In silico screening identifies SHPRH as a novel nucleosome acidic patch interactor.

Nucleosomes are the fundamental unit of eukaryotic chromatin. Diverse factors interact with nucleosomes to modulate chromatin architecture and facilitate DNA repair, replication, transcription, and other cellular processes. An important platform for chromatin binding is the H2A-H2B acidic patch. Here, we used AlphaFold-Multimer to screen over 7000 human proteins for nucleosomal acidic patch binding and identify 41 potential acidic patch binders. We determined the cryo-EM structure of one hit, SHPRH, with the nucleosome at 2.8 Å. The structure confirms the predicted acidic patch interaction, reveals that the SHPRH ATPase engages a different nucleosomal DNA location than other SF2-type ATPases, and clarifies the roles of SHPRH's domains in nucleosome recognition. Our results illustrate the use of in silico screening as a high throughput method to identify specific interaction types and expands the set of potential acidic patch binding factors. All the screening data is freely available at: https://predictomes.org/view/acidicpatch.

Targeted protein degradation in mycobacteria uncovers antibacterial effects and potentiates antibiotic efficacy.

Proteolysis-targeting chimeras (PROTACs) represent a new therapeutic modality involving selectively directing disease-causing proteins for degradation through proteolytic systems. Our ability to exploit targeted protein degradation (TPD) for antibiotic development remains nascent due to our limited understanding of which bacterial proteins are amenable to a TPD strategy. Here, we use a genetic system to model chemically-induced proximity and degradation to screen essential proteins in Mycobacterium smegmatis (Msm), a model for the human pathogen M. tuberculosis (Mtb). By integrating experimental screening of 72 protein candidates and machine learning, we find that drug-induced proximity to the bacterial ClpC1P1P2 proteolytic complex leads to the degradation of many endogenous proteins, especially those with disordered termini. Additionally, TPD of essential Msm proteins inhibits bacterial growth and potentiates the effects of existing antimicrobial compounds. Together, our results provide biological principles to select and evaluate attractive targets for future Mtb PROTAC development, as both standalone antibiotics and potentiators of existing antibiotic efficacy.

Predictomes: A classifier-curated database of AlphaFold-modeled protein-protein interactions.

Protein-protein interactions (PPIs) are ubiquitous in biology, yet a comprehensive structural characterization of the PPIs underlying biochemical processes is lacking. Although AlphaFold-Multimer (AF-M) has the potential to fill this knowledge gap, standard AF-M confidence metrics do not reliably separate relevant PPIs from an abundance of false positive predictions. To address this limitation, we used machine learning on well curated datasets to train a Structure Prediction and Omics informed Classifier called SPOC that shows excellent performance in separating true and false PPIs, including in proteome-wide screens. We applied SPOC to an all-by-all matrix of nearly 300 human genome maintenance proteins, generating ~40,000 predictions that can be viewed at predictomes.org, where users can also score their own predictions with SPOC. High confidence PPIs discovered using our approach suggest novel hypotheses in genome maintenance. Our results provide a framework for interpreting large scale AF-M screens and help lay the foundation for a proteome-wide structural interactome.

Is there a link between appendicitis and the risk of diverticular disease?: a large German cohort study.

