Ribosomal Research Articles

Systematic literature review of the diagnosis, prognosis, and treatment of peritoneal dialysis-related infection caused by nontuberculous mycobacteria

The number of peritoneal dialysis (PD) catheter-related infections and peritonitis caused by nontuberculous mycobacteria (NTM) has been increasing. Nonetheless, the optimal timing for the relocation of the exit site, removal and reinsertion of the PD catheter, prognosis, and duration of antibiotic treatment remain unclear. This literature review aimed to investigate the epidemiology of patient characteristics and evaluate the most effective diagnostic and treatment strategies for PD catheter-related infections and peritonitis caused by NTM. The systematic literature review was conducted on published cases of PD catheter-related infection and peritonitis caused by NTM in PubMed, Embase, and Ichushi databases up to August 2022. A total of 335 cases (64.1%, male; mean age, 53.4 years; mean dialysis duration, 25.4 months) were analyzed. The most common causative agent of infection was Mycobacterium abscessus (40.1%), followed by Mycobacterium fortuitum (24.8%) and Mycobacterium chelonae (16.6%). With respect to diagnosis, 42.9%, 28.1%, and 29.0% of cases were diagnosed as PD catheter-related infection only, peritonitis only, and both, respectively. The initial cultures were positive for NTM only, positive for any other bacteria, and negative for NTM only in 56.5%, 19.8%, and 23.7% of cases, respectively. Ultimately, more than 80% of cases were treated with multiple antibiotics. PD catheter removal was performed in 55.4% of patients with PD catheter-related infections only and 85.5% of those with PD peritonitis. PD continuation or resumption was possible in 62.2% and 16.0% of patients, respectively. In conclusion, our findings indicate that it is advisable to perform acid-fast bacilli stain and culture in order to promptly identify NTM. PD catheter removal may be an essential management strategy during the early stages of NTM infection.

The Impact of the Dialysis Event Prevention Bundle on the Reduction in Dialysis Event Rate in Patients with Catheters: A Retrospective and Prospective Cohort Study

Background: Dialysis-associated events such as bloodstream infections represent serious complications for hemodialysis patients, with the potential to increase morbidity and mortality. Aims: To assess the impact of implementing a comprehensive bundle of evidence-based practice on reducing dialysis event rates among catheter dialysis patients at Prince Mansour Military Hospital Dialysis Center. Participants and Methods: The study enrolled 111 hemodialysis participants. A comprehensive dialysis event prevention bundle consisting of 6 key components was implemented. Results: Implementation of the dialysis event prevention bundle showed a significant decrease in IV antimicrobial start (p = 0.003), positive blood culture (p = 0.039), and inflammation at the vascular access site eliminated (p = 0.004). There was a positive correlation between IV antimicrobial start and both patients’ age (p = 0.005) and the permanent catheter site (p = 0.002). Positive blood culture was significantly correlated with comorbidities (p = 0.000) and patients’ age (p = 0.320). A positive correlation between pus, redness, or increased swelling at the vascular access site with comorbidities (p = 0.034), patients’ age (p = 0.021), and the permanent catheter site (p = 0.002) was observed. Staff compliance with the dialysis event prevention bundle components has improved regarding hemodialysis catheter disconnection, catheter exit site care, and routine disinfection. Conclusions: Implementation of a comprehensive dialysis event prevention bundle can effectively reduce dialysis event rates and enhance patient safety.

Evaluating the use of tunneled hemodialysis catheters in the treatment of acute kidney disease patients requiring hemodialysis: a case-control study.

Tunneled hemodialysis catheters (TDCs) are increasingly used in the emergency management of severe acute kidney disease (AKD). This study aimed to evaluate the effectiveness of TDCs in AKD patients requiring hemodialysis. A case-control study was conducted in Khartoum, Sudan between February and September 2020. Adult patients admitted to the Baraha Medical City Intensive Care Unit with AKD due to non-infectious causes, and requiring hemodialysis were enrolled. Patients were randomly assigned to undergo hemodialysis using either tunneled or non-tunneled hemodialysis catheters (NTDCs). The performance and complications associated with TDCs were assessed during the hospital stay, after discharge, and until catheter removal. Data were analyzed using SPSS. A total of 122 patients with a mean age of 60.4 ± 5.7years were included. AKD was primarily due to acute tubular necrosis (67.2%) and interstitial nephritis (16.4%). Indications for hemodialysis were mostly acute pulmonary edema (64.8%) and symptomatic uremia (27.9%). TDCs were used in 54 (44.3%) patients, while NTDCs were used in 68 (55.7%). The right internal jugular vein was the most common insertion site (95.9%). TDCs were associated with significantly higher blood flow (P < 0.0001) and lower rates of exit site infections (P = 0.034), catheter-related bacteremia (P = 0.011), and catheter malfunction (P = 0.001). They showed a significantly longer functional duration compared to NTDCs (P < 0.0001). TDCs appear to be a safer and more effective option for AKD patients requiring urgent and prolonged hemodialysis, with fewer complications and longer catheter function.

