Annexins: the problem of assessing the biological role for a gene family of multifunctional calcium- and phospholipid-binding proteins

Recombinant human annexin A5 accelerates diabetic wounds healing by regulating skin inflammation

Background

One of the key obstacles to the healing of diabetic wound is the persistence of active inflammation. We previously demonstrated the potential of cell-free fat extract (CEFFE) to promote the healing of diabetic wounds, and annexin A5 (A5) is a crucial anti-inflammatory protein within CEFFE. This study aimed to evaluate the therapeutic potential of A5 in diabetic wounds.

Methods

A5 was loaded into GelMA hydrogels and applied to skin wounds of diabetic mice in vivo. The diabetic wounds with the treatment of GelMA-A5 were observed for 14 days and evaluated by histological analysis. Accessment of inflammation regulation were conducted through anti-CD68 staining, anti-CD86 and anti-CD206 staining, and qRT-PCR of wound tissue. In presence of A5, macrophages stimulated by lipopolysaccharide (LPS) in vitro, and detected through qRT-PCR, flow cytometry, and immunocytofluorescence staining. Besides, epithelial cells were co-cultured with A5 for epithelialization regulation by CCK-8 assay and cell migration assay.

Results

A5 could promote diabetic wound healing and regulate inflammations by promoting the transition of macrophages from M1 to M2 phenotype. In vitro experiments demonstrated that A5 exerted a significant effect on reducing pro-inflammatory factors and inhibiting the polarization of macrophages from M0 toward M1 phenotype. A5 significantly promoted the migration of epithelial cells.

Conclusion

Annexin A5 has a significant impact on the regulation of macrophage inflammation and promotion of epithelialization.

Impact of Annexin A2 on virus life cycles

Due to the limited size of viral genomes, hijacking host machinery by the viruses taking place throughout the virus life cycle is inevitable for the survival and proliferation of the virus in the infected hosts. Recent reports indicated that Annexin A2 (AnxA2), a calcium- and lipid-binding cellular protein, plays an important role as a critical regulator in various steps of the virus life cycle. The multifarious AnxA2 functions in cells, such as adhesion, adsorption, endocytosis, exocytosis, cell proliferation and division, inflammation, cancer metastasis, angiogenesis, etc., are intimately related to the various clinical courses of viral infection. Ubiquitous expression of AnxA2 across multiple cell types indicates the broad range of susceptibility of diverse species of the virus to induce disparate viral disease in various tissues, and intracellular expression of AnxA2 in the cytoplasmic membrane, cytosol, and nucleus suggests the involvement of AnxA2 in the regulation of the different stages of various virus life cycles within host cells. However, it is yet unclear as to the molecular processes on how AnxA2 and the infected virus interplay to regulate virus life cycles and thereby the virus-associated disease courses, and hence elucidation of the molecular mechanisms on AnxA2-mediated virus life cycle will provide essential clues to develop therapeutics deterring viral disease.

Annexin-A5 monomer as a membrane repair agent for the treatment of renal ischemia-reperfusion injury

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is one of the causes of acute kidney injury. Annexin A5 (AnxA5), a calcium-dependent cell membrane-binding protein, shows protective effects in various organ IRI models. This study explored the therapeutic effect of exogenous AnxA5 monomer protein on renal IRI and its potential mechanism of action.

METHODS AND RESULTS

Different doses of AnxA5 were injected intravenously to treat bilateral renal IRI in SD rats. This model confirmed the protective effects of AnxA5 on kidney structure and function. In vitro, HK-2 cells were subjected to hypoxia for 12 h, followed by restoration of normal oxygen supply to simulate IRI. In vitro experiments demonstrated the mechanism of action of AnxA5 by measuring cellular activity and permeability. A comparison of the mutant AnxA5 protein M23 and the application of a calcium-free culture medium further validated the protective effect of AnxA5 by forming a network structure.

CONCLUSIONS

Exogenous AnxA5 monomers prevented renal IRI by binding to the damaged renal tubular epithelial cell membrane, forming a two-dimensional network structure to maintain cell membrane integrity, and ultimately prevent cell death.

