Membrane Receptor Protein Research Articles

Programming DNA Nanoassemblies into Polyvalent Lysosomal Degraders for Potent Degradation of Pathogenic Membrane Proteins.

Lysosome-targeting chimera (LYTAC) shows great promise for protein-based therapeutics by targeted degradation of disease-associated membrane or extracellular proteins, yet its efficiency is constrained by the limited binding affinity between LYTAC reagents and designated proteins. Here, we established a programmable and multivalent LYTAC system by tandem assembly of DNA into a high-affinity protein degrader, a heterodimer aptamer nanostructure targeting both pathogenic membrane protein and lysosome-targeting receptor (insulin-like growth factor 2 receptor, IGF2R) with adjustable spatial distribution or organization pattern. The DNA-based multivalent LYTACs showed enhanced efficacy in removing immune-checkpoint protein programmable death-ligand 1 (PD-L1) and vascular endothelial growth factor receptor 2 (VEGFR2) in tumor cell membrane that respectively motivated a significant increase in T cell activity and a potent effect on cancer cell growth inhibition. With high programmability and versatility, this multivalent LYTAC system holds considerable promise for realizing protein therapeutics with enhanced activity.

Cryo-EM Structures of Clostridium perfringens Enterotoxin Bound to its Human Receptor, Claudin-4.

Pathogenic strains of Clostridium perfringens secrete an enterotoxin (CpE) that causes prevalent, severe, and sometimes deadly gastrointestinal disorders in humans and domesticated animals. CpE binds selectively to membrane protein receptors called claudins on the apical surfaces of small intestinal epithelium. Claudins normally construct tight junctions that regulate epithelial paracellular transport but are hijacked from doing so by CpE and are instead led to form claudin/CpE small complexes. Small complexes are building blocks for assembling oligomeric β-barrel pores that penetrate the plasma membrane and induce gut cytotoxicity. Here we present structures of CpE in complexes with its native claudin receptor in humans, claudin-4, at 4.0 and 2.8 Å using cryogenic electron microscopy. The structures reveal the overall architecture of the small complex, that the small complex can be kinetically trapped, and resolve its key features; like the residues used in claudin/CpE complex binding, the orientation of CpE relative to the membrane, and CpE-induced structural changes to claudin-4. Further, the structures allude to the biophysical procession from small complex to cytotoxic β-barrel pore used by CpE during pathogenesis and the role of trypsin in this process. In full, this work elucidates the structure and mechanism of claudin-bound CpE pore assembly and provides strategies to obstruct its formation to treat CpE-induced gastrointestinal diseases.

Mitophagy Promotes Hair Regeneration by Activating Glutathione Metabolism.

Mitophagy maintains tissue homeostasis by self-eliminating defective mitochondria through autophagy. How mitophagy regulates stem cell activity during hair regeneration remains unclear. Here, we found that mitophagy promotes the proliferation of hair germ (HG) cells by regulating glutathione (GSH) metabolism. First, single-cell RNA sequencing, mitochondrial probe, transmission electron microscopy, and immunofluorescence staining showed stronger mitochondrial activity and increased mitophagy-related gene especially Prohibitin 2 (Phb2) expression at early-anagen HG compared to the telogen HG. Mitochondrial inner membrane receptor protein PHB2 binds to LC3 to initiate mitophagy. Second, molecular docking and functional studies revealed that PHB2-LC3 activates mitophagy to eliminate the damaged mitochondria in HG. RNA-seq, single-cell metabolism, immunofluorescence staining, and functional validation discovered that LC3 promotes GSH metabolism to supply energy for promoting HG proliferation. Third, transcriptomics analysis and immunofluorescence staining indicated that mitophagy was down-regulated in the aged compared to young-mouse HG. Activating mitophagy and GSH pathways through small-molecule administration can reactivate HG cell proliferation followed by hair regeneration in aged hair follicles. Our findings open up a new avenue for exploring autophagy that promotes hair regeneration and emphasizes the role of the self-elimination effect of mitophagy in controlling the proliferation of HG cells by regulating GSH metabolism.

Binding activity and specificity of tail fiber protein 35Q for Salmonella pullorum.