Abstract 4135466: Feasibility of Using Existing Infection Surveillance Methods for Percutaneous Coronary Intervention-related Infections

Background: Percutaneous coronary intervention (PCI) is a treatment that requires attention in terms of infection control, as it necessitates aseptic procedures similar to surgical operations. However, surveillance practices for PCI-related infections are uncommon, and no standardized surveillance program has been established. Purpose: To assess the feasibility of using existing surveillance methods to detect PCI-related infectious diseases. Method: To identify PCI-related bloodstream infections of local access sites, four existing case definitions, namely, laboratory-confirmed bloodstream infections (LCBI), clinical sepsis (CSEP), local access site infection (LASI), and exit site infection (ESI), were retrospectively applied to 1,037 patients who underwent PCI between April 2018 and March 2021. Of these, 167 experienced fever, underwent blood culture testing, and/or received antibiotics within 6 days of PCI. To confirm consistent evaluation, two independent infection control experts evaluated each case record according to the four case definitions. Results: Twenty-three patients (2.2%) were diagnosed with PCI-related infections, including two patients according to LCBI, 21 according to CSEP, and none according to LASI and ESI. Thirteen patients (LCBI: 1, CSEP: 12) received circulatory assist devices such as intra-aortic balloon pumping. Of the remaining 11 patients, 10 underwent emergency PCI, and one underwent elective PCI ( P =0.0001). The average length of hospital stay was 16.1 days for patients with PCI-related infections and 4.7 days for non-infected patients ( P &lt;0.05). Conclusion: The positive diagnosis of PCI-related infections was predominantly based on CSEP. Many of these positive patients underwent emergency PCI and/or received circulatory assist devices. The results of the present study warrant further investigations with larger patient cohorts.

Midline vs Peripherally Inserted Central Catheter for Outpatient Parenteral Antimicrobial Therapy

Little is known about the safety of midline catheters vs peripherally inserted central catheters (PICCs) for outpatient parenteral antimicrobial therapy (OPAT). To compare outcomes from midline catheters vs PICCs for OPAT. This retrospective cohort study included patients who received antimicrobial therapy through a midline catheter or PICC between January 2017 and November 2023 across 69 Michigan hospitals. Because peripherally compatible OPAT was the indication of interest, vancomycin therapy was excluded. Data were analyzed from April to June 2024. Insertion of a midline catheter or PICC for OPAT following hospitalization. The primary outcome was major device complications (ie, catheter-related bloodstream infection or catheter-related venous thromboembolism). Secondary outcomes included minor device complications (eg, catheter dislodgement, occlusion, tip migration, infiltration, superficial thrombophlebitis, or exit site concerns) and device failure, defined as catheter removal following device complication. Cox proportional hazards regression models were fit to device type and outcomes, adjusting for patient and device confounders and device dwell. Of 2824 included patients, 1487 (53.5%) were male, and the median (IQR) age was 66.8 (55.9-77.1) years. Of 2824 devices placed for OPAT, 1999 (70.8%) were midline catheters and 825 (29.2%) were PICCs. The median (IQR) dwell time was 12 (8-17) days for midline catheters and 19 (12-27) days for PICCs (P < .001). A major device complication occurred in 44 patients (1.6%) overall, including 16 (0.8%) with midline catheters and 28 (3.4%) with PICCs (P < .001). OPAT delivered via midline catheters was associated with a lower risk of major complications vs PICCs (adjusted hazard ratio [aHR], 0.46; 95% CI, 0.23-0.91). Risks of minor complications and device failure were similar across device types (minor complications: 206 of 1999 [10.3%] vs 114 of 825 [13.8%]; aHR, 1.07; 95% CI, 0.83-1.38; device failure: 191 of 1999 [9.6%] vs 100 of 825 [12.1%]; aHR, 1.26; 95% CI, 0.96-1.65). For device dwell of 14 or fewer days, midline catheters were associated with a lower risk of major complications (12 of 1324 [0.9%] vs 16 of 304 [5.3%]; aHR, 0.29; 95% CI, 0.12-0.68) and similar risk of failure (151 of 1324 [11.4%] vs 52 of 304 [17.1%]; aHR, 0.79; 95% CI, 0.56-1.12) vs PICCs. For dwell longer than 14 days, no significant difference in rates of major complications (4 of 675 [0.6%] vs 12 of 521 [2.3%]; aHR, 0.42; 95% CI, 0.13-1.40) or device failure (40 of 675 [5.9%] vs 48 of 521 [9.2%]; aHR, 1.02; 95% CI, 0.64-1.61) were observed. In this study, midline catheters appeared to be safe alternatives to PICCs for OPAT, particularly if infusions were planned for 14 or fewer days.

