Metformin normalizes mitochondrial function to delay astrocyte senescence in a mouse model of Parkinson's disease through Mfn2-cGAS signaling.

BACKGROUND: Senescent astrocytes play crucial roles in age-associated neurodegenerative diseases, including Parkinson's disease (PD). Metformin, a drug widely used for treating diabetes, exerts longevity effects and neuroprotective activities. However, its effect on astrocyte senescence in PD remains to be defined. METHODS: Long culture-induced replicative senescence model and 1-methyl-4-phenylpyridinium/α-synuclein aggregate-induced premature senescence model, and a mouse model of PD were used to investigate the effect of metformin on astrocyte senescence in vivo and in vitro. Immunofluorescence staining and flow cytometric analyses were performed to evaluate the mitochondrial function. We stereotactically injected AAV carrying GFAP-promoter-cGAS-shRNA to mouse substantia nigra pars compacta regions to specifically reduce astrocytic cGAS expression to clarify the potential molecular mechanism by which metformin inhibited the astrocyte senescence in PD. RESULTS: We showed that metformin inhibited the astrocyte senescence in vitro and in PD mice. Mechanistically, metformin normalized mitochondrial function to reduce mitochondrial DNA release through mitofusin 2 (Mfn2), leading to inactivation of cGAS-STING, which delayed astrocyte senescence and prevented neurodegeneration. Mfn2 overexpression in astrocytes reversed the inhibitory role of metformin in cGAS-STING activation and astrocyte senescence. More importantly, metformin ameliorated dopamine neuron injury and behavioral deficits in mice by reducing the accumulation of senescent astrocytes via inhibition of astrocytic cGAS activation. Deletion of astrocytic cGAS abolished the suppressive effects of metformin on astrocyte senescence and neurodegeneration. CONCLUSIONS: This work reveals that metformin delays astrocyte senescence via inhibiting astrocytic Mfn2-cGAS activation and suggest that metformin is a promising therapeutic agent for age-associated neurodegenerative diseases.

S100A12 is involved in the pathology of osteoarthritis by promoting M1 macrophage polarization via the NF-κB pathway.

BACKGROUND: Osteoarthritis (OA) is a degenerative joint disease that affects millions worldwide. Synovitis and macrophage polarization are important factors in the development of OA. However, the specific components of synovial fluid (SF) responsible for promoting macrophage polarization remain unclear. METHODS: Semi-quantitative antibody arrays were used to outline the proteome of SF. Differential expression analysis and GO/KEGG were performed on the obtained data. Immunohistochemistry and ELISA were used to investigate the relationship between SF S100A12 levels and synovitis levels in clinalclinical samples. In vitro cell experiments were conducted to investigate the effect of S100A12 on macrophage polarization. Public databases were utilized to predict and construct an S100A12-centered lncRNA-miRNA-mRNA competing endogenous RNA network, which was preliminarily validated using GEO datasets. RESULTS: The study outlines the protein profile in OA and non-OA SF. The results showed that the S100A12 level was significantly increased in OA SF and inflammatory chondrocytes. The OA synovium had more severe synovitis and higher levels of S100A12 than non-OA synovium. Exogenous S100A12 upregulated the levels of M1 markers and phosphorylated p65 and promoted p65 nuclear translocation, while pretreatment with BAY 11-7082 reversed these changes. It was also discovered that LINC00894 was upregulated in OA and significantly correlated with S100A12, potentially regulating S100A12 expression by acting as a miRNA sponge. CONCLUSIONS: This study demonstrated that S100A12 promotes M1 macrophage polarization through the NF-κB pathway, and found that LINC00894 has the potential to regulate the expression of S100A12 as a therapeutic approach.

Cell-derived nanovesicle-mediated drug delivery to the brain: Principles and strategies for vesicle engineering.

