Attractant and repellent induce opposing changes in the four-helix bundle ligand-binding domain of a bacterial chemoreceptor.

Motile bacteria navigate toward favorable conditions and away from unfavorable environments using chemotaxis. Mechanisms of sensing attractants are well understood; however, molecular aspects of how bacteria sense repellents have not been established. Here, we identified malate as a repellent recognized by the MCP2201 chemoreceptor in a bacterium Comamonas testosteroni and showed that it binds to the same site as an attractant citrate. Binding determinants for a repellent and an attractant had only minor differences, and a single amino acid substitution in the binding site inverted the response to malate from a repellent to an attractant. We found that malate and citrate affect the oligomerization state of the ligand-binding domain in opposing way. We also observed opposing effects of repellent and attractant binding on the orientation of an alpha helix connecting the sensory domain to the transmembrane helix. We propose a model to illustrate how positive and negative signals might be generated.

Phase-encoded fMRI tracks down brainstorms of natural language processing with subsecond precision.

Natural language processing unfolds information overtime as spatially separated, multimodal, and interconnected neural processes. Existing noninvasive subtraction-based neuroimaging techniques cannot simultaneously achieve the spatial and temporal resolutions required to visualize ongoing information flows across the whole brain. Here we have developed rapid phase-encoded designs to fully exploit the temporal information latent in functional magnetic resonance imaging data, as well as overcoming scanner noise and head-motion challenges during overt language tasks. We captured real-time information flows as coherent hemodynamic waves traveling over the cortical surface during listening, reading aloud, reciting, and oral cross-language interpreting tasks. We were able to observe the timing, location, direction, and surge of traveling waves in all language tasks, which were visualized as "brainstorms" on brain "weather" maps. The paths of hemodynamic traveling waves provide direct evidence for dual-stream models of the visual and auditory systems as well as logistics models for crossmodal and cross-language processing. Specifically, we have tracked down the step-by-step processing of written or spoken sentences first being received and processed by the visual or auditory streams, carried across language and domain-general cognitive regions, and finally delivered as overt speeches monitored through the auditory cortex, which gives a complete picture of information flows across the brain during natural language functioning. PRACTITIONER POINTS: Phase-encoded fMRI enables simultaneous imaging of high spatial and temporal resolution, capturing continuous spatiotemporal dynamics of the entire brain during real-time overt natural language tasks. Spatiotemporal traveling wave patterns provide direct evidence for constructing comprehensive and explicit models of human information processing. This study unlocks the potential of applying rapid phase-encoded fMRI to indirectly track the underlying neural information flows of sequential sensory, motor, and high-order cognitive processes.

The ligand binding domain of a type IV pilus chemoreceptor PilJ has a different fold from that of another PilJ-type receptor McpN.

Bacterial chemoreceptors sense the extracellular signals and regulate bacterial motilities, biofilm formation, etc. The periplasmic ligand binding domains of chemoreceptors occur as different structural folds and recognize a diversity of chemical molecules. In Pseudomonas aeruginosa (PAO1), two bacterial chemoreceptors, McpN (PA2788) and PilJ (PA0411), are proposed to both contain a PilJ-like ligand-binding domain (LBD) (Pfam motif PF13675) and involved in nitrate chemotaxis and type IV pilus-mediated motility, respectively. The LBDs of McpN and PilJ consist of 135 and 263 residues, respectively, and share very low sequence identity, suggesting they might occur as different structures. Here, we found that PilJ-LBD folded into an HBM module, the same as the sensor domains of McpS-LBD and TorS-LBD, but it differed from that of McpN-LBD. We also observed a trimer in SEC and AUC and proposed a trimeric model based on the crystal structure. Based on the sequence, we classified the Pfam containing McpN-LBD and PilJ-LBD into three classes: sPilJ (single PilJ) represented by McpN-LBD with only one PilJ domain, dPilJ (dual PilJ) that contained dual PilJ domains, and hPilJ (hybrid PilJ) that comprises of a PilJ domain and another non-PilJ domain. Our work indicates a significant structural difference between the ligand binding domains of PilJ and McpN and will help our further study on both kinds of chemoreceptors.

TC2N inhibits distant metastasis and stemness of breast cancer via blocking fatty acid synthesis.

