Direct determination of oligomeric organization of integral membrane proteins and lipids from intact customizable bilayer.

Hierarchical organization of integral membrane proteins (IMP) and lipids at the membrane is essential for regulating myriad downstream signaling. A quantitative understanding of these processes requires both detections of oligomeric organization of IMPs and lipids directly from intact membranes and determination of key membrane components and properties that regulate them. Addressing this, we have developed a platform that enables native mass spectrometry (nMS) analysis of IMP-lipid complexes directly from intact and customizable lipid membranes. Both the lipid composition and membrane properties (such as curvature, tension, and fluidity) of these bilayers can be precisely customized to a target membrane. Subsequent direct nMS analysis of these intact proteolipid vesicles can yield the oligomeric states of the embedded IMPs, identify bound lipids, and determine the membrane properties that can regulate the observed IMP-lipid organization. Applying this method, we show how lipid binding regulates neurotransmitter release and how membrane composition regulates the functional oligomeric state of a transporter.

Mfsd2a utilizes a flippase mechanism to mediate omega-3 fatty acid lysolipid transport.

Major Facilitator Superfamily Domain containing 2a (Mfsd2a) is a sodium-dependent lysophosphatidylcholine (LPC) transporter expressed at the blood-brain barrier that constitutes the main pathway by which the brain obtains omega-3 fatty acids, such as docosahexanoic acid. Mfsd2a deficiency in humans results in severe microcephaly, underscoring the importance of LPC transport by Mfsd2a for brain development. Biochemical studies and recent cryo-electron microscopy (cryo-EM) structures of Mfsd2a bound to LPC suggest that Mfsd2a transports LPC via an alternating access mechanism between outward-facing and inward-facing conformational states in which the LPC inverts during transport between the outer and inner leaflet of a membrane. However, direct biochemical evidence of flippase activity by Mfsd2a has not been demonstrated and it is not understood how Mfsd2a could invert LPC between the outer and inner leaflet of the membrane in a sodium-dependent manner. Here, we established a unique in vitro assay using recombinant Mfsd2a reconstituted in liposomes that exploits the ability of Mfsd2a to transport lysophosphatidylserine (LPS) coupled with a small molecule LPS binding fluorophore that allowed for monitoring of directional flipping of the LPS headgroup from the outer to the inner liposome membrane. Using this assay, we demonstrate that Mfsd2a flips LPS from the outer to the inner leaflet of a membrane bilayer in a sodium-dependent manner. Furthermore, using cryo-EM structures as guides together with mutagenesis and a cell-based transport assay, we identify amino acid residues important for Mfsd2a activity that likely constitute substrate interaction domains. These studies provide direct biochemical evidence that Mfsd2a functions as a lysolipid flippase.

Distinct roles of the major binding residues in the cation-binding pocket of the melibiose transporter MelB.

Salmonella enterica serovar Typhimurium melibiose permease (MelBSt) is a prototype of the major facilitator superfamily (MFS) transporters, which play important roles in human health and diseases. MelBSt catalyzed the symport of galactosides with Na+, Li+, or H+ but prefers the coupling with Na+. Previously, we determined the structures of the inward- and outward-facing conformation of MelBSt and the molecular recognition for galactoside and Na+. However, the molecular mechanisms for H+- and Na+-coupled symport remain poorly understood. In this study, we solved two x-ray crystal structures of MelBSt, the cation-binding site mutants D59C at an unliganded apo-state and D55C at a ligand-bound state, and both structures display the outward-facing conformations virtually identical as published. We determined the energetic contributions of three major Na+-binding residues for the selection of Na+ and H+ by free energy simulations. Transport assays showed that the D55C mutant converted MelBSt to a solely H+-coupled symporter, and together with the free-energy perturbation calculation, Asp59 is affirmed to be the sole protonation site of MelBSt. Unexpectedly, the H+-coupled melibiose transport exhibited poor activities at greater bulky ΔpH and better activities at reversal ΔpH, supporting the novel theory of transmembrane-electrostatically localized protons and the associated membrane potential as the primary driving force for the H+-coupled symport mediated by MelBSt. This integrated study of crystal structure, bioenergetics, and free energy simulations, demonstrated the distinct roles of the major binding residues in the cation-binding pocket of MelBSt.

