Identification of the potassium-binding site in serotonin transporter.

Clearance of serotonin (5-hydroxytryptamine, 5-HT) from the synaptic cleft after neuronal signaling is mediated by serotonin transporter (SERT), which couples this process to the movement of a Na+ ion down its chemical gradient. After release of 5-HT and Na+ into the cytoplasm, the transporter faces a rate-limiting challenge of resetting its conformation to be primed again for 5-HT and Na+ binding. Early studies of vesicles containing native SERT revealed that K+ gradients can provide an additional driving force, via K+ antiport. Moreover, under appropriate conditions, a H+ ion can replace K+. Intracellular K+ accelerates the resetting step. Structural studies of SERT have identified two binding sites for Na+ ions, but the K+ site remains enigmatic. Here, we show that K+ antiport can drive substrate accumulation into vesicles containing SERT extracted from a heterologous expression system, allowing us to study the residues responsible for K+ binding. To identify candidate binding residues, we examine many cation binding configurations using molecular dynamics simulations, predicting that K+ binds to the so-called Na2 site. Site-directed mutagenesis of residues in this site can eliminate the ability of both K+ and H+ to drive 5-HT accumulation into vesicles and, in patch clamp recordings, prevent the acceleration of turnover rates and the formation of a channel-like state by K+ or H+. In conclusion, the Na2 site plays a pivotal role in orchestrating the sequential binding of Na+ and then K+ (or H+) ions to facilitate 5-HT uptake in SERT.

Enhancing osteogenic differentiation of diabetic tendon stem/progenitor cells through hyperoxia: Unveiling ROS/HIF-1α signalling axis.

Diabetic calcific tendinopathy is the leading cause of chronic pain, mobility restriction, and tendon rupture in patients with diabetes. Tendon stem/progenitor cells (TSPCs) have been implicated in the development of diabetic calcified tendinopathy, but the molecular mechanisms remain unclear. This study found that diabetic tendons have a hyperoxic environment, characterized by increased oxygen delivery channels and carriers. In hyperoxic environment, TSPCs showed enhanced osteogenic differentiation and increased levels of reactive oxygen species (ROS). Additionally, hypoxia-inducible factor-1a (HIF-1a), a protein involved in regulating cellular responses to hyperoxia, was decreased in TSPCs by the ubiquitin-proteasome system. By intervening with antioxidant N-acetyl-L-cysteine (NAC) and overexpressing HIF-1a, we discovered that blocking the ROS/HIF-1a signalling axis significantly inhibited the osteogenic differentiation ability of TSPCs. Animal experiments further confirmed that hyperoxic environment could cause calcification in the Achilles tendon tissue of rats, while NAC intervention prevented calcification. These findings demonstrate that hyperoxia in diabetic tendons promotes osteogenic differentiation of TSPCs through the ROS/HIF-1a signalling axis. This study provides a new theoretical basis and research target for preventing and treating diabetic calcified tendinopathy.

Chloride-dependent conformational changes in the GlyT1 glycine transporter.

The human GlyT1 glycine transporter requires chloride for its function. However, the mechanism by which Cl- exerts its influence is unknown. To examine the role that Cl- plays in the transport cycle, we measured the effect of Cl- on both glycine binding and conformational changes. The ability of glycine to displace the high-affinity radioligand [3H]CHIBA-3007 required Na+ and was potentiated over 1,000-fold by Cl- We generated GlyT1b mutants containing reactive cysteine residues in either the extracellular or cytoplasmic permeation pathways and measured changes in the reactivity of those cysteine residues as indicators of conformational changes in response to ions and substrate. Na+ increased accessibility in the extracellular pathway and decreased it in the cytoplasmic pathway, consistent with stabilizing an outward-open conformation as observed in other members of this transporter family. In the presence of Na+, both glycine and Cl- independently shifted the conformation of GlyT1b toward an outward-closed conformation. Together, Na+, glycine, and Cl- stabilized an inward-open conformation of GlyT1b. We then examined whether Cl- acts by interacting with a conserved glutamine to allow formation of an ion pair that stabilizes the closed state of the extracellular pathway. Molecular dynamics simulations of a GlyT1 homolog indicated that this ion pair is formed more frequently as that pathway closes. Mutation of the glutamine blocked the effect of Cl-, and substituting it with glutamate or lysine resulted in outward- or inward-facing transporter conformations, respectively. These results provide an unexpected insight into the role of Cl- in this family of transporters.