BACKGROUND: Tandem C2 domains, nuclear (TC2N) is a C2 domain-containing protein that belongs to the carboxyl-terminal type (C-type) tandem C2 protein family, and acts as an oncogenic driver in several cancers. Previously, we preliminarily reported that TC2N mediates the PI3K-Akt signaling pathway to inhibit tumor growth of breast cancer (BC) cells. Beyond that, its precise biological functions and detailed molecular mechanisms in BC development and progression are not fully understood. METHODS: Tumor tissues of 212 BC patients were subjected to tissue microarray and further assessed the associations of TC2N expression with pathological parameters and FASN expression. The protein levels of TC2N and FASN in cell lines and tumor specimens were monitored by qRT-PCR, WB, immunofluorescence and immunohistochemistry. In vitro cell assays, in vivo nude mice model was used to assess the effect of TC2N ectopic expression on tumor metastasis and stemness of breast cancer cells. The downstream signaling pathway or target molecule of TC2N was mined using a combination of transcriptomics, proteomics and lipidomics, and the underlying mechanism was explored by WB and co-IP assays. RESULTS: Here, we found that the expression of TC2N remarkedly silenced in metastatic and poorly differentiated tumors. Function-wide, TC2N strongly inhibits tumor metastasis and stem-like properties of BC via inhibition of fatty acid synthesis. Mechanism-wise, TC2N blocks neddylated PTEN-mediated FASN stabilization by a dual mechanism. The C2B domain is crucial for nuclear localization of TC2N, further consolidating the TRIM21-mediated ubiquitylation and degradation of FASN by competing with neddylated PTEN for binding to FASN in nucleus. On the other hand, cytoplasmic TC2N interacts with import proteins, thereby restraining nuclear import of PTEN to decrease neddylated PTEN level. CONCLUSIONS: Altogether, we demonstrate a previously unidentified role and mechanism of TC2N in regulation of lipid metabolism and PTEN neddylation, providing a potential therapeutic target for anti-cancer.

Gut microbiota modulation: a narrative review on a novel strategy for prevention and alleviation of ovarian aging.

The global rise in life expectancy corresponds with a delay in childbearing age among women. Ovaries, seen as the chronometers of female physiological aging, demonstrate features of sped up aging, evidenced by the steady decline in both the quality and quantity of ovarian follicles from birth. The multifaceted pathogenesis of ovarian aging has kindled intensive research interest from the biomedical and pharmaceutical sectors. Novel studies underscore the integral roles of gut microbiota in follicular development, lipid metabolism, and hormonal regulation, forging a nexus with ovarian aging. In this review, we outline the role of gut microbiota in ovarian function (follicular development, oocyte maturation, and ovulation), compile and present gut microbiota alterations associated with age-related ovarian aging. We also discuss potential strategies for alleviating ovarian aging from the perspective of gut microbiota, such as fecal microbiota transplantation and probiotics.

Clip-and-snare method with a pre-looping technique versus conventional method in the treatment of precancerous lesion and early gastric cancer: a retrospective study.

BACKGROUND: Low grade intraepithelial neoplasia (LGIN) and high grade intraepithelial neoplasia (HGIN) are potential precancerous lesion of gastric neoplasms. Endoscopic submucosal dissection (ESD) is the first option for the treatment of precancerous lesion and early gastric cancer (EGC). Traction is an effective method to improve efficiency, and reduce complications during ESD. In this study, we shared a useful traction method using the clip-and-snare method with a pre-looping technique (CSM-PLT) for precancerous lesion and EGC. METHODS: We retrospectively analyzed patients received ESD combined with CSM-PLT or conventional ESD from June 2018 to December 2021 in Shenzhen People's hospital. The primary outcome was resection speed. RESULTS: Forty-two patients were enrolled in ESD combined with CSM-PLT group and sixty-five patients in conventional ESD group respectively. Baseline characteristics were comparable among two groups (P>0.05). There were no significant differences in terms of R0 resection rate, en bloc resection rate (97.6% vs. 98.5%, P = 1.000 and 97.6% vs. 96.9%, P = 1.000, respectively), operation costs (933.7 (644.1-1102.4) dollars vs. 814.7 (614.6-988.3) dollars, P = 0.107), and hospital stays (8.0 ± 3.1 days vs. 7.3 ± 3.2 days, P = 0.236). In addition, no significant difference was observed with respect to complications (P>0.05). However, the resection speed of ESD combined with CSM-PLT was faster than that of conventional ESD (11.3 (9.4-14.9) mm2/min vs. 8.0 (5.8-10.9) mm2/min, P < 0.001), particularly lesions located in anterior wall and lesser curvature. In addition, the association between ESD combined with CSM-PLT and resection speed was still supported after propensity matching scores (PMS). CONCLUSIONS: CSM-PLT can help to improve ESD efficiency without reducing the en bloc resection rate or increasing the incidence of complications.