In vivo and in vitro characterizations of melibiose permease (MelB) conformation-dependent nanobodies reveal sugar-binding mechanisms.

Salmonella enterica serovar Typhimurium melibiose permease (MelBSt) is a prototype of the Na+-coupled major facilitator superfamily transporters, which are important for the cellular uptake of molecules including sugars and small drugs. Although the symport mechanisms have been well-studied, mechanisms of substrate binding and translocation remain enigmatic. We have previously determined the sugar-binding site of outward-facing MelBSt by crystallography. To obtain other key kinetic states, here we raised camelid single-domain nanobodies (Nbs) and carried out a screening against the WT MelBSt under 4 ligand conditions. We applied an in vivo cAMP-dependent two-hybrid assay to detect interactions of Nbs with MelBSt and melibiose transport assays to determine the effects on MelBSt functions. We found that all selected Nbs showed partial to complete inhibitions of MelBSt transport activities, confirming their intracellular interactions. A group of Nbs (714, 725, and 733) was purified, and isothermal titration calorimetry measurements showed that their binding affinities were significantly inhibited by the substrate melibiose. When titrating melibiose to the MelBSt/Nb complexes, Nb also inhibited the sugar-binding. However, the Nb733/MelBSt complex retained binding to the coupling cation Na+ and also to the regulatory enzyme EIIAGlc of the glucose-specific phosphoenolpyruvate/sugar phosphotransferase system. Further, EIIAGlc/MelBSt complex also retained binding to Nb733 and formed a stable supercomplex. All data indicated that MelBSt trapped by Nbs retained its physiological functions and the trapped conformation is similar to that bound by the physiological regulator EIIAGlc. Therefore, these conformational Nbs can be useful tools for further structural, functional, and conformational analyses.

Rational Approach to Improve Detergent Efficacy for Membrane Protein Stabilization.

Membrane protein structures are essential for the molecular understanding of diverse cellular processes and drug discovery. Detergents are not only widely used to extract membrane proteins from membranes but also utilized to preserve native protein structures in aqueous solution. However, micelles formed by conventional detergents are suboptimal for membrane protein stabilization, necessitating the development of novel amphiphilic molecules with enhanced protein stabilization efficacy. In this study, we prepared two sets of tandem malonate-derived glucoside (TMG) variants, both of which were designed to increase the alkyl chain density in micelle interiors. The alkyl chain density was modulated either by reducing the spacer length (TMG-Ms) or by introducing an additional alkyl chain between the two alkyl chains of the original TMGs (TMG-Ps). When evaluated with a few membrane proteins including a G protein-coupled receptor, TMG-P10,8 was found to be substantially more efficient at extracting membrane proteins and also effective at preserving protein integrity in the long term compared to the previously described TMG-A13. This result reveals that inserting an additional alkyl chain between the two existing alkyl chains is an effective way to optimize detergent properties for membrane protein study. This new biochemical tool and the design principle described have the potential to facilitate membrane protein structure determination.

[Examples of Professor MA Kun's treatment of infertility caused by uterine fibroids using method of tonifying kidney and activating blood].

Uterine fibroids are a prevalent factor that impacts fertility in women of reproductive age. This study discusses the theoretical foundation and formula principles of Professor MA Kun's clinical treatment for infertility caused by uterine fibroids. The kidney stores essence and is responsible for reproduction, while blood serves as a vital material basis for women's physiological functions. Kidney deficiency is the fundamental pathogenesis of infertility, and imbalances in kidney Qi and essence or deficiencies in kidney Yin and Yang can result in blood stasis. Blood stasis plays a significant role throughout this condition by impeding the flow of blood, which is crucial for nourishing Qi. Therefore, both kidney deficiency and blood stasis are key factors contributing to infertility caused by uterine fibroids. Professor MA Kun treats infertility caused by uterine fibroids using an approach that involves tonifying the kidneys and activating blood circulation based on changes in Qi and blood during the menstrual cycle as well as follicular growth processes. By identifying stage-specific evidence, appropriate treatments can be applied accordingly. During menstruation when the uterus opens and menstrual blood flows out, promoting follicular development through nourishing kidney Yin and activating blood circulation becomes essential. In later stages of menstruation, additional measures are taken to remove blood stasis, alleviate symptoms, disperse knots, attack pathogens while simultaneously replenishing vital energy. During intermenstrual periods when Yin holds greater importance than Yang, tonifying the kidneys and activating blood circulation helps facilitate smooth discharge of eggs by promoting transformation between Yin and Yang energies. Premenstrual period to warm kidney Yang to promote pregnant egg implantation, and at the same time to dredge the liver and regulate Qi, Qi elimination stagnation, complementary in the line, with the symptoms of additional subtractions. Clinical effect is remarkable, for the reference of colleagues.

