Influence of ALS-linked M337V mutation on the conformational ensembles of TDP-43321-340 peptide monomer and dimer.

The transactive response (TAR) DNA/RNA-binding protein 43 (TDP-43) can self-assemble into both functional stress granules via liquid-liquid phase separation (LLPS) and pathogenic amyloid fibrillary aggregates that are closely linked to amyotrophic lateral sclerosis. Previous experimental studies reported that the low complexity domain (LCD) of TDP-43 plays an essential role in the LLPS and aggregation of the full-length protein, and it alone can also undergo LLPS to form liquid droplets mainly via intermolecular interactions in the 321-340 region. And the ALS-associated M337V mutation impairs LCD's LLPS and facilitates liquid-solid phase transition. However, the underlying atomistic mechanism is not well understood. Herein, as a first step to understand the M337V-caused LLPS disruption of TDP-43 LCD mediated by the 321-340 region and the fibrillization enhancement, we investigated the conformational properties of monomer/dimer of TDP-43321-340 peptide and its M337V mutant by performing extensive all-atom explicit-solvent replica exchange molecular dynamic simulations. Our simulations demonstrate that M337V mutation alters the residue regions with high helix/ß-structure propensities and thus affects the conformational ensembles of both monomer and dimer. M337V mutation inhibits helix formation in the N-terminal Ala-rich region and the C-terminal mutation site region, while facilitating their long ß-sheet formation, albeit with a minor impact on the average probability of both helix structure and ß-structure. Further analysis of dimer system shows that M337V mutation disrupts inter-molecular helix-helix interactions and W334-W334 π-π stacking interactions which were reported to be important for the LLPS of TDP-43 LCD, whereas enhances the overall peptide residue-residue interactions and weakens peptide-water interactions, which is conducive to peptide fibrillization. This study provides mechanistic insights into the M337V-mutation-induced impairment of phase separation and facilitation of fibril formation of TDP-43 LCD.

Deciphering the mechanisms of HPV E6 mutations in the destabilization of E6/E6AP/p53 complex.

In epithelial tumors, oncoprotein E6 binds with the ubiquitin ligase E6AP to form E6/E6AP heterodimer; then this heterodimer recruits p53 to form E6/E6AP/p53 heterotrimer and induces p53 degradation. Recent experiments demonstrated that three E6 single-site mutants (F47R, R102A, and L50E) can inhibit the E6/E6AP/p53 heterotrimer formation and rescue p53 from the degradation pathway. However, the molecular mechanism underlying mutation-induced heterotrimer inhibition remains largely elusive. Herein, we performed extensive molecular dynamics simulations (totally ∼13 µs) on both heterodimer and heterotrimer to elucidate at an atomic level how each p53-degradation-defective HPV16 E6 mutant reduces the structural stabilities of the two complexes. Our simulations reveal that the three E6 mutations destabilize the structure of E6/E6AP/p53 complex through distinct mechanisms. Although F47RE6 mutation has no effect on the structure of E6/E6AP heterodimer, it results in an electrostatic repulsion between R47E6 and R290p53, which is unfavorable for E6-p53 binding. R102AE6 mutation destabilizes the structure of E6/E6AP heterodimer and significantly disrupts hydrophobic and cation-π interactions between F47E6 and E286p53/L298p53/R290p53. L50EE6 mutation impairs both E6 interdomain interactions (especially F47-K108 cation-π interaction) and E6-E6AP intermolecular interactions important for the stabilization of E6/E6AP heterodimer. This study identifies the intra- and intermolecular interactions crucial for the complex stability, which may provide mechanistic insights into the inhibition of complex formation by the three HPV16 E6 mutations.

Insights into the Atomistic Mechanisms of Phosphorylation in Disrupting Liquid-Liquid Phase Separation and Aggregation of the FUS Low-Complexity Domain.

