Abstract
Lipopolysaccharide (LPS) is an essential glycolipid and forms a protective permeability barrier for most Gram-negative bacteria. In
E. coli
, LPS levels are under feedback control, achieved ...by FtsH-mediated degradation of LpxC, which catalyzes the first committed step in LPS synthesis. FtsH is a membrane-bound AAA+ protease, and its protease activity toward LpxC is regulated by essential membrane proteins LapB and YejM. However, the regulatory mechanisms are elusive. We establish an in vitro assay to analyze the kinetics of LpxC degradation and demonstrate that LapB is an adaptor protein that utilizes its transmembrane helix to interact with FtsH and its cytoplasmic domains to recruit LpxC. Our YejM/LapB complex structure reveals that YejM is an anti-adaptor protein, competing with FtsH for LapB to inhibit LpxC degradation. Structural analysis unravels that LapB and LPS have overlapping binding sites in YejM. Thus, LPS levels control formation of the YejM/LapB complex to determine LpxC protein levels.
Genetic analyses have linked microRNA-137 (MIR137) to neuropsychiatric disorders, including schizophrenia and autism spectrum disorder. miR-137 plays important roles in neurogenesis and neuronal ...maturation, but the impact of miR-137 loss-of-function in vivo remains unclear. Here we show the complete loss of miR-137 in the mouse germline knockout or nervous system knockout (cKO) leads to postnatal lethality, while heterozygous germline knockout and cKO mice remain viable. Partial loss of miR-137 in heterozygous cKO mice results in dysregulated synaptic plasticity, repetitive behavior, and impaired learning and social behavior. Transcriptomic and proteomic analyses revealed that the miR-137 mRNA target, phosphodiesterase 10a (Pde10a), is elevated in heterozygous knockout mice. Treatment with the Pde10a inhibitor papaverine or knockdown of Pde10a ameliorates the deficits observed in the heterozygous cKO mice. Collectively, our results suggest that MIR137 plays essential roles in postnatal neurodevelopment and that dysregulation of miR-137 potentially contributes to neuropsychiatric disorders in humans.
Misfolded luminal endoplasmic reticulum (ER) proteins undergo ER-associated degradation (ERAD-L): They are retrotranslocated into the cytosol, polyubiquitinated, and degraded by the proteasome. ...ERAD-L is mediated by the Hrd1 complex (composed of Hrd1, Hrd3, Der1, Usa1, and Yos9), but the mechanism of retrotranslocation remains mysterious. Here, we report a structure of the active Hrd1 complex, as determined by cryo-electron microscopy analysis of two subcomplexes. Hrd3 and Yos9 jointly create a luminal binding site that recognizes glycosylated substrates. Hrd1 and the rhomboid-like Der1 protein form two "half-channels" with cytosolic and luminal cavities, respectively, and lateral gates facing one another in a thinned membrane region. These structures, along with crosslinking and molecular dynamics simulation results, suggest how a polypeptide loop of an ERAD-L substrate moves through the ER membrane.
Lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria is critical for the assembly of their cell envelopes. LPS synthesized in the cytoplasmic leaflet of the inner membrane is ...flipped to the periplasmic leaflet by MsbA, an ATP-binding cassette transporter. Despite substantial efforts, the structural mechanisms underlying MsbA-driven LPS flipping remain elusive. Here we use single-particle cryo-electron microscopy to elucidate the structures of lipid-nanodisc-embedded MsbA in three functional states. The 4.2 Å-resolution structure of the transmembrane domains of nucleotide-free MsbA reveals that LPS binds deep inside MsbA at the height of the periplasmic leaflet, establishing extensive hydrophilic and hydrophobic interactions with MsbA. Two sub-nanometre-resolution structures of MsbA with ADP-vanadate and ADP reveal an unprecedented closed and an inward-facing conformation, respectively. Our study uncovers the structural basis for LPS recognition, delineates the conformational transitions of MsbA to flip LPS, and paves the way for structural characterization of other lipid flippases.