Tris(hydroxymethyl)aminomethane Linker-Bearing Triazine-Based Triglucosides for Solubilization and Stabilization of Membrane Proteins.

High-resolution membrane protein structures are essential for a fundamental understanding of the molecular basis of diverse cellular processes and for drug discovery. Detergents are widely used to extract membrane-spanning proteins from membranes and maintain them in a functional state for downstream characterization. Due to limited long-term stability of membrane proteins encapsulated in conventional detergents, development of novel agents is required to facilitate membrane protein structural study. In the current study, we designed and synthesized tris(hydroxymethyl)aminomethane linker-bearing triazine-based triglucosides (TTGs) for solubilization and stabilization of membrane proteins. When these glucoside detergents were evaluated for four membrane proteins including two G protein-coupled receptors, a few TTGs including TTG-C10 and TTG-C11 displayed markedly enhanced behaviors toward membrane protein stability relative to two maltoside detergents [DDM (n-dodecyl-ß-d-maltoside) and LMNG (lauryl maltose neopentyl glycol)]. This is a notable feature of the TTGs as glucoside detergents tend to be inferior to maltoside detergents at stabilizing membrane proteins. The favorable behavior of the TTGs for membrane protein stability is likely due to the high hydrophobicity of the lipophilic groups, an optimal range of hydrophilic-lipophilic balance, and the absence of cis-trans isomerism.

STK25: a viable therapeutic target for cancer treatments?

Serine/threonine protein kinase 25 (STK25) is a critical regulator of ectopic lipid storage, glucose and insulin homeostasis, fibrosis, and meta-inflammation. More and more studies have revealed a strong correlation between STK25 and human diseases. On the one hand, STK25 can affect glucose and fatty acid metabolism in normal cells or tumors. On the other hand, STK25 participates in autophagy, cell polarity, cell apoptosis, and cell migration by activating various signaling pathways. This article reviews the composition and function of STK25, the energy metabolism and potential drugs that may target STK25, and the research progress of STK25 in the occurrence and development of tumors, to provide a reference for the clinical treatment of tumors.

SiO2 dust induces inflammation and pulmonary fibrosis in rat lungs through activation of ASMase/ceramide pathway.

The role of ASMase/ceramide signaling pathway in the development of silicosis needs to be verified by in vivo experiments. We investigated the role of the ASMase/ceramide signaling pathway in the progression of silicosis and the effect of desipramine (DMI) (1 mg/mL) on the development of silicosis, by establishing a silica (1 mL, 50 mg/mL) dust-contaminated rat silicosis model and administering the ASMase inhibitor, DMI, to the dust-contaminated rats. The results showed that the levels of interleukin (IL)-1ß and IL-6 were increased in the lung tissues of the rats in the dust-contaminated group at the initial stage after dusting; the inflammatory cell aggregation in the lung tissue was increased. With time progression, the hydroxyproline content in the lung tissue increased, and alpha-smooth muscle actin (α-SMA), collagen I, and vimentin substantially increased, suggesting that silicosis was formed in the lung tissue of the rats 28 days after SiO2 dust treatment. Moreover, the levels of ASMase, ceramide, and sphingosine-1-phosphate (S1P) were increased in the lung tissue of rats. The expression of ß-catenin, fibronectin, and caspase-3 protein was increased, and E-cadherin protein expression was decreased in the lung tissue of the rats in the late stage of dust contamination. The ASMase and ceramide in the lung tissues of the rats in the DMI intervention group were reduced, as were the lung tissue inflammation levels, collagen expression, and lung fibrosis. These results suggest that SiO2 dust may activate the ASMase/ceramide signaling pathway in rat lung tissue, promoting pulmonary fibrosis. DMI inhibited this activation, attenuated apoptosis, blocked epithelial-mesenchymal transition, and halted silica dust-induced silicofibrosis.

