0.001) and vitamin D deficiency (OR: 1.50 1.12-2.00, P = 0.006) were more likely to develop delirium than normal vitamin D levels. Subgroup analysis also revealed that low vitamin D concentrations were associated with a higher incidence of delirium, whether the cutoff point was 25 nmol/L (OR: 1.52 1.40-1.64, P<0.001), 50 nmol/L (OR: 1.47 1.19-1.82, P<0.001), or 75 nmol/L (OR: 1.54 1.21-1.96, P<0.001). The included studies scored medium and high on the Newcastle-Ottawa quality assessment scale.
Compared with normal vitamin D levels, severe vitamin D deficiency and vitamin D deficiency, but not vitamin D insufficiency, are associated with a higher incidence of delirium in hospitalized patients.
This review was registered in the PROSPERO database under identifier CRD42021271347. https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021271347.
A microgrid (MG) can operate in both grid-tied and autonomous mode. Without the support from the public utility, the control of an autonomous MG is more complex due to its poor system inertia. Though ...energy storage system (ESS) can act as a main power source to maintain system frequency and voltage stability, traditional droop control is usually invalid in practice due to the resistive line of low/medium voltage MG. Virtual impedance control can be a solution to decouple the active and reactive power allocations among ESSs. However, the control bandwidth is reduced since it requires low-pass filters with reduced bandwidth to calculate the average active and reactive power. In this paper, a novel ESSs control method is proposed with V/f droop control (VFDC) and P/Q droop control (PQDC) combined. It can distribute the active and reactive power precisely since the interference of line parameters uncertainty is prevented and system stability is enhanced. The comparison between traditional droop and the hybrid VFDC/PQDC is analyzed based on equivalent circuits. A hybrid VFDC/PQDC-based MG control scheme is proposed and its small-signal stability is analyzed. The proposed method is verified through experimental test on a MG platform with two 100 kVA ESS prototypes.
Research on Collaborative Writing (CW) has proliferated over recent decades, but the role that pair dynamics plays in second language (L2) learning remains unclear. This study compared the effect of ...dyadic interactions and proficiency pairing in CW on L2 learning. Sixty-two Chinese EFL learners participated in this study, forming three types of proficiency pairing, including 12 high-high pairs, 12 high-low pairs, and seven low-low pairs. All dialogs were audio-recorded and analyzed for dyadic patterns, as well as frequency, types, and solutions of Language-Related Episodes (LREs). The findings indicated that lexis-focused LREs took the largest proportion of LREs, followed by discourse-focused LREs and grammar-focused LREs in all groups. However, compared with proficiency pairing, the efficacy of dyadic interactions has a greater impact on L2 learning. Learners displaying collaborative patterns significantly produced more LREs and correctly solved the majority of the conflicts than those in non-collaborative interactions, while neither the total number nor solutions of LREs reached significance in different proficiency pairing groups. Pedagogical implications on implementing CW in L2 writing classrooms are discussed.
Newborn microglia rapidly replenish the whole brain after selective elimination of most microglia (>99%) in adult mice. Previous studies reported that repopulated microglia were largely derived from ...microglial progenitor cells expressing nestin in the brain. However, the origin of these repopulated microglia has been hotly debated. In this study, we investigated the origin of repopulated microglia by a series of fate-mapping approaches. We first excluded the blood origin of repopulated microglia via parabiosis. With different transgenic mouse lines, we then demonstrated that all repopulated microglia were derived from the proliferation of the few surviving microglia (<1%). Despite a transient pattern of nestin expression in newly forming microglia, none of repopulated microglia were derived from nestin-positive non-microglial cells. In summary, we conclude that repopulated microglia are solely derived from residual microglia rather than de novo progenitors, suggesting the absence of microglial progenitor cells in the adult brain.
Hypericin, one of the major antidepressant constituents of St. John's wort, was shown to exert antidepressant effects by affecting cerebral CYP enzymes, serotonin homeostasis, and neuroinflammatory ...signaling pathways. However, its exact mechanisms are unknown. Previous clinical studies reported that the mRNA modification N6-methyladenosine (m6A) interferes with the neurobiological mechanism in depressed patients, and it was also found that the antidepressant efficacy of tricyclic antidepressants (TCAs) is related to m6A modifications. Therefore, we hypothesize that the antidepressant effect of hypericin may relate to the m6A modification of epitranscriptomic regulation. We constructed a UCMS mouse depression model and found that hypericin ameliorated depressive-like behavior in UCMS mice. Molecular pharmacology experiments showed that hypericin treatment upregulated the expression of m6A-modifying enzymes METTL3 and WTAP in the hippocampi of UCMS mice. Next, we performed MeRIP-seq and RNA-seq to study m6A modifications and changes in mRNA expression on a genome-wide scale. The genome-wide m6A assay and MeRIP-qPCR results revealed that the m6A modifications of Akt3, Ntrk2, Braf, and Kidins220 mRNA were significantly altered in the hippocampi of UCMS mice after stress stimulation and were reversed by hypericin treatment. Transcriptome assays and qPCR results showed that the Camk4 and Arhgdig genes might be related to the antidepressant efficacy of hypericin. Further gene enrichment results showed that the differential genes were mainly involved in neurotrophic factor signaling pathways. In conclusion, our results show that hypericin upregulates m6A methyltransferase METTL3 and WTAP in the hippocampi of UCMS mice and stabilizes m6A modifications to exert antidepressant effects via the neurotrophin signaling pathway. This suggests that METTL3 and WTAP-mediated changes in m6A modifications may be a potential mechanism for the pathogenesis of depression and the efficacy of antidepressants, and that the neurotrophin signaling pathway plays a key role in this process.
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