Biased agonism of protease-activated receptor-1 regulates thromboinflammation in murine sickle cell disease.

ABSTRACT: Sickle cell disease (SCD) is a hereditary hemoglobinopathy marked by hemolytic anemia and vaso-occlusive events (VOEs). Chronic endothelial activation, inflammation, and coagulation activation contribute to vascular congestion, VOEs, and end-organ damage. Coagulation proteases such as thrombin and activated protein C (APC) modulate inflammation and endothelial dysfunction by activating protease-activated receptor 1 (PAR1), a G-protein-coupled receptor. Thrombin cleaves PAR1 at Arg41, while APC cleaves PAR1 at Arg46, initiating either proinflammatory or cytoprotective signaling, respectively, a signaling conundrum known as biased agonism. Our prior research established the role of thrombin and PAR1 in vascular stasis in an SCD mouse model. However, the role of APC and APC-biased PAR1 signaling in thrombin generation, inflammation, and endothelial activation in SCD remains unexplored. Inhibition of APC in SCD mice increased thrombin generation, inflammation, and endothelial activation during both steady state and tumor necrosis factor α challenge. To dissect the individual contributions of thrombin-PAR1 and APC-PAR1 signaling, we used transgenic mice with point mutations at 2 PAR1 cleavage sites, ArgR41Gln (R41Q) imparting insensitivity to thrombin and Arg46Gln (R46Q) imparting insensitivity to APC. Sickle bone marrow chimeras expressing PAR1-R41Q exhibited reduced thrombo-inflammatory responses compared with wild type PAR1 or PAR1-R46Q mice. These findings highlight the potential benefit of reducing thrombin-dependent PAR1 activation while preserving APC-PAR1 signaling in SCD thromboinflammation. These results also suggest that pharmacological strategies promoting biased PAR1 signaling could effectively mitigate vascular complications associated with SCD.

N-Terminal Fragment of Cardiac Myosin Binding Protein C Modulates Cooperative Mechanisms of Thin Filament Activation in Atria and Ventricles.

Cardiac myosin binding protein C (cMyBP-C) is one of the essential control components of the myosin cross-bridge cycle. The C-terminal part of cMyBP-C is located on the surface of the thick filament, and its N-terminal part interacts with actin, myosin, and tropomyosin, affecting both kinetics of the ATP hydrolysis cycle and lifetime of the cross-bridge, as well as calcium regulation of the actin-myosin interaction, thereby modulating contractile function of myocardium. The role of cMyBP-C in atrial contraction has not been practically studied. We examined effect of the N-terminal C0-C1-m-C2 (C0-C2) fragment of cMyBP-C on actin-myosin interaction using ventricular and atrial myosin in an in vitro motility assay. The C0-C2 fragment of cMyBP-C significantly reduced the maximum sliding velocity of thin filaments on both myosin isoforms and increased the calcium sensitivity of the actin-myosin interaction. The C0-C2 fragment had different effects on the kinetics of ATP and ADP exchange, increasing the affinity of ventricular myosin for ADP and decreasing the affinity of atrial myosin. The effect of the C0-C2 fragment on the activation of the thin filament depended on the myosin isoforms. Atrial myosin activates the thin filament less than ventricular myosin, and the C0-C2 fragment makes these differences in the myosin isoforms more pronounced.

A common protein C inhibitor exosite partially controls the heparin induced activation and inhibition of serine proteases.

Protein C inhibitor (PCI) maintains hemostasis by inhibiting both procoagulant and anticoagulant serine proteases, and plays important roles in coagulation, fibrinolysis, reproduction, and anti-angiogenesis. The reactive site loop of PCI traps and irreversibly inhibits the proteases like APC (activating protein C), thrombin (FIIa) and factor Xa (FXa). Previous studies on antithrombin (ATIII) had identified Tyr253 and Glu255 as functional exosites that interact and aid in the inhibition of factor IXa and FXa. Presence of exosite in PCI is not known, however a sequence comparison with the PCI from different vertebrate species and ATIII identified Glu239 to be absolutely conserved. PCI residues analogous to ATIII exosite residues were mutated to R238A and E239A. Purified variant PCI in the presence of heparin (10 µg/ml) showed a 2-4 fold decrease in the rate of inhibition of the proteases. However, the stoichiometry of inhibition of FIIa, APC, and FXa by native PCI, R238A and E239A variants were found to be close to 1.0, which also indicated the formation of stable complexes based on SDS-PAGE and western blot analysis with thrombin and APC. Our findings revealed the possible presence of an exosite in PCI that influences the protease inhibition rates.