Developing strategies toward safe and effective drug delivery into the central nervous system (CNS) with improved targeting abilities and reduced off-target effects is crucial. CNS-targeted drug carriers made of synthetic molecules raise concerns about their biodegradation, clearance, immune responses, and neurotoxicity. Cell-derived nanovesicles (CDNs) have recently been applied in CNS-targeted drug delivery, because of their intrinsic stability, biocompatibility, inherent homing capability, and the ability to penetrate through biological barriers, including the blood-brain barrier. Among these CDNs, extracellular vesicles and exosomes are the most studied because their surface can be engineered and modified to cater to brain targeting. In this review, we focus on the application of CDNs in brain-targeted drug delivery to treat neurological diseases. We cover recently developed methods of exosome derivation and engineering, including exosome-like particles, hybrid exosomes, exosome-associated adeno-associated viruses, and envelope protein nanocages. Finally, we discuss the limitations and project the future development of the CDN-based brain-targeted delivery systems, and conclude that engineered CDNs hold great potential in the treatment of neurological diseases.

Brain-derived extracellular vesicles: Potential diagnostic biomarkers for central nervous system diseases.

Extracellular vesicles (EVs) are membrane-enclosed nanovesicles secreted by cells into the extracellular space and contain functional biomolecules, e.g. signaling receptors, bioactive lipids, nucleic acids, and proteins, which can serve as biomarkers. Neurons and glial cells secrete EVs, contributing to various physiological and pathological aspects of brain diseases. EVs confer their role in the bidirectional crosstalk between the central nervous system (CNS) and the periphery owing to their distinctive ability to cross the unique blood-brain barrier (BBB). Thus, EVs in the blood, cerebrospinal fluid (CSF), and urine can be intriguing biomarkers, enabling the minimally invasive diagnosis of CNS diseases. Although there has been an enormous interest in evaluating EVs as promising biomarkers, the lack of ultra-sensitive approaches for isolating and detecting brain-derived EVs (BDEVs) has hindered the development of efficient biomarkers. This review presents the recent salient findings of exosomal biomarkers, focusing on brain disorders. We summarize highly sensitive sensors for EV detection and state-of-the-art methods for single EV detection. Finally, the prospect of developing advanced EV analysis approaches for the non-invasive diagnosis of brain diseases is presented.

Integrative analysis of genomic and epigenomic data reveal underlying superenhancer-mediated microRNA regulatory network for human bone mineral density.

Bone mineral density (BMD) is a highly heritable complex trait and is a key indicator for diagnosis and treatment for osteoporosis. In the last decade, numerous susceptibility loci for BMD and fracture have been identified by genome-wide association studies (GWAS); however, fine mapping of these loci is challengeable. Here, we proposed a new long-range fine-mapping approach that combined superenhancers (SEs) and microRNAs (miRNAs) data, which were two important factors in control of cell identity and specific differentiation, with the GWAS summary datasets in cell-type-restricted way. Genome-wide SE-based analysis found that the BMD-related variants were significantly enriched in the osteoblast SE regions, indicative of potential long-range effects of such SNPs. With the SNP-mapped SEs (mSEs), 13 accessible long-range mSE-interacted miRNAs (mSE-miRNAs) were identified by integrating osteoblast Hi-C and ATAC-seq data, including three known bone-related miRNAs (miR-132-3p, miR-212-3p and miR-125b-5p). The putative targets of the two newly identified mSE-miRNAs (miR-548aj-3p and miR-190a-3p) were found largely enriched in osteogenic-related pathway and processes, suggesting that these mSE-miRNAs could be functional in the regulation of osteoblast differentiation. Furthermore, we identified 54 genes with the long-range 'mSE-miRNA' approach, and 24 of them were previously reported to be related to skeletal development. Besides, enrichment analysis found that these genes were specifically enriched in the post-transcriptional regulation and bone formation processes. This study provided a new insight into the approach of fine-mapping of GWAS loci. A tool was provided for the genome-wide SE-based analysis and the detection of long-range osteoblast-restricted mSE-miRNAs (https://github.com/Zheng-Lab-Westlake/Osteo-Fine-Mapp-SNP2SE2miRNA).

Synthetic Multienzyme Assemblies for Natural Product Biosynthesis.