Efficacy and safety of tranexamic acid in elderly patients with femoral neck fracture treated with hip arthroplasty: A systematic review and meta-analysis.

BACKGROUND: Elderly patients with femoral neck fracture have high perioperative blood loss according to the trauma and hip arthroplasty surgery. Tranexamic acid is a fibrinolytic inhibitor and has been widely used in hip fracture patients to against perioperative anemia. The aim of the present meta-analysis was to evaluate the efficacy and safety of Tranexamic acid (TXA) in elderly patients with femoral neck fracture undergoing hip arthroplasty. METHODS: We performed search using Pubmed, EMBASE, Cochrane Reviews, and Web of Science databases to identify all relevant research studies published from inception to June 2022. Randomized controlled studies and high-quality cohort studies that reported the perioperative use of TXA in patients with femoral neck fractures treated with arthroplasty, and made a comparison with the control group were included. Meta-analysis was performed using Review Manager 5.3 to assess the efficacy and safety of TXA. Subgroup analysis was conducted to further investigate the impact caused by surgery types and administration routes on the efficacy and safety outcomes. RESULTS: Five randomized controlled trials (RCTs) and eight cohort studies published from January 2015 to June 2022 were included in this meta-analysis. The results showed significant reductions in the rate of allogeneic blood transfusion, total blood loss (TBL) and postoperative hemoglobin (Hb) drop in the TXA group compared with the control group, while no significant difference was found in the intraoperative blood loss, postoperative drainage, hospital length of stay (LOS), re-admission rate, and wound complications between the two groups. The incidence of thromboembolic events and mortality showed no significant difference. Subgroup analysis indicated that surgery types and administration routes did not change the overall tendency. CONCLUSION: The current evidence shows that both intravascular administration (IV) and topical administration of TXA can significantly decrease the perioperative transfusion rate and TBL without increasing the risk of thromboembolic complications in elderly patients with femoral neck fracture.

A Conserved Intramolecular Ion-Pair Plays a Critical but Divergent Role in Regulation of Dimerization and Transport Function among the Monoamine Transporters.

The monoamine transporters, including the serotonin transporter (SERT), dopamine transporter (DAT), and norepinephrine transporter (NET), are the therapeutic targets for the treatment of many neuropsychiatric disorders. Despite significant progress in characterizing the structures and transport mechanisms of these transporters, the regulation of their transport functions through dimerization or oligomerization remains to be understood. In the present study, we identified a conserved intramolecular ion-pair at the third extracellular loop (EL3) connecting TM5 and TM6 that plays a critical but divergent role in the modulation of dimerization and transport functions among the monoamine transporters. The disruption of the ion-pair interactions by mutations induced a significant spontaneous cross-linking of a cysteine mutant of SERT and an increase in cell surface expression but with an impaired specific transport activity. On the other hand, similar mutations of the corresponding ion-pair residues in both DAT and NET resulted in an opposite effect on their oxidation-induced dimerization, cell surface expression, and transport function. Reversible biotinylation experiments indicated that the ion-pair mutations slowed down the internalization of SERT but stimulated the internalization of DAT. In addition, cysteine accessibility measurements for monitoring SERT conformational changes indicated that substitution of the ion-pair residues resulted in profound effects on the rate constants for cysteine modification in both the extracellular and cytoplasmatic substrate permeation pathways. Furthermore, molecular dynamics simulations showed that the ion-pair mutations increased the interfacial interactions in a SERT dimer but decreased it in a DAT dimer. Taken together, we propose that the transport function is modulated by the equilibrium between monomers and dimers on the cell surface, which is regulated by a potential compensatory mechanism but with different molecular solutions among the monoamine transporters. The present study provided new insights into the structural elements regulating the transport function of the monoamine transporters through their dimerization.

Dislocations deteriorate postoperative functional outcomes in supination-external rotation ankle fractures.