The link between high factor VIII to protein C ratio values and poor liver function after major hepatectomy.

Our goal was to assess the coagulation profile in the immediate postoperative time after major liver surgery and its association with the liver function. Our hypothesis is that a decreased synthesis of the coagulation factor levels reflects an impaired liver synthesis following hepatic resection and will be associated with poor outcomes. This is a prospective, observational study recruiting consecutive patients scheduled for major liver resection in a tertiary hospital. Coagulation profile was assessed by conventional assays, viscoelastic assays and coagulation factor levels preoperatively and, on postoperative days 1, 2 and 6. Factor VIII to protein C (FVIII/PC) ratio has been used as a surrogate marker of hemostatic imbalance. Liver function was measured with conventional and indocyanine green (ICG) clearance tests, which were obtained preoperatively and on postoperative days 1 and 2. Sixty patients were recruited and 51 were included in the study. There is a clear increase in FVIII/PC ratio after surgery, which was significantly associated with low liver function, being more pronounced beyond postoperative day 2 and in patients with poorer liver function ( P  < 0.001). High FVIII/PC ratio values were significantly associated with higher postoperative morbidity, prolonged ICU and hospital stay and less survival ( P  < 0.05). High FVIII/PC ratio on postoperative day 2 was found to be predictor of posthepatectomy liver failure (PHLF; area under the ROC curve = 0.8129). Early postoperative high FVIII/PC ratio values are associated with low liver function, PHLF and poorer outcomes in patients undergoing major hepatic resection.

Efficient production of peptidylglycine α-hydroxylating monooxygenase in yeast for protein C-terminal functionalization.

Peptidylglycine α-hydroxylating monooxygenase (PHM) is pivotal for C-terminal amidation of bioactive peptides in animals, offering substantial potential for customized protein synthesis. However, efficient PHM production has been hindered by the complexity of animal cell culture and the absence of glycosylation in bacterial hosts. Here, we demonstrate the recombinant expression of Caenorhabditis elegans PHM in the yeast Pichia pastoris, achieving a remarkable space-time yield of 28.8 U/L/day. This breakthrough surpasses prior PHM production rates and eliminates the need for specialized cultivation equipment or complex transfection steps. Mass spectrometry revealed N-glycosylation at residue N182 of recombinant CePHM, which impacts the enzyme's activity as indicated by biochemical experiments. To showcase the utility of CePHM, we performed C-terminal amidation on ubiquitin at a substrate loading of 30 g/L, a concentration meeting the requirements for pharmaceutical peptide production. Overall, this work establishes an efficient PHM production method, promising advancements in scalable manufacturing of C-terminally modified bioactive peptides and probe proteins.

Analysis of laboratory parameters before the occurrence of hepatic sinusoidal obstruction syndrome in children, adolescents, and young adults after hematopoietic stem cell transplantation.