Biochemical insights into Paf1 complex-induced stimulation of Rad6/Bre1-mediated H2B monoubiquitination.

The highly conserved multifunctional polymerase-associated factor 1 (Paf1) complex (PAF1C), composed of five core subunits Paf1, Leo1, Ctr9, Cdc73, and Rtf1, participates in all stages of transcription and is required for the Rad6/Bre1-mediated monoubiquitination of histone H2B (H2Bub). However, the molecular mechanisms underlying the contributions of the PAF1C subunits to H2Bub are not fully understood. Here, we report that Ctr9, acting as a hub, interacts with the carboxyl-terminal acidic tail of Rad6, which is required for PAF1C-induced stimulation of H2Bub. Importantly, we found that the Ras-like domain of Cdc73 has the potential to accelerate ubiquitin discharge from Rad6 and thus facilitates H2Bub, a process that might be conserved from yeast to humans. Moreover, we found that Rtf1 HMD stimulates H2Bub, probably through accelerating ubiquitin discharge from Rad6 alone or in cooperation with Cdc73 and Bre1, and that the Paf1/Leo1 heterodimer in PAF1C specifically recognizes the histone H3 tail of nucleosomal substrates, stimulating H2Bub. Collectively, our biochemical results indicate that intact PAF1C is required to efficiently stimulate Rad6/Bre1-mediated H2Bub.

"Clip coupled with an elastic ring" internal traction for endoscopic submucosal dissection of a rectal neuroendocrine tumor: a junior endoscopist experience.

A 64-year-old female was found a rectal neuroendocrine tumor (NET) for cancer screening examination. Endoscopic ultrasonography (EUS) revealed a hypoechoic lesion (8.3*6.6 mm) originating from the submucosa layer. "Clip coupled with elastic ring" internal traction for endoscopic submucosal dissection (ESD) was used to remove the NET according to the procedure removal of a duodenal tumor1. The procedures are following: 1. Marking around the lesion with a margin of approximately 5 mm. 2. Submucosal injection and circumference incision around the lesion. 3. Applied clip coupled with elastic ring internal traction. 4. Submucosal injection. 5.Precise dissection was performed with the NET being en bloc resection. 5. Closed the mucosal defect. Finally, the Histopathology confirmed a neuroendocrine tumor.

A case of achalasia associated with early esophageal cancer.

A 65-year-old man was admitted to our hospital complaining of reflux for more than 20 years. After endoscopy and barium-swallow examination, he was diagnosed with achalasia as well as a squamous cell carcinoma. Therefore, peroral endoscopic myotomy (POEM) combined with endoscopic submucosal dissection (ESD) was performed simultaneously. During the procedure, a mucosal erosion with a clear boundary was shown in the middle segment of the esophagus. ESD was first performed and the lesion was removed en-bloc. Subsequent POEM therapy was performed after marking the left esophageal wall 10cm above the cardia. After submucosal injection, the submucosal plane was created through a length 2cm longitudinal incision, then the muscle was cut a length of 10 cm into the esophagus and 2 cm below the cardia, and finally the incision was closed by clips. Pathological examination revealed high-grade intraepithelial neoplasia of squamous epithelium (carcinoma in situ) with a negative margin. The patient was recovered without complication four days after the procedure. The endoscopy showed perfect healing of the esophageal lesions during two-months follow-up , and the reflux symptom was resolved.

A novel three traction rings device with endoscopic submucosal dissection (ESD) in the removal of a large superficial duodenal adenoma.