The Relevance, Predictability, and Utility of Annexin A5 for Human Physiopathology

As an important functional protein molecule in the human body, human annexin A5 (hAnxA5) is widely found in human cells and body fluids. hAnxA5, the smallest type of annexin, performs a variety of biological functions by reversibly and specifically binding phosphatidylserine (PS) in a calcium-dependent manner and plays an important role in many human physiological and pathological processes. The free state hAnxA5 exists in the form of monomers and usually forms a polymer in a specific self-assembly manner when exerting biological activity. This review systematically discusses the current knowledge and understanding of hAnxA5 from three perspectives: physiopathological relevance, diagnostic value, and therapeutic utility. hAnxA5 affects the occurrence and development of many physiopathological processes. Moreover, hAnxA5 can be used independently or in combination as a biomarker of physiopathological phenomena for the diagnosis of certain diseases. Importantly, based on the properties of hAnxA5, many novel drug candidates have been designed and prepared for application in actual medical practice. However, there are also some gaps and shortcomings in hAnxA5 research. This in-depth study will not only expand the understanding of structural and functional relationships but also promote the application of hAnxA5 in the field of biomedicine.

Molecular characterization and functional implications on mouse peripheral blood mononuclear cells of annexin proteins from Echinococcus granulosus sensu lato

BACKGROUND

Cystic echinococcosis (CE) is a life-threatening zoonotic disease caused by the larval stage of Echinococcus granulosus sensu lato, which employs various strategies to evade the host immune system for survival. Recent advances have revealed the role of annexins as excretory/secretory products, providing new insights into the immune regulation by these proteins in the pathogenesis of CE.

METHODS

Echinococcus granulosus annexin B proteins EgANXB2, EgANXB18, EgANXB20, and EgANXB23 were cloned, expressed, and analyzed using bioinformatic tools. Membrane binding analysis was used to assess their bioactivity, while their immunoreactivity and tissue distribution characteristics were determined experimentally using western blotting and immunofluorescence staining, respectively. Furthermore, quantitative real-time reverse transcription PCR (qRT-PCR) was used to analyze the mRNA expression profiles of EgANXBs in different developmental stages of E. granulosus. Finally, immunofluorescence staining, cell counting kit 8 assays, flow cytometry, transwell migration assays, and qRT-PCR were used to evaluate the functional effects of rEgANXB18 and rEgANXB20 on mouse peripheral blood mononuclear cells (PBMCs).

RESULTS

In this study, we identified four EgANXBs with conserved protein structures and calcium-dependent phospholipid binding activities. rEgANXBs were recognized by serum from sheep infected with E. granulosus and distributed in the germinal layer of fertile cysts. Interestingly, transcription levels of the four EgANXBs were significantly higher in protoscoleces than in 28-day strobilated worms. Moreover, we demonstrated that rEgANXB18 and rEgANXB20 were secretory proteins that could bind to PBMCs and regulate their function. Specifically, rEgANXB18 inhibited cell proliferation and migration while promoting cell apoptosis, NO production, and cytokine profile shifting. In contrast, rEgANXB20 showed limited effects on apoptosis but inhibited NO production.

CONCLUSIONS

Our findings suggested that among the four identified EgANXBs, EgANXB2 and EgANXB23 might play a pivotal role for the development of protoscoleces, while EgANXB18 and EgANXB20, as secretory proteins, appeared to participate in the host-parasite interaction by regulating the function of immune cells.

Comparative proteomics of saliva of healthy and gingivitis individuals from Rio de Janeiro

PURPOSE

In this work, we identified human and bacterial proteomes in the saliva from volunteers with gingivitis or healthy.

EXPERIMENTAL DESIGN

The reported population consisted of 18 volunteers (six with gingivitis and 12 healthy controls). Proteomics characterization was performed using a quantitative mass spectrometry method.

RESULTS

A total of 74 human and 116 bacterial proteins were identified in saliva. The major functional category that was modified in the human proteome was the immune response, followed by transport and protease inhibition. In the bacterial proteome, most of the proteins identified were from the Fusobacteria phylum, followed by Chlamydiae and Spirochaetes.

CONCLUSIONS AND CLINICAL RELEVANCE

We observed statistically relevant differences in the data between the groups. The 15 most important human proteins affecting the variation between case and control groups included cystatin S, alpha amylase, lactotransferrin, and negative elongation factor E. We found that bacterial proteins from Porphyromonas gingivalis and Fusobacterium nucleatum subsp. nucleatum related to the red and orange complexes were closely correlated with the occurrence of periodontal diseases.