Salmonella, a prevalent pathogen with significant implications for the poultry industry and food safety, presents a global public health concern. The rise in antibiotic resistance has exacerbated the challenge of prevention. Accurate and sensitive detection methods are essential in combating Salmonella infections. Bacteriophages, viruses capable of targeting and destroying bacteria, leverage their host specificity for accurate microbial detection. Notably, the tail fiber protein of bacteriophages plays a crucial role in recognizing specific hosts, making it a valuable tool for targeted microbial detection. This study focused on the tail fiber protein 35Q of Salmonella pullorum (SP) bacteriophage YSP2, identified through protein sequencing and genome analysis. Bioinformatics analysis revealed similarities between 35Q and other Salmonella bacteriophage tail fiber proteins. The protein was successfully expressed and purified using an Escherichia coli expression system, and its binding activity and specificity were confirmed. ELISA assays and adsorption experiments demonstrated that 35Q interacts with the outer membrane protein (OMP) receptor on bacterial surfaces. This investigation provides valuable insights for targeted Salmonella detection, informs the development of specific therapeutics, and enhances our understanding of the interaction between Salmonella bacteriophages and their hosts.

Exploring the therapeutic mechanisms of Astonia boonei in diabetes mellitus ligand-based virtual screening with TGR5 Receptor

The anti-diabetic effects of Astonia boonei have been demonstrated by several studies, but few have clarified the mode of action of compounds extracted from Astonia boonei as an agonist for the TGR5 pathways in the etiology of diabetes. TGR5 is a membrane protein receptor that has been linked to increased insulin-signaling and is an appropriate target for diabetes treatment. Nevertheless, no commercial medication that specifically targets TGR5 is currently available. This study looked into compounds that were found to be TGR5 agonists and may have therapeutic value in A. boonei. The compounds were selected from the literature and docked with TGR5 receptors. Following their filtration by Lipinski's rule of five (RO5), the compounds were utilized in a molecular docking investigation. Moderate indices for ADMET parameters and non-carcinogenicity were revealed by online web servers' predictions of the hit compounds' drug-likeness, pharmacokinetic, and toxicity features. The potential of compounds from A. boonei that might be explored as therapeutic options in the treatment of diabetes is thus illuminated by this study

Evaluation of non-clinical safety of Wsmol, a chitin binding lectin of Moringa oleifera seeds in adult zebrafish (Danio rerio)

Previous studies have shown several biotechnological and lectin biomedical activities provided from Moringa oleifera seeds. The Wsmol (water soluble chitin binding lectin) has affinity for n-acetyl-D-glucosamine-glycans present in various cell receptors and it is able to realize many biological activities. This study was conducted to evaluate the nonclinical safety of Wsmol in adult Zebrafish (Danio rerio). The action of Wsmol (1.0 mg / mL; 20 μL; ip) and Vehicle (0.9 % NaCl, 20 μL, ip) on the locomotor activity of adult zebrafish (ZFa; n = 6 / group) was evaluated in the open field test. A naïve group was included. After 24 h of treatments, mortality rate was analyzed and the concentration able to kill 50 % (LC50) of the zebrafish was calculated. Wsmol, active in the physiological environment of Zebrafish did not modify the locomotor activity nor did it prove to be toxic to the animals, suggesting that its lectin activity, although can promote pharmacological activities when recognizing glycans of several ion channels and membrane protein receptors, can not be associated with toxicity or locomotor damage.

Platelets: A Potential Factor that Offers Strategies for Promoting Bone Regeneration.

Bone defects represent a prevalent category of clinical injuries, causing significant pain and escalating health care burdens. Effectively addressing bone defects is thus of paramount importance. Platelets, formed from megakaryocyte lysis, have emerged as pivotal players in bone tissue repair, inflammatory responses, and angiogenesis. Their intracellular storage of various growth factors, cytokines, and membrane protein receptors contributes to these crucial functions. This article provides a comprehensive overview of platelets' roles in hematoma structure, inflammatory responses, and angiogenesis throughout the process of fracture healing. Beyond their application in conjunction with artificial bone substitute materials for treating bone defects, we propose the potential future use of anticoagulants such as heparin in combination with these materials to regulate platelet number and function, thereby promoting bone healing. Ultimately, we contemplate whether manipulating platelet function to modulate bone healing could offer innovative ideas and directions for the clinical treatment of bone defects.