PURPOSE: Appendicitis, characterized by inflammation of the vermiform appendix, is a common abdominal emergency necessitating appendectomy. Recent evidence suggests a potential link between appendicitis and subsequent diverticular disease, yet population-based studies investigating this association are limited. METHODS: Utilizing the Disease Analyzer database encompassing data from over 1000 primary care practices in Germany, we conducted a retrospective cohort study. We included 25,379 adults diagnosed with appendicitis and an equal number of matched controls without appendicitis. The incidence of diverticular disease over a 10-year follow-up period was compared between the two cohorts. Cox regression analysis was performed to assess the association between appendicitis and diverticular disease, adjusting for potential confounders. RESULTS: Our findings revealed a significant association between appendicitis and subsequent diverticular disease (HR: 1.76; 95% CI: 1.57-1.97), with an increased risk observed across all age groups. Notably, this association was stronger in men (HR: 2.00; 95% CI: 1.68-2.37) than in women (HR: 1.58; 95% CI: 1.36-1.84). The cumulative 10-year incidence of diverticular disease was higher in patients with appendicitis (6.5%) compared to those without (3.6%). Additionally, we observed a clear age-dependent increase in the incidence of diverticular disease. CONCLUSION: This large-scale population-based study provides valuable insights into the interaction between appendicitis and diverticular disease. The study underscores the need for further research elucidating the underlying mechanisms linking appendicitis to diverticular disease. Probiotics emerge as a potential therapeutic avenue warranting exploration in the management of both conditions. These findings have important implications for clinical practice, highlighting the importance of considering appendicitis as a potential risk factor for diverticular disease, particularly in men. Further investigation is warranted to validate these findings and explore potential therapeutic interventions targeting the shared pathophysiological pathways underlying both conditions.

Adapting an Isobaric Tag-Labeled Yeast Peptide Standard to Develop Targeted Proteomics Assays.

Targeted proteomics strategies present a streamlined hypothesis-driven approach to analyze specific sets of pathways or disease related proteins. goDig is a quantitative, targeted tandem mass tag (TMT)-based assay that can measure the relative abundance differences for hundreds of proteins directly from unfractionated mixtures. Specific protein groups or entire pathways of up to 200 proteins can be selected for quantitative profiling, while leveraging sample multiplexing permits the simultaneous analysis of up to 18 samples. Despite these benefits, implementing goDig is not without challenges, as it requires access to an instrument application programming interface (iAPI), an elution order and spectral library, a web-based method builder, and dedicated companion software. In addition, the absence of an example test assay may dissuade researchers from testing or implementing goDig. Here, we repurpose the TKO11 standard─which is commercially available but may also be assembled in-lab─and establish it as a de facto test assay for goDig. We build a proteome-wide goDig yeast library, quantify protein expression across several gene ontology (GO) categories, and compare these results to a fully fractionated yeast gold-standard data set. Essentially, we provide a guide detailing the goDig-based quantification of TKO11, which can also be used as a template for user-defined assays in other species.

Storage of packed red blood cells impairs an inherent coagulation property of erythrocytes.

Storage of packed red blood cells is associated with changes in erythrocytes that over time increasingly impair cellular function and potentially contribute to adverse effects associated with blood transfusion. Exposure of phosphatidylserine at the outer membrane leaflet of erythrocytes and shedding of microvesicles (MVs) during packed red blood cell storage are alterations assumed to increase the risk of prothrombotic events in recipients. Here, we used rotational thromboelastometry to study the coagulation process in blood samples with erythrocytes from stored PRBCs reconstituted with freshly prepared platelet-rich plasma. We explored the influence of following effects on the coagulation process: 1) PRBC storage duration, 2) differences between erythrocytes from stored PRBCs compared to freshly drawn erythrocytes, and 3) the contribution of added MVs. Interestingly, despite of a higher fraction of PS-positive cells, erythrocytes from PRBCs stored for 6 weeks revealed longer clotting times than samples with erythrocytes stored for 2 or 4 weeks. Further, clotting times and clot formation times were considerably increased in samples reconstituted with erythrocytes from stored PRBCs as compared to fresh erythrocytes. Moreover, MVs added to reconstituted samples elicited only comparably small and ambiguous effects on coagulation. Thus, this study provides no evidence for an amplified clotting process from prolonged storage of PRBCs but on the contrary implicates a loss of function, which may be of clinical significance in massive transfusion. Our observations add to the increasing body of evidence viewing erythrocytes as active players in the clotting process.

Outcome Quality After Colorectal Cancer Resection in Certified Colorectal Cancer Centers­Patient-Reported and Short-Term Clinical Outcomes.