Protein nanoarrays using the annexin A5 two-dimensional crystal on supported lipid bilayers

Protein nanoarrays are regularly ordered patterns of proteins fixed on a solid surface with a periodicity on the order of nanometers. They have significant potential applications as highly sensitive bioassays and biosensors. While several researchers have demonstrated the fabrication of protein nanoarrays with lithographic techniques and programmed DNA nanostructures, it has been difficult to fabricate a protein nanoarray containing a massive number of proteins on the surface. We now report the fabrication of nanoarrays of streptavidin molecules using a two-dimensional (2D) crystal of annexin A5 as a template on supported lipid bilayers that are widely used as cell membranes. The 2D crystal of annexin A5 has a six-fold symmetry with a period of about 18 nm. There is a hollow of a diameter of about 10 nm in the unit cell, surrounded by six trimers of annexin A5. We found that a hollow accommodates up to three streptavidin molecules with their orientation controlled, and confirmed that the molecules in the hollow maintain their specific binding capability to biotinylated molecules, which demonstrates that the fabricated nanoarray serves as an effective biosensing platform. This methodology can be directly applied to the fabrication of nanoarrays containing a massive number of any other protein molecules.

A Dominant-Negative Mutant of ANXA7 Impairs Calcium Signaling and Enhances the Proliferation of Prostate Cancer Cells by Downregulating the IP3 Receptor and the PI3K/mTOR Pathway

Annexin A7/ANXA7 is a calcium-dependent membrane fusion protein with tumor suppressor gene (TSG) properties, which is located on chromosome 10q21 and is thought to function in the regulation of calcium homeostasis and tumorigenesis. However, whether the molecular mechanisms for tumor suppression are also involved in the calcium- and phospholipid-binding properties of ANXA7 remain to be elucidated. We hypothesized that the 4 C-terminal endonexin-fold repeats in ANXA7 (GX(X)GT), which are contained within each of the 4 annexin repeats with 70 amino acids, are responsible for both calcium- and GTP-dependent membrane fusion and the tumor suppressor function. Here, we identified a dominant-negative triple mutant (DNTM/DN-ANXA7J) that dramatically suppressed the ability of ANXA7 to fuse with artificial membranes while also inhibiting tumor cell proliferation and sensitizing cells to cell death. We also found that the [DNTM]ANA7 mutation altered the membrane fusion rate and the ability to bind calcium and phospholipids. In addition, in prostate cancer cells, our data revealed that variations in phosphatidylserine exposure, membrane permeabilization, and cellular apoptosis were associated with differential IP3 receptor expression and PI3K/AKT/mTOR modulation. In conclusion, we discovered a triple mutant of ANXA7, associated with calcium and phospholipid binding, which leads to the loss of several essential functions of ANXA7 pertinent to tumor protection and highlights the importance of the calcium signaling and membrane fusion functions of ANXA7 for preventing tumorigenesis.

Role of calcium-sensor proteins in cell membrane repair

Cell membrane repair is a critical process used to maintain cell integrity and survival from potentially lethal chemical, and mechanical membrane injury. Rapid increases in local calcium levels due to a membrane rupture have been widely accepted as a trigger for multiple membrane-resealing models that utilize exocytosis, endocytosis, patching, and shedding mechanisms. Calcium-sensor proteins, such as synaptotagmins (Syt), dysferlin, S100 proteins, and annexins, have all been identified to regulate, or participate in, multiple modes of membrane repair. Dysfunction of membrane repair from inefficiencies or genetic alterations in these proteins contributes to diseases such as muscular dystrophy (MD) and heart disease. The present review covers the role of some of the key calcium-sensor proteins and their involvement in membrane repair.

Enhancing Milk Production by Nutrient Supplements: Strategies and Regulatory Pathways

The enhancement of milk production is essential for dairy animals, and nutrient supplements can enhance milk production. This work summarizes the influence of nutrient supplements-including amino acids, peptides, lipids, carbohydrates, and other chemicals (such as phenolic compounds, prolactin, estrogen and growth factors)-on milk production. We also attempt to provide possible illuminating insights into the subsequent effects of nutrient supplements on milk synthesis. This work may help understand the strategy and the regulatory pathway of milk production promotion. Specifically, we summarize the roles and related pathways of nutrients in promoting milk protein and fat synthesis. We hope this review will help people understand the relationship between nutritional supplementation and milk production.