PURPOSE: Hepatic sinusoidal obstruction syndrome (SOS) is a serious complication following hematopoietic stem cell transplantation (HSCT) in which early diagnosis improves patient outcome. The aim of our study was to detect laboratory parameters following HSCT that can predict the occurrence of SOS. METHODS: This retrospective study included 182 children, adolescents, and young adults who underwent allogeneic or autologous HSCT for the first time (median age 7.2 years). The diagnosis of SOS was based on the pediatric criteria of European Society for Blood and Marrow Transplantation (EBMT). We investigated 15 laboratory parameters after HSCT before the onset of SOS. RESULTS: The overall incidence of SOS was 14.8%. SOS developed in 24 of 126 allogeneic (19.1%) and in 3 of 56 autologous (5.4%) HSCT patients at a median time of 13 days after HSCT. We observed a low SOS mortality rate of 11.1% within 100 days after HSCT. International normalized ratio (INR) ≥ 1.3, activated partial thromboplastin time (aPTT) ≥ 40 s, reptilase time ≥ 18.3 s, factor VIII ≤ 80%, antithrombin III ≤ 75%, protein C ≤ 48%, D-dimer ≥ 315 µg/L, bilirubin ≥ 9 µmol/L, and ferritin ≥ 3100 µg/L showed significant associations with the onset of SOS in the univariate analyses. In the multivariate analysis, INR ≥ 1.3 [odds ratio (OR) = 8.104, p = 0.006], aPTT ≥ 40 s (OR = 10.174, p = 0.001), protein C ≤ 48% (OR = 5.215, p = 0.014), and ferritin ≥ 3100 µg/L (OR = 7.472, p = 0.004) could be confirmed as independent risk factors after HSCT before SOS. If three of the four significant cut-off values were present, the probability of developing SOS was more than 70%. The probability of SOS was 96%, if all four laboratory parameters were changed according to the cut-off values. The values of factor XIII, von Willebrand factor (vWF), von Willebrand factor activity (vWF activity), protein S, fibrinogen, and alanine aminotransferase (ALT) were not relevant for the occurrence of SOS. CONCLUSION: In summary, the laboratory parameters INR, aPTT, protein C, and ferritin were very useful to predict the occurrence of SOS. In addition, this is the first report on a significant association between SOS and high values of INR and aPTT after HSCT before SOS.

Rapid clearing CT-001 restored hemostasis in mice with coagulopathy induced by activated protein C.

BACKGROUND: Activated protein C (APC) is one of the mechanisms contributing to coagulopathy, which is associated with high mortality. The counteraction of the APC pathway could help ameliorate bleeding. However, patients also transform frequently from a hemorrhagic state to a prothrombotic state at a later time. Therefore, a prohemostatic therapeutic intervention should take this thrombotic risk into consideration. OBJECTIVES: CT-001 is a novel factor VIIa (FVIIa) with enhanced activity and desialylated N-glycans for rapid clearance. We assessed CT-001 clearance in multiple species and its ability to reverse APC-mediated coagulopathic blood loss. METHODS: The N-glycans on CT-001 were characterized by liquid chromatography-mass spectrometry. Three species were used to evaluate the pharmacokinetics of the molecule. The potency and efficacy of CT-001 under APC pathway-induced coagulopathic conditions were assessed by coagulation assays and bleeding models. RESULTS: The N-glycosylation sites of CT-001 had high occupancy of desialylated N-glycans. CT-001 exhibited 5 to 16 times higher plasma clearance in human tissue factor knockin mice, rats, and cynomolgus monkeys than wildtype FVIIa. CT-001 corrected the activated partial thromboplastin time and thrombin generation of coagulopathic plasma to normal in in vitro studies. In an APC-mediated saphenous vein bleeding model, 3 mg/kg of CT-001 reduced bleeding time in comparison with wildtype FVIIa. The correction of bleeding by CT-001 was also observed in a coagulopathic tail amputation severe hemorrhage mouse model. The efficacy of CT-001 is independent of the presence of tranexamic acid, and the combination of CT-001 and tranexamic acid does not lead to increased thrombogenicity. CONCLUSION: CT-001 corrected APC pathway-mediated coagulopathic conditions in preclinical studies and could be a potentially safe and effective procoagulant agent for addressing APC-mediated bleeding.

Hemostatic balance between pro- and anticoagulant is maintained during glucocorticoid treatment.