Role of PI3K/Akt/mTOR pathway-mediated macrophage autophagy in affecting the phenotype transformation of lung fibroblasts induced by silica dust exposure. / PI3K/Akt/mTOR通路介导巨噬细胞自噬影响矽尘致肺成纤维细胞表型转化.

OBJECTIVES: The phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is one of the main signaling pathways related to autophagy. Autophagy plays a key role in the formation of silicosis fibrosis. The phenotypic transformation of lung fibroblasts into myofibroblasts is a hallmark of the transition from the inflammatory phase to the fibrotic phase in silicosis. This study aims to investigate whether the PI3K/Akt/mTOR pathway affects the phenotypic transformation of silicosis-induced lung fibroblasts into myofibroblasts via mediating macrophage autophagy. METHODS: The human monocytic leukemia cell line THP-1 cells were differentiated into macrophages by treating with 100 ng/mL of phorbol ester for 24 h. Macrophages were exposed to different concentrations (0, 25, 50, 100, 200, 400 µg/mL) and different times (0, 6, 12, 24, 48 h) of SiO2 dust suspension. The survival rate of macrophages was measured by cell counting kit-8 (CCK-8) method. Enzyme linked immunosorbent assay (ELISA) was used to measure the contents of transforming growth factor-ß1 (TGF-ß1) and tumor necrosis factor-α (TNF-α) in the cell supernatant. The co-culture system of macrophages and HFL-1 cells was established by transwell. A blank control group, a SiO2 group, a LY294002 group, a SC79 group, a LY294002+SiO2 group, and a SC79+SiO2 group were set up in this experiment. Macrophages in the LY294002+SiO2 group were pretreated with LY294002 (PI3K inhibitor) for 18 hours, and macrophages in the SC79+SiO2 group were pretreated with SC79 (Akt activator) for 24 hours, and then exposed to SiO2 (100 µg/mL) dust suspension for 12 hours. The expression of microtubule-associated protein 1 light chain 3 (LC3) protein in macrophages was detected by the immunofluorescence method. The protein expressions of PI3K, Akt, mTOR, Beclin-1, LC3 in macrophages, and collagen III (Col III), α-smooth muscle actin (α-SMA), fibronectin (FN), matrix metalloproteinase-1 (MMP-1), tissue metalloproteinase inhibitor-1 (TIMP-1) in HFL-1 cells were measured by Western blotting. RESULTS: After the macrophages were exposed to SiO2 dust suspension of different concentrations for 12 h, the survival rates of macrophages were gradually decreased with the increase of SiO2 concentration. Compared with the 0 µg/mL group, the survival rates of macrophages in the 100, 200, and 400 µg/mL groups were significantly decreased, and the concentrations of TGF-ß1 and TNF-α in the cell supernatant were obviously increased (all P<0.05). When 100 µg/mL SiO2 dust suspension was applied to macrophages, the survival rates of macrophages were decreased with the prolonged exposure time. Compared with the 0 h group, the survival rates of macrophages were significantly decreased (all P<0.05), the concentrations of TGF-ß1 and TNF-α in the cell supernatant were significantly increased, and the protein expression levels of Beclin-1 and LC3II were increased markedly in the 6, 12, 24, and 48 h groups (all P<0.05). Immunofluorescence results demonstrated that after exposure to SiO2 (100 µg/mL) dust for 12 h, LC3 exhibited punctate aggregation and significantly higher fluorescence intensity compared to the blank control group (P<0.05). Compared with the blank control group, the protein expressions of Col III, FN, α-SMA, MMP-1, and TIMP-1 in HFL-1 cells were up-regulated in the SiO2 group (all P<0.05). Compared with the SiO2 group, the protein expressions of PI3K, Akt, and mTOR were down-regulated and the protein expressions of LC3II and Beclin-1 were up-regulated in macrophages (all P<0.05), the contents of TNF-α and TGF-ß1 in the cell supernatant were decreased (both P<0.01), and the protein expressions of Col III, FN, α-SMA, MMP-1, and TIMP-1 in HFL-1 cells were down-regulated (all P<0.05) in the LY294002+SiO2 group. Compared with the SiO2 group, the protein expressions of PI3K, Akt, and mTOR were up-regulated and the protein expressions of LC3II and Beclin-1 were down-regulated in macrophages (all P<0.05), the contents of TNF-α and TGF-ß1 in the cell supernatant were increased (both P<0.01), and the protein expressions of Col III, FN, α-SMA, MMP-1, and TIMP-1 in HFL-1 cells were up-regulated (all P<0.05) in the SC79+SiO2 group. CONCLUSIONS: Silica dust exposure inhibits the PI3K/Akt/mTOR pathway, increases autophagy and concentration of inflammatory factors in macrophages, and promotes the phenotype transformation of HFL-1 cells into myofibroblasts. The regulation of the PI3K/Akt/mTOR pathway can affect the autophagy induction and the concentration of inflammatory factors of macrophages by silica dust exposure, and then affect the phenotype transformation of HFL-1 cells into myofibroblasts induced by silica dust exposure.