BACKGROUND: In this observational study, patient-reported outcomes and short-term clinical outcome parameters in patients with colorectal cancer were studied 12 months after the start of treatment. Outcomes were also compared across German Certified Colorectal Cancer Centres. METHODS: Data were collected from 4239 patients with colorectal cancer who had undergone elective tumor resection in one of 102 colorectal cancer centers and had responded to a quality-of-life questionnaire before treatment (EORTC QLQ-C30 and -CR29). 3142 (74.1%) of these patients completed a post-treatment questionnaire 12 months later. Correlation analyses were calculated and case-mix adjusted comparisons across centers were made for selected patient-reported outcomes, anastomotic insufficiency, and 30-day-mortality. RESULTS: At 12 months, mild improvements were seen in mean quality-of-life scores (66 vs. 62 points), constipation (16 vs. 19), and abdominal pain (15 vs. 17). Worsening was seen in physical function (75 vs. 82) and pain (22 vs. 19). Better patient-reported outcomes at 12 months were associated with better scores before treatment. Better results in at least three of the five scores were associated with male sex, higher educational level, higher age, and private health insurance. Major worsening of fecal incontinence was seen among patients with rectal cancer without a stoma. The largest differences across centers were found with respect to physical function. Anastomotic insufficiency was found in 4.3% of colon cancer patients and 8.2% of rectal cancer patients. 1.9% of patients died within 30 days after their resection. CONCLUSION: Clinicians can use these findings to identify patients at higher risk for poorer patient-reported outcomes. The differences among cancer centers that were found imply that measures for quality improvement would be desirable.

Packed red blood cell transfusion in preterm infants.

Premature infants commonly receive adult packed red blood cells (pRBCs) during their hospital stay. As adult erythrocytes differ substantially from those of preterm infants, transfusion of adult pRBCs into preterm infants can be considered inappropriate for the physiology of a preterm infant. An absence of standardisation of transfusion protocols makes it difficult to compare and interpret pertinent clinical data, as reflected by unclear associations between pRBC transfusion and complications related to prematurity, such as bronchopulmonary dysplasia, neurodevelopmental impairment, retinopathy of prematurity, or necrotising enterocolitis. The difficulty in interpreting clinical data is further increased by differences in study designs that either overestimate pRBC-associated complications of prematurity or have not yet been designed to directly link pRBC transfusions to their respective complications. Thus, neonatal transfusion practice has become an ongoing difficulty, in which differences in transfusion guidelines hinder the ability to generate comparable clinical data, and heterogeneity in clinical data prevents the implementation of standardised transfusion protocols. To overcome these issues, novel approaches with biochemical-clinical translational designs could enable clinicians to gather causal evidence instead of circumstantial correlation.

Operationalizing Community Assessment Results to Enhance Preparedness for a Radiological Emergency.

OBJECTIVE: A radiological emergency such as the detonation of a radiological dispersal device would have catastrophic health, environmental, and economic consequences. Community assessments can provide useful information about radiological and other emergency preparedness at the household level. Tools such as logic models can be applied to link data collected in a community assessment to planned activities and targeted outcomes. This study sought to answer how public health departments can use the results of a community assessment to improve preparedness for radiological and other types of emergencies and to present a sample logic model demonstrating how questions asked in a community assessment can be used to drive intended outcomes. DESIGN: Surveys were fielded in 2019 to professionals with experience in radiological emergency preparedness, state and local health and emergency management, and journalism. Questions included the role of health departments in radiological emergency preparedness, the operationalization of results from a community assessment for preparedness, and information sharing in a radiological emergency. Descriptive statistics and a modified framework approach were used for open-ended questions. RESULTS: Nearly three-fourths of state/local officials reported that it would be at least somewhat difficult (73%; 11 of 15 state/local officials) for a local health department to operationalize the results of a community health assessment for radiological emergency preparedness. Potential barriers included competing priorities, lack of funds, and limited staff. Resources such as pretested communication materials, tailored messaging, and technical tools and training can assist health departments and emergency management agencies in using the information collected from a community assessment. CONCLUSIONS: To address implementation challenges in operationalizing the results of a community assessment, officials can use tools such as logic models to illustrate how the information gathered from a community health assessment will create an intended preparedness outcome and to advocate for funds for this type of assessment.