In nature, enzymes that catalyze sequential reactions are often assembled as clusters or complexes. The formation of multienzyme complexes, or metabolons, brings the enzyme active sites into proximity to promote intermediate transfer, decrease intermediate leakage, and streamline the metabolic flux towards the desired products. We and others have developed synthetic versions of metabolons through various strategies to enhance the catalytic rates for synthesizing valuable chemicals inside microbes. Synthetic multienzyme complexes range from static enzyme nanostructures to dynamic enzyme coacervates. Enzyme complexation optimizes the metabolic fluxes inside microbes, increases the product titer, and supplies the field with high-yield microbe strains that are amenable to large-scale fermentation. Enzyme complexes constructed inside microbial cells can be separated as independent entities and catalyze biosynthetic reactions ex vivo; such a feature gains these complexes another name, "synthetic organelles" - new subcellular entities with independent structures and functions. Still, the field is seeking new strategies to better balance dynamicity and confinement and to achieve finer control of local compartmentalization in the cells, as the natural multienzyme complexes do. Industrial applications of synthetic multienzyme complexes for the large-scale production of valuable chemicals are yet to be realized. This review focuses on synthetic multienzyme complexes that are constructed and function inside microbial cells.

Enhancement of the therapeutic efficacy of mesenchymal stem cell-derived exosomes in osteoarthritis.

Osteoarthritis (OA), a common joint disorder with articular cartilage degradation as the main pathological change, is the major source of pain and disability worldwide. Despite current treatments, the overall treatment outcome is unsatisfactory. Thus, patients with severe OA often require joint replacement surgery. In recent years, mesenchymal stem cells (MSCs) have emerged as a promising therapeutic option for preclinical and clinical palliation of OA. MSC-derived exosomes (MSC-Exos) carrying bioactive molecules of the parental cells, including non-coding RNAs (ncRNAs) and proteins, have demonstrated a significant impact on the modulation of various physiological behaviors of cells in the joint cavity, making them promising candidates for cell-free therapy for OA. This review provides a comprehensive overview of the biosynthesis and composition of MSC-Exos and their mechanisms of action in OA. We also discussed the potential of MSC-Exos as a therapeutic tool for modulating intercellular communication in OA. Additionally, we explored bioengineering approaches to enhance MSC-Exos' therapeutic potential, which may help to overcome challenges and achieve clinically meaningful OA therapies.

Safeguarding intestine cells against enteropathogenic Escherichia coli by intracellular protein reaction, a preventive antibacterial mechanism.

A critical problem in the fight against bacterial infection is the rising rates of resistance and the lack of new antibiotics. The discovery of new targets or new antibacterial mechanisms is a potential solution but is becoming more difficult. Here we report an antibacterial mechanism that safeguards intestine cells from enteropathogenic Escherichia coli (EPEC) by shutting down an infection-responsive signal of the host intestine cell. A key step in EPEC infection of intestinal cells involves Tir-induced actin reorganization. Nck mediates this event by binding with Tir through its SH2 domain (Nck-SH2) and with WIP through its second SH3 domain (Nck-SH3.2). Here we report the design of a synthetic peptide that reacts precisely with a unique cysteine of the Nck-SH3.2 domain, blocks the binding site of the Nck protein, and prevents EPEC infection of Caco-2 cells. Oral update of this nontoxic peptide before EPEC administration safeguards mice from EPEC infection and diarrhea. This study demonstrates domain-specific blockage of an SH3 domain of a multidomain adaptor protein inside cells and the inhibition of Tir-induced rearrangement of the host actin cytoskeleton as a previously unknown antibacterial mechanism.

Comparison of different fibula procedures in tibiotalocalcaneal arthrodesis with a retrograde intramedullary nail: a mid-term retrospective study.

BACKGROUND: Tibiotalocalcaneal (TTC) arthrodesis with a retrograde intramedullary nail for severe tibiotalar and talocalcaneal arthritis has a high fusion rate; however, no studies have focused on how to handle the fibula intraoperatively to achieve better results. This study aimed to compare the efficacies of various fibular procedures. METHODS: We retrospectively reviewed the cases of severe tibiotalar and talocalcaneal arthritis in adults treated with TTC arthrodesis using a retrograde intramedullary nail between January 2012 and July 2017. The patients were divided into three groups according to different fibular procedures: Fibular osteotomy (FO), fibular strut (FS), and fibular preservation (FP). Functional outcomes and pain were assessed using the American Orthopedic Foot and Ankle Society (AOFAS) ankle and hindfoot score and visual analog scales (VAS), respectively. The operation time, fusion time, radiographic evaluation, and complications were also recorded. RESULTS: Fifty-eight patients with an average age of 53.2 (range, 32-69) years were enrolled in the final analysis. The numbers of patients enrolled in the three groups were 21, 19, and 18 in the FO, FS, and FP groups, respectively. The mean postoperative follow-up time was 66.0 (range, 60-78) months. All groups showed a high fusion rate (90.5% for FO, 94.7% for FS, and 94.4% for FP) and significant improvement in AOFAS ankle and hindfoot scores and VAS scores at the latest follow-up. There were no significant differences in these parameters among the three groups. The mean operation time of FS (131.3 ± 17.1 min) was longer than that of FO (119.3 ± 11.7 min) and FS (112.2 ± 12.6 min), but the fusion time was shorter (15.1 ± 2.8 weeks for FS, 17.2 ± 1.9 weeks for FO, and 16.8 ± 1.9 weeks for FP). Statistically significant differences were observed in these parameters. CONCLUSIONS: TTC arthrodesis using a retrograde intramedullary nail is an effective procedure with a high rate of fusion to treat severe tibiotalar and talocalcaneal arthritis in adults; however, FSs can shorten fusion time when compared with FO and FP. LEVEL OF CLINICAL EVIDENCE: Level 3.