Complete cysteine-scanning mutagenesis of the Salmonella typhimurium melibiose permease.

The melibiose permease of Salmonella typhimurium (MelBSt) catalyzes the stoichiometric symport of galactopyranoside with a cation (H+, Li+, or Na+) and is a prototype for Na+-coupled major facilitator superfamily (MFS) transporters presenting from bacteria to mammals. X-ray crystal structures of MelBSt have revealed the molecular recognition mechanism for sugar binding; however, understanding of the cation site and symport mechanism is still vague. To further investigate the transport mechanism and conformational dynamics of MelBSt, we generated a complete single-Cys library containing 476 unique mutants by placing a Cys at each position on a functional Cys-less background. Surprisingly, 105 mutants (22%) exhibit poor transport activities (<15% of Cys-less transport), although the expression levels of most mutants were comparable to that of the control. The affected positions are distributed throughout the protein. Helices I and X and transmembrane residues Asp and Tyr are most affected by cysteine replacement, while helix IX, the cytoplasmic middle-loop, and C-terminal tail are least affected. Single-Cys replacements at the major sugar-binding positions (K18, D19, D124, W128, R149, and W342) or at positions important for cation binding (D55, N58, D59, and T121) abolished the Na+-coupled active transport, as expected. We mapped 50 loss-of-function mutants outside of these substrate-binding sites that suffered from defects in protein expression/stability or conformational dynamics. This complete Cys-scanning mutagenesis study indicates that MelBSt is highly susceptible to single-Cys mutations, and this library will be a useful tool for further structural and functional studies to gain insights into the cation-coupled symport mechanism for Na+-coupled MFS transporters.

Glyco-Steroidal Amphiphiles (GSAs) for Membrane Protein Structural Study.

Integral membrane proteins pose considerable challenges to high resolution structural analysis. Maintaining membrane proteins in their native state during protein isolation is essential for structural study of these bio-macromolecules. Detergents are the most commonly used amphiphilic compounds for stabilizing membrane proteins in solution outside a lipid bilayer. We previously introduced a glyco-diosgenin (GDN) detergent that was shown to be highly effective at stabilizing a wide range of membrane proteins. This steroidal detergent has additionally gained attention due to its compatibility with membrane protein structure study via cryo-EM. However, synthetic inconvenience limits widespread use of GDN in membrane protein study. To improve its synthetic accessibility and to further enhance detergent efficacy for protein stabilization, we designed a new class of glyco-steroid-based detergents using three steroid units: cholestanol, cholesterol and diosgenin. These new detergents were efficiently prepared and showed marked efficacy for protein stabilization in evaluation with a few model membrane proteins including two G protein-coupled receptors. Some new agents were not only superior to a gold standard detergent, DDM (n-dodecyl-ß-d-maltoside), but were also more effective than the original GDN at preserving protein integrity long term. These agents represent valuable alternatives to GDN, and are likely to facilitate structural determination of challenging membrane proteins.

Foldable Detergents for Membrane Protein Study: Importance of Detergent Core Flexibility in Protein Stabilization.

Membrane proteins are of biological and pharmaceutical significance. However, their structural study is extremely challenging mainly due to the fact that only a small number of chemical tools are suitable for stabilizing membrane proteins in solution. Detergents are widely used in membrane protein study, but conventional detergents are generally poor at stabilizing challenging membrane proteins such as G protein-coupled receptors and protein complexes. In the current study, we prepared tandem triazine-based maltosides (TZMs) with two amphiphilic triazine units connected by different diamine linkers, hydrazine (TZM-Hs) and 1,2-ethylenediamine (TZM-Es). These TZMs were consistently superior to a gold standard detergent (DDM) in terms of stabilizing a few membrane proteins. In addition, the TZM-Es containing a long linker showed more general protein stabilization efficacy with multiple membrane proteins than the TZM-Hs containing a short linker. This result indicates that introduction of the flexible1,2-ethylenediamine linker between two rigid triazine rings enables the TZM-Es to fold into favourable conformations in order to promote membrane protein stability. The novel concept of detergent foldability introduced in the current study has potential in rational detergent design and membrane protein applications.