PURPOSE: To assess the relationship between dislocation and functional outcomes in supination-external rotation (SER) ankle fractures. METHODS: A retrospective case series study was performed on patients with ankle fractures treated surgically at a large trauma center from January 2015 to December 2021. The inclusion criteria were young and middle-aged patients of 18-65 years with SER ankle fractures that can be classified by Lauge-Hansen classification and underwent surgery at our trauma center. Exclusion criteria were serious life-threatening diseases, open fractures, fractures delayed for more than 3 weeks, fracture sites ≥2, etc. Then patients were divided into dislocation and no-dislocation groups. Patient demographics, injury characteristics, surgery-related outcomes, and postoperative functional outcomes were collected and analyzed. The functional outcomes of SER ankle fractures were assessed postoperatively at 1-year face-to-face follow-up using the foot and ankle outcome score (FAOS) and American orthopedic foot and ankle society score and by 2 experienced orthopedic physicians. Relevant data were analyzed using SPSS version 22.0 by Chi-square or t-test. RESULTS: During the study period, there were 371 ankle fractures. Among them, 190 (51.2%) were SER patterns with 69 (36.3%) combined with dislocations. Compared with the no-dislocation group, the dislocation group showed no statistically significant differences in gender, age composition, fracture type, preoperative complications with diabetes, smoking history, preoperative waiting time, operation time, and length of hospital stay (all p > 0.05), but a significantly higher Lauge-Hansen injury grade (p < 0.001) and syndesmotic screw fixation rate (p = 0.033). Moreover, the functional recovery was poorer, revealing a significantly lower FAOS in the sport/rec scale (p < 0.001). Subgroup analysis showed that among SER IV ankle fracture patients, FAOS was much lower in pain (p = 0.042) and sport/rec scales (p < 0.001) for those with dislocations. American orthopedic foot and ankle society score revealed no significant difference between dislocation and no-dislocation patients. CONCLUSION: Dislocation in SER ankle fractures suggests more severe injury and negatively affects functional recovery, mainly manifested as more pain and poorer motor function, especially in SER IV ankle cases.

The regulative effect and repercussion of probiotics and prebiotics on osteoporosis: involvement of brain-gut-bone axis.

Osteoporosis (OP) is a systemic disease characterized by decreased bone mass and degeneration of bone microstructure. In recent years, more and more researches have focused on the close relationship between gut microbiota (GM) and the occurrence and progression of OP, and the regulation of probiotics and prebiotics on bone metabolism has gradually become a research hotspot. Based on the influence of brain-gut-bone axis on bone metabolism, this review expounds the potential mechanisms of probiotics and prebiotics on OP from next perspectives: regulation of intestinal metabolites, regulation of intestinal epithelial barrier function, involvement of neuromodulation, involvement of immune regulation and involvement of endocrine regulation, so as to provide a novel and promising idea for the prevention and treatment of OP in the future.

Linking the relation between gut microbiota and glucocorticoid-induced osteoporosis.

Osteoporosis (OP) is the most prevalent metabolic bone disease, characterized by the low bone mass and microarchitectural deterioration of bone tissue. Glucocorticoid (GC) clinically acts as one of the anti-inflammatory, immune-modulating, and therapeutic drugs, whereas the long-term use of GC may cause rapid bone resorption, followed by prolonged and profound suppression of bone formation, resulting in the GC-induced OP (GIOP). GIOP ranks the first among secondary OP and is a pivotal risk for fracture, as well as high disability rate and mortality, at both societal and personal levels, vital costs. Gut microbiota (GM), known as the "second gene pool" of human body, is highly correlated with maintaining the bone mass and bone quality, and the relation between GM and bone metabolism has gradually become a research hotspot. Herein, combined with recent studies and based on the cross-linking relationship between GM and OP, this review is aimed to discuss the potential mechanisms of GM and its metabolites on the OP, as well as the moderating effects of GC on GM, thereby providing an emerging thought for prevention and treatment of GIOP.

General Anesthesia Versus Regional Anesthesia in the Elderly Patients Undergoing Hip Fracture Surgeries: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.