Colostomy formation in a peritoneal dialysis patient.

This case report discusses the complex management of a 46-year-old man with poorly controlled type 1 diabetes mellitus, stage 5 chronic kidney disease, and severe neuropathic complications, which led to bilateral leg amputations. The patient experienced persistent diarrhea due to diabetic neuropathy, significantly impairing his daily functioning. Despite transitioning from hemodialysis to peritoneal dialysis, the diarrhea persisted. A colostomy was subsequently performed, which, although it did not completely resolve the diarrhea, allowed for better control, improving the patient's self-care and independence. Notably, the catheter exit site was maintained on the opposite side of the abdomen. Despite initial concerns about the feasibility of peritoneal dialysis (PD) in patients with stomas, including the challenges of creating a stoma in patients with an existing PD catheter, this case demonstrates the successful continuation of PD following a colostomy. Traditionally, intestinal stomas have been viewed as a relative contraindication to PD due to risks such as leakage and infection. However, current guidelines recommend using extended catheters with a presternal exit site to minimize these risks. The patient's quality of life improved significantly after the colostomy, with no major complications observed during follow-up. This report underscores the importance of tailoring treatment to individual patient needs, balancing risks with potential well-being benefits, and highlights the necessity of interdisciplinary collaboration and adherence to best practices. Given the limited literature on PD in patients with intestinal stomas, this case contributes valuable clinical insights for future management.

Pathogenic Mechanisms of Collagen TypeⅦA1 (COL7A1) and Transporter Protein Transport and Golgi Organization 1 (TANGO1) in Rheumatoid Arthritis: A New Therapeutic Target

Rheumatoid arthritis (RA) is an autoimmune disorder causing chronic inflammation primarily due to collagen regulation and transport imbalances. Collagen VII A1(COL7A1), a major component of anchoring fibrils, regulates inflammation via interacting with its transporter protein Transport and Golgi organization 2 homologs (TANGO1). The study revealed a significant increase in COL7A1 levels in both the plasma and PBMCs of RA patients. Additionally, a positive correlation between COL7A1 and ACCPA (anti-cyclic citrullinated peptide antibody) levels was observed among RA patients. TANGO1 mRNA expression was also found to be elevated in PBMCs. The knockdown of COL7A1 in RA synoviocytes using siRNA affected the expression of TANGO1 and inflammatory genes. Western blot analysis showed that COL7A1 si-RNA in TNF-α-induced SW982 cells reduced the expression of COL7A1, TANGO1, and NF-kBp65. The mRNA expression of inflammatory genes TNF-α, NF-kB p65, and IL-6 simultaneously decreased after the knockdown of COL7A1, as measured by qRT-PCR. An in silico analysis found 20 common interacting proteins of COL7A1 and TANGO1, with pathway enrichment analysis linking them to antigen presentation, class I and II MHC, and adaptive immunity pathways in RA. Among the common proteins, The DisGeNET database depicted that COL1A1, MIA3, SERPINH1, and GORASP1 are directly linked to RA. The molecular docking analysis of COL7A1 and TANGO1 revealed strong interaction with a −1013.4 energy-weighted score. Common RA-used drugs such as Adalimumab, Golimumab, and Infliximab were found to inhibit the interaction between COL7A1 and TANGO1, which can further impede the transport of COL7A1 from ER exit sites, indicating COL7A1 and TANGO1 as potential therapeutic targets to diminish RA progression.