Clinical significance and potential regulatory mechanism of overexpression of pituitary tumor-transforming gene transcription factor in bladder cancer.

BACKGROUND: Pituitary tumor transforming gene-1 (PTTG1) transcription factor is identified as carcinogenic and associated with tumor invasiveness, but its role in bladder cancer (BLCA) remains obscure. This research is intended to analyze the aberrant expression and clinical significance of PTTG1 in BLCA, explore the relationship between PTTG1 and tumor microenvironment characteristics and predict its potential transcriptional activity in BLCA tissue. METHODS: We compared the expression discrepancy of PTTG1 mRNA in BLCA and normal bladder tissue, using the BLCA transcriptomic datasets from GEO, ArrayExpress, TCGA, and GTEx. In-house immunohistochemical staining was implemented to determine the PTTG1 protein intensity. The prognostic value of PTTG1 was evaluated using the Kaplan-Meier Plotter. CRISPR screen data was utilized to estimate the effect PTTG1 interference has on BLCA cell lines. We predicted the abundance of the immune cells in the BLCA tumor microenvironment using the microenvironment cell populations-counter and ESTIMATE algorithms. Single-cell RNA sequencing data was applied to identify the major cell types in BLCA, and the dynamics of BLCA progression were revealed using pseudotime analysis. PTTG1 target genes were predicted by CistromeDB. RESULTS: The elevated expression level of PTTG1 was confirmed in 1037 BLCA samples compared with 127 non-BLCA samples, with a standardized mean difference value of 1.04. Higher PTTG1 expression status exhibited a poorer BLCA prognosis. Moreover, the PTTG1 Chronos genetic effect scores were negative, indicating that PTTG1 silence may inhibit the proliferation and survival of BLCA cells. With PTTG1 mRNA expression level increasing, higher natural killer, cytotoxic lymphocyte, and monocyte lineage cell infiltration levels were observed. A total of four candidate targets containing CHEK2, OCIAD2, UBE2L3, and ZNF367 were determined ultimately. CONCLUSIONS: PTTG1 mRNA over-expression may become a potential biomarker for BLCA prognosis. Additionally, PTTG1 may correlate with the BLCA tumor microenvironment and exert transcriptional activity by targeting CHEK2, OCIAD2, UBE2L3, and ZNF367 in BLCA tissue.

The interplay between ASMase signaling pathway and NLRP3 in the epithelial to mesenchymal transition of HBE cells induced by silica.

Epithelial-mesenchymal transition (EMT) is an important part of pulmonary fibrosis. Our earlier study illustrated that the acid sphingomyelinase (ASMase) pathway plays significant role in silica (SiO2 )-induced transformation of lung fibroblasts into myofibroblasts. The metabolite of ASMase, ceramide (Cer), activates the inflammatory response by activating Nod-like receptor protein 3 (NLRP3) in macrophages, and NLRP3 is also involved in the EMT process. However, whether ASMase and NLRP3 are involved in regulating SiO2 -induced EMT has not been confirmed. In this study, an in vitro model of EMT in human bronchial epithelial (HBE) cells was established by SiO2 dust staining to investigate the role of ASMase and NLRP3 in EMT and to provide new clues for the molecular mechanism of silicosis. HBE cells were stained with 100 µg/ml SiO2 dust for 72 h to establish the EMT model. The ASMase inhibitor desipramine decreased the level of S1P and the expression of α-smooth muscle actin (α-SMA) and NLRP3 in SiO2 dust-stained HBE cells, whereas the expression of E-cadherin (E-cad) increased. The NLRP3 inhibitor MCC950 inhibited the secretion of interleukin-1ß (IL-1ß) and decreased the expression of NLRP3, Caspase-1, and α-SMA in SiO2 dust-stained HBE cells, whereas E-cad expression increased and ASMase activity and S1P levels decreased. It was concluded that SiO2 dust increases the release of the inflammatory factor and induces EMT in HBE cells. Inhibition of ASMase activity or NLRP3 expression reduced the SiO2 dust-induced cell inflammatory response and slowed the occurrence of EMT in HBE cells. Therefore, NLRP3 and ASMase may interact in SiO2 dust-induced EMT in HBE cells.