A Potential Citrate Shunt in Erythrocytes of PKAN Patients Caused by Mutations in Pantothenate Kinase 2.

Pantothenate kinase-associated neurodegeneration (PKAN) is a progressive neurodegenerative disease caused by mutations in the pantothenate kinase 2 (PANK2) gene and associated with iron deposition in basal ganglia. Pantothenate kinase isoforms catalyze the first step in coenzyme A (CoA) biosynthesis. Since PANK2 is the only isoform in erythrocytes, these cells are an excellent ex vivo model to study the effect of PANK2 point mutations on expression/stability and activity of the protein as well as on the downstream molecular consequences. PKAN erythrocytes containing the T528M PANK2 mutant had residual enzyme activities but variable PANK2 abundances indicating an impaired regulation of the protein. Patients with G521R/G521R, G521R/G262R, and R264N/L275fs PANK2 mutants had no residual enzyme activity and strongly reduced PANK2 abundance. G521R inactivates the catalytic activity of the enzyme, whereas G262R and the R264N point mutations impair the switch from the inactive to the active conformation of the PANK2 dimer. Metabolites in cytosolic extracts were analyzed by gas chromatography-mass spectrometry and multivariate analytic methods revealing changes in the carboxylate metabolism of erythrocytes from PKAN patients as compared to that of the carrier and healthy control. Assuming low/absent CoA levels in PKAN erythrocytes, changes are consistent with a model of altered citrate channeling where citrate is preferentially converted to α-ketoglutarate and α-hydroxyglutarate instead of being used for de novo acetyl-CoA generation. This finding hints at the importance of carboxylate metabolism in PKAN pathology with potential links to reduced cytoplasmic acetyl-CoA levels in neurons and to aberrant brain iron regulation.

International Core Outcome Set for Acute Simple Appendicitis in Children: Results of a Systematic Review, Delphi Study, and Focus Croups With Young People.

OBJECTIVE: To develop an international core outcome set (COS), a minimal collection of outcomes that should be measured and reported in all future clinical trials evaluating treatments of acute simple appendicitis in children. SUMMARY OF BACKGROUND DATA: A previous systematic review identified 115 outcomes in 60 trials and systematic reviews evaluating treatments for children with appendicitis, suggesting the need for a COS. METHODS: The development process consisted of 4 phases: (1) an updated systematic review identifying all previously reported outcomes, (2) a 2-stage international Delphi study in which parents with their children and surgeons rated these outcomes for inclusion in the COS, (3) focus groups with young people to identify missing outcomes, and (4) international expert meetings to ratify the final COS. RESULTS: The systematic review identified 129 outcomes which were mapped to 43 unique outcome terms for the Delphi survey. The first-round included 137 parents (8 countries) and 245 surgeons (10 countries), the second-round response rates were 61% and 85% respectively, with 10 outcomes emerging with consensus. After 2 young peoples' focus groups, 2 additional outcomes were added to the final COS (12): mortality, bowel obstruction, intraabdominal abscess, recurrent appendicitis, complicated appendicitis, return to baseline health, readmission, reoperation, unplanned appendectomy, adverse events related to treatment, major and minor complications. CONCLUSION: An evidence-informed COS based on international consensus, including patients and parents has been developed. This COS is recommended for all future studies evaluating treatment ofsimple appendicitis in children, to reduce heterogeneity between studies and facilitate data synthesis and evidence-based decision-making.

Hypothermic Machine Perfusion as a National Standard Preservation Method for Deceased Donor Kidneys.