Fused in sarcoma (FUS), a nuclear RNA binding protein, can not only undergo liquid-liquid phase separation (LLPS) to form dynamic biomolecular condensates but also aggregate into solid amyloid fibrils which are associated with the pathology of amyotrophic lateral sclerosis and frontotemporal lobar degeneration diseases. Phosphorylation in the FUS low-complexity domain (FUS-LC) inhibits FUS LLPS and aggregation. However, it remains largely elusive what are the underlying atomistic mechanisms of this inhibitory effect and whether phosphorylation can disrupt preformed FUS fibrils, reversing the FUS gel/solid phase toward the liquid phase. Herein, we systematically investigate the impacts of phosphorylation on the conformational ensemble of the FUS37-97 monomer and dimer and the structure of the FUS37-97 fibril by performing extensive all-atom molecular dynamics simulations. Our simulations reveal three key findings: (1) phosphorylation shifts the conformations of FUS37-97 from the ß-rich, fibril-competent state toward a helix-rich, fibril-incompetent state; (2) phosphorylation significantly weakens protein-protein interactions and enhances protein-water interactions, which disfavor FUS-LC LLPS as well as aggregation and facilitate the dissolution of the preformed FUS-LC fibril; and (3) the FUS37-97 peptide displays a high ß-strand probability in the region spanning residues 52-67, and phosphorylation at S54 and S61 residues located in this region is crucial for the disruption of LLPS and aggregation of FUS-LC. This study may pave the way for ameliorating phase-separation-related pathologies via site-specific phosphorylation.

ALS-associated A315E and A315pT variants exhibit distinct mechanisms in inducing irreversible aggregation of TDP-43312-317 peptides.

Amyotrophic lateral sclerosis (ALS) is intensively associated with insoluble aggregates formed by transactivation response element DNA-binding protein 43 (TDP-43) in the cytoplasm of neuron cells. A recent experimental study reported that two ALS-linked familial variants, A315E and A315pT (pT, phosphorylated threonine), can induce irreversible aggregation of the TDP-43 312NFGAFS317 segment (TDP-43312-317). However, the underlying molecular mechanism remains largely elusive. Here, we investigated the early aggregation process of the wild type (WT) 312NFGAFS317 segment and its A315E and A315pT variants by performing multiple microsecond all-atom molecular dynamics simulations. Our simulations show that the two variants display lower fluidity than WT, consistent with their decreased labilities observed in previous denaturation assay experiments. Despite each of the two variants carrying one negative charge, unexpectedly, we find that both A315E mutation and A315pT phosphorylation enhance intermolecular interactions and result in the formation of more compact oligomers. Compared to WT, A315E oligomers possess low ß-sheet content but a compact hydrophobic core, while A315pT oligomers have high ß-sheet content and large ß-sheets. Side chain hydrogen-bonding and hydrophobic interactions as well as N312-E315 salt bridges contribute most to the increased aggregation propensity of the A315E mutant. By contrast, main chain and side chain hydrogen-bonding interactions, side chain hydrophobic and aromatic interactions, are crucial to the enhanced aggregation capability of the A315pT variant. These results indicate that glutamate mutation and phosphorylation at position 315 induce the irreversible aggregation of TDP-43312-317 peptides through differential mechanisms, which remind us that we should be careful in the investigation of the phosphorylation effect on protein aggregation by using phosphomimetic substitutions. This study provides mechanistic insights into the A315E/A315pT-induced irreversible aggregation of TDP-43312-317, which may be helpful for the in-depth understanding of ALS-mutation/phosphorylation-associated liquid-to-solid phase transition of TDP-43 protein aggregates.

Mechanistic insight into the destabilization of p53TD tetramer by cancer-related R337H mutation: a molecular dynamics study.

The p53 protein is a tumor suppressor crucial for cell cycle and genome integrity. In a very large proportion of human cancers, p53 is frequently inactivated by mutations located in its DNA-binding domain (DBD). Some experimental studies reported that the inherited R337H mutation located in the p53 tetramerization domain (p53TD) can also result in destabilization of the p53 protein, and consequently lead to an organism prone to cancer setup. However, the underlying R337H mutation-induced structural destabilization mechanism is not well understood. Herein, we investigate the structural stability and dynamic property of the wild type p53TD tetramer and its cancer-related R337H mutant by performing multiple microsecond molecular dynamics simulations. It is found that R337H mutation destroys the R337-D352 hydrogen bonds, weakens the F341-F341 π-π stacking interaction and the hydrophobic interaction between aliphatic hydrocarbons of R337 and M340, leading to more solvent exposure of all the hydrophobic cores, and thus disrupting the structural integrity of the tetramer. Importantly, our simulations show for the first time that R337H mutation results in unfolding of the α-helix starting from the N-terminal region (residues 335RER(H)FEM340). Consistently, community network analyses reveal that R337H mutation reduces dynamical correlation and global connectivity of p53TD tetramer, which destabilizes the structure of the p53TD tetramer. This study provides the atomistic mechanism of R337H mutation-induced destabilization of p53TD tetramer, which might be helpful for in-depth understanding of the p53 loss-of-function mechanism.

