Annexin A6 Research Articles

CD9 mediates the uptake of extracellular vesicles from cancer-associated fibroblasts that promote pancreatic cancer cell aggressiveness.

In pancreatic ductal adenocarcinoma (PDAC), signaling from stromal cells is implicated in metastatic progression. Tumor-stroma cross-talk is often mediated through extracellular vesicles (EVs). We previously reported that EVs derived from cancer-associated stromal fibroblasts (CAFs) that are abundant in annexin A6 (ANXA6+ EVs) support tumor cell aggressiveness in PDAC. Here, we found that the cell surface glycoprotein and tetraspanin CD9 is a key component of CAF-derived ANXA6+ EVs for mediating this cross-talk. CD9 was abundant on the surface of ANXA6+ CAFs isolated from patient PDAC samples and from various mouse models of PDAC. CD9 colocalized with CAF markers in the tumor stroma, and CD9 abundance correlated with tumor stage. Blocking CD9 impaired the uptake of ANXA6+ EVs into cultured PDAC cells. Signaling pathway arrays and further analyses revealed that the uptake of CD9+ANXA6+ EVs induced mitogen-activated protein kinase (MAPK) pathway activity, cell migration, and epithelial-to-mesenchymal transition (EMT). Blocking either CD9 or p38 MAPK signaling impaired CD9+ANXA6+ EV-induced cell migration and EMT in PDAC cells. Analysis of bioinformatic datasets indicated that CD9 abundance was an independent marker of poor prognosis in patients with PDAC. Our findings suggest that CD9-mediated stromal cell signaling promotes PDAC progression.

A conserved annexin A6-mediated membrane repair mechanism in muscle, heart, and nerve.

Membrane instability and disruption underlie myriad acute and chronic disorders. Anxa6 encodes the membrane-associated protein annexin A6 and was identified as a genetic modifier of muscle repair and muscular dystrophy. To evaluate annexin A6’s role in membrane repair in vivo, we inserted sequences encoding green fluorescent protein (GFP) into the last coding exon of Anxa6. Heterozygous Anxa6gfp mice expressed a normal pattern of annexin A6 with reduced annexin A6GFP mRNA and protein. High-resolution imaging of wounded muscle fibers showed annexin A6GFP rapidly formed a repair cap at the site of injury. Injured cardiomyocytes and neurons also displayed repair caps after wounding, highlighting annexin A6–mediated repair caps as a feature in multiple cell types. Using surface plasmon resonance, we showed recombinant annexin A6 bound phosphatidylserine-containing lipids in a Ca2+- and dose-dependent fashion with appreciable binding at approximately 50 μM Ca2+. Exogenously added recombinant annexin A6 localized to repair caps and improved muscle membrane repair capacity in a dose-dependent fashion without disrupting endogenous annexin A6 localization, indicating annexin A6 promotes repair from both intracellular and extracellular compartments. Thus, annexin A6 orchestrates repair in multiple cell types, and recombinant annexin A6 may be useful in additional chronic disorders beyond skeletal muscle myopathies.

Possible involvement of annexin A6 in preferential sperm penetration in the germinal disk region.

Graphical abstract During fertilization, avian sperm preferentially penetrate into the perivitelline membrane that covers the germinal disk region where the female nucleus is present. This phenomenon has been observed not only in domestic birds but also in wild birds; however, the mechanisms controlling sperm preference are still unclear. In this study, we investigated the possible involvement of annexin family protein in sperm–egg interaction in Japanese quail. Microscopic examination of fertilized eggs indicated that quail sperm penetration only occurred in the germinal disk region, and sperm localized outside the germinal disk were trapped in the perivitelline membrane. Western blot analysis and immunofluorescence microscopy revealed the presence of annexin A1 and A6 in the oocyte membrane, while annexin A6 localized in the perivitelline space of the germinal disk region. Further, our sperm binding assay using recombinant annexin A6 demonstrated that ejaculated sperm specifically bound to annexin A6 expressed in mammalian cell lines. These results suggest that annexin A6, which is expressed on the surface of oocytes, may function in sperm–egg interaction in the germinal disk region and that this binding may ensure sperm retention on the surface of the egg plasma membrane until fertilization takes place in Japanese quail.Lay summaryIn bird species, fertilization takes place immediately after ovulation of the egg. Sperm preferentially penetrate a specific area of the egg coating that covers the ‘germinal disk region’ – this area contains the cell that needs to be fertilized by a sperm. However, since the bird egg is extremely large in size and sperm must reach the ‘germinal disk region’ to achieve fertilization, it is unclear how this happens. Annexin proteins support fertilization in mammals, and we found that annexin A6 protein exhibits a unique localization in the germinal disk region in the eggs of Japanese quail. To test this interaction, we incubated quail sperm with cells that produced annexin A6 and found that ejaculated sperm bound to the cells. These results suggest that annexin A6 may have a role in the sperm–egg interaction in the germinal disk region in Japanese quail.