BACKGROUND: Surgery is the preferred treatment option for the elderly patients with hip fractures. However, the choice of general anesthesia (GA) or regional anesthesia (RA) remains controversial. The quality of evidence has further improved with the advent of several high-quality randomized clinical trials (RCTs) in the last two years. The purpose of this study was to compare the clinical outcomes of two anesthetic techniques in elderly patients undergoing hip fracture surgeries. METHODS: Eligible studies were identified from PubMed/MEDLINE, Web of Science, Scopus, EMBASE and reference lists from January 2000 to June 2022 in this current systematic review and meta-analysis. The outcomes included the surgery-related outcomes (duration of surgery, duration of anesthesia, intraoperative blood loss and number of transfusions) and postoperative outcomes (30-day mortality, postoperative delirium,cardiovascular events and other complications). RESULTS: A total of 10 RCTs were included, and a total of 3594 patients were analyzed. RA was associated with shorter duration of surgery, shorter length of hospital stays and less intraoperative blood loss compared to GA. There were no significant differences between the two groups in the number of blood transfusions, duration of anesthesia, 30-day mortality or postoperative delirium. CONCLUSIONS: Our pooled analysis identified no significant differences in terms of the safety between RA and GA, while RA reduces intraoperative blood loss, length of hospital stays and duration of surgery. These results suggest that RA appears to be preferable for the elderly patients with hip fractures.

Short report: relationship between self-reported sleep characteristics and falls-associated fractures in elderly individuals: a population-based study.

Currently, the data for effect of sleep on falls-associated fractures in elderly individuals are still limited. This current study was aimed to assess the link between self-reported sleep characteristics and falls-associated fractures in elderly individuals. This study included a total of 20,497 participants from National Health and Nutritional Examination Survey (NHANES) 2005-2008, and 6,174 participants aged 45 years and older were identified. Self-reported sleep characteristics and conditions of falls-associated fractures of individuals were obtained via the method of personal questionnaires. In a total of 610 participants with exact history of fractures, 168 individuals with falls-associated fractures were identified, and the prevalence was 27.5%. The mean age of falls-associated fractures group was (72.1 ± 8.8) years, and the female (P < 0.001) occupied a higher proportion. Factors of living alone (P = 0.003), combined with hypertension (P = 0.003) and osteoporosis (P < 0.001), sleeping less or more (P = 0.009), and frequent snoring (P = 0.007) were linked to falls-associated fractures. Compared with sleep duration of 6 to 8 h/night, sleep duration of ≤4 h/night (odds ratio [OR] 1.858, 95% confidence interval [CI] 1.115-3.094) and of ≥9 h/night (OR 1.932, 95% CI 1.195-3.123) were related to an increased risk of falls-associated fractures. Collectively, our nationwide data noted that sleep characteristics were closely related to falls-associated fractures in elderly individuals, and a longer sleep duration may exhibit a protective effect against the falls-associated fractures, but it should be limited within 9 h/night.

Unique Substrate Recognition and Sodium-Substrate Binding Stoichiometry in a Bacterial Serotonin Transporter, TuriSERT.

All resolved high-resolution structures of the transporters in the neurotransmitter sodium symporter (NSS) family revealed that the NSS members share common structural and mechanistic features for substrate and ion binding and transport. However, a recently reported bacterial orthologue of the human serotonin transporter (hSERT), TuriSERT, possesses a structural characteristic specific for amino acid substrate binding but does transport a biogenic amine. The unique structural feature of TuriSERT requires a novel configuration for coordinating its substrate and ions. In the present study, we characterized TuriSERT expressed in Escherichia coli cells with a fluorescent substrate by biochemical, structural, and pharmacological approaches. Substrate transport by TuriSERT requires Na+ but not Cl-. Replacement of Asp262 by asparagine renders TuriSERT Cl--dependent. Substitutions of the corresponding Na1 residues did not alter Na+ dependence on substrate transport, whereas the mutation of a Na2 site residue led to a loss of transport activity, suggesting that Na+ binds only to the Na2 site in TuriSERT. In addition, substitutions of several residues essential for recognizing 5-hydroxytryptamine (5-HT) in hSERT had little effect on 5-HT displacement potency in transport assay for TuriSERT. In contrast, mutations of the residues that are proposed to coordinate with 5-HT in our docking model dramatically reduced 5-HT displacement. Furthermore, our results indicated that all tested antidepressants showed a weak inhibitory effect on TuriSERT. The present study demonstrated the existence of a unique substrate binding site and 1:1 stoichiometry of sodium-substrate binding in TuriSERT, a novel structural finding for the NSS transporters.