The destructive mechanism of Aß1-42 protofibrils by norepinephrine revealed via molecular dynamics simulations.

Amyloid-ß (Aß) fibrillary plaques represent the main hallmarks of Alzheimer's disease (AD), in addition to tau neurofibrillary tangles. Disrupting early-formed Aß protofibrils is considered to be one of the primary therapeutic strategies to interfere with AD. Our previous work showed that norepinephrine (NE), an important neurotransmitter in the brain, can effectively inhibit the aggregation of the Aß1-42 peptide. However, whether and how NE molecules disassemble Aß1-42 protofibrils remains to be elucidated. Herein we investigate the influence of NE (in protonated and deprotonated states) on the recently cryo-EM solved LS-shaped Aß1-42 protofibrils and the underlying molecular mechanism by performing all-atom molecular dynamics simulations. Our simulations showed that protonated and deprotonated NE exhibited distinct disruptive mechanisms on Aß1-42 protofibrils. Protonated NE could significantly disrupt the N-terminal (residues D1-H14) structure of Aß1-42 protofibrils and destabilize the global structure of the protofibril. It preferentially bound with N-terminal residues of Aß1-42 protofibrils and formed hydrogen bonds with E3, D7, E11, Q15, E22, and D23 residues and π-π stackings with H6, H13, and F20 residues, and thus destroyed the hydrogen bonds between H6 and E11 and increased the kink angle around Y10. Compared to protonated NE, deprotonated NE displayed a higher disruptive capability on Aß1-42 protofibrils, and stronger hydrophobic and π-π stacking interactions with the protofibril structure. This study revealed the molecular mechanism of NE in the destruction of Aß1-42 protofibrils, which may be helpful in the design of potent drug candidates against AD.

Molecular mechanisms of resveratrol and EGCG in the inhibition of Aß42 aggregation and disruption of Aß42 protofibril: similarities and differences.

The aggregation of amyloid-ß protein (Aß) into fibrillary deposits is implicated in Alzheimer's disease (AD), and inhibiting Aß aggregation and clearing Aß fibrils are considered as promising strategies to treat AD. It has been reported that resveratrol (RSV) and epigallocatechin-3-gallate (EGCG), two of the most extensively studied natural polyphenols, are able to inhibit Aß fibrillization and remodel the preformed fibrillary aggregates into amorphous, non-toxic species. However, the mechanisms by which RSV inhibits Aß42 aggregation and disrupts Aß42 protofibril, as well as the inhibitory/disruptive mechanistic similarities and differences between RSV and EGCG, remain mostly elusive. Herein, we performed extensive all-atom molecular dynamics (MD) simulations on Aß42 dimers (the early aggregation state of Aß42) and protofibrils (the intermediate of Aß42 fibril formation and elongation) in the absence/presence of RSV or EGCG molecules. Our simulations show that both RSV and EGCG can bind with Aß42 monomers and inhibit the dimerization of Aß42. The binding of RSV with Aß42 peptide is mostly viaπ-π stacking interactions, while the binding of EGCG with Aß42 is mainly through hydrophobic, π-π stacking, and hydrogen-bonding interactions. Moreover, both RSV and EGCG disrupt the ß-sheet structure and K28-A42 salt bridges, leading to a disruption of Aß42 protofibril structure. RSV mainly binds with residues whose side-chains point inwards from the surface of the protofibril, while EGCG mostly binds with residues whose side-chains point outwards from the surface of the protofibril. Furthermore, RSV interacts with Aß42 protofibrils mostly viaπ-π stacking interactions, while EGCG interacts with Aß42 protofibrils mainly via hydrogen-bonding and hydrophobic interactions. For comparison, we also explore the effects of RSV/EGCG molecules on the aggregation inhibition and protofibril disruption of the Iowa mutant (D23N) Aß. Our findings may pave the way for the design of more effective drug candidates as well as the utilization of cocktail therapy using RSV and EGCG for the treatment of AD.