Endoscopic treatment is generally recommended for the duodenal epithelial adenoma. Although underwater endoscopic mucosal resection (UEMR) has become established as an effective modality for the superficial duodenal adenoma. However, it is difficult to completely remove a large superficial duodenal adenoma with en bloc resection. Endoscopic submucosal dissection (ESD) is commonly performed to remove a large superficial duodenal adenoma, whereas which is technically challenged with severe adverse events. It has reported that entire traction using clip-and-nylon ring with ESD was effective and safe in the removal of a large rectal sessile serrated adenoma (SSA). Herein, we shared our experience of the novel three traction rings device in the treatment of a large superficial duodenal adenoma.

One stone two birds - Submucosal tunneling endoscopic resection for a large esophageal submucosal mass and esophageal diverticulum.

A-35-year-old woman presented our hospital with half a year's history of solid food dysphagia. An upper gastrointestinal endoscopy revealed a large submucosal mass in an esophageal diverticulum near the gastroesophageal junction. Endoscopic ultrasound (EUS) confirmed a hypoechoic lesion arising from the muscularis propria layer with the size of 25*14 mm. Therefore, submucosal tunneling endoscopic resection (STER) was proposed to remove the large submucosal lesion in addition to targeted septotomy of the esophageal diverticula. A 2-cm longitudinal mucosal access was made at 3 cm above the submucosal lesion, and a submucosal longitudinal tunnel was created until the submucosal lesion revealed using a DualKnife (Olympus, Japan). Meticulous resection was performed with the DualKnife, and the lateral border of the lesion was dissected from muscularis propria layer. It was completely removed the lesion with en bolc resection, and dissected the septum of the diverticulum using the DualKnife. The tunnel access was closed with several hemoclips. Finally, it has been demonstrated to achieve a perfect outcome for the patient. The patient was discharged three days later with symptom resolved on follow-up and to date.

New options for endoscopic treatment of gastric varices.

BACKGROUND: Gastric venous bleeding is one of the most common adverse events in liver cirrhosis. The therapeutic effect of isolated gastric varices is relatively clear. However, there is no appropriate clinical and endoscopic treatment for extensive variceal bleeding in the gastric fundus and body. METHODS: In this patient with non-isolated gastric varices, we decided to perform endoscopic multi-point ligation of the obvious varices in the gastric fundus and body. RESULTS: In this patient, endoscopic treatment of gastric varices with bleeding after surgery achieved a significant therapeutic effect. Reexamination of gastroscopy at 3 months after operation showed that multiple scars were formed in the gastric fundus and fundus, and no obvious varices were found. CONCLUSIONS: For patients with non-isolated gastric varices, endoscopic multi-point ligation is a safe and effective treatment option for the varices with obvious gastric fundus and body.

An unpredictable gastrointestinal bleed.

A 65-year-old male complained of persistent melena for 6 days, and displayed anemia symptoms without hematemesis, vomiting, and abdominal distention. He was diagnosed as ruptured aneurysm of aortic sinus Valsalva, and had received coronary artery occlusion 1 month ago. After the operation, he was continually prescribed clopidogrel 75 mg once daily. The laboratory examination showed blood hemoglobin concentration was 60 g/L without other conspicuous abnormality. Unfortunately, neither esophagogastroduodenoscopy (EGD) nor colonoscopy found no obvious bleeding lesions. And abdominal computed tomography angiography (CTA) and enhanced computed tomography (CT) showed no obvious abnormal findings. Moreover, capsule endoscopy revealed small intestinal with mucosal erosion (Figure 1A). After discontinued clopidogrel, blood transfusion, and support therapy, his symptoms was resolved with negative fecal occult blood, continued clopidogrel 75 mg once daily, and uneventfully discharged 1 week later.

A ghost epigastric pain.

A 16-year-old woman complained of intermittent epigastric pain for one year. The gastroscopy, colonoscopy and laboratory findings were normal. Physical examination was unremarkable other than upper abdominal tenderness. The symptom was not relieved in past medical treatment. The abdominal computed tomography (CT) scan revealed appendix wall swelling and suspected appendicitis. Endoscopic retrograde appendicitis therapy (ERAT) with eyeMax (Micro-tech, China) was proposed to perform after informed consent obtained. A colonoscopy with a transparent cap (Olympus, Japan) attached to the tip was inserted into the cecum, and advanced the level of appendicular orifice. Subsequently, the Gerlach's valve was pushed aside using the transparent cap. Finally, the eyeMax was placed in the appendicular orifice, slowly moved forward in appendicular lumen. The eyeMax showed a lot of appendicular stones, and irrigated repeatedly. The stones were expulsed smoothly. The patient was discharged two days later without recurrent epigastric pain on follow-up and to date.