Ca2+ and Annexins - Emerging Players for Sensing and Transferring Cholesterol and Phosphoinositides via Membrane Contact Sites

Maintaining lipid composition diversity in membranes from different organelles is critical for numerous cellular processes. However, many lipids are synthesized in the endoplasmic reticulum (ER) and require delivery to other organelles. In this scenario, formation of membrane contact sites (MCS) between neighbouring organelles has emerged as a novel non-vesicular lipid transport mechanism. Dissecting the molecular composition of MCS identified phosphoinositides (PIs), cholesterol, scaffolding/tethering proteins as well as Ca²⁺ and Ca²⁺-binding proteins contributing to MCS functioning. Compelling evidence now exists for the shuttling of PIs and cholesterol across MCS, affecting their concentrations in distinct membrane domains and diverse roles in membrane trafficking. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) at the plasma membrane (PM) not only controls endo-/exocytic membrane dynamics but is also critical in autophagy. Cholesterol is highly concentrated at the PM and enriched in recycling endosomes and Golgi membranes. MCS-mediated cholesterol transfer is intensely researched, identifying MCS dysfunction or altered MCS partnerships to correlate with de-regulated cellular cholesterol homeostasis and pathologies. Annexins, a conserved family of Ca²⁺-dependent phospholipid binding proteins, contribute to tethering and untethering events at MCS. In this chapter, we will discuss how Ca²⁺ homeostasis and annexins in the endocytic compartment affect the sensing and transfer of cholesterol and PIs across MCS.

A Role for Two-Pore Channel Type 2 (TPC2)-Mediated Regulation of Membrane Contact Sites During Zebrafish Notochord Biogenesis?

We have previously shown that in the developing trunk of zebrafish embryos, two-pore channel type 2 (TPC2)-mediated Ca2+ release from endolysosomes plays a role in the formation of the skeletal slow muscle. In addition, TPC2-mediated Ca2+ signaling is required for axon extension and the establishment of synchronized activity in the primary motor neurons. Here, we report that TPC2 might also play a role in the development of the notochord of zebrafish embryos. For example, when tpcn2 was knocked down or out, increased numbers of small vacuoles were formed in the inner notochord cells, compared with the single large vacuole in the notochord of control embryos. This abnormal vacuolation was associated with embryos displaying attenuated body axis straightening. We also showed that TPC2 has a distinct pattern of localization in the notochord in embryos at ∼24 hpf. Finally, we conducted RNAseq to identify differentially expressed genes in tpcn2 mutants compared to wild-type controls, and found that those involved in actin filament severing, cellular component morphogenesis, Ca2+ binding, and structural constituent of cytoskeleton were downregulated in the mutants. Together, our data suggest that TPC2 activity plays a key role in notochord biogenesis in zebrafish embryos.

Interplay of membrane crosslinking and curvature induction by annexins

Efficient plasma membrane repair (PMR) is required to repair damage sustained in the cellular life cycle. The annexin family of proteins, involved in PMR, are activated by Ca²⁺ influx from extracellular media at the site of injury. Mechanistic studies of the annexins have been overwhelmingly performed using a single annexin, despite the recruitment of multiple annexins to membrane damage sites in living cells. Hence, we investigate the effect of the presence of the crosslinking annexins, annexin A1, A2 and A6 (ANXA1, ANXA2 and ANXA6) on the membrane curvature induction of annexin A4 (ANXA4) in model membrane systems. Our data support a mechanistic model of PMR where ANXA4 induced membrane curvature and ANXA6 crosslinking promotes wound closure. The model now can be expanded to include ANXA1 and ANXA2 as specialist free edge membrane crosslinkers that act in concert with ANXA4 induced curvature and ANXA6 crosslinking.

Pathobiological functions and clinical implications of annexin dysregulation in human cancers

Annexins are an extensive superfamily of structurally related calcium- and phospholipid-binding proteins, largely conserved and widely distributed among species. Twelve human annexins have been identified, referred to as Annexin A1-13 (A12 remains as of yet unassigned), whose genes are spread throughout the genome on eight different chromosomes. According to their distinct tissue distribution and subcellular localization, annexins have been functionally implicated in a variety of biological processes relevant to both physiological and pathological conditions. Dysregulation of annexin expression patterns and functions has been revealed as a common feature in multiple cancers, thereby emerging as potential biomarkers and molecular targets for clinical application. Nevertheless, translation of this knowledge to the clinic requires in-depth functional and mechanistic characterization of dysregulated annexins for each individual cancer type, since each protein exhibits varying expression levels and phenotypic specificity depending on the tumor types. This review specifically and thoroughly examines the current knowledge on annexin dysfunctions in carcinogenesis. Hence, available data on expression levels, mechanism of action and pathophysiological effects of Annexin A1-13 among different cancers will be dissected, also further discussing future perspectives for potential applications as biomarkers for early diagnosis, prognosis and molecular-targeted therapies. Special attention is devoted to head and neck cancers (HNC), a complex and heterogeneous group of aggressive malignancies, often lately diagnosed, with high mortality, and scarce therapeutic options.