Heparin remodels the microtubule-binding repeat R3 of Tau protein towards fibril-prone conformations.

Abnormal aggregation of proteins into pathological amyloid fibrils is implicated in a wide range of devastating human neurodegenerative diseases. Intracellular fibrillary inclusions formed by Tau protein are characterized as the hallmark of tauopathies, including Alzheimer's disease and frontotemporal dementia. Heparin has been often used to trigger Tau aggregation in in vitro studies. However, the conformational changes induced by heparin and the underlying mechanism of promotion of Tau aggregation by heparin are not well understood. Structural characterization of Tau oligomers in the early stage of fibrillation is of great importance but remains challenging due to their dynamic and heterogeneous nature. R3, the third microtubule-binding repeat of Tau, contains the fibril-nucleating core (PHF6) and is crucial for Tau aggregation. In this study, utilizing extensive all-atom replica-exchange molecular dynamic simulations, we explored the conformational ensembles of R3 monomer/dimer in the absence and presence of heparin. Our results show that without heparin, both monomeric and dimeric R3 preferentially adopt collapsed ß-sheet-containing conformations and PHF6 plays an important role in the formation of interchain ß-sheet structures, while in the presence of heparin, R3 can populate relatively extended disordered states where chain dimension is similar to that of R3 in Tau filaments. Through electrostatic, hydrogen-bonding and hydrophobic interactions, heparin has a preference for interacting with residues V306/Q307/K317/K321/H329/H330/K331 which distribute throughout the entire sequence of R3, in turn acting as a template to extend R3 conformations. More importantly, heparin alters intramolecular/intermolecular interaction patterns of R3 and increases the intermolecular contact regions. Our results suggest that heparin remodels the conformations of R3 towards fibril-prone structures by increasing chain dimension and intermolecular contact regions, which may shed light on the atomic mechanism of heparin-induced amyloid fibrillization of Tau protein.

Differential expression of circular RNA in patients with white matter hyperintensity and cognitive impairment. / è„‘ç™½è´¨é«˜ä¿¡å·ä¼´è®¤çŸ¥åŠŸèƒ½éšœç¢æ‚£è€ çŽ¯çŠ¶RNA的差异性表达.

OBJECTIVES: White matter hyperintensity (WMH) is an important factor leading to cognitive impairment, and the mechanism has not been clarified. In recent years, studies have found that circular RNA (circRNA) has differential expression in cerebrovascular diseases. This study aims to analyze the expression profile of circRNA in peripheral blood mononuclear cell (PBMC) of patients with WMH with cognitive impairment, to screen the differentially expressed circRNA, and to explore the possible role of circRNA in WMH with cognitive impairment. METHODS: CircRNA microarray was used to detect the circRNA expression profile of PBMC in patients with WMH with cognitive impairment, and in patients with WMH without cognitive impairment as well as in normal controls (3 cases each, male to female ratio of 2꞉1). The differentially expressed circRNA in patients with WMH with cognitive impairment was screened. The screening criteria for differentially expressed circRNA was fold change (FC) ≥2.0 (|log2FC ≥1) and P<0.05. TargetScan and miRanda target gene analysis software were used to predict the relevant target miRNA, and Genespring software was used to predict the target genes. RESULTS: Compared with the control group, there were 5 significantly up-regulated circRNA and 3 down-regulated circRNA in the WMH with cognitive impairment group; 8 circRNA were significantly up-regulated and 2 were down-regulated in the WMH without cognitive impairment group. When compared with the WMH with cognitive impairment group, no co-differentially expressed circRNA was found in WMH without cognitive impairment group and control group. Compared with the control group, the expression of hsa_circ_0092222 was up-regulated and the expressions of hsa_circ_0000662 and hsa_circ_0083773 were down-regulated in the WMH with cognitive impairment group and the WMH without cognitive impairment group, and there was no significant difference between the 2 groups (all P>0.05). Two target miRNA (hsa-miR-19a-3p and hsa-miR-19b-3p) of hsa_circ_0092222 were predicted, and the target gene was ribosomal protein S4, Y-linked 1 (RPS4Y1). Hsa_circ_0000662 predicted a target miRNA (hsa-miR-194) with axis inhibitor 1 (AXIN1) as the target gene. Hsa_circ_0083773 predicted 7 target miRNA, and the target gene was recombinant scavenger receptor class A member 3 (SCARA3). CONCLUSIONS: The circRNA expression profile of patients with WMH is changed significantly. The differentially expressed circRNA may be the cause of WMH; Hsa_circ_0092222, hsa_circ_0000662, and hsa_circ_0083773 may regulate the expression of target genes by targeting adsorption of the target miRNA, leading to brain white matter damage through Janus kinase 2 (JAK2)/signal transducers and activators of transcription (STAT3) signal pathway and Wnt signal pathway.There is no significant difference in circRNA expression profile between WMH with or without cognitive impairment. Cognitive impairment in patients with WMH may have other reasons.