Successful removal of a duodenal lesion in difficult location using "a sandwich method".

A 69-year-old woman was diagnosed with a duodenal adenoma near major duodenal papilla during cancer screening examination (Figure 1A). Therefore, endoscopic mucosal resection (EMR) was proposed to remove the duodenal lesion. Unfortunately, satisfactory visualization of the duodenal lesion was not obtained during gastroscopic operation. Unexpectedly, duodenoscopy provided optimal visualization of the duodenal lesion. Consequently, the "sandwich method" using duodenoscopy-gastroscopy-duodenoscopy was successfully performed to remove the challenging duodenal lesion. Firstly, the duodenoscopy was used to create a submucosal bleb through injecting saline containing 0.3 % indigo carmine. Subsequently, the gastroscopy with a transparent capwas used to remove the duodenal lesion with en bloc resection. Then, the duodenoscopy was reused to close the mucosal defect. Finally, pathologic examination showed a tubule-villous adenoma. The patient was recovered uneventfully, and discharged 2 days later.

Identification and characterization of a novel hydroxylamine oxidase, DnfA, that catalyzes the oxidation of hydroxylamine to N2.

Nitrogen (N2) gas in the atmosphere is partially replenished by microbial denitrification of ammonia. Recent study has shown that Alcaligenes ammonioxydans oxidizes ammonia to dinitrogen via a process featuring the intermediate hydroxylamine, termed "Dirammox" (direct ammonia oxidation). However, the unique biochemistry of this process remains unknown. Here, we report an enzyme involved in Dirammox that catalyzes the conversion of hydroxylamine to N2. We tested previously annotated proteins involved in redox reactions, DnfA, DnfB, and DnfC, to determine their ability to catalyze the oxidation of ammonia or hydroxylamine. Our results showed that none of these proteins bound to ammonia or catalyzed its oxidation; however, we did find DnfA bound to hydroxylamine. Further experiments demonstrated that, in the presence of NADH and FAD, DnfA catalyzed the conversion of 15N-labeled hydroxylamine to 15N2. This conversion did not happen under oxygen (O2)-free conditions. Thus, we concluded that DnfA encodes a hydroxylamine oxidase. We demonstrate that DnfA is not homologous to any known hydroxylamine oxidoreductases and contains a diiron center, which was shown to be involved in catalysis via electron paramagnetic resonance experiments. Furthermore, enzyme kinetics of DnfA were assayed, revealing a Km of 92.9 ± 3.0 µM for hydroxylamine and a kcat of 0.028 ± 0.001 s-1. Finally, we show that DnfA was localized in the cytoplasm and periplasm as well as in tubular membrane invaginations in HO-1 cells. To the best of our knowledge, we conclude that DnfA is the first enzyme discovered that catalyzes oxidation of hydroxylamine to N2.

Chemoreceptors from the commensal gut Roseburia rectibacter bind to mucin and trigger chemotaxis.

Chemotaxis is crucial for bacterial adherence and colonization of the host gastrointestinal tract. Previous studies have demonstrated that chemotaxis affects the virulence of causative pathogens and the infection in the host. However, the chemotactic abilities of non-pathogenic and commensal gut bacteria have rarely been explored. We observed that Roseburia rectibacter NSJ-69 exhibited flagella-dependent motility and chemotaxis to a variety of molecules, including mucin and propionate. A genome-wide analysis revealed that NSJ-69 has 28 putative chemoreceptors, 15 of which have periplasmic ligand-binding domains (LBDs). These LBD-coding genes were chemically synthesized and expressed heterologously in Escherichia coli. Intensive screening of ligands revealed four chemoreceptors bound to mucin and two bound to propionate. When expressed in Comamonas testosteroni or E. coli, these chemoreceptors elicited chemotaxis toward mucin and propionate. Hybrid chemoreceptors were constructed, and results showed that the chemotactic responses to mucin and propionate were dependent on the LBDs of R. rectibacter chemoreceptors. Our study identified and characterized R. rectibacter chemoreceptors. These results will facilitate further investigations on the involvement of microbial chemotaxis in host colonization.

