GolpHCat (TMEM87A), a unique voltage-dependent cation channel in Golgi apparatus, contributes to Golgi-pH maintenance and hippocampus-dependent memory.

Impaired ion channels regulating Golgi pH lead to structural alterations in the Golgi apparatus, such as fragmentation, which is found, along with cognitive impairment, in Alzheimer's disease. However, the causal relationship between altered Golgi structure and cognitive impairment remains elusive due to the lack of understanding of ion channels in the Golgi apparatus of brain cells. Here, we identify that a transmembrane protein TMEM87A, renamed Golgi-pH-regulating cation channel (GolpHCat), expressed in astrocytes and neurons that contributes to hippocampus-dependent memory. We find that GolpHCat displays unique voltage-dependent currents, which is potently inhibited by gluconate. Additionally, we gain structural insights into the ion conduction through GolpHCat at the molecular level by determining three high-resolution cryogenic-electron microscopy structures of human GolpHCat. GolpHCat-knockout mice show fragmented Golgi morphology and altered protein glycosylation and functions in the hippocampus, leading to impaired spatial memory. These findings suggest a molecular target for Golgi-related diseases and cognitive impairment.

A dual role of the conserved PEX19 helix in safeguarding peroxisomal membrane proteins.

Accurate localization of membrane proteins is essential for proper cellular functioning and the integrity of cellular membranes. Post-translational targeting of peroxisomal membrane proteins (PMPs) is mediated by the cytosolic chaperone PEX19 and its membrane receptor PEX3. However, the molecular mechanisms underlying PMP targeting are poorly understood. Here, using biochemical and mass spectrometry analysis, we find that a conserved PEX19 helix, αd, is critical to prevent improper exposure of the PEX26 transmembrane domain (TMD) to cytosolic chaperones. Furthermore, the αd helix of PEX19 interacts with the cytosolic domain of the PEX3 receptor, thereby triggering PEX26 release at the correct destination membrane. The peroxisome-deficient PEX3-G138E mutant completely abolishes this secondary interaction, leading to lack of PEX3-induced PEX26 release from PEX19. These findings elucidate a dual molecular mechanism that is essential to membrane protein protection and destination-specific release by a molecular chaperone.

Atomically accurate de novo design of single-domain antibodies.

Despite the central role that antibodies play in modern medicine, there is currently no way to rationally design novel antibodies to bind a specific epitope on a target. Instead, antibody discovery currently involves time-consuming immunization of an animal or library screening approaches. Here we demonstrate that a fine-tuned RFdiffusion network is capable of designing de novo antibody variable heavy chains (VHH's) that bind user-specified epitopes. We experimentally confirm binders to four disease-relevant epitopes, and the cryo-EM structure of a designed VHH bound to influenza hemagglutinin is nearly identical to the design model both in the configuration of the CDR loops and the overall binding pose.

[Analysis of Short-Term Results after Introduction of Robotic Gastrectomy for Gastric Cancer at Our Hospital].

BACKGROUND: Robotic gastrectomy(RG)for gastric cancer(GC)has been covered by health insurance since 2018. In this study, we examined the results of RG for GC at our hospital during the initial period of its introduction. MATERIALS AND METHOD: From August 2022 to May 2023, we retrospectively examined the surgical outcomes and short-term postoperative outcomes of the first 9 patients who underwent RG for GC at our hospital. RESULTS: The median patient age was 77(67-82) years, gender was 4 males and 5 females, and distal gastrectomy was performed in all patients. The median operative time was 410(323-486)min, blood loss was 5(1-140)mL, postoperative hospital stay was less than 9 days in all patients, and there was no conversion to laparoscopic or open surgery. There were no postoperative complications of Clavien-Dindo Grade Ⅱ or above. CONCLUSION: In this study, RG for GC was performed safely without intraoperative or postoperative complications.

De novo design of protein minibinder agonists of TLR3.

Toll-like Receptor 3 (TLR3) is a pattern recognition receptor that initiates antiviral immune responses upon binding double-stranded RNA (dsRNA). Several nucleic acid-based TLR3 agonists have been explored clinically as vaccine adjuvants in cancer and infectious disease, but present substantial manufacturing and formulation challenges. Here, we use computational protein design to create novel miniproteins that bind to human TLR3 with nanomolar affinities. Cryo-EM structures of two minibinders in complex with TLR3 reveal that they bind the target as designed, although one partially unfolds due to steric competition with a nearby N-linked glycan. Multimeric forms of both minibinders induce NF-κB signaling in TLR3-expressing cell lines, demonstrating that they may have therapeutically relevant biological activity. Our work provides a foundation for the development of specific, stable, and easy-to-formulate protein-based agonists of TLRs and other pattern recognition receptors.

Polymorphic Self-Assembly with Procedural Flexibility for Monodisperse Quaternary Protein Structures of DegQ Enzymes.