Binding of protofibrillar Aß trimers to lipid bilayer surface enhances Aß structural stability and causes membrane thinning.

Alzheimer's disease, a common neurodegenerative disease, is characterized by the aggregation of amyloid-ß (Aß) peptides. The interactions of Aß with membranes cause changes in membrane morphology and ion permeation, which are responsible for its neurotoxicity and can accelerate fibril growth. However, the Aß-lipid interactions and how these induce membrane perturbation and disruption at the atomic level and the consequences for the Aß organization are not entirely understood. Here, we perform multiple atomistic molecular dynamics simulations on three protofibrillar Aß9-40 trimers. Our simulations show that, regardless of the morphologies and the initial orientations of the three different protofibrillar Aß9-40 trimers, the N-terminal ß-sheet of all trimers preferentially binds to the membrane surface. The POPG lipid bilayers enhance the structural stability of protofibrillar Aß trimers by stabilizing inter-peptide ß-sheets and D23-K28 salt-bridges. The interaction causes local membrane thinning. We found that the trimer structure related to Alzheimer's disease brain tissue () is the most stable both in water solution and at membrane surface, and displays slightly stronger membrane perturbation capability. These results provide mechanistic insights into the membrane-enhanced structural stability of protofibrillar Aß oligomers and the first step of Aß-induced membrane disruption at the atomic level.

Fabrication of ZnS-Bi-TiO2 composites and investigation of their sunlight photocatalytic performance.

The ZnS-Bi-TiO2 composites were prepared by the sol-gel method and were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS). It is found that the doped Bi as Bi(4+)/Bi(3+) species existed in composites, and the introducing of ZnS enhanced further the light absorption ability of TiO2 in visible region and reduced the recombination of photogenerated electrons and holes. As compared to pure TiO2, the ZnS-Bi-TiO2 exhibited enhanced photodegradation efficiency under xenon lamp irradiation, and the kinetic constant of methyl orange removal with ZnS-Bi-Ti-0.005 (0.0141 min(-1)) was 3.9 times greater than that of pure TiO2 (0.0029 min(-1)), which could be attributed to the existence of Bi(4+)/Bi(3+) species, the ZnS/TiO2 heterostructure.

Elucidating the reversible and irreversible self-assembly mechanisms of low-complexity aromatic-rich kinked peptides and steric zipper peptides.

Many RNA-binding proteins such as fused-in sarcoma (FUS) can self-assemble into reversible liquid droplets and fibrils through the self-association of their low-complexity (LC) domains. Recent experiments have revealed that SYG-rich segments in the FUS LC domains play critical roles in the reversible self-assembly behaviors of FUS. These FUS LC segments alone can self-assemble into reversible kinked fibrils, which are markedly different from the canonical irreversible steric zipper ß-sheet fibrils. However, the molecular determinants underlying the reversible and irreversible self-assembly are poorly understood. Herein we conducted extensive all-atom and coarse-grained molecular dynamics simulations of four representative hexapeptides: two low-complexity aromatic-rich kinked peptides from the amyotrophic lateral sclerosis-related FUS protein, FUS37-42 (SYSGYS) and FUS54-59 (SYSSYG); and two steric zipper peptides from Alzheimer's-associated Aß and Tau proteins, Aß16-21 (KLVFFA) and Tau306-311 (VQIVYK). We dissected their reversible and irreversible self-assembly dynamics, predicted their phase separation behaviors, and elucidated the underpinning molecular interactions. Our simulations showed that alternating stickers (Tyr) and spacers (Gly and Ser) in FUS37-42 and FUS54-59 facilitate the formation of highly dynamic coil-rich oligomers and lead to reversible self-assembly, while consecutive hydrophobic residues of LVFF in Aß16-21 and IVY in Tau306-311 act as hydrophobic patches, favoring the formation of stable ß-sheet-rich oligomers and driving the irreversible self-assembly. Intriguingly, we found that FUS37-42 and FUS54-59 peptides, possessing the same amino acid composition and the same number of sticker and spacer residues, display differential self-assembly propensities. This finding suggests that the self-assembly behaviors of FUS peptides are fine-tuned by the site-specific patterning of spacer residues (Ser and Gly). This study provides significant mechanistic insights into reversible and irreversible peptide self-assembly, which would be helpful for understanding the molecular mechanisms underlying the formation of biological liquid condensates and pathological solid amyloid fibrils.