Molecular analysis of Annexin expression in cancer

Background

Uptake of apoptotic cells induces a tolerogenic phenotype in phagocytes and promotes peripheral tolerance. The highly conserved Annexin core domain, present in all members of the Annexin family, becomes exposed on the apoptotic cell-surface and triggers tolerogenic signalling in phagocytes via the Dectin-1 receptor. Consequently, Annexins exposed on tumour cells upon cell death are expected to induce tolerance towards tumour antigens, inhibiting tumour rejection.

Methods

Expression analysis for all Annexin family members was conducted in cancer cell lines of diverse origins. Presentation of Annexins on the cell surface during apoptosis of cancer cell lines was investigated using surface washes and immunoblotting. Expression data from the GEO database was analysed to compare Annexin levels between malignant and healthy tissue.

Results

Six Annexins at least were consistently detected on mRNA and protein level for each investigated cell line. AnxA1, AnxA2 and AnxA5 constituted the major part of total Annexin expression. All expressed Annexins translocated to the cell surface upon apoptosis induction in all cell lines. Human expression data indicate a correlation between immune infiltration and overall Annexin expression in malignant compared to healthy tissue.

Conclusions

This study is the first comprehensive analysis of expression, distribution and presentation of Annexins in cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10075-8.

ANNEXIN A1: Roles in Placenta, Cell Survival, and Nucleus

The unbiased approaches of the last decade have enabled the collection of new data on the biology of annexin A1 (ANXA1) in a variety of scientific aspects, creating opportunities for new biomarkers and/or therapeutic purposes. ANXA1 is found in the plasma membrane, cytoplasm, and nucleus, being described at low levels in the nuclear and cytoplasmic compartments of placental cells related to gestational diabetic diseases, and its translocation from the cytoplasm to the nucleus has been associated with a response to DNA damage. The approaches presented here open pathways for reflection upon, and intrinsic clarification of, the modulating action of this protein in the response to genetic material damage, as well as its level of expression and cellular localization. The objective of this study is to arouse interest, with an emphasis on the mechanisms of nuclear translocation of ANXA1, which remain underexplored and may be beneficial in new inflammatory therapies.

Saliva changes in composition associated to COVID-19: a preliminary study

The coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV 2), is usually associated with a wide variety of clinical presentations from asymptomatic to severe cases. The use of saliva as a diagnostic and monitoring fluid has gained importance since it can be used to investigate the immune response and to direct quantification of antibodies against COVID-19. Additionally, the use of proteomics in saliva has allowed to increase  our understanding of the underlying pathophysiology of diseases, bringing new perspectives on diagnostics, monitoring, and treatment. In this work, we compared the salivary proteome of 10 patients with COVID-19, (five patients with mild and five patients with severe COVID-19) and ten control healthy patients. Through the application of proteomics, we have identified 30 proteins whose abundance levels differed between the COVID-19 groups and the control group. Two of these proteins (TGM3 and carbonic anhydrase-CA6) were validated by the measurement of gGT and TEA respectively, in 98 additional saliva samples separated into two groups: (1) COVID-19 group, integrated by 66 patients who tested positive for COVID-19 (2) control group, composed of 32 healthy individuals who did not show any sign of disease for at least four weeks and were negative for COVID-19 in RT-PCR. In the proteomic study there were observed upregulations in CAZA1, ACTN4, and ANXA4, which are proteins related to the protective response against the virus disturbance, and the upregulation of TGM3, that is correlated to the oxidative damage in pulmonary tissue. We also showed the downregulation in cystatins and CA6 that can be involved in the sensory response to stimulus and possibly related to the presence of anosmia and dysgeusia during the COVID-19. Additionally, the presence of FGB in patients with severe COVID-19 but not in mild COVID-19 patients could indicate a higher viral aggregation and activation in these cases. In conclusion, the salivary proteome in patients with COVID-19 showed changes in proteins related to the protective response to viral infection, and the altered sensory taste perception that occur during the disease. Moreover, gGT and TEA could be potential biomarkers of respiratory complications that can occurs during COVID 19 although further larger studies should be made to corroborate this.