Cadmium exposure activates mitophagy through downregulating thyroid hormone receptor/PGC1α signal in preeclampsia

Gestational cadmium exposure increases the risk of preeclampsia. Placenta mitophagy was activated in preeclampsia. The aim of present study was to explore the mechanism of cadmium-induced mitophagy activation and its association with preeclampsia. Mitophagy markers expression levels were detected by quantitative real-time PCR, Western blot, immunofluorescence and immunochemistry in preeclampsia placenta. JEG3 cells were treated with CdCl2, iopanoic acid (IOP), 3-methyladenine and PGC1α SiRNA to verify mechanism of cadmium-induced mitophagy. Mitophagy marker LC3BII/I and P62 expression were increased and mitochondrial membrane receptor protein TOM20 and FUNDC1 expression were decreased in preeclampsia placenta as compared with that in normotension control. Mitophagy marker LC3BII/I and P62 expression were increased and TOM20 and FUNDC1 expression was decreased in CdCl2-treated JEG3 cells. Meanwhile, mitochondrial biogenesis regulator, PGC1α expression was decreased in preeclampsia and CdCl2-treated JEG3 cells. The expressions of LC3B and P62 were increased and the expressions of TOM20, FUNDC1 and PGC1α were decreased in IOP-treated cell. PGC1α SiRNA transfection led to increased expression of LC3BII/I and P62 and decreased expression of TOM20 and FUNDC1. The expression of sFlt1 was increased in preeclampsia placenta, CdCl2-treated cells, in IOP-treated cells and in PGC1α SiRNA transfected cells. 3-methyladenine treatment protected the increased expression of sFlt1 in CdCl2-treated cells, in IOP-treated cells and in PGC1α SiRNA transfected cells. Meanwhile, co-treatment of cadmium and IOP or PGC1αSiRNA led to a reduce expressions of OPA1, MFN1, MFN2 and FUNDC1 as compared to cadmium-treated, IOP-treated and PGC1α SiRNA-treated cells. These results elucidated that maternal cadmium exposure activated placenta mitophagy through downregulation of thyroid hormone receptor signal mediated decreased expression of PGC1α and was associated with the occurrence of preeclampsia.

EH domain-containing protein 2 (EHD2): Overview, biological function, and therapeutic potential.

EH domain-containing protein 2 (EHD2) is a member of the EHD protein family and is mainly located in the plasma membrane, but can also be found in the cytoplasm and endosomes. EHD2 is also a nuclear-cytoplasmic shuttle protein. After entering the cell nuclear, EHD2 acts as a corepressor of transcription to inhibit gene transcription. EHD2 regulates a series of biological processes. As a key regulator of endocytic transport, EHD2 is involved in the formation and maintenance of endosomal tubules and vesicles, which are critical for the intracellular transport of proteins and other substances. The N-terminal of EHD2 is attached to the cell membrane, while its C-terminal binds to the actin-binding protein. After binding, EHD2 connects with the actin cytoskeleton, forming the curvature of the membrane and promoting cell endocytosis. EHD2 is also associated with membrane protein trafficking and receptor signaling, as well as in glucose metabolism and lipid metabolism. In this review, we highlight the recent advances in the function of EHD2 in various cellular processes and its potential implications in human diseases such as cancer and metabolic disease. We also discussed the prospects for the future of EHD2. EHD2 has a broad prospect as a therapeutic target for a variety of diseases. Further research is needed to explore its mechanism, which could pave the way for the development of targeted treatments.