Extravasation of immune and tumor cells from an endothelial perspective.

Crossing the vascular endothelium is a necessary stage for circulating cells aiming to reach distant organs. Leukocyte passage through the endothelium, known as transmigration, is a multistep process during which immune cells adhere to the vascular wall, migrate and crawl along the endothelium until they reach their exit site. Similarly, circulating tumor cells (CTCs), which originate from the primary tumor or reseed from early metastatic sites, disseminate using the blood circulation and also must cross the endothelial barrier to set new colonies in distant organs. CTCs are thought to mimic arrest and extravasation utilized by leukocytes; however, their extravasation also requires processes that, from an endothelial perspective, are specific to cancer cells. Although leukocyte extravasation relies on maintaining endothelial impermeability, it appears that cancer cells can indoctrinate endothelial cells into promoting their extravasation independently of their normal functions. In this Review, we summarize the common and divergent mechanisms of endothelial responses during extravasation of leukocytes (in inflammation) and CTCs (in metastasis), and highlight how these might be leveraged in the development of anti-metastatic treatments.

Comprehensive pan-cancer analysis of CD73: Explore its association with prognosis and tumor immune microenvironment

BackgroundCD73 is adenosine generation molecule, which is involved in the immune regulation. However, the roles of CD73 in the tumor microenvironment remain unknown. MethodsCD73 expression levels in pan-cancers were analyzed, based on The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx) and Human Protein ALTAS (HPA) databases. Kaplan-Meier (KM) plotter was used to analyze the prognostic values of CD73. Immune scores in pan-cancers was evaluated by ESTIMATE. TIMER2.0 and UCSCXena were used to explore the correlation between CD73 and immune infiltration/immune checkpoints/tumor mutation burden (TMB)/microsatellite instability (MSI). CD73 expression correlated genes in tumor tissues were screened by using LinkedOmics tool. ResultsFirstly, CD73 was significant increased in following cancer types: esophageal carcinoma (ESCA), glioblastoma multiforme (GBM), head and neck squamous cell carcinoma (HNSC), brain lower grade glioma (LGG), lung adenocarcinoma (LUAD), pancreatic adenocarcinoma (PAAD) and stomach adenocarcinoma (STAD). Secondly, high CD73 expression was associated with poor overall survival in patients with breast invasive carcinoma (BRCA), CESC, HNSC, liver hepatocellular carcinoma (LIHC), LUAD, lung squamous cell carcinoma (LUSC), PAAD and STAD. However, in KIRC and UCEC, patients high CD73 expression showed a favorable prognosis. Thirdly, the immune scores of the high CD73 expression in bladder urothelial carcinoma (BLCA), BRCA, kidney chromophobe (KICH), LUAD, LUSC, ovarian serous cystadenocarcinoma (OV), pheochromocytoma and paraganglioma (PCPG), prostate adenocarcinoma (PRAD), and skin cutaneous melanoma (SKCM) were significant higher than that of patients with low CD73 expression. Furthermore, we observed a positive correlation between CD73 and the multiple immune cells infiltration, including CD4+ memory T cells, CD8+ T cells, Treg cells, myeloid DC and macrophage, particularly in BRCA and LUAD. There was no strong correlation between CD73 and TMB/MSI. In LUAD, CD73 expression correlated genes were mainly enrichment in positive regulation of cell proliferation, cell adhesion, positive regulation of kinase activity, cellular response to LPS. However, in UCEC, CD73 correlated genes were mainly associated with fatty acid omega-oxidation, protein localization to endoplasmic reticulum exit site, endoplasmic reticulum to Golgi vesicle-mediated transport. ConclusionCD73 could be used to predict the prognosis of patients with several cancers. The potential functional mechanism of CD73 involved in cancer progress may not only dependent on its immunomodulatory effects.

Treatment of subcutaneous lipomas in the horse.