Chitosan/Alginate Nanoparticles for the Enhanced Oral Antithrombotic Activity of Clam Heparinoid from the Clam Coelomactra antiquata.

Chitosan/alginate nanoparticles (DG1-NPs and DG1/Cur-NPs) aiming to enhance the oral antithrombotic activity of clam heparinoid DG1 were prepared by ionotropic pre-gelation. The influence of parameters, such as the concentration of sodium alginate (SA), chitosan (CTS), CaCl2, clam heparinoid DG1, and curcumin (Cur), on the characteristics of the nanoparticles, were investigated. Results indicate that chitosan and alginate can be used as polymer matrices to encapsulate DG1, and nanoparticle characteristics depend on the preparation parameters. Nano-particles should be prepared using 0.6 mg/mL SA, 0.33 mg/mL CaCl2, 0.6 mg/mL CTS, 7.2 mg/mL DG1, and 0.24 mg/mL Cur under vigorous stirring to produce DG1-NPS and DG1/Cur-NPS with small size, high encapsulation efficiency, high loading capacity, and negative zeta potential from approximately -20 to 30 mV. Data from scanning electron microscopy, Fourier-transform infrared spectrometry, and differential scanning calorimetry analyses showed no chemical reaction between DG1, Cur, and the polymers; only physical mixing. Moreover, the drug was loaded in the amorphous phase within the nanoparticle matrix. In the acute pulmonary embolism murine model, DG1-NPs enhanced the oral antithrombotic activity of DG1, but DG1/Cur-NPs did not exhibit higher antithrombotic activity than DG1-NPs. Therefore, the chitosan/alginate nanoparticles enhanced the oral antithrombotic activity of DG1, but curcumin did not further enhance this effect.

Structure, function, and ion-binding properties of a K+ channel stabilized in the 2,4-ion-bound configuration.

Here, we present the atomic resolution crystallographic structure, the function, and the ion-binding properties of the KcsA mutants, G77A and G77C, that stabilize the 2,4-ion-bound configuration (i.e., water, K+, water, K+-ion-bound configuration) of the K+ channel's selectivity filter. A full functional and thermodynamic characterization of the G77A mutant revealed wild-type-like ion selectivity and apparent K+-binding affinity, in addition to showing a lack of C-type inactivation gating and a marked reduction in its single-channel conductance. These structures validate, from a structural point of view, the notion that 2 isoenergetic ion-bound configurations coexist within a K+ channel's selectivity filter, which fully agrees with the water-K+-ion-coupled transport detected by streaming potential measurements.

Combined intervention with N-acetylcysteine and desipramine alleviated silicosis development by regulating the Nrf2/HO-1 and ASMase/ceramide signaling pathways.