A narrative review of the moderating effects and repercussion of exercise intervention on osteoporosis: ingenious involvement of gut microbiota and its metabolites.

Osteoporosis (OP) is a systemic bone disease characterized by the decreased bone mass and destruction of bone microstructure, which tends to result in the enhanced bone fragility and related fractures, as well as high disability rate and mortality. Exercise is one of the most common, reliable and cost-effective interventions for the prevention and treatment of OP currently, and numerous studies have revealed the close association between gut microbiota (GM) and bone metabolism recently. Moreover, exercise can alter the structure, composition and abundance of GM, and further influence the body health via GM and its metabolites, and the changes of GM also depend on the choice of exercise modes. Herein, combined with relevant studies and based on the inseparable relationship between exercise intervention-GM-OP, this review is aimed to discuss the moderating effects and potential mechanisms of exercise intervention on GM and bone metabolism, as well as the interaction between them.

Fecal microbiota transplantation as a promising treatment option for osteoporosis.

Osteoporosis is a systemic metabolic bone disease characterized by the descending bone mass and destruction of bone microstructure, which tends to result in the increased bone fragility and associated fractures, as well as high disability rate and mortality. The relation between gut microbiota and bone metabolism has gradually become a research hotspot, and it has been verified that gut microbiota is closely associated with reduction of bone mass and incidence of osteoporosis recently. As a novel "organ transplantation" technique, fecal microbiota transplantation (FMT) mainly refers to the transplantation of gut microbiota from healthy donors to recipients with gut microbiota imbalance, so that the gut microbiota in recipients can be reshaped and play a normal function, and further prevent or treat the diseases related to gut microbiota disorder. Herein, based on the gut-bone axis and proven regulatory effects of gut microbiota on osteoporosis, this review expounds relevant basic researches and clinical practice of FMT on osteoporosis, thus demonstrating the potentials of FMT as a therapeutic option for osteoporosis and further providing certain reference for the future researches.

The Efficacy and Safety of Intravenous Iron in Geriatric Hip Fracture Surgeries: A Systematic Review and Meta-Analysis.

BACKGROUND: With the increasing evidence provided by recent high-quality studies, the intravenous iron appears to be a reliable therapy for blood administration in geriatric patients with hip fractures. Here, this systematic review and meta-analysis were aimed to assess the effectiveness and safety of intravenous iron in geriatric patients sustaining hip fractures. METHODS: Potential pertinent literatures evaluating the effects of intravenous iron in the geriatric patients undergoing hip fractures were identified from Web of Science, PubMed, Embase, and Scopus. We performed a pairwise meta-analysis using fixed- and random-effects models, and the pooling of data was carried out by using RevMan 5.1. RESULTS: Four randomized controlled trials and four observational studies conform to inclusion criteria. The results of meta-analysis showed that intravenous iron reduced transfusion rates compared to the control group, yet the result did not reach statistical significance. The intravenous iron was related to lower transfusion volumes, shorter length of stay, and a reduced risk of nosocomial infections. And there was no significant difference in terms of the mortality and other complications between the treatment group and the control group. CONCLUSION: Current evidence suggests that intravenous iron reduces the transfusion volume, length of hospital stay, and risk of nosocomial infections. It takes about 7 days for intravenous iron to elevate hemoglobin by 1 g/dl and about 1 month for 2 g/dl. The safety profile of intravenous iron is also reassuring, and additional high-quality studies are needed.

Cross-Linking and Functional Analyses for Dimerization of a Cysteine Mutant of Glycine Transporter 1.

