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Zinc transporters take up/release zinc ions (Zn2+) across biological membranes and maintain intracellular and intra-organellar Zn2+ homeostasis. Since this process requires a series of conformational changes in the transporters, detailed information about the structures of different reaction intermediates is required for a comprehensive understanding of their Zn2+ transport mechanisms. Recently, various Zn2+ transport systems have been identified in bacteria, yeasts, plants, and humans. Based on structural analyses of human ZnT7, human ZnT8, and bacterial YiiP, we propose updated models explaining their mechanisms of action to ensure efficient Zn2+ transport. We place particular focus on the mechanistic roles of the histidine-rich loop shared by several zinc transporters, which facilitates Zn2+ recruitment to the transmembrane Zn2+-binding site. This review provides an extensive overview of the structures, mechanisms, and physiological functions of zinc transporters in different biological kingdoms.

Time-resolved direct observations of proteins in action provide essential mechanistic insights into biological processes. Here, we present mechanisms of action of protein disulfide isomerase (PDI)—the most versatile disulfide-introducing enzyme in the endoplasmic reticulum—during the catalysis of oxidative protein folding. Single-molecule analysis by high-speed atomic force microscopy revealed that oxidized PDI is in rapid equilibrium between open and closed conformations, whereas reduced PDI is maintained in the closed state. In the presence of unfolded substrates, oxidized PDI, but not reduced PDI, assembles to form a face-to-face dimer, creating a central hydrophobic cavity with multiple redox-active sites, where substrates are likely accommodated to undergo accelerated oxidative folding. Such PDI dimers are diverse in shape and have different lifetimes depending on substrates. To effectively guide proper oxidative protein folding, PDI regulates conformational dynamics and oligomeric states in accordance with its own redox state and the configurations or folding states of substrates. Single-molecule analysis by high-speed atomic force microscopy reveals that oxidized protein disulfide isomerase adopts a dynamic conformation in the absence of substrates and forms face-to-face dimers to accelerate oxidative folding in the presence of substrates.

Complicated and sophisticated protein homeostasis (proteostasis) networks in the endoplasmic reticulum (ER), comprising disulfide catalysts, molecular chaperones, and their regulators, help to maintain cell viability. Newly synthesized proteins inserted into the ER need to fold and assemble into unique native structures to fulfill their physiological functions, and this is assisted by protein disulfide isomerase (PDI) family. Herein, we focus on recent advances in understanding the detailed mechanisms of PDI family members as guides for client folding and assembly to ensure the efficient production of secretory proteins.

Zinc ions (Zn 2+ ) are imported into the early secretory pathway by Golgi-resident transporters, but their handling and functions are not fully understood. Here, we show that Zn 2+ binds with high affinity to the pH-sensitive chaperone ERp44, modulating its localization and ability to retrieve clients like Ero1α and ERAP1 to the endoplasmic reticulum (ER). Silencing the Zn 2+ transporters that uptake Zn 2+ into the Golgi led to ERp44 dysfunction and increased secretion of Ero1α and ERAP1. High-resolution crystal structures of Zn 2+ -bound ERp44 reveal that Zn 2+ binds to a conserved histidine-cluster. The consequent large displacements of the regulatory C-terminal tail expose the substrate-binding surface and RDEL motif, ensuring client capture and retrieval. ERp44 also forms Zn 2+ -bridged homodimers, which dissociate upon client binding. Histidine mutations in the Zn 2+ -binding sites compromise ERp44 activity and localization. Our findings reveal a role of Zn 2+ as a key regulator of protein quality control at the ER-Golgi interface. Zinc ions (Zn 2+ ) are imported by Golgi-resident transporters but the function of zinc in the early secretory pathway has remained unknown. Here the authors find that Zn 2+ regulates protein quality control in the early secretory pathway by demonstrating that the pH-sensitive chaperone ERp44 binds Zn 2+ and solving the Zn 2+ -bound ERp44 structure.