As large molecular tertiary structures, some proteins can act as small robots that find, bind, and chaperone target protein clients, showing the potential to serve as smart building blocks in self-assembly fields. Instead of using such intrinsic functions, most self-assembly methodologies for proteins aim for de novo-designed structures with accurate geometric assemblies, which can limit procedural flexibility. Here, a strategy enabling polymorphic clustering of quaternary proteins, exhibiting simplicity and flexibility of self-assembling paths for proteins in forming monodisperse quaternary cage particles is presented. It is proposed that the enzyme protomer DegQ, previously solved at low resolution, may potentially be usable as a threefold symmetric building block, which can form polyhedral cages incorporated by the chaperone action of DegQ in the presence of protein clients. To obtain highly monodisperse cage particles, soft, and hence, less resistive client proteins, which can program the inherent chaperone activity of DegQ to efficient formations of polymorphic cages, depending on the size of clients are utilized. By reconstructing the atomic resolution cryogenic electron microscopy DegQ structures using obtained 12- and 24-meric clusters, the polymorphic clustering of DegQ enzymes is validated in terms of soft and rigid domains, which will provide effective routes for protein self-assemblies with procedural flexibility.

Ginsenoside F2 Restrains Hepatic Steatosis and Inflammation by Altering the Binding Affinity of Liver X Receptor Coregulators.

Background: Ginsenoside F2 (GF2), the protopanaxadiol-type constituent in Panax ginseng, has been reported to attenuate metabolic dysfunction-associated steatotic liver disease (MASLD). However, the mechanism of action is not fully understood. Here, this study investigates the molecular mechanism by which GF2 regulates MASLD progression through liver X receptor (LXR). Methods: To demonstrate the effect of GF2 on LXR activity, computational modeling of protein-ligand binding, Time-resolved fluorescence resonance energy transfer (TR-FRET) assay for LXR cofactor recruitment, and luciferase reporter assay were performed. LXR agonist T0901317 was used for LXR activation in hepatocytes and macrophages. MASLD was induced by high-fat diet (HFD) feeding with or without GF2 administration in WT and LXRα-/- mice. Results: Computational modeling showed that GF2 had a high affinity with LXRα. LXRE-luciferase reporter assay with amino acid substitution at the predicted ligand binding site revealed that the S264 residue of LXRα was the crucial interaction site of GF2. TR-FRET assay demonstrated that GF2 suppressed LXRα activity by favoring the binding of corepressors to LXRα while inhibiting the accessibility of coactivators. In vitro, GF2 treatments reduced T0901317-induced fat accumulation and pro-inflammatory cytokine expression in hepatocytes and macrophages, respectively. Consistently, GF2 administration ameliorated hepatic steatohepatitis and improved glucose or insulin tolerance in WT but not in LXRα-/- mice. Conclusion: GF2 alters the binding affinities of LXRα coregulators, thereby interrupting hepatic steatosis and inflammation in macrophages. Therefore, we propose that GF2 might be a potential therapeutic agent for the intervention in patients with MASLD.

[A Case of Sigmoid Rectal Cancer with a Vesicoconstrictor Fistula Curatively Resected after Neoadjuvant Chemotherapy].

A 50-year-old man presented with fecaluria and was diagnosed with sigmoid colon cancer with a colovesical fistula. Total bladder resection was determined to be necessary for curative resection at the time of diagnosis. In anticipation of bladder preservation, 6 courses of mFOLFOX6 plus panitumumab were administered after transverse colostomy, resulting in marked tumor regression and a decision to proceed with surgery. The patient underwent robotic-assisted low anterior resection of the rectum and partial cystectomy, which yielded pathological radical treatment. We report a case of sigmoid colon cancer with a colovesical fistula complicated by bladder invasion, in which preoperative chemotherapy was effective and total cystectomy was avoided, allowing bladder preservation.

[A Rare Case of Advanced Gastric Cancer with Duodenal Intramural Metastasis].

Here we report the case of a patient with advanced gastric cancer who presented with duodenal intramural metastasis based on the pathological results after surgery. The patient was 78-year-old female, who was referred to our department for further evaluation and treatment of upper abdominal pain. An upper gastrointestinal series demonstrated a tumor occupying the lesser curvature of the gastric body. Biopsy specimens from the tumor demonstrated moderately to poorly differentiated adenocarcinoma. A computed tomography scan showed thickening of the gastric wall and swelling of the regional lymph nodes. The patient underwent distal gastrectomy and D2 lymph node dissection for gastric cancer. A histopathological examination disclosed that the gastric tumor was poorly differentiated adenocarcinoma with severe lymphatic permeation and also demonstrated the other poorly differentiated adenocarcinoma occupying the part of the muscularis propria layer of the duodenum. The gastric tumor was not contiguous with the duodenal tumor, and the duodenal cancer cells had the same pathological characteristics as the primary gastric cancer cells; therefore, we diagnosed the duodenal tumor as an intramural metastasis from gastric cancer. The patient's disease was staged as pT4aN3bM1, Stage Ⅳ according to the TNM classification. We report this rare case along with a discussion of the literature.