COMP promotes pancreatic fibrosis by activating pancreatic stellate cells through CD36-ERK/AKT signaling pathways

BackgroundPancreatic fibrosis is one of the most important pathological features of chronic pancreatitis (CP) and pancreatic stellate cells (PSCs) are the key cells of fibrosis. As an extracellular matrix (ECM) glycoprotein, cartilage oligomeric matrix protein (COMP) is critical for collagen assembly and ECM stability and recent studies showed that COMP exert promoting fibrosis effect in the skin, lungs and liver. However, the role of COMP in activation of PSCs and pancreatic fibrosis remain unclear. We aimed to investigate the role and specific mechanisms of COMP in regulating the profibrotic phenotype of PSCs and pancreatic fibrosis. MethodsELISA method was used to determine serum COMP in patients with CP. Mice model of CP was established by repeated intraperitoneal injection of cerulein and pancreatic fibrosis was evaluated by Hematoxylin-Eosin staining (H&E) and Sirius red staining. Immunohistochemical staining was used to detect the expression changes of COMP and fibrosis marker such as α-SMA and Fibronectin in pancreatic tissue of mice. Cell Counting Kit-8, Wound Healing and Transwell assessed the proliferation and migration of human pancreatic stellate cells (HPSCs). Western blotting, qRT-PCR and immunofluorescence staining were performed to detect the expression of fibrosis marker, AKT and MAPK family proteins in HPSCs. RNA-seq omics analysis as well as small interfering RNA of COMP, recombinant human COMP (rCOMP), MEK inhibitors and PI3K inhibitors were used to study the effect and mechanism of COMP on activation of HPSCs. ResultsELISA showed that the expression of COMP significantly increased in the serum of CP patients. H&E and Sirius red staining analysis showed that there was a large amount of collagen deposition in the mice in the CP model group and high expression of COMP, α-SMA, Fibronectin and Vimentin were observed in fibrotic tissues. TGF-β1 stimulates the activation of HPSCs and increases the expression of COMP. Knockdown of COMP inhibited proliferation and migration of HPSCs. Further, RNA-seq omics analysis and validation experiments in vitro showed that rCOMP could significantly promote the proliferation and activation of HPSCs, which may be due to promoting the phosphorylation of ERK and AKT through membrane protein receptor CD36. rCOMP simultaneously increased the expression of α-SMA, Fibronectin and Collagen I in HPSCs. ConclusionIn conclusion, this study showed that COMP was up-regulated in CP fibrotic tissues and COMP induced the activation, proliferation and migration of PSCs through the CD36-ERK/AKT signaling pathway. COMP may be a potential therapeutic candidate for the treatment of CP. Interfering with the expression of COMP or the communication between COMP and CD36 on PSCs may be the next direction for therapeutic research.

Electric field induced the changes in structure and function of human transforming growth factor beta receptor type I: from molecular dynamics to docking

The transforming growth factor beta (TGF-β) signaling pathway is believed to play essential roles in several physiological activities, including cancer. TGF-β receptor type I (TBR-I) is a key membrane receptor protein in the TGF-β signaling pathway, which relates to many intracellular biological effects. In recent years, cold atmospheric plasma (CAP) has been found to have promising prospects in selective anticancer therapy and has confirmed its essential role in the TGF-β signaling pathway. However, the ambiguous effect of CAP-induced electric field (EF) on TBR-I still limits the application of CAP in clinical therapy. Molecular dynamics is applied to assess the effect of EF on the structure of the extracellular domain of TBR-I using a series of indicators and methods, and then we discuss the ligand binding ability of TBR-I. Results show that moderate EF intensities’ structural restraints may contribute to the structural stability and ligand-binding ability of TBR-I, but an EF higher than 0.1 V/nm will be harmful. What’s more, EF induces a change in the docking interface of TBR-I, showing the conformation and position of special sequences of residues decide the ligand binding surface. The relevant results suggest that CAP-induced EF plays a crucial role in receptor-receptor interaction and provides significant guidelines for EF-related anticancer therapy. Communicated by Ramaswamy H. Sarma

Systemic and local immunosuppression in glioblastoma and its prognostic significance.