Background Hypocalcemia is cited as a complication of massive transfusion. However, this is not well studied as a primary outcome in trauma patients. Our primary outcome was to determine if transfusion of packed red blood cells (pRBC) was an independent predictor of severe hypocalcemia (ionized calcium ≤ 3.6 mg/dL). Methods Retrospective, single-center study (01/2004–12/2014) including all trauma patients ≥ 18 yo presenting to the ED with an ionized calcium (iCa) level drawn. Variables extracted included demographics, interventions, outcomes, and iCa. Regression models identified independent risk factors for severe hypocalcemia (SH). Results Seven thousand four hundred and thirty-one included subjects, 716 (9.8%) developed SH within 48 h of admission. Median age: 39 (Range: 18–102), systolic blood pressure: 131 (IQR: 114–150), median Glasgow Coma Scale (GCS): 15 (IQR: 10–15), Injury Severity Score (ISS): 14 (IQR: 9–24). SH patients were more likely to have depressed GCS (13 vs 15, p  < 0.0001), hypotension (23.2% vs 5.1%, p  < 0.0001) and tachycardia (57.0% vs 41.9%, p  < 0.0001) compared to non-SH patients. They also had higher emergency operative rate (71.8% vs 29%, p  < 0.0001) and higher blood administration prior to minimum iCa [pRBC: (8 vs 0, p  < 0.0001), FFP: (4 vs 0, p  < 0.0001), platelet: (1 vs 0, p  < 0.0001)]. Multivariable analysis revealed penetrating mechanism (AOR: 1.706), increased ISS (AOR: 1.029), and higher pRBC (AOR: 1.343) or FFP administered (AOR: 1.097) were independent predictors of SH. SH was an independent predictor of mortality (AOR: 2.658). Regression analysis identified a significantly higher risk of SH at pRBC + FFP administration of 4 units (AOR: 18.706, AUC:. 897 (0.884–0.909). Conclusion Transfusion of pRBC is an independent predictor of SH and is associated with increased mortality. The predicted probability of SH increases as pRBC + FFP administration increases.

Cysteine hydropersulfide (CysSSH) occurs in abundant quantities in various organisms, yet little is known about its biosynthesis and physiological functions. Extensive persulfide formation is apparent in cysteine-containing proteins in Escherichia coli and mammalian cells and is believed to result from post-translational processes involving hydrogen sulfide-related chemistry. Here we demonstrate effective CysSSH synthesis from the substrate l-cysteine, a reaction catalyzed by prokaryotic and mammalian cysteinyl-tRNA synthetases (CARSs). Targeted disruption of the genes encoding mitochondrial CARSs in mice and human cells shows that CARSs have a crucial role in endogenous CysSSH production and suggests that these enzymes serve as the principal cysteine persulfide synthases in vivo. CARSs also catalyze co-translational cysteine polysulfidation and are involved in the regulation of mitochondrial biogenesis and bioenergetics. Investigating CARS-dependent persulfide production may thus clarify aberrant redox signaling in physiological and pathophysiological conditions, and suggest therapeutic targets based on oxidative stress and mitochondrial dysfunction.

ERGIC-53 transports certain subsets of newly synthesized secretory proteins and membrane proteins from the endoplasmic reticulum to the Golgi apparatus. Despite numerous structural and functional studies since its identification, the overall architecture and mechanism of action of ERGIC-53 remain unclear. Here we present cryo-EM structures of full-length ERGIC-53 in complex with its functional partner MCFD2. These structures reveal that ERGIC-53 exists as a homotetramer, not a homohexamer as previously suggested, and comprises a four-leaf clover-like head and a long stalk composed of three sets of four-helix coiled-coil followed by a transmembrane domain. 3D variability analysis visualizes the flexible motion of the long stalk and local plasticity of the head region. Notably, MCFD2 is shown to possess a Zn 2+ -binding site in its N-terminal lid, which appears to modulate cargo binding. Altogether, distinct mechanisms of cargo capture and release by ERGIC- 53 via the stalk bending and metal binding are proposed. ERGIC-53 engages in the ER-to-Golgi transport of secretory and membrane proteins by unknown mechanisms. Here authors report a long flexible tetrameric structure of full-length ERGIC-53 complexed with its functional partner MCFD2 by cryo-EM.