BACKGROUND: Glucocorticoids are associated with an increased risk of venous thrombosis. Glucocorticoid treatment increases coagulation factor and anticoagulant levels; however, its effect on hemostatic function remains unclear. This study aimed to investigate the changes in comprehensive coagulation profiles after glucocorticoid treatment in noninflammatory diseases to elucidate the direct contribution of glucocorticoids to hemostatic function. PROCEDURE: Patients diagnosed with primary immune thrombocytopenia requiring glucocorticoid treatment were prospectively enrolled in this study. Changes in coagulation factors and anticoagulants during glucocorticoid treatment and changes in thrombin generation potential were determined in the absence and presence of soluble thrombomodulin (sTM). RESULTS: Seven treatment cases (four for steroid pulse therapy and three for oral glucocorticoid therapy) in six patients with immune thrombocytopenia were examined. After glucocorticoid treatment, activated partial thromboplastin time significantly shortened, and activities of factor VIII, IX, XI, and XII significantly increased, except for von Willebrand factor antigen. Moreover, antithrombin and protein C (PC) activities significantly increased after glucocorticoid treatment. Two major parameters of thrombin generation potential, endogenous thrombin potential (ETP) and peak thrombin (Peak), significantly increased in the absence of sTM after glucocorticoid treatment. However, no significant increases in either parameter were observed in the presence of sTM. ETP-TM and Peak-TM ratios, which represent resistance to the anticoagulant effect of the PC pathway, significantly decreased after glucocorticoid treatment, suggesting that anticoagulant function via the PC pathway is elevated after glucocorticoid treatment. CONCLUSIONS: As glucocorticoids increase intrinsic coagulation factor and anticoagulant levels, hemostatic balance between pro- and anticoagulant functions is maintained.

Mitigation of trauma-induced endotheliopathy by activated protein C: A potential therapeutic for postinjury thromboinflammation.

BACKGROUND: Activated Protein C (aPC) plays dual roles after injury, driving both trauma-induced coagulopathy (TIC) by cleaving, and thus inactivating, factors Va and VIIIa and depressing fibrinolysis while also mediating an inflammomodulatory milieu via protease activated receptor-1 (PAR-1) cytoprotective signaling. Because of this dual role, it represents and ideal target for study and therapeutics after trauma. A known aPC variant, 3K3A-aPC, has been engineered to preserve cytoprotective activity while retaining minimal anticoagulant activity rendering it potentially ideal as a cytoprotective therapeutic after trauma. We hypothesized that 3K3A-aPC would mitigate the endotheliopathy of trauma by protecting against endothelial permeability. METHODS: We used electric cell-substrate impedance sensing to measure permeability changes in real time in primary endothelial cells. These were cultured, grown to confluence, and treated with a 2 µg/mL solution of 3K3A-aPC at 180 minutes, 120 minutes, 60 minutes, 30 minutes prior to stimulation with ex vivo plasma taken from severely injured trauma patients (Injury Severity Score > 15 and BD < -6) (trauma plasma [TP]). Cells treated with thrombin and untreated cells were included in this study as control groups. Permeability changes were recorded in real time via electric cell-substrate impedance sensing for 30 minutes after treatment with TP. We quantified permeability changes in the control and treatment groups as area under the curve (AUC). Rac1/RhoA activity was also compared between these groups. Statistical significance was determined by one-way ANOVA followed by a post hoc analysis using Tukey's multiple comparison's test. RESULTS: Treatment with aPC mitigated endothelial permeability induced by ex vivo trauma plasma at all pre-treatment time points. The AUC of the 30-minute 3K3A-aPC pretreatment group was higher than TP alone (mean diff. 22.12 95% CI [13.75, 30.49], p < 0.0001) (Figure). Moreover, the AUC of the 60-minute, 120-minute, and 180-minute pretreatment groups was also higher than TP alone (mean diff., 16.30; 95% confidence interval [CI], 7.93-24.67; 19.43; 95% CI, 11.06-27.80, and 18.65; 95% CI, 10.28-27.02;, all p < 0.0001, respectively). Rac1/RhoA activity was higher in the aPC pretreatment group when compared with all other groups ( p < 0.01). CONCLUSION: Pretreatment with 3K3A-aPC, which retains its cytoprotective function but has only ~5% of its anticoagulant function, abrogates the effects of trauma-induced endotheliopathy. This represents a potential therapeutic treatment for dysregulated thromboinflammation for injured patients by minimizing aPC's role in trauma-induced coagulopathy while concurrently amplifying its essential cytoprotective function. LEVEL OF EVIDENCE: Prognostic and Epidemiological; Level III.

The clinical and genetic landscape of early-onset thrombophilia in Japan.

OBJECTIVES: To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan. METHODS/RESULTS: Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019). CONCLUSIONS: We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.

C-terminal modification and functionalization of proteins via a self-cleavage tag triggered by a small molecule.