Activated polymorphonuclear derived extracellular vesicles are potential biomarkers of periprosthetic joint infection.

Extracellular vesicles (EVs) are considered as crucial players in a wide variety of biological processes. Although their importance in joint diseases or infections has been shown by numerous studies, much less is known about their function in periprosthetic joint infection (PJI). Our aim was to investigate activated polymorphonuclear (PMN)-derived synovial EVs in patients with PJI. (1) Is there a difference in the number and size of extracellular vesicles between periprosthetic joint aspirates of patients with PJI and aseptic loosening? (2) Are these vesicles morphologically different in the two groups? (3) Are there activated PMN-derived EVs in septic samples evaluated by flow cytometry after CD177 labelling? (4) Is there a difference in the protein composition carried by septic and aseptic vesicles? Thirty-four patients (n = 34) were enrolled into our investigation, 17 with PJI and 17 with aseptic prosthesis loosening. Periprosthetic joint fluid was aspirated and EVs were separated. Samples were analysed by nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) and flow cytometry (after Annexin V and CD177 labelling). The protein content of the EVs was studied by mass spectrometry (MS). NTA showed particle size distribution in both groups between 150 nm and 450 nm. The concentration of EVs was significantly higher in the septic samples (p = 0.0105) and showed a different size pattern as compared to the aseptic ones. The vesicular nature of the particles was confirmed by TEM and differential detergent lysis. In the septic group, FC analysis showed a significantly increased event number both after single and double labelling with fluorochrome conjugated Annexin V (p = 0.046) and Annexin V and anti-CD177 (p = 0.0105), respectively. MS detected a significant difference in the abundance of lactotransferrin (p = 0.00646), myeloperoxidase (p = 0.01061), lysozyme C (p = 0.04687), annexin A6 (p = 0.03921) and alpha-2-HS-glycoprotein (p = 0.03146) between the studied groups. An increased number of activated PMN derived EVs were detected in the synovial fluid of PJI patients with a characteristic size distribution and a specific protein composition. The activated PMNs-derived extracellular vesicles can be potential biomarkers of PJI.

Annexins A1 and A2 are recruited to larger lysosomal injuries independently of ESCRTs to promote repair.

Damaged lysosomes can be repaired by calcium release-dependent recruitment of the ESCRT machinery. However, the involvement of annexins, another group of calcium-responding membrane repair proteins, has not been fully addressed. Here, we show that although all ubiquitously expressed annexins (ANXA1, A2, A4, A5, A6, A7, and A11) localize to damaged lysosomes, only ANXA1 and ANXA2 are important for repair. Their recruitment is calcium-dependent, ESCRT-independent, and selective towards lysosomes with large injuries. Lysosomal leakage was more severe when ANXA1 or ANXA2 was depleted compared to that of ESCRT components. These findings suggest that ANXA1 and ANXA2 constitute an additional repair mechanism that serves to minimize leakage from damaged lysosomes.