The effectiveness of tumor therapy, especially immunotherapy and oncolytic virotherapy, critically depends on the activity of the host immune cells. However, various local and systemic mechanisms of immunosuppression operate in cancer patients. Tumor-associated immunosuppression involves deregulation of many components of immunity, including a decrease in the number of T lymphocytes (lymphopenia), an increase in the levels or ratios of circulating and tumor-infiltrating immunosuppressive subsets [e.g., macrophages, microglia, myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs)], as well as defective functions of subsets of antigen-presenting, helper and effector immune cell due to altered expression of various soluble and membrane proteins (receptors, costimulatory molecules, and cytokines). In this review, we specifically focus on data from patients with glioblastoma/glioma before standard chemoradiotherapy. We discuss glioblastoma-related immunosuppression at baseline and the prognostic significance of different subsets of circulating and tumor-infiltrating immune cells (lymphocytes, CD4+ and CD8+ T cells, Tregs, natural killer (NK) cells, neutrophils, macrophages, MDSCs, and dendritic cells), including neutrophil-to-lymphocyte ratio (NLR), focus on the immune landscape and prognostic significance of isocitrate dehydrogenase (IDH)-mutant gliomas, proneural, classical and mesenchymal molecular subtypes, and highlight the features of immune surveillance in the brain. All attempts to identify a reliable prognostic immune marker in glioblastoma tissue have led to contradictory results, which can be explained, among other things, by the unprecedented level of spatial heterogeneity of the immune infiltrate and the significant phenotypic diversity and (dys)functional states of immune subpopulations. High NLR is one of the most repeatedly confirmed independent prognostic factors for shorter overall survival in patients with glioblastoma and carcinoma, and its combination with other markers of the immune response or systemic inflammation significantly improves the accuracy of prediction; however, more prospective studies are needed to confirm the prognostic/predictive power of NLR. We call for the inclusion of dynamic assessment of NLR and other blood inflammatory markers (e.g., absolute/total lymphocyte count, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, and systemic immune response index) in all neuro-oncology studies for rigorous evaluation and comparison of their individual and combinatorial prognostic/predictive significance and relative superiority.

Surface-Patterned DNA Origami Rulers Reveal Nanoscale Distance Dependency of the Epidermal Growth Factor Receptor Activation.

The nanoscale arrangement of ligands can have a major effect on the activation of membrane receptor proteins and thus cellular communication mechanisms. Here we report on the technological development and use of tailored DNA origami-based molecular rulers to fabricate "Multiscale Origami Structures As Interface for Cells" (MOSAIC), to enable the systematic investigation of the effect of the nanoscale spacing of epidermal growth factor (EGF) ligands on the activation of the EGF receptor (EGFR). MOSAIC-based analyses revealed that EGF distances of about 30-40 nm led to the highest response in EGFR activation of adherent MCF7 and Hela cells. Our study emphasizes the significance of DNA-based platforms for the detailed investigation of the molecular mechanisms of cellular signaling cascades.

Structure of the murine CD94-NKG2A receptor in complex with Qa-1b presenting an MHC-I leader peptide.

The heterodimeric natural killer cells antigen CD94 (CD94)-NKG2-A/NKG2-B type II integral membrane protein (NKG2A) receptor family expressed on human and mouse natural killer (NK) cells monitors global major histocompatibility complex (MHC) class I cell surface expression levels through binding to MHC class Ia-derived leader sequence peptides presented by HLA class I histocompatibility antigen, alpha chain E (HLA-E; in humans) or H-2 class I histocompatibility antigen, D-37 (Qa-1b; in mice). Although the molecular basis underpinning human CD94-NKG2A recognition of HLA-E is known, the equivalent interaction in the murine setting is not. By determining the high-resolution crystal structure of murine CD94-NKG2A in complex with Qa-1b presenting the Qa-1 determinant modifier peptide (QDM), we resolved the mode of binding. Compared to the human homologue, the murine CD94-NKG2A-Qa-1b-QDM displayed alterations in the distribution of interactions across CD94 and NKG2A subunits that coincide with differences in electrostatic complementarity of the ternary complex and the lack of cross-species reactivity. Nevertheless, we show that Qa-1b could be modified through W65R + N73I mutations to mimic HLA-E, facilitating binding with both human and murine CD94-NKG2A. These data underscore human and murine CD94-NKG2A cross-species heterogeneity and provide a foundation for humanising Qa-1b in immune system models.