Potassium and nitrogen are essential mineral elements for plant growth and development. The protein kinase LKS1/CIPK23 is involved in both K+ and NH4+ uptake in Arabidopsis root. The transcripts of ...LKS1 can be induced by low K+ (0.1 mM) and high NH4+ (30 mM); however, the molecular mechanism is still unknown. In this study, we isolated the transcription factor STOP1 that positively regulates LKS1 transcription in Arabidopsis responses to both low-K+ and high-NH4+ stresses. STOP1 proteins can directly bind to the LKS1 promoter, promoting its transcription. The stop1 mutants displayed a leaf chlorosis phenotype similar to lks1 mutant when grown on low-K+ and high-NH4+ medium. On the other hand, STOP1 overexpressing plants exhibited a similar tolerant phenotype to LKS1 overexpressing plants. The transcript level of STOP1 was only upregulated by low K+ rather than high NH4+; however, the accumulation of STOP1 protein in the nucleus was required for the upregulation of LKS1 transcripts in both low-K+ and high-NH4+ responses. Our data demonstrate that STOP1 positively regulates LKS1 transcription under low-K+ and high-NH4+ conditions; therefore, LKS1 promotes K+ uptake and inhibits NH4+ uptake. The STOP1/LKS1 pathway plays crucial roles in K+ and NH4+ homeostasis, which coordinates potassium and nitrogen balance in plants in response to external fluctuating nutrient levels.
Considerable evidence has shown that neuroinflammation and oxidative stress play an important role in the pathophysiology of postoperative cognitive dysfunction (POCD) and other progressive ...neurodegenerative disorders. Increasing evidence suggests that acetaminophen (APAP) has unappreciated antioxidant and anti-inflammatory properties. However, the impact of APAP on the cognitive sequelae of inflammatory and oxidative stress is unknown. The objective of this study is to explore whether APAP could have neuroprotective effects on lipopolysaccharide (LPS)-induced cognitive impairment in mice.
A mouse model of LPS-induced cognitive impairment was established to evaluate the neuroprotective effects of APAP against LPS-induced cognitive impairment. Adult C57BL/6 mice were treated with APAP half an hour prior to intracerebroventricular microinjection of LPS and every day thereafter, until the end of the study period. The Morris water maze was used to assess cognitive function from postinjection days 1 to 3. Animal behavioural tests as well as pathological and biochemical assays were performed to evaluate LPS-induced hippocampal damage and the neuroprotective effect of APAP.
Mice treated with LPS exhibited impaired performance in the Morris water maze without changing spontaneous locomotor activity, which was ameliorated by treatment with APAP. APAP suppressed the accumulation of pro-inflammatory cytokines and microglial activation induced by LPS in the hippocampus. In addition, APAP increased SOD activity, reduced MDA levels, modulated glycogen synthase kinase 3β (GSK3β) activity and elevated brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Moreover, APAP significantly decreased the Bax/Bcl-2 ratio and neuron apoptosis in the hippocampus of LPS-treated mice.
Our results suggest that APAP may possess a neuroprotective effect against LPS-induced cognitive impairment and inflammatory and oxidative stress via mechanisms involving its antioxidant and anti-inflammatory properties, as well as its ability to inhibit the mitochondrial permeability transition (MPT) pore and the subsequent apoptotic pathway.
Hard carbon is the most promising anode for sodium-ion battery applications due to the wide availability and low work voltage. However, it often delivers worse electrochemical performance in ...ester-based electrolytes. Herein, a hierarchically porous loose sponge-like hard carbon with a highly disordered phase, prepared from the biomass of platanus bark, exhibits superior rate performance with a capacity of 165 mAh·g
−1
at a high current of 1 A·g
−1
, and high retention of 71.5% after 2000 cycles in an ester-based electrolyte. The effect of the hierarchically porous loose sponge-like structure on the formation dynamics of solid electrolyte interphase (SEI), and related properties, was studied via cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS) analysis. These results reveal that the hierarchically porous structure can construct continued connecting channels and accelerate the electrolyte transport, which is beneficial to the reaction kinetics of SEI. Moreover, the mesoporous structure is conducive to good contact between electrolyte and materials and shortens the Na
+
diffusion path, which in turn facilitates the charge transfer kinetics in the material.