Photo-Responsive Phase-Separating Fluorescent Molecules for Intracellular Protein Delivery.

Cellular membranes, including the plasma and endosome membranes, are barriers to outside proteins. Various vehicles have been devised to deliver proteins across the plasma membrane, but in many cases, the payload gets trapped in the endosome. Here we designed a photo-responsive phase-separating fluorescent molecule (PPFM) with a molecular weight of 666.8 daltons. The PPFM compound condensates as fluorescent droplets in the aqueous solution by liquid-liquid phase separation (LLPS), which disintegrate upon photoirradiation with a 405 nm light-emitting diode (LED) lamp within 20 min or a 405 nm laser within 3 min. The PPFM coacervates recruit a wide range of peptides and proteins and deliver them into mammalian cells. Photolysis disperses the payload from condensates into the cytosolic space. Altogether, a type of small molecules that are photo-responsive and phase separating are discovered; their coacervates can serve as transmembrane vehicles for intracellular delivery of proteins, whereas photo illumination triggers the cytosolic distribution of the payload.

Site-Selective Lysine Acetylation of Human Immunoglobulin G for Immunoliposomes and Bispecific Antibody Complexes.

Site-selective acetylation of a single lysine residue in a protein that reaches a lysine acetyltransferase's accuracy, precision, and reliability is challenging. Here, we report a peptide-guided, proximity-driven group transfer reaction that acetylates a single lysine residue, Lys 248, of the fragment crystallizable region (Fc region) in the heavy chain of the human Immunoglobulin G (IgG). An Fc-interacting peptide bound with the Fc domain and positioned a phenolic ester close to Lys 248, which induced a nucleophilic reaction and resulted in the transfer of an acetyl group to Lys 248. The acetylation reaction proceeded to a decent yield under the physiological condition without the need for deglycosylation, unnatural amino acids, or catalysts. Along with acetylation, functional moieties such as azide, alkyne, fluorescent molecules, or biotin could also be site-selectively installed on Lys 248, allowing IgG's further derivatization. We then synthesized an antibody-lipid conjugate and constructed antibody-conjugated liposomes (immunoliposomes), targeting HER2-positive (HER2+) cancer cells. We also built a bispecific antibody complex (bsAbC) covalently linking an anti-HER2 antibody and an anti-CD3 antibody. The bsAbC showed in vitro effector-cell-mediated cytotoxicity at nanomolar concentrations. Compared with bispecific antibodies (bsAbs), bsAbCs are constructed based on native IgGs and contain two antigen-binding sites to each antigen, twice that of bsAbs. Altogether, this work reports a method of site-selective acetylation of native antibodies, highlights a facile way of site-selective IgG functionalization, and underscores the potential of bsAbCs in cancer immunotherapy.

Both indirect maternal and direct fetal genetic effects reflect the observational relationship between higher birth weight and lower adult bone mass.