Comparative genomics studies on the stk gene family in vertebrates: From the bighead carp (Hypophthalmichthys nobilis) genome.

The mammalian sterile 20-like (MST) family belongs to the serine/threonine protein kinase (STK) superfamily and participates in a variety of biological processes, such as cell apoptosis, polarity, migration, immune regulation, inflammatory responses, and cancer. In the economically important bighead carp (Hypophthalmichthys nobilis), the STK gene family and immune-related biological functions may be helpful in increasing its economic yield. However, the comprehensive role of STKs in the bighead carp remains unclear. In this study, the five stk sequences from the bighead carp were divided into two classes: stk3/4 and stk24/25/26. Gene structure and motif prediction analyses confirmed that stk is conserved in the bighead carp. Compared to 26 other vertebrate species, teleosts (including bighead carp) possess more stk members because of teleost-specific whole-genome duplication. Synteny analysis revealed that stk3, stk24, stk25, and stk26 have been relatively conserved in bighead carp during evolution. Meanwhile, stk4 was lost in most Cyprinid species, including bighead carp, during evolution. RNA-seq data revealed that STK expression was associated with various pathogens, and the expression of these STKs (Hnstk3, Hnstk24a, Hnstk24b, Hnstk25, and Hnstk26) was different in seven tissues of bighead carp. In addition, we showed that STK expression levels were dramatically altered in the head kidney and that stk24 was involved in defense against Aeromonas hydrophila. This study provides a molecular basis for the analysis of stk function in bighead carp, and can be used as a reference for further phylogenomics.

Synthesis of α-allenic aldehydes/ketones from homopropargylic alcohols using a visible-light irradiation system.

A visible-light irradiation tandem oxidative aryl migration/carbonyl formation reaction, mediated by K2S2O8 and visible-light photoredox catalysis, has been discovered. The presented transformation provides a straightforward access to important α-allenic aldehyde/ketone derivatives from readily available homopropargylic alcohol derivatives in a regioselective manner of 1,4-aryl shift concomitant with carbonyl formation. The operational simplicity and broad substrate scope demonstrate the great potential of this method for the synthesis of highly functional α-allenic aldehyde/ketone derivatives.

The sulfonamide-resistance dihydropteroate synthase gene is crucial for efficient biodegradation of sulfamethoxazole by Paenarthrobacter species.

Sulfonamide antibiotics (SAs) are serious pollutants to ecosystems and environments. Previous studies showed that microbial degradation of SAs such as sulfamethoxazole (SMX) proceeds via a sad-encoded oxidative pathway, while the sulfonamide-resistant dihydropteroate synthase gene, sul, is responsible for SA resistance. However, the co-occurrence of sad and sul genes, as well as how the sul gene affects SMX degradation, was not explored. In this study, two SMX-degrading bacterial strains, SD-1 and SD-2, were cultivated from an SMX-degrading enrichment. Both strains were Paenarthrobacter species and were phylogenetically identical; however, they showed different SMX degradation activities. Specifically, strain SD-1 utilized SMX as the sole carbon and energy source for growth and was a highly efficient SMX degrader, while SD-2 did could not use SMX as a sole carbon or energy source and showed limited SMX degradation when an additional carbon source was supplied. Genome annotation, growth, enzymatic activity tests, and metabolite detection revealed that strains SD-1 and SD-2 shared a sad-encoded oxidative pathway for SMX degradation and a pathway of protocatechuate degradation. A new sulfonamide-resistant dihydropteroate synthase gene, sul918, was identified in strain SD-1, but not in SD-2. Moreover, the lack of sul918 resulted in low SMX degradation activity in strain SD-2. Genome data mining revealed the co-occurrence of sad and sul genes in efficient SMX-degrading Paenarthrobacter strains. We propose that the co-occurrence of sulfonamide-resistant dihydropteroate synthase and sad genes is crucial for efficient SMX biodegradation. KEY POINTS: • Two sulfamethoxazole-degrading strains with distinct degrading activity, Paenarthrobacter sp. SD-1 and Paenarthrobacter sp. SD-2, were isolated and identified. • Strains SD-1 and SD-2 shared a sad-encoded oxidative pathway for SMX degradation. • A new plasmid-borne SMX resistance gene (sul918) of strain SD-1 plays a crucial role in SMX degradation efficiency.