Glycine transporter 1 (GlyT1) is responsible for the reuptake of glycine, which regulates glutamate signaling as a co-agonist with N-methyl-D-aspartic acid (NMDA) receptors in the excitatory synapse and has been proposed to be a potential target in the development of therapies for a broad range of disorders of the central nervous system. Despite significant progress in characterizing structure and transport mechanism of the transporter, the regulation of transport function through oligomerization remains to be understood. In the present work, association of two forms of GlyT1 into dimers and higher order oligomers was detected by coimmunoprecipitation. To investigate functional properties of dimers of a GlyT1 cysteine mutant L288C, we performed oxidative cross-linking of the positioned cysteine residues in extracellular loop 3 (EL3) near the extracellular end of TM6. By analyzing the effect of copper phenanthroline (CuP)-induced dimerization on transport function, cross-linking of L288C was found to inhibit transport activity. In addition, an intramolecular ion pair Lys286-Glu289 was revealed to be critical for stabilizing EL3 in a conformation that modulates CuP-induced dimerization and transport function of the GlyT1 L288C mutant. Furthermore, the influence of transporter conformation on GlyT1 L288C dimerization was investigated. The substrate glycine, in the presence of both Na+ and Cl-, significantly reduced oxidative cross-linking, suggesting a large-scale rotation of the bundle domain during substrate transport impairs interfacial interactions between L288C protomers. The present study provides new insights into structural and functional elements regulating GlyT1 transport activity through its dimerization or oligomerization.

Determining Ligand and Ion-Induced Conformational Changes in Serotonin Transporter with Its Fluorescent Substrates.

Conformational changes are fundamental events in the transport mechanism. The serotonin transporter (SERT) catalyzes reuptake of the neurotransmitter serotonin after its release by serotonergic neurons and is the molecular target for antidepressant drugs and psychostimulants. Despite significant progress in characterizing the structure-function relationship of SERT, its conformational mechanism has not been fully understood. We present here a cell-based method for determining conformational changes in SERT with its fluorescent substrates by fluorescence imaging analysis. This method fluorometrically measures accessibility of strategically positioned cysteine residues in the substrate permeation pathway to calculate the rate constants of reactivity with MTS reagents in live or permeabilized cells. We validated this method by investigating ligand and ion-induced conformational changes in both the extracellular and cytoplasmic pathways of SERT. Furthermore, we applied this method for examining the influence of Cl- binding and vilazodone inhibition on SERT conformation. Our results showed that Cl- ion, in the presence of Na+, facilitates the conformational conversion from outward to inward open states, and that vilazodone binding stabilizes SERT in an outward open and inward-closed conformation. The present work provided insights into the conformational mechanism of SERT and also indicated that the cell-based fluorometric method is robust, straightforward to perform, and potentially applicable to any monoamine transporters in exploring the transport mechanism and mechanism of action of therapeutic agents for the treatment of several psychiatric disorders.

3D Mapping of the Lateral Malleolus Fractures for Predicting Syndesmotic Injuries in Supination External Rotation Type Ankle Fractures.

Supination external rotation (SER) type ankle fracture is the most common ankle fracture in the Lauge-Hansen classification and is often accompanied with syndesmotic injury. However, the mechanism of this injury is indistinct and a suggestive role can be given by preoperative imaging. This study was to preoperatively predict whether SER type ankle fractures are accompanied with syndesmotic injuries by the means of lateral malleolus fracture mapping. One hundred and forty-eight patients diagnosed with SER type ankle fractures were retrospectively enrolled in this study. The baseline data were collected and computed tomography data were reconstructed in 3-dimensional (3D) model. Patients were divided into stable and unstable groups according to intraoperative Cotton test and whether the inferior tibiofibular screw was placed. All fracture lines were superimposed on the ankle template to create a fracture map, and the data on the fracture map were further measured. Logistic regression was conducted to identify relevant factors and the cutoff values were given using receiver operating characteristic curves. Forty-one patients were enrolled in the unstable group and 107 patients were enrolled in the stable group. The lateral malleolus fracture lines of the unstable group were higher and steeper than that in the stable group on lateral and posterior views. The fracture height of the posterior cortex and peak height were the significant contributing factors, and the cut-off values of posterior cortex, peak height and inclination angle were 40.35 mm (sensitivity: 78%, specificity: 82%), 55.34 mm (sensitivity: 85%, specificity: 70%) and 55.6° (sensitivity: 66%, specificity: 86%), respectively. In general, when the fracture lines of the lateral malleolus were high and steep, it was usually indicative of a syndesmotic injury and can be predicted by the preoperative 3D reconstruction of fracture height of posterior cortex, peak height and inclination angle. If the cut-off values of these indicators are exceeded, the syndesmotic injuries may be presented and need to be verified in the intraoperative Cotton test to decide whether to insert an inferior tibiofibular screw.