BACKGROUND: Birth weight is considered not only to undermine future growth, but also to induce lifelong diseases; the aim of this study is to explore the relationship between birth weight and adult bone mass. METHODS: We performed multivariable regression analyses to assess the association of birth weight with bone parameters measured by dual-energy X-ray absorptiometry (DXA) and by quantitative ultrasound (QUS), independently. We also implemented a systemic Mendelian randomization (MR) analysis to explore the causal association between them with both fetal-specific and maternal-specific instrumental variables. RESULTS: In the observational analyses, we found that higher birth weight could increase the adult bone area (lumbar spine, ß-coefficient= 0.17, P < 2.00 × 10-16; lateral spine, ß-coefficient = 0.02, P = 0.04), decrease bone mineral content-adjusted bone area (BMCadjArea) (lumbar spine, ß-coefficient= - 0.01, P = 2.27 × 10-14; lateral spine, ß-coefficient = - 0.05, P = 0.001), and decrease adult bone mineral density (BMD) (lumbar spine, ß-coefficient = - 0.04, P = 0.007; lateral spine; ß-coefficient = - 0.03, P = 0.02; heel, ß-coefficient = - 0.06, P < 2.00 × 10-16), and we observed that the effect of birth weight on bone size was larger than that on BMC. In MR analyses, the higher fetal-specific genetically determined birth weight was identified to be associated with higher bone area (lumbar spine; ß-coefficient = 0.15, P = 1.26 × 10-6, total hip, ß-coefficient = 0.15, P = 0.005; intertrochanteric area, ß-coefficient = 0.13, P = 0.0009; trochanter area, ß-coefficient = 0.11, P = 0.03) but lower BMD (lumbar spine, ß-coefficient = - 0.10, P = 0.01; lateral spine, ß-coefficient = - 0.12, P = 0.0003, and heel ß-coefficient = - 0.11, P = 3.33 × 10-13). In addition, we found that the higher maternal-specific genetically determined offspring birth weight was associated with lower offspring adult heel BMD (ß-coefficient = - 0.001, P = 0.04). CONCLUSIONS: The observational analyses suggested that higher birth weight was associated with the increased adult bone area but decreased BMD. By leveraging the genetic instrumental variables with maternal- and fetal-specific effects on birth weight, the observed relationship could be reflected by both the direct fetal and indirect maternal genetic effects.

Modification of mesenchymal stem cells for cartilage-targeted therapy.

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by the destruction of the articular cartilage, sclerosis of the subchondral bone, and joint dysfunction. Its pathogenesis is attributed to direct damage and mechanical destruction of joint tissues. Mesenchymal stem cells (MSCs), suggested as a potential strategy for the treatment of OA, have shown therapeutic effects on OA. However, the specific fate of MSCs after intraarticular injection, including cell attachment, proliferation, differentiation, and death, is still unclear, and there is no guarantee that stem cells can be retained in the cartilage tissue to enact repair. Direct homing of MSCs is an important determinant of the efficacy of MSC-based cartilage repair. Recent studies have revealed that the unique homing capacity of MSCs and targeted modification can improve their ability to promote tissue regeneration. Here, we comprehensively review the homing effect of stem cells in joints and highlight progress toward the targeted modification of MSCs. In the future, developments of this targeting system that accelerate tissue regeneration will benefit targeted tissue repair.

Bacteriophage endolysins against gram-positive bacteria, an overview on the clinical development and recent advances on the delivery and formulation strategies.

Facing the increasing threat of multi-drug antimicrobial resistance (AMR), humans strive to search for antibiotic drug candidates and antibacterial alternatives from all possible places, from soils in remote areas to deep in the sea. In this "gold rush for antibacterials," researchers turn to the natural enemy of bacterial cells, bacteriophage (phages), and find them a rich source of weapons for AMR bacteria. Endolysins (lysins), the enzymes phages use to break the bacterial cells from within, have been shown to be highly selective and efficient in killing their target bacteria from outside while maintaining a low occurrence of bacterial resistance. In this review, we start with the structures and mechanisms of action of lysins against Gram-positive (GM+) bacteria. The developmental history of lysins is also outlined. Then, we detail the latest preclinical and clinical research on their safety and efficacy against GM+ bacteria, focusing on the formulation strategies of these enzymes. Finally, the challenges and potential hurdles are discussed. Notwithstanding these limitations, the trends in development indicate that the first, approved lysin drugs will be available soon in the near future. Overall, this review presents a timely summary of the current progress on lysins as antibacterial enzymes for AMR GM+ bacteria, and provides a guidebook for biomaterial researchers who are dedicating themselves to the battle against bacterial infections.

Clinical validation of a multiplex droplet digital PCR for diagnosing suspected bloodstream infections in ICU practice: a promising diagnostic tool.