Abstract PO-148: The role of annexin A6 in triple-negative breast cancer metabolism and disease progression

Abstract Triple-negative breast cancer (TNBC), which accounts for up to 17% of all breast cancer cases in the Unites States, disproportionately affects premenopausal African American and Hispanic women. Here, we report the synergistic function of the tumor suppressor annexin-A6 (AnxA6) and Lapatinib-resistance (Lap-R) in the context of cellular bioenergetics. Metabolic profiling of TNBC cell lines show extensive diversity amongst basal-like (BSL) vs mesenchymal-like (MSL) molecular subtypes. Down regulation of AnxA6 in AnxA6- expressing and Lap-R cell lines attenuated mitochondrial respiration, glycolytic function, and cellular ATP production capacity, decreasing the overall metabolic plasticity of the cell. Additionally, AnxA6-depletion altered lipid metabolism by enhancing the mitochondrial uptake of cytosolic fatty acids for β-oxidation. NMR-based metabolomics revealed that AnxA6 depleted and/or Lap-R TNBC cells have a greater dependency on gluconeogenic precursors including glycine, alanine, lactic acid, and oxaloacetic acid as survival mechanisms. Taken together, this study proposes that altered expression of AnxA6 is accompanied by significant bioenergetic adaptations and hence provide novel insights into the failure of EGFR-targeted therapies as therapeutic options and disease progression in patients with triple-negative breast cancer. Citation Format: Stephen D. Williams, Sarrah E. Widatalla, Amos M. Sakwe. The role of annexin A6 in triple-negative breast cancer metabolism and disease progression [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-148.

Annexin A3: a newly identified player in store‑operated calcium entry

Store‑operated calcium entry (SOCE) is important for refilling endoplasmic reticulum (ER) Ca2+ stores and Ca2+ signaling. Extracellular Ca2+ is conducted by highly Ca2+‑selective Orai channels that are activated by stromal interaction molecule proteins (STIMs), which are sensitive ER Ca2+ sensors. We found an approximately five‑fold increase in annexin A3a (anxa3a) expression levels in stim2b knockout zebrafish. The present study investigated whether annexin A3 protein is involved in SOCE. We used Ca2+ imaging and electrophysiological recordings to determine the effect of annexin A2, A3, and A6 overexpression on SOCE and Orai-dependent Ca2+ currents (ICRAC) in cultured cells. Annexin A3 increased SOCE amplitude and potentiated Ca2+ ICRAC currents. These results suggest that annexin A3 is a positive modulator of SOCE.

Mechanism of annexin A6 promoting differentiation and development of neural progenitor cells into oligodendrocytes

Mechanism of annexin A6 promoting differentiation and development of neural progenitor cells into oligodendrocytes

Novel biomarkers for the early prediction of pediatric cystic echinococcosis post-surgical outcomes

This study aims to search for reliable serological biomarkers allowing the early prediction of cystic echinococcosis (CE) post-operative outcomes. We applied immunoprecipitation (IP) of Echinococcus granulosus protoscolex antigens with pediatric CE patients' plasma collected at 1-month and 1-year post-surgery, followed by Liquid Chromatography with tandem mass spectrometry (LC-MS/MS). We compared IP proteomic content from relapsed patients within the first-year post-surgery (RCE) to cases with no relapses until 3 post-operative years (NRCE). Selected proteins were recombinantly synthesized and assessed for their prognostic performance by Enzyme-linked immunosorbent assay (ELISA). A total of 305 immunoreactive parasitic proteins were identified, 59 of which were significantly more abundant in RCE than NRCE for both time-points. Four proteins showed the most promising characteristics for predicting CE outcomes: cytoplasmic malate dehydrogenase (Eg-cMDH), citrate synthase (Eg-CS), annexin A6 and severin. ELISA-IgG against the four markers were significantly lower at 1-year post-surgery than 1-month in NRCE, in contrast to RCE that displayed either stable or higher levels. The Eg-cMDH and Eg-CS showed the best prognostic performance, with respective probabilities of being "relapse-free" of 83% and 81%, if a decrease of IgG levels occurred between 1-month and 1-year post-surgery. The Eg-cMDH and Eg-CS are promising biomarkers to predict early CE post-surgical outcomes.

Therapeutic Potential of Annexins in Sepsis and COVID-19.