Structural elements required for coupling ion and substrate transport in the neurotransmitter transporter homolog LeuT.

The coupled transport of ions and substrates allows transporters to accumulate substrates using the energy of transmembrane ion gradients and electrical potentials. During transport, conformational changes that switch accessibility of substrate and ion binding sites from one side of the membrane to the other must be controlled so as to prevent uncoupled movement of ions or substrates. In the neurotransmitter:sodium symporter (NSS) family, Na+ stabilizes the transporter in an outward-open state, thus decreasing the likelihood of uncoupled Na+ transport. Substrate binding, in a step essential for coupled transport, must overcome the effect of Na+, allowing intracellular substrate and Na+ release from an inward-open state. However, the specific elements of the protein that mediate this conformational response to substrate binding are unknown. Previously, we showed that in the prokaryotic NSS transporter LeuT, the effect of Na+ on conformation requires the Na2 site, where it influences conformation by fostering interaction between two domains of the protein. Here, we used cysteine accessibility to measure conformational changes of LeuT in Escherichia coli membranes. We identified a conserved tyrosine residue in the substrate binding site required for substrate to convert LeuT to inward-open states by establishing an interaction between the two transporter domains. We further identify additional required interactions between the two transporter domains in the extracellular pathway. Together with our previous work on the conformational effect of Na+, these results identify mechanistic components underlying ion-substrate coupling in NSS transporters.

Efficacy and Prognosis of 3D Printing Technology in Treatment of High-Energy Trans-Syndesmotic Ankle Fracture Dislocation - "Log-Splitter" Injury.

BACKGROUND This study aimed to retrospectively assess the feasibility and efficacy of three-dimensional (3D) printing technology in the treatment of high-energy trans-syndesmotic ankle fracture dislocation - "log-splitter" injury - and to evaluate the efficacy and prognosis. MATERIAL AND METHODS We included 29 patients (17 males and 12 females; mean age, 44.0±13.2 years) with log-splitter injury from June 2011 to December 2016, divided into a routine group (n=13) and a 3D printing group (n=16) according to the surgical method used. Operation time, intraoperative blood loss, fluoroscopy times, fracture union time, functional outcomes based on AOFAS (American Orthopedic Foot and Ankle Society) score, and postoperative complications were observed and recorded. RESULTS Compared with the routine treatment group, 3D printing technology had better safety and efficacy for the treatment of log-splitter injury and the advantages of shorter operation time, less intraoperative blood loss, fewer fluoroscopies needed, and higher rate of good functional outcome (P<0.001, P<0.001, P<0.001, and P=0.017, respectively). However, no significant difference was noted in the rate of anatomical reduction, mean AOFAS score at the last follow-up (mean time, 19.9±2.8 months), or postoperative complications between the 2 groups (P=0.370, P=0.156, and P=0.485, respectively). CONCLUSIONS Surgery assisted by 3D printing technology to treat log-splitter injury is feasible and effective, and may be a good optional approach to formulate a reasonable personalized surgical plan and to optimize the outcomes.

Progress of the Anterior Transpedicular Screw in Lower Cervical Spine: A Review.

The anterior transpedicular screws (ATPS) fixation is a valuable discovery in the field of lower cervical spine (LCS) reconstruction, as it has the advantages of both anterior and posterior approaches. In recent years, with in-depth research on ATPS fixation related to anatomy, biomechanical tests, and clinical applications, its firm stability and excellent biomechanical properties have been recognized by more and more surgeons. Although ATPS fixation has been gradually applied in clinic settings under the promotion of emerging distinctive instruments, its long-term efficacy still needs to be further clarified due to the lack of large sample size studies and long-term follow-up. Nevertheless, it is believed that with the maturity of digital devices and the development of precision medicine, ATPS fixation has a promising prospect.