To describe the treatment of subcutaneous lipomas in the horse. 3 horses. The horses were aged 1 to 2 years old, with lipoma of the abdomen, prepuce, and tarsus. All cases had surgical removal of the masses under general anesthesia. Recurrence of an invasive abdominal lipoma occurred in case 1 at the exit site of a passive drain. The recurrence was treated unsuccessfully with injectable cisplatin, and a second revision surgery with the use of an active drain resulted in resolution. In case 2, complete resection of an encapsulated lipoma of the lateral prepuce was successful with no recurrence. In case 3, incomplete resection of a tarsal lipoma resulted in a sound horse, with no further growth. Histopathologic analysis revealed that all masses were composed of well-differentiated adipocytes with no evidence of malignancy. Subcutaneous lipomas are relatively rare and affect horses primarily ≤ 2 years of age. They are benign, although their presence can be deleterious due to invasion of local structures or the impact on normal locomotion. The margins of invasive tumors are difficult to identify due to their integration with normal tissue. Incomplete removal may allow for mass recurrence. Active suctions drains are beneficial if dead space is a concern.

Molybdenum temporary epicardial pacing wires: function and biodegradation

Abstract Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Wires typically begin to fail around postoperative day four and are extracted. Occasionally, TEPW cannot be mechanically removed, have to stay in the thorax and may rarely cause serious complications like migration and infection. We aim to develop novel, bioresorbable TEPW which will dissolve over time, even if postoperative removal is unsuccessful. We manufactured prototypical braided molybdenum (Mo) leads (16 Mo wires of 40 µM diameter each, length 18 cm for ex vivo, 7.5 cm for in vivo experiments) coated with the biodegradable polymers poly(lactide-co-glycolic acid) (PLGA, inner coating) and polycaprolactone (PCL, outer coating) for shaping and electrical insulation. Mo electrodes showed similar pacing and sensing properties to conventional steel electrodes (Osypka) in Langendorff-perfused rat hearts, even with somewhat lower stimulation thresholds. In artificial body fluid at 37°C, the polymer-coated Mo electrodes dissolved at a rate of 1.6 ± 0.3 µg/cm2·d (n = 5) compared to uncoated electrodes with 30.3 ± 0.8 µg/cm2·d (n = 4, p &amp;lt; 0.001). Assessing apoptosis and necrosis in human cardiomyocytes and cardiac fibroblasts, we detected no toxicity at Mo concentrations up to 0.52 mM. To test the in vivo properties of Mo TEPW, we sutured them epicardially onto the anterior wall of the heart of female Wistar rats, led them out of the thorax through an intercostal space and placed them in a subcutaneous pocket. We tested electrophysiological properties directly after implantation and after different time periods. Mo TEPW showed similar pacing and sensing properties directly upon implantation and after 2 weeks, with only impedance and slew rate of the sensed R-wave decreasing time-dependently. After one month, all but one pair of Mo electrodes were mechanically broken at their exit from the thorax, the site of assumedly highest mechanical stress. Progressive Mo degradation led to multiple fragmentation of the Mo TEPW after 6 months. The conventional steel TEPW we used as control had similar electrical properties directly after implantation, after 2 weeks and one month without signs of broken electrodes. After 6 months, all but one pair of steel electrodes were mechanically broken at their thorax exit site. Comparing urinary Mo concentration of Mo TEPW treated rats to controls, we saw similar values of 1.9 ± 1.9 µM (n = 6) vs. 0.6 ± 0.2 µM (n = 5, n.s.) after one week. In contrast, we saw a significant increase of 12.1 ± 9.7 µM (n = 5) vs. 1.0 ± 0.9 µM (n = 5, p &amp;lt; 0.001) after 6 months, reflecting the degradation progress. We demonstrate that Mo TEPW are a feasible option for epicardial pacing in vivo for up to 2 weeks and observed the progress of Mo degradation up to 6 months. These findings represent an important step in the development of bioresorbable TEPW as a novel and even safer approach to temporary epicardial pacing.Graphical AbstractIn Vivo Degradation Progress

Accuracy of a non-invasive mapping system for the localisation of re-entrant VT site of origin and its relationship to myocardial scar on cross-sectional imaging