Discovery of potential novel CRBN modulators by virtual screening and bioassay

The incidence of malignant tumor with high mortality is increasing yearly. CRBN E3 ubiquitin ligase was proved to be an antitumor target. It was found that thalidomide and its analogs could bind to CRBN E3 ubiquitin ligase and modulate CRBN. CRBN modulators could promote the binding of CRBN to specific target proteins or block the binding of CRBN to some endogenous proteins. In this way, CRBN modulators suppress various tumor cells by modulating the interactions between CRBN and various antitumor target proteins. However, almost all CRBN modulators reported include glutarimide scaffold. Therefore, the aim of this study is to developed novel CRBN modulators. Virtual screening methods and bioassay methods, including structural similarity search, molecular docking, substructure search, antitumor evaluation and apoptosis assay were used to search novel potential CRBN modulators in Specs database. Finally, 15 compounds exhibited strong inhibition activity against A549 cells. Among these active compounds, The IC₅₀ value against A549 of AG6033 was 0.853 ± 0.030 μM. Apoptosis assay demonstrated that AG6033 could promote apoptosis of A549 cells. Further mechanism studies suggested that AG6033 caused remarkable decrease of GSPT1 and IKZF1, the substrates of CRBN, and AG6033 induced cytotoxic effects was CRBN-dependent.

Pine defense against eggs of an herbivorous sawfly is elicited by an annexin-like protein present in egg-associated secretion

Known elicitors of plant defenses against eggs of herbivorous insects are low-molecular-weight organic compounds associated with the eggs. However, previous studies provided evidence that also proteinaceous compounds present in secretion associated with eggs of the herbivorous sawfly Diprion pini can elicit defensive responses in  Pinus sylvestris. Pine responses induced by the proteinaceous secretion are known to result in enhanced emission of (E)-β-farnesene, which attracts egg parasitoids killing the eggs. Here, we aimed to identify the defense-eliciting protein and elucidate its function. After isolating the defense-eliciting protein from D. pini egg-associated secretion by ultrafiltration and gel electrophoresis, we identified it by MALDI-TOF mass spectrometry as an annexin-like protein, which we named 'diprionin'. Further GC-MS analyses showed that pine needles treated with heterologously expressed diprionin released enhanced quantities of (E)-β-farnesene. Our bioassays confirmed attractiveness of diprionin-treated pine to egg parasitoids. Expression of several pine candidate genes involved in terpene biosynthesis and regulation of ROS homeostasis was similarly affected by diprionin and natural sawfly egg deposition. However, the two treatments had different effects on expression of pathogenesis-related genes (PR1, PR5). Diprionin is the first egg-associated proteinaceous elicitor of indirect plant defense against insect eggs described so far.

From NSAIDs to Glucocorticoids and Beyond

Our interest in inflammation and its treatment stems from ancient times. Hippocrates used willow bark to treat inflammation, and many centuries later, salicylic acid and its derivative aspirin’s ability to inhibit cyclooxygenase enzymes was discovered. Glucocorticoids (GC) ushered in a new era of treatment for both chronic and acute inflammatory disease, but their potentially dangerous side effects led the pharmaceutical industry to seek other, safer, synthetic GC drugs. The discovery of the GC-inducible endogenous anti-inflammatory protein annexin A1 (AnxA1) and other endogenous proresolving mediators has opened a new era of anti-inflammatory therapy. This review aims to recapitulate the last four decades of research on NSAIDs, GCs, and AnxA1 and their anti-inflammatory effects.