Cellular localization and potential ligands of a novel scavenger receptor class B/CD36 protein homolog (Pt-SRB2) identified in the marine crab, Portunustrituberculatus

The scavenger receptor class B family proteins (SRB) are multiligand membrane receptor proteins. Herein, a novel SRB homolog (Pt-SRB2) was identified in Portunus trituberculatus. The open reading frame of Pt-SRB2 was predicted to encode 520 amino acid residues comprising a typical CD36 domain. Phylogenetic analysis showed that Pt-SRB2 distinctly clustered with the SRB homologs of most crustaceans and Drosophila but was separate from all vertebrate CD36/SRB. Semi-quantitative and Real-time quantitative PCR revealed that the abundance of Pt-SRB2 transcripts was the highest in hepatopancreas than in other tested tissues. Overexpressed Pt-SRB2 was distributed primarily in the cell membrane and cytoplasm of HEK293T or Drosophila Schneider 2 cells. In crab hemocytes, Pt-SRB2 was distributed primarily in the cell membrane by immunofluorescence staining. In addition, the immunofluorescence staining showed that green fluorescence signals were mainly located in the inner lumen membrane of the hepatopancreatic tubules. Moreover, solid-phase enzyme-linked immunosorbent assay revealed that rPt-SRB2-L exhibited relative high affinity with lipopolysaccharides, and relative moderate binding affinity with lipoteichoic acid or peptidoglycan. Of note, rPt-SRB2-L showed high binding affinity with eicosapentaenoic acid among a series of long-chain polyunsaturated fatty acids. Taken together, this study provided valuable data for understanding the functions of the crab CD36/SRB.

ISX-9 Promotes KGF Secretion From MSCs to Alleviate ALI Through NGFR-ERK-TAU-β-Catenin Signaling Axis.

Mesenchymal stem cells (MSCs) have been widely studied to alleviate acute lung injury (ALI) due to their paracrine function. However, the microenvironment of inflammatory outbreaks significantly restricted the factors secreted from MSCs like keratinocyte growth factor (KGF). KGF is a growth factor with tissue-repaired ability. Is there a better therapeutic prospect for MSCs in combination with compounds that promote their paracrine function? Through compound screening, we screened out isoxazole-9 (ISX-9) to promote MSCs derived KGF secretion and investigated the underlying mechanisms of action. Compounds that promote KGF secretion were screened by a dual-luciferase reporter gene assay. The TMT isotope labeling quantitative technique was used to detect the differential proteins upon ISX-9 administrated to MSCs. The expressions of NGFR, ERK, TAU, and β-catenin were detected by Western blot. In the ALI model, we measured the inflammatory changes by HE staining, SOD content detection, RT-qPCR, immunofluorescence, etc. The influence of ISX-9 on the residence time of MSCs transplantation was explored by optical in vivo imaging. We found out that ISX-9 can promote the expression of KGF in MSCs. ISX-9 acted on the membrane receptor protein NGFR, upregulated phosphorylation of downstream signaling proteins ERK and TAU, downregulated phosphorylation of β-catenin, and accelerated β-catenin into the nucleus to further increase the expression of KGF. In the ALI model, combined ISX-9 with MSCs treatments upgraded the expression of KGF in the lung, and enhanced the effect of MSCs in reducing inflammation and repairing lung damage compared with MSCs alone. ISX-9 facilitated the secretion of KGF from MSCs both in vivo and in vitro. The combination of ISX-9 with MSCs enhanced the paracrine function and anti-inflammatory effect of MSCs compared with MSCs applied alone in ALI. ISX-9 played a contributive role in the transplantation of MSCs for the treatment of ALI.

A thermodynamic model for the formation of protein aggregates on a matrix

The development of many neurodegenerative diseases is associated with the formation of pathological protein aggregates. In some cases, these aggregates can be formed by multilayer adsorption of ligands on a matrix, for example, the set of membrane protein receptors. The paper proposes a thermodynamic model describing the formation of linear aggregates in which ligands can be stacked. The cases when these stacks consist of complexes of one or two different types are considered. The developed model can be applied to the study of pathological aggregation of proteins of different nature, primarily beta-amyloid and its isoforms. The mean, variance and entropy of the theoretical distributions of aggregate sizes are calculated. A comparison with other theoretical models of the formation of amyloid aggregates is made.