Abstract Introduction View in ventricular onset (VIVO) is a non-invasive mapping system used for localising the site of earliest activation in ventricular arrhythmia, utilising a mathematical algorithm, patient specific cardiac model (constructed using cross-sectional imaging data), 3D images of the patient’s torso (for localising surface electrodes), and a 12-lead electrocardiogram (ECG).(1, 2) Several publications have examined its role in the localisation of premature ventricular contractions (PVCs), and a 5 patient case series assessed its role in scar related re-entrant VT.(1-4) However, its validity in a larger cohort and of the relationship to the relevant myocardial scar has not been investigated. Objective Assess the accuracy of the VIVO mapping system in localising the VT-SoO for patients with scar related re-entrant VT and its relationship to the relevant myocardial scar on cross-sectional imaging. Methods 20 patients with structural heart disease (18 ischaemic cardiomyopathy (ICM), 1 dilated cardiomyopathy (DCM), 1 hypertrophic cardiomyopathy (HCM)) (Male n=18, 63±14 years) and recent cross-sectional cardiac imaging, were recruited over a 16-month period (table 1). All patients had a clinical indication for VT ablation and were on optimal medical therapy, 19 had an implantable cardiac defibrillator. Invasive electro-anatomical mapping (EAM) was performed with the Advisor HD Grid multipolar catheter and maps were generated using Omnipolar electrograms (EGMs). The VT-SoO was identified using an activation- or pace-map by an experienced operator and the location defined using the American heart association’s 17 segment model of the left ventricle during the procedure.(5) VIVO maps were reviewed by a second independent operator and a segment allocated, scar segments were obtained from cross-sectional imaging. A "complete match" was defined as exact segment concordance between allocated segments, "partial match" as adjacent segments, and "no match" if it does not satisfy either of those requirements. Results Mean left ventricular ejection fraction was 35.5 ± 10.6%. Mean procedure time was 242 ± 70 minutes, with a mean ablation time of 20 ± 11.1 minutes. A total of 32 re-entrant VTs were mapped. The VT exit site was identified in all cases (11 activation-map; 21 pace-map). A complete match between the EAM and VIVO map was seen in 75% of VTs and partial match in a further 15% (table 2). The VT-SoO was located withing the myocardial scar (or directly adjacent to is) in 83% of accurately mapped VTs. Procedural success (defined as freedom from device treated episodes) was seen in 90% of patients at mean follow up of 7.3 ± 4.7 months. Conclusion VIVO non-invasive mapping system was able to accurately map the VT-SoO in scar dependent VT, and identify the relevant myocardial scar as seen on cross sectional imaging. Further research assessing its ability to accurately identify relevant ablation targets is ongoing.

Safety and complications associated with tunneling and pseudotunneling techniques during PICC and Midline insertion.

Peripherally Inserted Central Catheters and Midline Catheters are particularly attractive because of their favorable risk/benefit ratio. If the ideal venipuncture site is in an area inappropriate for catheter emergence, a valid alternative is the tunneling technique, which allows the exit site to be moved to reach the optimal position. There are two main types of tunneling techniques: standard tunnel, using a tunneling device (metal tunneler or peel-away tunneler), and pseudo-tunnel. As much as both are recognized as appropriate and safe, there are still few literature data indicating the criteria for choosing and using the two techniques and the possible related complications. This retrospective observational investigation analyzed data regarding intra- and post-procedural complications of tunneled catheters inserted using two different techniques. The sample was stratified into three subgroups: (1) Standard Tunnel (patients with no PLT or INR disorders), (2) Pseudotunnel (patients with no PLT or INR disorders), and (3) Pseudotunnel (patients with any PLT or INR disorder). Data regarding the procedure, at 24 h and 7 days were collected and analyzed. A total of 143 patients who underwent tunneled catheter insertion were included in the study. Among these, 113 patients were divided into subgroups 1 and 2 and 30 were assigned to subgroup 3. No significant differences were found among the three subgroups regarding immediate, short, and medium-term tunnel complications. The findings of this study suggest that both standard and pseudo-tunnels provide comparable levels of safety and comfort for patients. It was noted that Pseudotunnel offers an equivalent level of safety for patients with coagulation disorders related to PLT and INR, rendering it comparable to a "minimally invasive procedure," which necessitates the same precautions as a non-tunneled PICC.