A novel BRET based genetic coded biosensor for apoptosis detection at deep tissue level in live animal

ANNEXIN V belongs to a family of phospholipid binding proteins which is able to bind to negatively charged phospholipids such as phosphatidylserine (PS) in the presence of a high affinity Ca²⁺ ion. When apoptosis occurs, even at early stage, PS will be exposed to the outside of the cell surface from the cytoplasm side of membrane leaflets., Therefore ANNEXIN V has been suggested as a bio-marker for imaging early apoptotic events of various cell death including those in disease conditions. However, most ANNEXIN V-based apoptotic detecting techniques were in vitro approaches. Here, we presented a new BRET (Bioluminescence Resonance Energy Transfer) based genetic coded biosensor by fusing ANNEXIN V and a BRET version of NanoLuc (teLuc) for both in vitro and in vivo apoptosis detection. The BRET feature of this new sensor makes it convenient to be applied to both conventional fluorescent-based in vitro apoptosis detection and bioluminescence-based animal live imaging for in vivo study. Because of its robust bioluminescence signal, it is possible to perform the evaluation of the disease-induced apoptotic damage and recovery process directly at deep tissue level in live animal.

Urinary proteomics investigations into contrast-induced acute kidney injury

Some patients have a decline in renal function after contrast medium injection, and this phenomenon is called contrast-induced acute kidney injury (CI-AKI); a small number of people even suffer severe renal failure. To date, the mechanism of CI-AKI remains unclear. We aimed to identify novel potential biomarkers in the urine of patients with CI-AKI through LC-MS/MS and bioinformatics analysis. We enrolled patients who underwent coronary angiography (contrast agent: iohexol). The CI-AKI group included 4 cases, and the non-CI-AKI group included 20 cases. We mixed the 4 CI-AKI samples and 20 non-CI-AKI samples. Then, a 0.6 ml urine sample was used for proteome analysis with LC-MS/MS approach. Metascape, ExPASy, and the Human Protein Atlas were utilized for bioinformatics analysis. We obtained 724 and 830 urine proteins from the CI-AKI and non-CI-AKI groups, respectively. The distribution of the pI values and molecular weights (MWs) of postoperative urine proteins showed no significant difference between the CI-AKI group and the non-CI-AKI group. A total of 99differentially expressed proteins (DEPs) were detected, among which 18 proteins were detected only in tubule cells, and 19 proteins were detected in both tubule cells and glomeruli. With GO analysis, the GEPs were mainly associated with immune response and inflammation. Although biomarkers cannot be asserted from this single pilot study, our results may help advance the understanding of the mechanisms of CI-AKI and identify potential novel biomarkers for further investigation.

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.

Assessment of Chemopreventive Potential of the Plant Extracts against Liver Cancer Using HepG2 Cell Line

The edible parts of the plants Camellia sinensis, Vitis vinifera and Withania somnifera were extensively used in ancient practices such as Ayurveda, owing to their potent biomedical significance. They are very rich in secondary metabolites such as polyphenols, which are very good antioxidants and exhibit anti-carcinogenic properties. This study aims to evaluate the anti-cancerous properties of these plant crude extracts on human liver cancer HepG2 cells. The leaves of Camellia sinensis, Withania somnifera and the seeds of Vitis vinifera were collected and methanolic extracts were prepared. Then, these extracts were subjected to DPPH, α- amylase assays to determine the antioxidant properties. A MTT assay was performed to investigate the viability of the extracts of HepG2 cells, and the mode of cell death was detected by Ao/EtBr staining and flow cytometry with PI Annexin- V FITC dual staining. Then, the protein expression of BAX and BCl2 was studied using fluorescent dye to determine the regulation of the BAX and BCl2 genes. We observed that all the three extracts showed the presence of bioactive compounds such as polyphenols or phytochemicals. The W. somnifera bioactive compounds were found to have the highest anti-proliferative activity on human liver cancer cells.

Annexin A3, a Calcium-Dependent Phospholipid-Binding Protein: Implication in Cancer

Annexin A3 (ANXA3), also known as lipocortin III and placental anticoagulant protein III, has been reported to be dysregulated in tumor tissues and cancer cell lines, and harbors pronounced diagnostic and prognostic value for certain malignancies, such as breast, prostate, colorectal, lung and liver cancer. Aberrant expression of ANXA3 promotes tumor cell proliferation, invasion, metastasis, angiogenesis, and therapy resistance to multiple chemotherapeutic drugs including platinum-based agents, fluoropyrimidines, cyclophosphamide, doxorubicin, and docetaxel. Genetic alterations on the ANXA3 gene have also been reported to be associated with the propensity to form certain inherited, familial tumors. These diverse functions of ANXA3 in tumors collectively indicate that ANXA3 may serve as an attractive target for novel anticancer therapies and a powerful diagnostic and prognostic biomarker for early tumor detection and population risk screening. In this review, we dissect the role of ANXA3 in cancer in detail.