BackgroundSince 2007, clinical practice guidelines by the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) recommend early surgical management with laparoscopic cholecystectomy for pregnant women with symptomatic gallbladder disease regardless of trimester. However, little is known about practice patterns in the management of pregnant patients with acute cholecystitis. This study aims to examine nationwide trends in the surgical management of acute cholecystitis, as well as their impact on clinical outcomes during pregnancy.MethodsThe National Inpatient Sample was queried for all pregnant women diagnosed with acute cholecystitis between January 2003 and September 2015. After applying appropriate weights, multivariate regression analysis adjusted for patient- and hospital-level characteristics and quantified the impact of discharge year (2003–2007 versus 2008–2015) on cholecystectomy rates and timing of surgery. Multivariate regression analysis was also used to examine the impact of same admission cholecystectomy and its timing on maternal and fetal outcomes.ResultsA total of 23,939 pregnant women with acute cholecystitis satisfied our inclusion criteria. The median age was 26 years (interquartile range: 22–30). During the study period, 36.3% were managed non-operatively while 59.6% and 4.1% underwent laparoscopic and open cholecystectomy, respectively. After adjusting for covariates, laparoscopic cholecystectomy was more commonly performed after 2007 (odds ratio [OR] 1.333, p < 0.001). Furthermore, time from admission to surgery was significantly shorter in the latter study period (regression coefficient -0.013, p < 0.001). Compared to non-operative management, laparoscopic cholecystectomy for acute cholecystitis was significantly associated with lower rates of preterm delivery, labor, or abortion (OR 0.410, p < 0.001). Each day that laparoscopic cholecystectomy was delayed significantly associated with an increased risk of fetal complications (OR 1.173, p < 0.001).ConclusionsThis nationwide study exhibits significant trends favoring surgical management of acute cholecystitis during pregnancy. Although further studies are still warranted, early laparoscopic cholecystectomy should be considered in pregnant patients with acute cholecystitis.

Postoperative adhesions are a significant health problem with major implications on quality of life and health care expenses. The purpose of this review was to investigate the efficacy of preventative techniques and adhesion barriers and identify those patients who are most likely to benefit from these strategies. The National Library of Medicine, Medline, Embase, and Cochrane databases were used to identify articles related to postoperative adhesions. Ileal pouch–anal anastomosis, open colectomy, and open gynecologic procedures are associated with the highest risk of adhesive small-bowel obstruction (class I evidence). Based on expert opinion (class III evidence) intraoperative preventative principles, such as meticulous hemostasis, avoiding excessive tissue dissection and ischemia, and reducing remaining surgical material have been published. Laparoscopic techniques, with the exception of appendicitis, result in fewer adhesions than open techniques (class I evidence). Available bioabsorbable barriers, such as hyaluronic acid/carboxymethylcellulose and icodextrin 4% solution, have been shown to reduce adhesions (class I evidence). Postoperative adhesions are a significant health problem with major implications on quality of life and health care. General intraoperative preventative techniques, laparoscopic techniques, and the use of bioabsorbable mechanical barriers in the appropriate cases reduce the incidence and severity of peritoneal adhesions.

In this issue of Trauma Surgery & Acute Care Open, Omoto et al report a retrospective multicenter study of adult blunt trauma patients with Gustilo-Anderson type IIIB or IIIC open extremity fractures treated between 2013 and 2024 in two tertiary care centers in Japan.3 In this cohort, a MESS≥8 was found to be a more appropriate threshold to predict amputation, demonstrating increased specificity compared with MESS≥7. Strengths of the study include examination of each factor in the MESS and subgroup analysis of immediate versus delayed amputations. Retrospectively applying the MESS to a cohort in which MESS may not have factored into management decisions is also an important limitation.