The precise modification or functionalization of the protein C-terminus is essential but full of challenges. Herein, a chemical approach to modify the C-terminus is developed by fusing a cysteine protease domain on the C-terminus of the protein of interest, which could achieve the non-enzymatic C-terminal functionalization by InsP6-triggered cysteine protease domain self-cleavage. This method demonstrates a highly efficient way to achieve protein C-terminal functionalization and is compatible with a wide range of amine-containing molecules and proteins. Additionally, a reversible C-terminal de-functionalization is found by incubating the C-terminal modified proteins with cysteine protease domain and InsP6, providing a tool for protein functionalization and de-functionalization. Last, various applications of protein C-terminal functionalization are provided in this work, as demonstrated by the site-specific assembly of nanobody drug conjugates, the construction of a bifunctional antibody, the C-terminal fluorescent labeling, and the C-terminal transpeptidation and glycosylation.

BRCA1 frameshift variants leading to extended incorrect protein C termini.

Carriers of BRCA1 germline pathogenic variants are at substantially higher risk of developing breast and ovarian cancer than the general population. Accurate identification of at-risk individuals is crucial for risk stratification and the implementation of targeted preventive and therapeutic interventions. Despite significant progress in variant classification efforts, a sizable portion of reported BRCA1 variants remain as variants of uncertain clinical significance (VUSs). Variants leading to premature protein termination and loss of essential functional domains are typically classified as pathogenic. However, the impact of frameshift variants that result in an extended incorrect terminus is not clear. Using validated functional assays, we conducted a systematic functional assessment of 17 previously reported BRCA1 extended incorrect terminus variants (EITs) and concluded that 16 constitute loss-of-function variants. This suggests that most EITs are likely to be pathogenic. However, one variant, c.5578dup, displayed a protein expression level, affinity to known binding partners, and activity in transcription and homologous recombination assays comparable to the wild-type BRCA1 protein. Twenty-three additional carriers of c.5578dup were identified at a US clinical diagnostic lab and assessed using a family history likelihood model providing, in combination with the functional data, a likely benign interpretation. These results, consistent with family history data in the current study and available data from ClinVar, indicate that most, but not all, BRCA1 variants leading to an extended incorrect terminus constitute loss-of-function variants and underscore the need for comprehensive assessment of individual variants.

Characterization of degradation signals at protein C-termini.

Protein termini are critical for protein functions. They are often more accessible than internal regions and thus are frequently subjected to various modifications that affect protein function. Protein termini also contribute to regulating protein lifespan. Recent studies have revealed a series of degradation signals located at protein C-termini, termed C-degrons or C-end degrons. C-degrons have been implicated as underlying a protein quality surveillance system that eliminates truncated, cleaved and mislocalized proteins. Despite the importance of C-degrons, our knowledge of them remains sparse. Here, we describe an established framework for the characterization of C-degrons by Global Protein Stability (GPS) profiling assay, a fluorescence-based reporter system for measuring protein stability in cellulo. Furthermore, we apply an approach that couples GPS with random peptide libraries for unbiased and context-independent characterization of C-degron motifs. Our methodology provides a robust and efficient platform for analyzing the degron potencies of C-terminal peptides, which can significantly accelerate our understanding of C-degrons.

Association between acute complications in PMM2-CDG patients and haemostasis anomalies: Data from a multicentric study and suggestions for acute management.

OBJECTIVES: Patients with PMM2-CDG develop acute events (stroke-like episodes (SLEs), thromboses, haemorrhages, seizures, migraines) associated with both clotting factors (factor XI) and coagulation inhibitors (antithrombin, protein C and protein S) deficiencies. The aim of the study was to correlate acute events to haemostasis and propose practical guidelines. METHODS: In this multicentric retrospective study, we evaluated clinical, radiological, haemostasis and electroencephalography data for PMM2-CDG patients hospitalized for acute events. Cerebral events were classified as thrombosis, haemorrhage, SLE, or "stroke mimic" (SM: normal brain imaging or evoking a migraine). RESULTS: Thirteen patients had a total of 31 acute episodes: 27 cerebral events with 7 SLEs, 4 venous thromboses, 4 haemorrhages (3 associated with thrombosis), 15 SMs at a mean age of 7.7 years; 4 non-cerebral thromboses, one of which included bleeding. A trigger was frequently involved (infection, head trauma). Although sometimes normal at baseline state, factor XI, antithrombin and protein C levels decreased during these episodes. No correlation between haemostasis anomalies and type of acute event was found. DISCUSSION: Acute events in PMM2-CDG are not negligible and are associated with haemostasis anomalies. An emergency protocol is proposed for their prevention and treatment (https://www.filiere-g2m.fr/urgences). For cerebral events, brain Magnetic Resonance Imaging with perfusion weight imaging and diffusion sequences, electroencephalogram and haemostasis protein levels guide the treatment: anticoagulation, antithrombin or fresh frozen plasma supplementation, antiepileptic therapy. Preventing bleeding and thrombosis is required in cases of surgery, prolonged immobilization, hormone replacement therapy. CONCLUSION: Acute events in PMM2-CDG are associated with abnormal haemostasis, requiring practical guidance.