BACKGROUND: Recently, continuous nonoxygenated hypothermic machine perfusion (HMP) has been implemented as standard preservation method for deceased donor kidneys in the Netherlands. This study was designed to assess the effect of the implementation of HMP on early outcomes after transplantation. METHODS: Kidneys donated in the Netherlands in 2016 and 2017 were intended to be preserved by HMP. A historical cohort (2010-2014) preserved by static cold storage was chosen as the control group. Primary outcome was delayed graft function (DGF). Additional analyses were performed on safety, graft function, and survival up until 2 y after transplantation. RESULTS: Data were collected on 2493 kidneys. Analyses showed significantly more donation after circulatory death, preemptive transplantation, and retransplants in the project cohort. Of the 681 kidneys that were transplanted during the project, 81% were preserved by HMP. No kidneys were discarded due to HMP-related complications. DGF occurred in 38.2% of the project cohort versus 43.7% of the historical cohort (P < 0.001), with a significantly shorter duration within the project cohort (7 versus 9 d, P = 0.003). Multivariate regression analysis showed an odds ratio of 0.69 (95% confidence interval, 0.553-0.855) for the risk of DGF when using HMP compared with cold storage (P = 0.001). There was no significant difference in kidney function, graft survival, and recipient survival up until 2 y posttransplantation. CONCLUSIONS: This study showed that HMP as a standard preservation method for deceased donor kidneys is safe and feasible. HMP was associated with a significant reduction of DGF.

Redox Properties of Human Erythrocytes Are Adapted for Vitamin C Recycling.

Ascorbic acid (AA; or vitamin C) is an important physiological antioxidant and radical scavenger. Some mammalian species, including homo sapiens, have lost the ability to synthetize AA and depend on its nutritional uptake. Erythrocytes from AA-auxotroph mammals express high amounts of the glucose transporter GLUT1. This isoform enables rapid uptake of glucose as well as dehydroascorbate (DHA), the fully oxidized form of AA. Here, we explored the effects of DHA uptake on the redox metabolism of human erythrocytes. DHA uptake enhanced plasma membrane electron transport (PMET) activity. This process is mediated by DCytb, a membrane bound cytochrome catalyzing extracellular reduction of Fe3+ and ascorbate free radical (AFR), the first oxidized form of AA. DHA uptake also decreased cellular radical oxygen species (ROS) levels. Both effects were massively enhanced in the presence of physiological glucose concentrations. Reduction of DHA to AA largely depleted intracellular glutathione (GSH) and induced the efflux of its oxidized form, GSSG. GSSG efflux could be inhibited by MK-571 (IC 50 = 5 µM), indicating involvement of multidrug resistance associated protein (MRP1/4). DHA-dependent GSH depletion and GSSG efflux were completely rescued in the presence of 5 mM glucose and, partially, by 2-deoxy-glucose (2-DG), respectively. These findings indicate that human erythrocytes are physiologically adapted to recycle AA both intracellularly via GLUT1-mediated DHA uptake and reduction and extracellularly via DCytb-mediated AFR reduction. We discuss the possibility that this improved erythrocyte-mediated AA recycling was a prerequisite for the emergence of AA auxotrophy which independently occurred at least twice during mammalian evolution.

Developing an instrument to measure household radiological emergency preparedness using the Community Assessment for Public Health Emergency Response (CASPER) methodology: An evidence-informed approach.

INTRODUCTION: Community assessments to measure emergency preparedness can inform policies, planning, and communication to the public to improve readiness and response if an emergency was to occur. Public health and emergency management officials need an effective assessment tool to measure community preparedness for a radiological emergency. METHODS: The authors created a survey instrument to collect data on household radiological emergency preparedness that could be implemented using the Community Assessment for Public Health Emergency Response (CASPER) methodology, developed by the U.S. Centers for Disease Control and Prevention. To inform the development of the tool, the authors examined existing CASPER surveys, focusing on identifying best practices for creating a survey instrument, as well as analyzing the results of a survey of radiation preparedness experts and state/local health and emergency management officials. RESULTS: The developed survey tool includes 32 questions covering four domains: communication in an emergency, preparedness planning, physical/behavioral health, and demographics. The instrument captures information related to identified barriers in communicating in a radiological emergency as well as self-reported behaviors that could potentially be influenced through awareness and education. DISCUSSION: Using the proposed survey instrument and following the existing rapid assessment methodology provided by CASPER, public health and emergency management agencies can collect valuable information on the radiation preparedness needs of their communities, which can then be used to improve household readiness for an emergency.