Sepsis is a continuing problem in modern healthcare, with a relatively high prevalence, and a significant mortality rate worldwide. Currently, no specific anti-sepsis treatment exists despite decades of research on developing potential therapies. Annexins are molecules that show efficacy in preclinical models of sepsis but have not been investigated as a potential therapy in patients with sepsis. Human annexins play important roles in cell membrane dynamics, as well as mediation of systemic effects. Most notably, annexins are highly involved in anti-inflammatory processes, adaptive immunity, modulation of coagulation and fibrinolysis, as well as protective shielding of cells from phagocytosis. These discoveries led to the development of analogous peptides which mimic their physiological function, and investigation into the potential of using the annexins and their analogous peptides as therapeutic agents in conditions where inflammation and coagulation play a large role in the pathophysiology. In numerous studies, treatment with recombinant human annexins and annexin analogue peptides have consistently found positive outcomes in animal models of sepsis, myocardial infarction, and ischemia reperfusion injury. Annexins A1 and A5 improve organ function and reduce mortality in animal sepsis models, inhibit inflammatory processes, reduce inflammatory mediator release, and protect against ischemic injury. The mechanisms of action and demonstrated efficacy of annexins in animal models support development of annexins and their analogues for the treatment of sepsis. The effects of annexin A5 on inflammation and platelet activation may be particularly beneficial in disease caused by SARS-CoV-2 infection. Safety and efficacy of recombinant human annexin A5 are currently being studied in clinical trials in sepsis and severe COVID-19 patients.

SARS-CoV-2 Infection Remodels the Phenotype and Promotes Angiogenesis of Primary Human Lung Endothelial Cells.

SARS-CoV-2-associated acute respiratory distress syndrome (ARDS) and acute lung injury are life-threatening manifestations of severe viral infection. The pathogenic mechanisms that lead to respiratory complications, such as endothelialitis, intussusceptive angiogenesis, and vascular leakage remain unclear. In this study, by using an immunofluorescence assay and in situ RNA-hybridization, we demonstrate the capability of SARS-CoV-2 to infect human primary lung microvascular endothelial cells (HL-mECs) in the absence of cytopathic effects and release of infectious particles. Preliminary data point to the role of integrins in SARS-CoV-2 entry into HL-mECs in the absence of detectable ACE2 expression. Following infection, HL-mECs were found to release a plethora of pro-inflammatory and pro-angiogenic molecules, as assessed by microarray analyses. This conditioned microenvironment stimulated HL-mECs to acquire an angiogenic phenotype. Proteome analysis confirmed a remodeling of SARS-CoV-2-infected HL-mECs to inflammatory and angiogenic responses and highlighted the expression of antiviral molecules as annexin A6 and MX1. These results support the hypothesis of a direct role of SARS-CoV-2-infected HL-mECs in sustaining vascular dysfunction during the early phases of infection. The construction of virus-host interactomes will be instrumental to identify potential therapeutic targets for COVID-19 aimed to inhibit HL-mEC-sustained inflammation and angiogenesis upon SARS-CoV-2 infection.

Exosomal annexin A6 induces gemcitabine resistance by inhibiting ubiquitination and degradation of EGFR in triple-negative breast cancer

Exosomes are carriers of intercellular information that regulate the tumor microenvironment, and they have an essential role in drug resistance through various mechanisms such as transporting RNA molecules and proteins. Nevertheless, their effects on gemcitabine resistance in triple-negative breast cancer (TNBC) are unclear. In the present study, we examined the effects of exosomes on TNBC cell viability, colony formation, apoptosis, and annexin A6 (ANXA6)/EGFR expression. We addressed their roles in gemcitabine resistance and the underlying mechanism. Our results revealed that exosomes derived from resistant cancer cells improved cell viability and colony formation and inhibited apoptosis in sensitive cancer cells. The underlying mechanism included the transfer of exosomal ANXA6 from resistant cancer cells to sensitive cancer cells. Isobaric peptide labeling–liquid chromatography–tandem mass spectrometry and western blotting revealed that ANXA6 was upregulated in resistant cancer cells and their derived exosomes. Sensitive cancer cells exhibited resistance with increased viability and colony formation and decreased apoptosis when ANXA6 was stably overexpressed. On the contrary, knockdown ANXA6 restored the sensitivity of cells to gemcitabine. Co-immunoprecipitation expression and GST pulldown assay demonstrated that exosomal ANXA6 and EGFR could interact with each other and exosomal ANXA6 was associated with the suppression of EGFR ubiquitination and downregulation. While adding lapatinib reversed gemcitabine resistance induced by exosomal ANXA6. Moreover, ANXA6 and EGFR protein expression was correlated in TNBC tissues, and exosomal ANXA6 levels at baseline were lower in patients with highly sensitive TNBC than those with resistant TNBC when treated with first-line gemcitabine-based chemotherapy. In conclusion, resistant cancer cell-derived exosomes induced gemcitabine resistance via exosomal ANXA6, which was associated with the inhibition of EGFR ubiquitination and degradation. Exosomal ANXA6 levels in the serum of patients with TNBC might be predictive of the response to gemcitabine-based chemotherapy.