BACKGROUND: Droplet digital PCR (ddPCR) has emerged as a promising tool of pathogen detection in bloodstream infections (BSIs) in critical care medicine. However, different ddPCR platforms have variable sensitivity and specificity for diverse microorganisms at various infection sites. There is still a lack of prospective clinical studies aimed at validating and interpreting the discrepant ddPCR results for diagnosing BSI in intensive care unit (ICU) practice. METHODS: A prospective diagnostic study of multiplex ddPCR panels was conducted in a general ICU from May 21, 2021, to December 22, 2021. Paired blood cultures (BCs) and ddPCRs (2.5 h) were obtained synchronously to detect the 12 most common BSI pathogens and three antimicrobial resistance (AMR) genes. Firstly, ddPCR performance was compared to definite BSI. Secondly, clinical validation of ddPCR was compared to composite clinical diagnosis. Sensitivity, specificity, and positive and negative predictive values were calculated. Thirdly, the positive rate of AMR genes and related analysis was presented. RESULTS: A total of 438 episodes of suspected BSIs occurring in 150 critical patients were enrolled. BC and ddPCR were positive for targeted bacteria in 40 (9.1%) and 180 (41.1%) cases, respectively. There were 280 concordant and 158 discordant. In comparison with BCs, the sensitivity of ddPCR ranged from 58.8 to 86.7% with an aggregate of 72.5% in different species, with corresponding specificity ranging from 73.5 to 92.2% with an aggregate of 63.1%. Furthermore, the rate of ddPCR+/BC- results was 33.6% (147/438) with 87.1% (128 of 147) cases was associated with probable (n = 108) or possible (n = 20) BSIs. When clinically diagnosed BSI was used as true positive, the final sensitivity and specificity of ddPCR increased to 84.9% and 92.5%, respectively. In addition, 40 blaKPC, 3blaNDM, and 38 mecA genes were detected, among which 90.5% were definitely positive for blaKPC. Further, 65.8% specimens were predicted to be mecA-positive in Staphylococcus sp. according to all microbiological analysis. CONCLUSIONS: The multiplexed ddPCR is a flexible and universal platform, which can be used as an add-on complementary to conventional BC. When combined with clinical infection evidence, ddPCR shows potential advantages for rapidly diagnosing suspected BSIs and AMR genes in ICU practice.

Phase-Separated Multienzyme Compartmentalization for Terpene Biosynthesis in a Prokaryote.

Liquid-liquid phase separation (LLPS) forms biomolecular condensates or coacervates in cells. Metabolic enzymes can form phase-separated subcellular compartments that enrich enzymes, cofactors, and substrates. Herein, we report the construction of synthetic multienzyme condensates that catalyze the biosynthesis of a terpene, α-farnesene, in the prokaryote E. coli. RGGRGG derived from LAF-1 was used as the scaffold protein to form the condensates by LLPS. Multienzyme condensates were then formed by assembling two enzymes Idi and IspA through an RIAD/RIDD interaction. Multienzyme condensates constructed inside E. coli cells compartmentalized the cytosolic space into regions of high and low enzyme density and led to a significant enhancement of α-farnesene production. This work demonstrates LLPS-driven compartmentalization of the cytosolic space of prokaryotic cells, condensation of a biosynthetic pathway, and enhancement of the biosynthesis of α-farnesene.

Exosomes as Targeted Delivery Platform of CRISPR/Cas9 for Therapeutic Genome Editing.

Therapeutic genome editing harnesses the power of genome editing tools to correct erroneous genes associated with disease pathology. To bring the CRISPR/Cas9 tool from the bench to the bedside, a critical hurdle is the safe and efficient delivery of this nucleic acid tool to the desired type of cells in patients. This review discusses the use of natural carriers, extracellular vesicles (EVs), in particular exosomes, to fill the gap. Exosomes are lipid-containing nanovesicle released by various types of cells to mediate cell-cell communications. Their inherent long-distance transportation capability, biocompatibility, and engineerability have made EVs potential vehicles for delivering therapeutic drugs. We summarize the recent progress of harnessing exosomes as delivery vehicles for the CRISPR/Cas system to achieve therapeutic gene editing for disease treatment, with a focus on various strategies to achieve selective delivery to a particular type of cell and efficient packaging of the genome editing tools in the vesicles. Critical issues and possible solutions in the design and engineering of the targeting vehicles are highlighted. Taken together, we demonstrate EV/exosome-mediated packaging of the nucleic acid/protein tools and the cell/tissue-targeted delivery to be a viable way towards the clinical translation of the CRISPR/Cas9 technology.