SARS-CoV-2 infection rewires host cell metabolism and is potentially susceptible to mTORC1 inhibition.

Viruses hijack host cell metabolism to acquire the building blocks required for replication. Understanding how SARS-CoV-2 alters host cell metabolism may lead to potential treatments for COVID-19. Here we profile metabolic changes conferred by SARS-CoV-2 infection in kidney epithelial cells and lung air-liquid interface (ALI) cultures, and show that SARS-CoV-2 infection increases glucose carbon entry into the TCA cycle via increased pyruvate carboxylase expression. SARS-CoV-2 also reduces oxidative glutamine metabolism while maintaining reductive carboxylation. Consistent with these changes, SARS-CoV-2 infection increases the activity of mTORC1 in cell lines and lung ALI cultures. Lastly, we show evidence of mTORC1 activation in COVID-19 patient lung tissue, and that mTORC1 inhibitors reduce viral replication in kidney epithelial cells and lung ALI cultures. Our results suggest that targeting mTORC1 may be a feasible treatment strategy for COVID-19 patients, although further studies are required to determine the mechanism of inhibition and potential efficacy in patients.

Packed red blood cells inhibit T-cell activation via ROS-dependent signaling pathways.

Numerous observations indicate that red blood cells (RBCs) affect T-cell activation and proliferation. We have studied effects of packed RBCs (PRBCs) on T-cell receptor (TCR) signaling and the molecular mechanisms whereby (P)RBCs modulate T-cell activation. In line with previous reports, PRBCs attenuated the expression of T-cell activation markers CD25 and CD69 upon costimulation via CD3/CD28. In addition, T-cell proliferation and cytokine expression were markedly reduced when T-cells were stimulated in the presence of PRBCs. Inhibitory activity of PRBCs required direct cell-cell contact and intact PRBCs. The production of activation-induced cellular reactive oxygen species, which act as second messengers in T-cells, was completely abrogated to levels of unstimulated T-cells in the presence of PRBCs. Phosphorylation of the TCR-related zeta chain and thus proximal TCR signal transduction was unaffected by PRBCs, ruling out mechanisms based on secreted factors and steric interaction restrictions. In large part, downstream signaling events requiring reactive oxygen species for full functionality were affected, as confirmed by an untargeted MS-based phosphoproteomics approach. PRBCs inhibited T-cell activation more efficiently than treatment with 1 mM of the antioxidant N-acetyl cysteine. Taken together, our data imply that inflammation-related radical reactions are modulated by PRBCs. These immunomodulating effects may be responsible for clinical observations associated with transfusion of PRBCs.

Asparagine couples mitochondrial respiration to ATF4 activity and tumor growth.

Mitochondrial respiration is critical for cell proliferation. In addition to producing ATP, respiration generates biosynthetic precursors, such as aspartate, an essential substrate for nucleotide synthesis. Here, we show that in addition to depleting intracellular aspartate, electron transport chain (ETC) inhibition depletes aspartate-derived asparagine, increases ATF4 levels, and impairs mTOR complex I (mTORC1) activity. Exogenous asparagine restores proliferation, ATF4 and mTORC1 activities, and mTORC1-dependent nucleotide synthesis in the context of ETC inhibition, suggesting that asparagine communicates active respiration to ATF4 and mTORC1. Finally, we show that combination of the ETC inhibitor metformin, which limits tumor asparagine synthesis, and either asparaginase or dietary asparagine restriction, which limit tumor asparagine consumption, effectively impairs tumor growth in multiple mouse models of cancer. Because environmental asparagine is sufficient to restore tumor growth in the context of respiration impairment, our findings suggest that asparagine synthesis is a fundamental purpose of tumor mitochondrial respiration, which can be harnessed for therapeutic benefit to cancer patients.

Prioritizing Communication About Radiation Risk Reduction in the United States: Results from a Multi-criteria Decision Analysis.