Deleterious nonsynonymous single nucleotide polymorphisms in human solute carriers: the first comparison of three prediction methods.

Abundant nsSNPs have been found in genes coding for human solute carrier (SLC) transporters, but there is little known about the relationship between the genotype and phenotype of nsSNPs in these membrane proteins. It is unknown which prediction method is better suited for the prediction of nonneutral nsSNPs of SLC transporters. We have identified 2,958 validated nsSNPs in human SLC family members 1-47 from the Ensembl genome database and the NCBI SNP database. Using three different algorithms, 37-45 % of nsSNPs in SLC genes were predicted to have functional impacts on transporter function. Predictions largely agreed with the available experimental annotations. Overall, 76.5, 74.4, and 73.5 % of nonneutral nsSNPs were predicted correctly as damaging by SNAP, SIFT, and PolyPhen, respectively, while 67.4, 66.3, and 76.7 % of neutral nsSNPs were predicted correctly as nondamaging by the three methods, respectively. This study identified many amino acids that were likely to be functionally critical but have not yet been studied experimentally. There was a significant concordance between the predicted results of different methods. Evolutionarily nonneutral (destabilizing) amino acid substitutions are predicted to be the basis for the pathogenic alteration of SLC transporter activity that is associated with disease susceptibility and altered drug/xenobiotic response.

Interface-mediated synthesis of monodisperse ZnS nanoparticles with sulfate-reducing bacterium culture.

We have created a new method of ZnS nanospheres synthesis. By interface-mediated precipitation method (IMPM), monodisperse ZnS nanoparticles was synthesized on the particle surface of sulfate-reducing bacterium nutritious agar culture. Sulfate-reducing bacterium (SRB) was used as a sulfide producer because of its dissimilatory sulfate reduction capability, meanwhile produced a variety of amino acids acting as templates for nanomaterials synthesis. Then zinc acetate was dispersed into nutritious agar plate. Subsequently agar plate was broken into particles bearing much external surface, which successfully mediated the synthesis of monodisperse ZnS nanoparticles. The morphology of monodisperse ZnS nanospheres and SRB were examined by scanning electron microscopy (SEM), and the microstructure was investigated by X-ray diffraction (XRD). The thermostability of ZnS nanoparticles was determined by thermo gravimetric-differential thermo gravimetric (TG-DTG). The maximum absorption wavelengh was analysed with an ultraviolet-visible spectrophotometer within a range of 199-700 nm. As a result, monodisperse ZnS nanoparticles were successfully synthesized, with an average diameter of 80 nm. Maximum absorption wavelengh was 228 nm, and heat decomposed temperature of monodisperse ZnS nanoparticles was 596°C.

Thermal-controlled cellular uptake of "hot" nanoparticles.