Oxidation and Phenolysis of Peptide/Protein C-Terminal Hydrazides Afford Salicylaldehyde Ester Surrogates for Chemical Protein Synthesis.

With the growing popularity of serine/threonine ligation (STL) and cysteine/penicillamine ligation (CPL) in chemical protein synthesis, facile and general approaches for the preparation of peptide salicylaldehyde (SAL) esters are urgently needed, especially those viable for obtaining expressed protein SAL esters. Herein, we report the access of SAL ester surrogates from peptide hydrazides (obtained either synthetically or recombinantly) via nitrite oxidation and phenolysis by 3-(1,3-dithian-2-yl)-4-hydroxybenzoic acid (SAL(-COOH)PDT). The resulting peptide SAL(-COOH)PDT esters can be activated to afford the reactive peptide SAL(-COOH) esters for subsequent STL/CPL. While being operationally simple for both synthetic peptides and expressed proteins, the current strategy facilitates convergent protein synthesis and combined application of STL with NCL. The generality of the strategy is showcased by the N-terminal ubiquitination of the growth arrest and DNA damage-inducible protein (Gadd45a), the efficient synthesis of ubiquitin-like protein 5 (UBL-5) via a combined N-to-C NCL-STL strategy, and the C-to-N semisynthesis of a myoglobin (Mb) variant.

3K3A-Activated Protein C Inhibits Choroidal Neovascularization Growth and Leakage and Reduces NLRP3 Inflammasome, IL-1ß, and Inflammatory Cell Accumulation in the Retina.

3K3A-Activated Protein C (APC) is a recombinant variant of the physiological anticoagulant APC with cytoprotective properties and reduced bleeding risks. We studied the potential use of 3K3A-APC as a multi-target therapeutic option for choroidal neovascularization (CNV), a common cause of vision loss in age-related macular degeneration. CNV was induced by laser photocoagulation in a murine model, and 3K3A-APC was intravitreally injected. The impact of 3K3A-APC treatment on myeloid and microglia cell activation and recruitment and on NLRP3 inflammasome, IL-1ß, and VEGF levels was assessed using cryosection, retinal flat-mount immunohistochemistry and vascular imaging. Additionally, we evaluated the use of fluorescein angiography as a surrogate marker for in vivo evaluation of the efficacy of 3K3A-APC treatment against leaking CNV lesions. Our results demonstrated that 3K3A-APC treatment significantly reduced the accumulation and activation of myeloid cells and microglia in the CNV area and decreased the NLRP3 and IL-1ß levels at the CNV site and the surrounding retina. Furthermore, 3K3A-APC treatment resulted in leakage regression and CNV growth suppression. These findings indicate that the anti-inflammatory activities of 3K3A-APC contribute to CNV inhibition. Our study suggests the potential use of 3K3A-APC as a novel multi-target treatment for CNV.

Negative enrichment strategy combined with site-specific derivatization for the C-terminomics.