Annexins A1 and A2 Accumulate and Are Immobilized at Cross-Linked Membrane-Membrane Interfaces.

Rapid membrane repair is required to ensure cell survival after rupture of the plasma membrane. The annexin family of proteins is involved in plasma membrane repair (PMR) and is activated by the influx of Ca2+ from the extracellular medium at the site of injury. Annexins A1 and A2 (ANXA1 and ANXA2, respectively) are structurally similar and bind to negatively charged phosphatidylserine (PS) to induce membrane cross-linking and to promote fusion, which are both essential processes that occur during membrane repair. The degree of annexin accumulation and the annexin mobility at cross-linked membranes are important aspects of ANXA1 and ANXA2 function in repair. Here, we quantify ANXA1- and ANXA2-induced membrane cross-linking between giant unilamellar vesicles (GUVs). Time-lapse measurements show that ANXA1 and ANXA2 can induce membrane cross-linking on a time scale compatible with PMR. Cross-linked membrane-membrane interfaces between the GUVs persist in time without fusion, and quantification of confocal microscopy images demonstrates that ANXA1, ANXA2, and, to a lesser extent, PS lipids accumulate at the double membrane interface. Fluorescence recovery after photobleaching shows that the annexins are fully immobilized at the double membrane interface, whereas PS lipids display a 75% decrease in mobility. In addition, the complete immobilization of annexins between two membranes indicates a high degree of network formation between annexins, suggesting that membrane cross-linking is mainly driven by protein-protein interactions.

Annexins A2, A6 and Fetuin-A Affect the Process of Mineralization in Vesicles Derived from Human Osteoblastic hFOB 1.19 and Osteosarcoma Saos-2 Cells.

The mineralization process is initiated by osteoblasts and chondrocytes during intramembranous and endochondral ossifications, respectively. Both types of cells release matrix vesicles (MVs), which accumulate Pi and Ca2+ and form apatites in their lumen. Tissue non-specific alkaline phosphatase (TNAP), a mineralization marker, is highly enriched in MVs, in which it removes inorganic pyrophosphate (PPi), an inhibitor of apatite formation. MVs then bud from the microvilli of mature osteoblasts or hypertrophic chondrocytes and, thanks to the action of the acto-myosin cortex, become released to the extracellular matrix (ECM), where they bind to collagen fibers and propagate mineral growth. In this report, we compared the mineralization ability of human fetal osteoblastic cell line (hFOB 1.19 cells) with that of osteosarcoma cell line (Saos-2 cells). Both types of cells were able to mineralize in an osteogenic medium containing ascorbic acid and beta glycerophosphate. The composition of calcium and phosphate compounds in cytoplasmic vesicles was distinct from that in extracellular vesicles (mostly MVs) released after collagenase-digestion. Apatites were identified only in MVs derived from Saos-2 cells, while MVs from hFOB 1.19 cells contained amorphous calcium phosphate complexes. In addition, AnxA6 and AnxA2 (nucleators of mineralization) increased mineralization in the sub-membrane region in strongly mineralizing Saos-2 osteosarcoma, where they co-localized with TNAP, whereas in less mineralizing hFOB 1.19 osteoblasts, AnxA6, and AnxA2 co-localizations with TNAP were less visible in the membrane. We also observed a reduction in the level of fetuin-A (FetuA), an inhibitor of mineralization in ECM, following treatment with TNAP and Ca channels inhibitors, especially in osteosarcoma cells. Moreover, a fraction of FetuA was translocated from the cytoplasm towards the plasma membrane during the stimulation of Saos-2 cells, while this displacement was less pronounced in stimulated hFOB 19 cells. In summary, osteosarcoma Saos-2 cells had a better ability to mineralize than osteoblastic hFOB 1.19 cells. The formation of apatites was observed in Saos-2 cells, while only complexes of calcium and phosphate were identified in hFOB 1.19 cells. This was also evidenced by a more pronounced accumulation of AnxA2, AnxA6, FetuA in the plasma membrane, where they were partly co-localized with TNAP in Saos-2 cells, in comparison to hFOB 1.19 cells. This suggests that both activators (AnxA2, AnxA6) and inhibitors (FetuA) of mineralization were recruited to the membrane and co-localized with TNAP to take part in the process of mineralization.