Substrate specificity controlled by the exit site of human P4-ATPases, revealed by de novo point mutations in neurological disorders

The maintenance of lipid asymmetry on the plasma membrane is regulated by flippases, such as ATP8A2, ATP11A, and ATP11C, which translocate phosphatidylserine and phosphatidylethanolamine from the outer leaflet to the inner leaflet. We previously identified a patient-derived point mutation (Q84E) in ATP11A at the phospholipid entry site, which acquired the ability to flip phosphatidylcholine (PtdCho). This mutation led to elevated levels of sphingomyelin (SM) in the outer leaflet of the plasma membrane. We herein present two de novo ATP11A dominant mutations (E114G and S399L) in heterozygous patients exhibiting neurological and developmental disorders. These mutations, situated near the predicted phospholipid exit site, similarly confer the ability for ATP11A to recognize PtdCho as a substrate, resulting in its internalization into cells. Cells expressing these mutants had increased SM levels on their surface, attributed to the up-regulated expression of the sphingomyelin synthase-1 gene, rendering them more susceptible to SM phosphodiesterase-mediated cell lysis. Corresponding mutations in ATP11C and ATP8A2, paralogs of ATP11A, exerted similar effects on PtdCho-flipping activity and increased SM levels on the cell surface. Molecular dynamics simulations, based on the ATP11C structure, suggest that the E114G and S399L mutations enhance ATP11C's affinity toward PtdCho. These findings underscore the importance of the well-conserved exit and entry sites in determining phospholipid substrate specificity and indicate that aberrant flipping of PtdCho contributes to neurological disorders.

TDP43 aggregation at ER-exit sites impairs ER-to-Golgi transport

Protein aggregation plays key roles in age-related degenerative diseases, but how different proteins coalesce to form inclusions that vary in composition, morphology, molecular dynamics and confer physiological consequences is poorly understood. Here we employ a general reporter based on mutant Hsp104 to identify proteins forming aggregates in human cells under common proteotoxic stress. We identify over 300 proteins that form different inclusions containing subsets of aggregating proteins. In particular, TDP43, implicated in Amyotrophic Lateral Sclerosis (ALS), partitions dynamically between two distinct types of aggregates: stress granule and a previously unknown non-dynamic (solid-like) inclusion at the ER exit sites (ERES). TDP43-ERES co-aggregation is induced by diverse proteotoxic stresses and observed in the motor neurons of ALS patients. Such aggregation causes retention of secretory cargos at ERES and therefore delays ER-to-Golgi transport, providing a link between TDP43 aggregation and compromised cellular function in ALS patients.

Regulation of Cx36 trafficking through the early secretory pathway by COPII cargo receptors and Grasp55

Gap junctions formed by the major neuronal connexin Cx36 function as electrical synapses in the nervous system and provide unique functions such as synchronizing neuron activities or supporting network oscillations. Although the physiological significance of electrical synapses for neuronal networks is well established, little is known about the pathways that regulate the transport of its main component: Cx36. Here we have used HEK293T cells as an expression system in combination with siRNA and BioID screens to study the transition of Cx36 from the ER to the cis Golgi. Our data indicate that the C-terminal tip of Cx36 is a key factor in this process, mediating binding interactions with two distinct components in the early secretory pathway: the COPII complex and the Golgi stacking protein Grasp55. The C-terminal amino acid valine serves as an ER export signal to recruit COPII cargo receptors Sec24A/B/C at ER exit sites, whereas the PDZ binding motif “SAYV” mediates an interaction with Grasp55. These two interactions have opposing effects in their respective compartments. While Sec24 subunits carry Cx36 out of the ER, Grasp55 stabilizes Cx36 in the Golgi as shown in over expression experiments. These early regulatory steps of Cx36 are expected to be essential for the formation, function, regulation and plasticity of electrical synapses in the developing and mature nervous system.

Structural mechanism of HP1⍺-dependent transcriptional repression and chromatin compaction

Heterochromatin protein 1 (HP1) plays a central role in establishing and maintaining constitutive heterochromatin. However, the mechanisms underlying HP1-nucleosome interactions and their contributions to heterochromatin functions remain elusive. Here, we present the cryoelectron microscopy (cryo-EM) structure of an HP1α dimer bound to an H2A.Z-nucleosome, revealing two distinct HP1α-nucleosome interfaces. The primary HP1α binding site is located at the N terminus of histone H3, specifically at the trimethylated lysine 9(K9me3) region, while a secondary binding site is situated near histone H2B, close to nucleosome superhelical location 4 (SHL4). Our biochemical data further demonstrates that HP1α binding influences the dynamics of DNA on the nucleosome. It promotes DNA unwrapping near the nucleosome entry and exit sites while concurrently restricting DNA accessibility in the vicinity of SHL4. Our study offers a model for HP1α-mediated heterochromatin maintenance and gene silencing. It also sheds light on the H3K9me-independent role of HP1 in responding to DNA damage.