Effects of uranium mining on soil bacterial communities and functions in the Qinghai-Tibet plateau

The microecological effects of plateau uranium mining are still unknown. In this study, we used 16S rRNA high-throughput sequencing to analyze the impact of plateau uranium mining on the microbial diversity and community structure of tailings soil, tunnel soil, and soil at different depths in an open pit. The results showed that uranium mining significantly reduced soil microbial community richness and diversity indicators, including Chao1, Pielou evenness, and Shannon index (P < 0.05). Uranium mining activities significantly reduced the abundance of RB41, Vicinamidactaceae, and Nitrospira (P < 0.05). Interestingly, the abundance of Thiobacillus, Sphingomonas, and Sulfuriferula significantly increased in the soil samples from various environments and depths during uranium mining (P < 0.05). Beta diversity analysis found that uranium mining resulted in the differentiation of soil microbial communities. Functional enrichment analysis found that uranium mining resulted in the functional enrichment of DNA binding response regulator, DNA helicase, methyl-accepting chemotaxis protein, and Helicase conserved C-terminal domain, whereas cell wall synthesis, nonspecific serine/threonine protein kinase, RNA polymerase sigma-70 factor, and ATP binding cassette transporter were significantly affected by uranium mining (P < 0.05). In addition, we also found that different uranium mining environments and soil depths enriched diverse microbial populations and functions to cope with the environmental pressures that were elicited by uranium mining, including Gaiella, Gemmatimonas, Lysobacter, Pseudomonas, signal transformation histidine kinase, DNA-directed DNA polymerase, and iron complex outer membrane receptor protein functions (P < 0.05). The results have enhanced our understanding of the impact of uranium mining on plateau soil microecological stability and the mechanism of microbial response to uranium mining activities for the first time and aided us in screening microbial strains that can promote the environmental remediation of uranium mining in plateaus.

Structural Basis of Clostridium perfringens Enterotoxin Activation and Oligomerization by Trypsin.

Clostridium perfringens enterotoxin (CpE) is a β-pore forming toxin that disrupts gastrointestinal homeostasis in mammals by binding membrane protein receptors called claudins. Although structures of CpE fragments bound to claudins have been determined, the mechanisms that trigger CpE activation and oligomerization that lead to the formation of cytotoxic β-pores remain undetermined. Proteolysis of CpE in the gut by trypsin has been shown to play a role in this and subsequent cytotoxicity processes. Here, we report solution structures of full-length and trypsinized CpE using small-angle X-ray scattering (SAXS) and crystal structures of trypsinized CpE and its C-terminal claudin-binding domain (cCpE) using X-ray crystallography. Mass spectrometry and SAXS uncover that removal of the CpE N-terminus by trypsin alters the CpE structure to expose areas that are normally unexposed. Crystal structures of trypsinized CpE and cCpE reveal unique dimer interfaces that could serve as oligomerization sites. Moreover, comparisons of these structures to existing ones predict the functional implications of oligomerization in the contexts of cell receptor binding and β-pore formation. This study sheds light on trypsin's role in altering CpE structure to activate its function via inducing oligomerization on its path toward cytotoxic β-pore formation. Its findings can incite new approaches to inhibit CpE-based cytotoxicity with oligomer-disrupting therapeutics.

Sweet Taste: From Perception to Evaluation

Abstract—Sweetness is the strongest gustatory modality, which shapes eating behavior and influences homeostasis. The review summarizes data on the perception and encoding of taste signals at the level of taste receptors and brain centers during consumption of sweet substances. We focus on the molecular and cellular mechanisms of sweet taste identification and determination of food caloric content, including the role of membrane receptor proteins T1R2/T1R3 and signal transduction enzyme cascades, as well as a metabolic mechanism for estimating the concentration of glucose in the cytoplasm. Genetic aspects of sweet sensitivity and the influence of sweet taste receptor gene polymorphisms on sensitivity to sugar and low-calorie sweeteners are described. The review presents results of modern studies of endocrine, paracrine and autocrine modulation of sweet taste perception and evaluation depending on the metabolic state of the body. The assumption of a promising research area on the problem is made.