The Impact of ANxA6 Gene Polymorphism on the Efficacy of Methotrexate Treatment in Psoriasis Patients

Background: There are great interindividual variations in the clinical efficacy of methotrexate (MTX) treatment and patients’ genetic background seems promising in its explanation. Objectives: The study aimed to test whether the polymorphism of annexin A6 (ANxA6) gene, a susceptibility factor for psoriasis, was associated with the clinical response to MTX therapy. Methods: A total of 325 patients enrolled in the study received oral MTX treatment, of whom 310 completed the 1-year study and performed the genotype analysis. They were defined as responders (a reduction of Psoriasis Area and Severity Index [PASI] score ≥75%) and nonresponders (a reduction of PASI <50%) compared to baseline after 12 weeks of short-time therapy. On 1-year treatment, they were defined as responders if they achieved PASI75 and absolute PASI ≤3, otherwise as nonresponders. The genotypes of 4 single-nucleotide polymorphisms (SNPs) in the ANxA6 gene were verified using the Sequenom platform. Potential predictors associated with the treatment outcome of MTX were assessed by binary logistic regression. Results: We found significant associations for the ANxA6 SNPs of rs11960458, rs960709, and rs13168551 with psoriasis severity. Patients with rs11960458 CC genotype and rs960709 GG genotype showed higher percentages of PASI75 and improvement rates of PASI at 12 weeks. And on 1-year treatment, statistical difference occurred in rs11960458 rather than other SNPs compared between responders and nonresponders that the frequency of CC genotype was higher in responders (p = 0.019). After adjustment for potential confounders, patients with rs11960458 TT/CT genotype (at 12 weeks: OR 0.483, 95% CI 0.245–0.951, p = 0.035; at 1 year: OR 0.483, 95% CI 0.280–0.833, p = 0.009) were significantly more likely to not respond to MTX both on the short-term and long-term treatment, while rs960709 and rs13168551 polymorphisms were only associated with the short-term efficacy of MTX (p = 0.018 and p = 0.036, respectively). Conclusions: The CC ge­notype of ANxA6 (rs11960458) was significantly associated with a better response when compared to those patients with the TT/CT genotype, thus being a potential predictor for the clinical efficacy of MTX.

ANO5 ensures trafficking of annexins in wounded myofibers.

Mutations in ANO5 (TMEM16E) cause limb-girdle muscular dystrophy R12. Defective plasma membrane repair is a likely mechanism. Using myofibers from Ano5 knockout mice, we show that trafficking of several annexin proteins, which together form a cap at the site of injury, is altered upon loss of ANO5. Annexin A2 accumulates at the wound to nearly twice the level observed in WT fibers, while annexin A6 accumulation is substantially inhibited in the absence of ANO5. Appearance of annexins A1 and A5 at the cap is likewise diminished in the Ano5 knockout. These changes are correlated with an alteration in annexin repair cap fine structure and shedding of annexin-positive vesicles. We conclude that loss of annexin coordination during repair is disrupted in Ano5 knockout mice and underlies the defective repair phenotype. Although ANO5 is a phospholipid scramblase, abnormal repair is rescued by overexpression of a scramblase-defective ANO5 mutant, suggesting a novel, scramblase-independent role of ANO5 in repair.