Nanoparticles (NPs) have shown immense potential in the field of biomedical applications, particularly in NP-based photothermal therapy, which offers a remote-controlled approach to achieve precise temperature control for site-specific heating and sub-cellular tumor treatment. However, the molecular mechanisms underlying related cellular activities, such as the cellular uptake behavior of irradiated NPs in photothermal effects, remain elusive. In this study, we conducted a thorough investigation of the interaction between an irradiated NP with elevated temperature (ranging from 270 to 360 K) and a model bilayer membrane composed of DPPC or DOPC using nonequilibrium coarse-grained molecular dynamics simulations with the implicit-solvent Dry Martini force field. We observe that the interaction between a "hot" NP and a membrane is thermally regulated. In addition, the wrapping of membranes around NPs exhibits a strong dependence on the temperature of the irradiated NP, demonstrating a step-like change in behavior. This membrane wrapping effect is attributed to the heat conduction between NPs and membrane lipids, which occurs almost simultaneously with the membrane deformation and wrapping of NPs during the NP-membrane interaction process. Especially, during the process of heat conduction, a gel-to-fluid phase transition of the membrane may occur, which plays a crucial role in determining the deformation behavior of the membrane. Moreover, it is found that the membrane lipids in the two leaflets exhibit obvious and asymmetric molecular-level responses to heat flux, characterized by significant changes in packing states (e.g., the order parameter of lipid tails and area per lipid) and possible interdigitation between lipids. Furthermore, the thermal-controlled wrapping effect is tightly linked to the properties of NPs (e.g., size, NP-lipid affinity) and lipid species. Our findings are valuable for comprehending the thermal-regulated cellular internalization of NPs and offer insights into devising strategies to precisely modulate NP endocytosis by exploiting the interplay between heating and NP properties.

Membrane-Active Peptides Attack Cell Membranes in a Lipid-Regulated Curvature-Generating Mode.

Membrane-active peptides (MAPs) exhibit great potential in biomedical applications due to their unique ability to overcome the cell membrane barrier. However, the interactions between MAPs and membranes are complex, and little is known about the possibility of MAP action being specific to certain types of membranes. In this study, a combination of molecular dynamics simulations and theoretical analysis was utilized to investigate the interactions between typical MAPs and realistic cell membrane systems. Remarkably, the simulations revealed that MAPs can attack membranes by generating and sensing positive mean curvature, which is dependent on lipid composition. Furthermore, theoretical calculations demonstrated that this lipid-regulated curvature-based membrane attack mechanism is an integrated result of multiple effects, including peptide-induced membrane wedge and softening effects, the lipid shape effect, the area-difference elastic effect, and the boundary edge effect of formed peptide-lipid nanodomains. This study enhances our comprehension of MAP-membrane interactions and highlights the potential for developing membrane-specific MAP-based agents.

Targeted therapy for intractable cancer on the basis of molecular profiles: An open-label, phase II basket trial (Long March Pathway).

Purpose: We evaluated he effects of molecular guided-targeted therapy for intractable cancer. Also, the epidemiology of druggable gene alterations in Chinese population was investigated. Materials and methods: The Long March Pathway (ClinicalTrials.gov identifier: NCT03239015) is a non-randomized, open-label, phase II trial consisting of several basket studies examining the molecular profiles of intractable cancers in the Chinese population. The trial aimed to 1) evaluate the efficacy of targeted therapy for intractable cancer and 2) identify the molecular epidemiology of the tier II gene alterations among Chinese pan-cancer patients. Results: In the first stage, molecular profiles of 520 intractable pan-cancer patients were identified, and 115 patients were identified to have tier II gene alterations. Then, 27 of these 115 patients received targeted therapy based on molecular profiles. The overall response rate (ORR) was 29.6% (8/27), and the disease control rate (DCR) was 44.4% (12/27). The median duration of response (DOR) was 4.80 months (95% CI, 3.33-27.2), and median progression-free survival (PFS) was 4.67 months (95% CI, 2.33-9.50). In the second stage, molecular epidemiology of 17,841 Chinese pan-cancer patients demonstrated that the frequency of tier II gene alterations across cancer types is 17.7%. Bladder cancer had the most tier-II alterations (26.1%), followed by breast cancer (22.4%), and non-small cell lung cancer (NSCLC; 20.2%). Conclusion: The Long March Pathway trial demonstrated a significant clinical benefit for intractable cancer from molecular-guided targeted therapy in the Chinese population. The frequency of tier II gene alterations across cancer types supports the feasibility of molecular-guided targeted therapy under basket trials.

Atomistic Insights into A315E Mutation-Enhanced Pathogenicity of TDP-43 Core Fibrils.