Sec23IP recruits VPS13B/COH1 to ER exit site-Golgi interface for tubular ERGIC formation.

VPS13B/COH1 is the only known causative factor for Cohen syndrome, an early-onset autosomal recessive developmental disorder with intellectual inability, developmental delay, joint hypermobility, myopia, and facial dysmorphism as common features, but the molecular basis of VPS13B/COH1 in pathogenesis remains largely unclear. Here, we identify Sec23 interacting protein (Sec23IP) at the ER exit site (ERES) as a VPS13B adaptor that recruits VPS13B to ERES-Golgi interfaces. VPS13B interacts directly with Sec23IP via the VPS13 adaptor binding domain (VAB), and the interaction promotes the association between ERES and the Golgi. Disease-associated missense mutations of VPS13B-VAB impair the interaction with Sec23IP. Knockout of VPS13B or Sec23IP blocks the formation of tubular ERGIC, an unconventional cargo carrier that expedites ER-to-Golgi transport. In addition, depletion of VPS13B or Sec23IP delays ER export of procollagen, suggesting a link between procollagen secretion and joint laxity in patients with Cohen disease. Together, our study reveals a crucial role of VPS13B-Sec23IP interaction at the ERES-Golgi interface in the pathogenesis of Cohen syndrome.

Functional Diversification of Sec13 Isoforms for Storage Protein Trafficking in Rice Endosperm Cells.

Coat protein complex II (COPII) vesicles play crucial roles in mediating the endoplasmic reticulum (ER) exit of newly synthesized proteins to the Golgi in eukaryotic cells. However, the molecular functions of COPII components and their functional diversifications in plant seeds remain obscure. Here, we showed that the rice (Oryza sativa) glutelin precursor accumulation12 (gpa12) mutant is defective in storage protein export from the ER, resulting in the formation of aggregated protein bodies. Map-based cloning revealed that GPA12 encodes a COPII outer layer protein, Sec13a, that mainly localizes to endoplasmic reticulum exit sites (ERES) and partially localizes to the Golgi. Biochemical experiments verified that Sec13a physically interacts with Sec31 and Sec16, and mutation in Sec13 compromises its interaction with Sec31 and Sec16, thereby affecting the membrane association of the inner complex components Sar1b and Sec23c. Apart from Sec13a, the rice genome encodes two other Sec13 isoforms, Sec13b and Sec13c. Notably, we observed an abnormal accumulation of globular ER structures in the sec13bc double mutant but not in the single mutants, suggesting a functional redundancy of Sec13b and Sec13c in modulating ER morphology. Taken together, our results substantiated that Sec13a plays an important role in regulating storage protein export from the ER, while Sec13b and Sec13c are required for maintaining ER morphology in rice endosperm cells. Our findings provide insights into the functional diversification of COPII components in plants.

Residual flow of the radial artery in the presence of an arterial catheter: A single-centre retrospective observational study

Background: Arterial catheterisation is a common procedure used to manage critically ill patients. The radial artery, both for its favourable anatomical position and the presence of ulnar collateral circulation, is the most used. While there is a consensus for a catheter/vein ratio of ⩽33% for venous catheterisation, there are no strong indications for arterial catheterisation. Some authors have hypothesised that a catheter/artery ratio of less than 45% is advisable. This study aimed to explore the relationship between residual flow in the Radial Artery, the catheter/artery ratio, and ulnar compensation. Methods: This retrospective observational study included patients with radial artery catheters in general wards and intensive care units of a tertiary hospital in Italy. Residual flow in the radial artery was calculated by measuring the Peak Systolic Velocity and diameter of the artery at the midpoint of the arm. The reverse Barbeau test was used to assess the residual perfusion. The sample was stratified and analysed to the catheter/artery ratio being greater or less than 33% and 45% and to the score obtained during the reverse Barbeau test. Results: The data obtained showed a significant statistical correlation between residual flow, catheter/artery ratio, and the reverse Barbeau test ( p &lt; 0.0001 and p = 0.0074 respectively). Almost 80% of the sample had a catheter with an exit site less than 4 cm from the wrist crease. Conclusion: Adhering to the current guidelines, especially using ultrasound to ensure a catheter/artery ratio of at least 45%, can help maintain preserved perfusion through the cannulated radial artery. Ulnar compensation appears to be crucial for maintaining good tissue perfusion and should always be evaluated before catheterisation. Therefore, further studies are warranted.