Spontaneous fibrinolysis and possibilities of its acceleration in pulmonary embolism

This review contains the data concerning the mechanisms of spontaneous fibrinolysis in pulmonary vessels and possibilities of its acceleration in pulmonary embolism. The spontaneous fibrinolysis system is known to be sequential and multifactorial, with the interaction of accelerators (t-PA and u-PA) and inhibitors (alpha-2-antiplasmin, PAI-1, TAFI). The fibrinolytic processes take place in case of prevailing reactions of accelerating factors over inhibiting ones. The endothelium of pulmonary vessels possesses pronounced antithrombogenic and profibrinolytic properties, therefore, the processes of fibrinolysis in the pulmonary vascular bed normally occur more intensively than in the vessels of the systemic circulation. The membrane proteins of the endothelium annexins A2 activate plasminogen, whereas thrombomodulin inhibits the activity of PAI-1. The main approaches to increase the fibrinolysis intensity in conditions of pulmonary embolism may be aimed at elevating the activity of fibrinolytic enzymes (enhancing the synthesis of annexins A2, the use of NMDA-receptor antagonists) and suppressing its inhibitors (the use of monoclonal antibodies to alpha-2-antiplasmin, as well as plasminogen activator inhibitor-1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI). Promising directions for future research can be the synthesis of a new generation of tissue-type plasminogen activators, and investigations of the possibility of clinical application of antithrombin and thrombomodulin, angiotensin converting enzyme inhibitors and cortisol antagonists. To meet these challenges, it is necessary to develop new models of venous thrombosis and acute pulmonary embolism in different animal species, with the assessment of the changes in the venous haemodynamics and pulmonary microcirculation on the background of administration of a new class of fibrinolytic agents.

Lack of Annexin A6 Exacerbates Liver Dysfunction and Reduces Lifespan of Niemann-Pick Type C Protein–Deficient Mice

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized by cholesterol accumulation caused by loss-of-function mutations in the Npc1 gene. NPC disease primarily affects the brain, causing neuronal damage and affecting motor coordination. In addition, considerable liver malfunction in NPC disease is common. Recently, we found that the depletion of annexin A6 (ANXA6), which is most abundant in the liver and involved in cholesterol transport, ameliorated cholesterol accumulation in Npc1 mutant cells. To evaluate the potential contribution of ANXA6 in the progression of NPC disease, double-knockout mice (Npc1-/-/Anxa6-/-) were generated and examined for lifespan, neurologic and hepatic functions, as well as liver histology and ultrastructure. Interestingly, lack of ANXA6 in NPC1-deficient animals did not prevent the cerebellar degeneration phenotype, but furtherdeteriorated their compromised hepatic functions and reduced their lifespan. Moreover, livers of Npc1-/-/Anxa6-/- mice contained a significantly elevated number of foam cells congesting the sinusoidal space, a feature commonly associated with inflammation. We hypothesize that ANXA6deficiency in Npc1-/- mice not only does not reverse neurologic and motor dysfunction, but further worsens overall liver function, exacerbating hepatic failure in NPC disease.

ANXA6 suppresses the tumorigenesis of cervical cancer through autophagy induction.

BackgroundAutophagy is an intracellular degradation pathway conserved in eukaryotes. ANXA6 (annexin A6) belongs to a family of calcium‐dependent membrane and phospholipid‐binding proteins. Here, we identify ANXA6 as a newly synthesized protein in starvation‐induced autophagy and validate it as a novel autophagy modulator that regulates autophagosome formation.Results ANXA6 knockdown attenuates starvation‐induced autophagy, while restoration of its expression enhances autophagy. GO (gene ontology) analysis of ANXA6 targets showed that ANXA6 interacts with many RAB GTPases and targets endocytosis and phagocytosis pathways, indicating that ANXA6 exerts its function through protein trafficking. ATG9A (autophagy‐related 9A) is the sole multispanning transmembrane protein and its trafficking through recycling endosomes is an essential step for autophagosome formation. Our results showed that ANXA6 enables appropriate ATG9A+ vesicle trafficking from endosomes to autophagosomes through RAB proteins or F‐actin. In addition, restoration of ANXA6 expression suppresses mTOR (mammalian target of rapamycin) activity through the inhibition of the PI3K (phosphoinositide 3‐kinase)‐AKT and ERK (extracellular signal‐regulated kinase) signaling pathways, which is a negative regulator of autophagy. Functionally, ANXA6 expression is correlated with LC3 (microtubule‐associated protein 1 light chain 3) expression in cervical cancer, and ANXA6 inhibits tumorigenesis through autophagy induction.ConclusionsOur results reveal an important mechanism for ANXA6 in tumor suppression and autophagy regulation.

Revealing the localization of Annexin A6 in matrix vesicles during physiological mineralization

Revealing the localization of Annexin A6 in matrix vesicles during physiological mineralization