Graphic abstract
The fungus
sp. Z184, harvested from the leaves of
(L.) Á. Löve, has been isolated for the first time. Chemical investigation on the methanol extract of the culture broth of the titles strain led to ...the discovery of three new pyranone derivatives, called fallopiaxylaresters A-C (
-
), and a new bisabolane-type sesquiterpenoid, named fallopiaxylarol A (
), along with the first complete set of spectroscopic data for the previously reported pestalotiopyrone M (
). Known pyranone derivatives (
-
), sesquiterpenoids (
-
), isocoumarin derivatives (
-
), and an aromatic allenic ether (
) were also co-isolated in this study. All new structures were elucidated by the interpretation of HRESIMS, 1D, 2D NMR spectroscopy, and quantum chemical computation approach. The in vitro antimicrobial, anti-inflammatory, and α-glucosidase-inhibitory activities of the selected compounds and the crude extract were evaluated. The extract was shown to inhibit nitric oxide (NO) production induced by lipopolysaccharide (LPS) in murine RAW264.7 macrophage cells, with an inhibition rate of 77.28 ± 0.82% at a concentration of 50 μg/mL. The compounds
,
, and
displayed weak antibacterial activity against
subsp.
at a concentration of 100 μM.
Mutations in AT‐rich interactive domain‐containing protein 1A (ARID1A) cause Coffin‐Siris syndrome (CSS), a rare genetic disorder that results in mild to severe intellectual disabilities. However, ...the biological role of ARID1A in the brain remains unclear. In this study, we report that the haploinsufficiency of ARID1A in excitatory neurons causes cognitive impairment and defects in hippocampal synaptic transmission and dendritic morphology in mice. Similarly, human embryonic stem cell‐derived excitatory neurons with deleted ARID1A exhibit fewer dendritic branches and spines, and abnormal electrophysiological activity. Importantly, supplementation of acetate, an epigenetic metabolite, can ameliorate the morphological and electrophysiological deficits observed in mice with Arid1a haploinsufficiency, as well as in ARID1A‐null human excitatory neurons. Mechanistically, transcriptomic and ChIP‐seq analyses demonstrate that acetate supplementation can increase the levels of H3K27 acetylation at the promoters of key regulatory genes associated with neural development and synaptic transmission. Collectively, these findings support the essential roles of ARID1A in the excitatory neurons and cognition and suggest that acetate supplementation could be a potential therapeutic intervention for CSS.
Synopsis
Mutations in ARID1A cause Coffin‐Siris syndrome (CSS), a rare genetic disorder with severe neurodevelopmental deficits. This study investigates the genetic basis of the pathophysiological role of ARID1A in CSS and proposes a potential therapeutic intervention.
Arid1a haploinsufficiency in mouse excitatory neurons leads to spatial memory defects.
ARID1A is required for neuron dendritic and synapse growth in mice and humans.
Acetate supplementation rescues the neuronal deficits by increasing H3K27 acetylation levels at the promoters of neuronal genes in both Arid1a haploinsufficient mice and ARID1A KO hESC‐derived neurons.
Mutations in ARID1A cause Coffin‐Siris syndrome (CSS), a rare genetic disorder with severe neurodevelopmental deficits. This study investigates the genetic basis of the pathophysiological role of ARID1A in CSS and proposes a potential therapeutic intervention.
Background
Postoperative cognitive dysfunction (POCD) is one of the common postoperative complications, which is more common in aged patients. POCD mainly manifests as cognitive function changes ...after surgery, such as memory decline and inattention. In some severe cases, patients may suffer from personality changes and (or) social behavior decline. The aim of the current study is to confirm the effect and elucidate the mechanism of bone marrow mesenchymal stem cells (BMSCs) in postoperative central inflammatory mice.
Methods
Mice were randomly assigned to four groups: sham, sham+BMSCs, model, and BMSCs group. In the model group, mice were intraperitoneally injected 8 mg/kg per day lipopolysaccharide for 5 days. In sham+BMSCs and BMSCs group, BMSCs (1 × 10
7) in 100 µL saline were injected into sham mice and model mice, respectively.
Results
In the model group, transforming growth factor β (TGF‐β) protein expression was significantly increased, compared with that in the sham group. BMSCs were treated into postoperative central inflammatory mice, which resulted in a decreased of TGF‐β protein expression. TGF‐β and smad2 protein expression were suppressed, and apoptosis rate and inflammation were inhibited in coculture with BMSCs. The suppression of TGF‐β inhibited the effects of BMSCs on apoptosis rate and inflammation in postoperative central inflammatory through a smad2 signaling pathway. The promotion of TGF‐β reduced the effects of BMSCs on apoptosis rate and inflammation in postoperative central inflammatory through a smad2 signaling pathway.
Conclusion
The present study demonstrates that BMSCs regulates TGF‐β to adjust neuroinflammation in postoperative central inflammatory mice.
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