The aggregation of TAR DNA-binding protein of 43 kDa (TDP-43) into fibrillary deposits is implicated in amyotrophic lateral sclerosis (ALS), and some hereditary mutations localized in the low complexity domain (LCD) facilitate the formation of pathogenic TDP-43 fibrils. A recent cryo-EM study reported the atomic-level structures of the A315E TDP-43 LCD (residues 288-319, TDP-43288-319) core fibril in which the protofilaments have R-shaped structures and hypothesized that A315E U-shaped protofilaments can readily convert to R-shaped protofilaments compared to the wild-type (WT) ones. There are no atomic structures of WT protofilaments available yet. Herein, we performed extensive all-atom explicit-solvent molecular dynamics simulations on A315E and WT protofilaments starting from both the cryo-EM-determined R-shaped and our constructed U-shaped structures. Our simulations show that WT protofilaments also adopt the R-shaped structures but are less stable than their A315E counterparts. Except for R293-E315 salt bridges, N312-F316 hydrophobic interactions and F316-F316 π-π stacking interactions are also crucial for the stabilization of the neck region of the R-shaped A315E protofilaments. The loss of R293-E315 salt bridges and the weakened interactions of N312-F316 and F316-F316 result in the reduced stability of the R-shaped WT protofilaments. Simulations starting from U-shaped folds reveal that A315E protofilaments can spontaneously convert to the cryo-EM-derived R-shaped protofilaments, whereas WT protofilaments convert to R-shape-like structures with remodeled neck regions. The R-shape-like WT protofilaments could act as intermediate states slowing down the U-to-R transition. This study reveals that A315E mutation can not only enhance the structural stability of the R-shaped TDP-43288-319 protofilaments but also promote the U-to-R transition, which provides atomistic insights into the A315E mutation-enhanced TDP-43 pathogenicity in ALS.

Green tea extract EGCG plays a dual role in Aß42 protofibril disruption and membrane protection: A molecular dynamic study.

Amyloid plaques accumulated by the amyloid-ß (Aß) fibrillar aggregates are the major pathological hallmark of the Alzheimer's disease (AD). Inhibiting aggregation and disassembling preformed fibrils of Aß by natural small molecules have developed into a promising therapeutic strategy for AD. Previous experiments reported that the green tea extract epigallocatechin-3-gallate (EGCG) can disrupt Aß fibril and reduce Aß cytotoxicity. The inhibitory ability of EGCG can also be affected by cellular membranes. Thus, it is essential to consider the membrane influences in the investigation of protofibril-disruptive capability of EGCG. Here, we performed multiple all-atom molecular dynamic simulations to investigate the effect of EGCG on the Aß42 protofibril in the presence of a mixed POPC/POPG (7:3) lipid bilayer and the underlying molecular mechanisms of action. Our simulations show that in the presence of membrane bilayers, EGCG has a preference to bind to the membrane, and this binding alters the binding modes between Aß42 protofibril and the lipid bilayer, leading to a reduced membrane thinning, indicative of a protective effect of EGCG on the membrane. And EGCG still displays a disruptive effect on Aß42 protofibril, albeit with a lesser extent of disruption than that in the membrane-free environment. EGCG destabilizes the two hydrophobic core regions (L17-F19-I31 and F4-L34-V36), and disrupts the intrachain K28-A42 salt bridges. Our results reveal that in the presence of lipid bilayers, EGCG plays a dual role in Aß42 protofibril disruption and membrane protection, suggesting that EGCG could be a potential effective drug candidate for the treatment of AD.

Molecular dynamics simulations reveal the destabilization mechanism of Alzheimer's disease-related tau R3-R4 Protofilament by norepinephrine.

Aggregation of Tau protein into neurofibrillary tangles is associated with the pathogenesis of Alzheimer's disease (AD) which has no cure yet. Clearing neurofibrillary tangles is one of major therapeutic strategies. Experimental studies reported that norepinephrine (NE) has the ability to disrupt Tau filament and cause Tau degradation. However, the underlying mechanism remains elusive. Herein, we performed molecular dynamic simulations to investigate the influence of NE on the C-shaped Tau R3-R4 protofilament. Our simulations show that NE compound destabilizes Tau protofilament by mostly disrupting ß6/ß8 and altering the ß2-ß3 and ß6-ß7 angles. NE binds mainly with aromatic residues Y310/P312/H374/F378 through ππ stacking and charged residues E338/E342/D348/D358/E372 via hydrogen-bonding interactions. Our results, together with the findings that exercise can markedly increase NE level, suggest that exercise might be a potent therapy against AD. This study reveals the disruptive mechanism of Tau protofilament by NE molecules, which may provide new clues for AD drug candidate design.