Protein C-termini containing valuable biological information plays a vital role in various physiological processes, such as protein localization, protein recognition, and signal transduction in organisms. However, C-terminal peptide identification is still challenging due to their low abundance and similar physicochemical properties to other digested peptides. Herein, we developed a simple and mild strategy for the enrichment of C-terminal peptides that incorporates selectively 2-pyridinecarbaldehyde (2-PCA) derivatization of α-amine with negative enrichment by NHS resin. Two synthesized peptides were utilized to evaluate the efficiency of 2-PCA derivatization and optimize the coupling conditions of NHS resin. The feasibility of the method was further validated by enriching the C-terminus of the bovine serum albumin (BSA). Finally, this method was successfully applied to the C-terminus analysis of mouse brain tissue, identifying 404 protein C-termini with physicochemical properties unbiasedly. Additionally, the GO and KEGG analyses revealed that these identified proteins are crucial for proper brain function. In summary, our proposed method is effective and has the potential to facilitate comprehensive C-terminal analysis of proteins. SIGNIFICANCE: Effective enrichment methods are essential for the identification of the proteins C-terminus. In this study, a mild and simple method for negative C-terminal enrichment combined with site-specific derivatization was developed. The enrichment process was simplified and minimized sample loss simultaneously, using 2-PCA derivatization which has high α-amino specificity. Up to 346C-terminal proteins were identified in mouse brain tissue unbiasedly and reliably. This approach has the potential to facilitate comprehensive analysis of protein C-termini in a variety of biological contexts.

Association between fatty liver index and blood coagulation markers: a population-based study.

BACKGROUND: Population-based studies investigating the association between blood coagulation markers and non-alcoholic fatty liver disease (NAFLD) are rare. Thus, we aimed to investigate the relationship between the Fatty Liver Index (FLI) as a measure of hepatic steatosis and plasma concentrations of antithrombin III, D-dimer, fibrinogen D, protein C, protein S, factor VIII, activated partial thromboplastin time (aPTT), quick value and international thromboplastin time (INR) in the general population. METHODS: After the exclusion of participants with anticoagulative treatment, 776 participants (420 women and 356 men, aged 54-74 years) of the population-based KORA Fit study with analytic data on hemostatic factors were included in the present analysis. Linear regression models were used to explore the associations between FLI and hemostatic markers, adjusted for sex, age, alcohol consumption, education, smoking status, and physical activity. In a second model, additional adjustments were made for the history of stroke, hypertension, myocardial infarction, serum non-HDL cholesterol levels, and diabetes status. In addition, analyses were stratified by diabetes status. RESULTS: In the multivariable models (with or without health conditions), significantly positive associations with FLI were obtained for plasma concentrations of D-dimers, factor VIII, fibrinogen D, protein C, protein S, and quick value, while INR and antithrombin III were inversely associated. These associations were weaker in pre-diabetic subjects and largely disappeared in diabetic patients. CONCLUSION: In this population-based study, an increased FLI is clearly related to changes in the blood coagulation system, possibly increasing the risk of thrombotic events. Due to a generally more pro-coagulative profile of hemostatic factors, such an association is not visible in diabetic subjects.

VPS37C facilitates erythroid differentiation by promoting EKLF stability.

The process of erythroid differentiation is orchestrated at the molecular level by a complex network of transcription factors. Erythroid Krüppel-like factor (EKLF/KLF1) is a master erythroid gene regulator that directly regulates most aspects of terminal erythroid differentiation. However, the underlying regulatory mechanisms of EKLF protein stability are still largely unknown. In this study, we identified Vacuolar protein sorting 37 C (VPS37C), a core subunit of the Endosomal sorting complex required for transport-I (ESCRT-I) complex, as an essential regulator of EKLF stability. Our study showed that VPS37C interacts with EKLF and prevents K48-linked polyubiquitination of EKLF and proteasome-mediated EKLF degradation, thus enhancing EKLF protein stability and transcriptional activity. VPS37C overexpression in murine erythroleukemia (MEL) cells promotes hexamethylene bisacetamide (HMBA)-induced erythroid differentiation manifested by up-regulating erythroid-specific EKLF target genes and increasing benzidine-positive cells. In contrast, VPS37C knockdown inhibits HMBA-induced MEL cell erythroid differentiation. Particularly, the restoration of EKLF expression in VPS37C-knockdown MEL cells reverses erythroid-specific gene expression and hemoglobin production. Collectively, our study demonstrated VPS37C is a novel regulator of EKLF ubiquitination and degradation, which plays a positive role in erythroid differentiation of MEL cells by enhancing EKLF protein stability.