OBJECTIVES: The lack of radiation knowledge among the general public continues to be a challenge for building communities prepared for radiological emergencies. This study applied a multi-criteria decision analysis (MCDA) to the results of an expert survey to identify priority risk reduction messages and challenges to increasing community radiological emergency preparedness. METHODS: Professionals with expertise in radiological emergency preparedness, state/local health and emergency management officials, and journalists/journalism academics were surveyed following a purposive sampling methodology. An MCDA was used to weight criteria of importance in a radiological emergency, and the weighted criteria were applied to topics such as sheltering-in-place, decontamination, and use of potassium iodide. Results were reviewed by respondent group and in aggregate. RESULTS: Sheltering-in-place and evacuation plans were identified as the most important risk reduction measures to communicate to the public. Possible communication challenges during a radiological emergency included access to accurate information; low levels of public trust; public knowledge about radiation; and communications infrastructure failures. CONCLUSIONS: Future assessments for community readiness for a radiological emergency should include questions about sheltering-in-place and evacuation plans to inform risk communication.

PKAN neurodegeneration and residual PANK2 activities in patient erythrocytes.

OBJECTIVE: Pantothenate kinase 2-associated neurodegeneration (PKAN) is a rare neurodegenerative disease caused by mutations in the pantothenate kinase 2 (PANK2) gene. PKAN is associated with iron deposition in the basal ganglia and, occasionally, with the occurrence of misshaped erythrocytes (acanthocytes). The aim of this study was to assess residual activity of PANK2 in erythrocytes of PKAN patients and to correlate these data with the type of PANK2 mutations and the progression of neurodegeneration. METHODS: Residual PANK2 activities in erythrocytes of 14 PKAN patients and 14 related carriers were assessed by a radiometric assay. Clinical data on neurodegeneration included the Barry-Albright Dystonia Scale (BAD-Scale) besides further general patient features. A molecular visualization and analysis program was used to rationalize the influence of the PKAN causing mutations on a molecular level. RESULTS: Erythrocytes of PKAN patients had markedly reduced or no PANK2 activity. However, patients with at least one allele of the c.1583C > T (T528M) or the c.833G > T (R278L) variant exhibited 12-56% of residual PANK2 activity. In line, molecular modeling indicated only minor effects on enzyme structure for these point mutations. On average, these patients with c.1583C > T or c.833G > T variant had lower BAD scores corresponding to lower symptom severity than patients with other PANK2 point mutations. INTERPRETATION: Residual erythrocyte PANK2 activity could be a predictor for the progression of neurodegeneration in PKAN patients. Erythrocytes are an interesting patient-derived cell system with still underestimated diagnostic potential.

Lysophosphatidic acid-induced pro-thrombotic phosphatidylserine exposure and ionophore-induced microvesiculation is mediated by the scramblase TMEM16F in erythrocytes.

Recent studies indicate that erythrocytes actively modulate blood clotting and thrombus formation. The lipid mediator lysophosphatidic acid (LPA) is produced by activated platelets, and triggers a signaling process in erythrocytes. This results in cellular calcium uptake and exposure of phosphatidylserine (PS) at the cell surface, thereby generating activated membrane binding sites for factors of the clotting cascade. Moreover, erythrocytes of patients with a bleeding disorder and mutations in the scramblase TMEM16F show impaired PS exposure and microvesiculation upon treatment with calcium ionophore. We report that TMEM16F inhibitors tannic acid (TA) and epigallocatechin-3-gallate (EGCG) inhibit LPA-induced PS exposure and calcium uptake at low micromolar concentrations; fluoxetine, an antidepressant and a known activator of TMEM16F, enhances these processes. These effectors likewise modulate erythrocyte PS exposure and microvesicle shedding induced by calcium ionophore treatment. Further, LPA-treated erythrocytes triggered thrombin generation in platelet-free plasma which was partially impaired in the presence of TA and EGCG. Thus, this study suggests that LPA activates the scramblase TMEM16F in erythrocytes, thereby possibly mediating a pro-thrombotic function in these cells. EGCG as well as fluoxetine, substances with potentially high plasma concentrations due to alimentation or medical treatment, should be considered as potential effectors of systemic hemostatic regulation.