GB Tags: Small Covalent Peptide Tags Based on Protein Fragment Reconstitution.

Developing peptide tags that can bind target proteins covalently under mild conditions is of great importance for a myriad of applications, ranging from chemical biology to biotechnology. Here we report the development of a small covalent peptide tag system, termed as GB tags, that can covalently label the target protein with high specificity and high yield under oxidizing conditions. The GB tags consist of a pair of short peptides, GN and GC (GN contains 45 residues and GC contains 19 residues). GN and GC, which are split from a parent protein GB1, can undergo protein fragment reconstitution to reconstitute the folded structure of the parent protein spontaneously. The engineered cysteines in GN and GC can readily form a disulfide bond oxidized by air oxygen after protein reconstitution. Using thermally stable variants of GB1, we identified two pairs of GB tags that display improved thermodynamic stability and binding affinity. They can serve as efficient covalent peptide tags for various applications, including specific labeling of mammalian cell surface receptors. We anticipate that these new GB tags will find applications in biochemical labeling as well as biomaterials, such as protein hydrogels.

Mobilization and geochemistry of nutrients in sediment evaluated by diffusive gradients in thin films: Significance for lake management.

Investigation of in-situ mobilization of both nitrogen (N) and phosphate (PO43-) in sediment is important for lake management strategy. In this paper, diffusion gradients in thin films (DGT) and DGT induced flux in sediments (DIFS) model are newly designed for in-situ measurement of iron (Fe), PO43-, nitrate (NO3-N) and ammonium (NH4-N), and nutrients' mobility in sediment in Lake Nanhu (China). According to DGT profiles together with physicochemical properties in sediment, (I) PO43- is released from (i) Fe-bound P plus loosely sorbed P in anoxic sediment and (ii) the loosely sorbed P in oxic sediment; (II) anoxic sediment inhibits nitrification and NO3-N release, but it favors denitrification and dissimilatory nitrate reduction to ammonium (DNRA), leading to NH4-N release; (III) Eh and organic matter are two key influence factors on mobility of PO43-, NO3-N and NH4-N. According to DIFS calculation, the dynamics of desorption and diffusion at two sites belong to (i) slow rate of resupply and (ii) fast resupply cases, respectively. Internal loadings are estimated to be 92.74 (PO43-), 268.1 (NH4-N) and -2466 kg a-1 (NO3-N), which reflects sediment mainly acts as a source for PO43- and NH4-N, and a sink for NO3-N in water. Based on sediment P release risk index (SPRRI), P release risks in lake sediments are estimated, ranging from light to relative high level. DGT and SPRRI aid choice of restoration methods for sediment, including sediment dredging, phytoremediation and in-situ inactivation.

Host-Guest Protein Assembly for Affinity Purification of Methyllysine Proteomes.

Protein-protein interactions drive self-assembly of biomacromolecules and thus enable important physiological functions at a cellular level. Supramolecular chemists have developed artificial host-guest interactions that are similar with, yet distinct from and orthogonal to, the natural protein-protein interactions. For instance, cucurbit[n]urils are synthetic receptors that can specifically recognize proteins with N-terminal aromatic residues with high affinities, yet this interaction can be reversed by the competition of small molecules such as amantadine. Herein, we develop a site-specific, oriented protein-display method by combining the host-guest interaction based on cucurbit[7]uril and a covalent protein-peptide reaction. A methyllysine-binding protein HP1ß chromodomain (CD) is immobilized via host-guest interactions and used as the "bait" to capture methyllysine proteomes from cancer cells. The captured "fish"-methyllysine-containing proteins-can be released via competitive displacement by amantadine in a nondenaturing and traceless manner. This affinity purification method found 73 novel methyllysine sites from 101 identified sites among 66 methylated proteins from 255 HP1ß CD-binding proteins in cancer cells via subsequent mass spectrometric analysis. This work thereby presents a new strategy of artificial host-guest protein assembly in affinity purification of methyllysine proteins in coupling to mass spectrometry.