Silicosis is a systemic disease characterized by diffuse fibrosis of the lung tissue caused by long-term inhalation of large amounts of free silica (SiO2) dust. The pathogenesis of silicosis has not been fully elucidated, and there is a lack of effective treatment methods. N-acetylcysteine (NAC) can potentially treat pulmonary fibrosis by exerting antioxidant effects. Desipramine (DMI) can influence pulmonary fibrosis development by inhibiting acid sphingomyelinase (ASMase) activity and regulating ceramide concentrations. Both can interfere with pulmonary fibrosis through different mechanisms, but the intervention effects of NAC combined with DMI on silicosis fibrosis have not been reported. Therefore, this study established a rat silicosis model using a single tracheal drip of SiO2 dust suspension in Wistar rats to investigate the effect of NAC combined with DMI on SiO2 dust-induced silicosis and its related molecular mechanisms. The histopathological examination of the SiO2 dust-induced silicosis rats suggested that NAC and DMI alone or in combination could decrease the severity of pulmonary fibrosis in rats. The combined intervention had a better effect on reducing fibrosis than the individual interventions. NAC and DMI, alone or in combination, decreased the levels of markers related to pulmonary fibrosis in rats (smooth muscle α-actin (α-SMA), collagen (Col) I, Col III, hydroxyproline (HYP), inflammatory factors (transforming growth factor-ß1 (TGF-ß1) and tumor necrosis factor-α (TNF-α)), and lipid peroxidase malondialdehyde (MDA)). The nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme-oxygenase-1 (HO-1) and ASMase/ceramide pathways were inhibited to some extent by increasing the superoxide dismutase (SOD) levels of antioxidant enzymes and 8-iso-prostaglandin F2α (8-iso-PGF2α) levels of lipid peroxides. The combined intervention and NAC alone inhibited the SiO2 dust-induced elevation of matrix metalloproteinase 1 (MMP-1) and tissue inhibitor matrix metalloproteinase 1 (TIMP-1), but the effect was not significant in the DMI-treated group. Combining DMI and NAC inhibited Col I deposition and reduced HO-1, TIMP-1, and ASMase levels in lung tissues compared to individual treatments. In summary, the SiO2 dust could induce oxidative stress and inflammation in rats, resulting in an imbalance in extracellular matrix (ECM) synthesis/catabolism and ASMase/ceramide signaling pathway activation, leading to silicosis development.The combined intervention of DMI and NAC may synergistically regulate the Nrf2/HO-1 pathway, maintain the anabolic balance of the ECM, inhibit ASMase/ceramide signaling pathway activation by suppressing the inflammatory response and effectively delay silicosis fibrosis progression.

SiO2 stimulates macrophage stress to induce the transformation of lung fibroblasts into myofibroblasts and its relationship with the sphingomyelin metabolic pathway.

Silicosis is a serious occupational disease with the highest incidence in China. However, its pathogenesis has not been fully elucidated. Studies have shown that the sphingomyelin signaling pathway may play an important role in different fibrotic diseases but its role in silicosis-mediated fibrosis is still unclear. In this study, the supernatant of human peripheral blood mononuclear cell line (THP-1)-derived macrophages exposed to silica (SiO2 ) was used to stimulate the transformation of human embryonic lung fibroblast cell line (HFL-1) into myofibroblasts, and the intervention effect of recombinant human acid ceramidase (rAC) was observed. The results showed that SiO2 stimulated the production of reactive oxygen species and malondialdehyde in the supernatant of THP-1-derived macrophages and increased the secretion of TGF-ß1, TNF-α, and IL-8. In addition, we found that the expression levels of α-SMA, FN, Col I, and Col III in HFL-1 cells increased. Meanwhile, the activities of ASMase and ACase and the expression levels of Cer, Sph, and S1P were increased. Intervention by rAC can suppress these changes to different degrees. In conclusion, the present study shows that SiO2 dust poisoning may stimulate HFL-1 cell differentiation into myofibroblasts by inducing oxidative stress in THP-1-derived macrophages, thereby promoting the secretion of a variety of inflammatory factors and activating the sphingolipid signaling pathway in HFL-1 cells. Exogenous rAC can effectively interfere with the stimulation of HFL-1 cells by silica in vitro.

Diastereomeric Cyclopentane-Based Maltosides (CPMs) as Tools for Membrane Protein Study.

Amphiphilic agents, called detergents, are invaluable tools for studying membrane proteins. However, membrane proteins encapsulated by conventional head-to-tail detergents tend to denature or aggregate, necessitating the development of structurally distinct molecules with improved efficacy. Here, a novel class of diastereomeric detergents with a cyclopentane core unit, designated cyclopentane-based maltosides (CPMs), were prepared and evaluated for their ability to solubilize and stabilize several model membrane proteins. A couple of CPMs displayed enhanced behavior compared with the benchmark conventional detergent, n-dodecyl-ß-d-maltoside (DDM), for all the tested membrane proteins including two G-protein-coupled receptors (GPCRs). Furthermore, CPM-C12 was notable for its ability to confer enhanced membrane protein stability compared with the previously developed conformationally rigid NBMs [J. Am. Chem. Soc. 2017, 139, 3072] and LMNG. The effect of the individual CPMs on protein stability varied depending on both the detergent configuration (cis/trans) and alkyl chain length, allowing us draw conclusions on the detergent structure-property-efficacy relationship. Thus, this study not only provides novel detergent tools useful for membrane protein research but also reports on structural features of the detergents critical for detergent efficacy in stabilizing membrane proteins.