Synthesis and anticancer activity of ethyl 5-amino-1-N-substituted-imidazole-4-carboxylate building blocks

A series of 5-amino-1-N-substituted-imidazole-4-carboxylate building blocks was synthesized and assayed for their antiproliferative potential against human cancer cell lines, including HeLa (cervical), HT-29, HCT-15 (colon), A549 (lung), and MDA-MB-231 (breast) cells. The preliminary screening results revealed that several derivatives containing alkyl chains at the N-1 position of the imidazole core demonstrate a certain inhibitory effect on growth and proliferation. A significant effect was observed following ethyl 5-amino-1-dodecyl-1H-imidazole-4-carboxylate (5e) treatment for 72 h. The IC₅₀ value for HeLa cells was 0.737 ± 0.05 μM, whereas that for HT-29 cells was 1.194 ± 0.02 μM. Further investigations revealed that 5e significantly inhibited tumor cell colony formation and migration, and it exhibited antiadhesive effects on HeLa cells as well as antitubulin activity along with the induction of early apoptosis of HeLa and HT-29 cells. In addition, derivative 5e significantly reduced the cell mitochondrial membrane potential in a dose-dependent manner and induced early apoptosis of HeLa and HT-29 cells, indicating that 5e may serve as a lead compound for further drug discovery and development.

Simultaneous membrane binding of Annexin A4 and A5 suppresses 2D lattice formation while maintaining curvature induction

HYPOTHESIS

Annexin A4 and A5 (ANXA4, ANXA5), both shown to be required for efficient plasma membrane repair (PMR) in living cells, bind as trimers to anionic membranes in the presence of calcium. Both annexins induce membrane curvature and self-assemble into crystal arrays on membranes, observations that have been associated with PMR. However, in-vitro studies of annexins have traditionally been performed using single annexins, despite the recruitment of multiple annexins to the damage site in cells. Hence, we study the potential cooperativity of ANXA4 and ANXA5 during membrane binding.

EXPERIMENTS

Laser injury experiments were performed on MCF7 cells transfected to transiently express labelled ANXA4 and ANXA5 to study the localization of the proteins at the damage site. Using free-edged DOPC/DOPS (9:1) membranes we investigated the annexin-induced membrane rolling by fluorescence microscopy and the lateral arrangement of annexin trimers on the membrane surface by atomic force microscopy (AFM).

FINDING

ANXA4 and ANXA5 colocalise at the damage site of MCF7 cells during repair. A (1:1) mixture of ANXA4 and ANXA5 induces membrane rolling with a time constant intermediate between the value for the pure annexins. While binding of the pure annexins creates crystal lattices, the (1:1) mixture generates a random arrangement of trimers. Thus, curvature induction remains as a functional property of annexin mixtures in PMR rather than crystal formation.

Advances in cancer treatment: a new therapeutic target, Annexin A2

Annexin A2 (ANXA2) is a calcium regulated phospholipid-binding protein. It is expressed in some tumor cells, endothelial cells, macrophages, and mononuclear cells, affecting cell survival and mediating interactions between intercellular and extracellular microenvironment. Aberrant expression of ANXA2 can be used as a potential predictive factor, diagnostic biomarker and therapeutic target in cancer therapy. Investigators used various technologies to target ANXA2 in a preclinical model of human cancers and demonstrated encouraging results. In this review article, we discuss the diagnosis and prognosis latent capacity of ANXA2 in progressive cancers, focus on the exploration of restorative interventions targeting ANXA2 in cancer treatment. Further, we comment on a promising candidate therapy that is conceivable for clinical translation.

Low Annexin A1 level in HTLV-1 infected patients is a potential biomarker for the clinical progression and diagnosis of HAM/TSP

BACKGROUND

Human T-lymphotropic virus 1 (HTLV-1) is etiologically associated with the chronic inflammatory neurodegenerative disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) Annexin A1 (AnxA1) is an anti-inflammatory protein with proposed neuroprotective and anti-neuroinflammatory functions. We hypothesized that ANXA1 gene expression may be dysregulated in HTLV-1-infected HAM/TSP patients.

METHODS

This study involved 37 individuals infected with HTLV-1, including 21 asymptomatic (AS) carriers and 16 with HAM/TSP, and a control group of 30 individuals negative for HTLV-1 and HTLV-2. For AS HTLV-1-positive and HAM/TSP patients, ANXA1 and formyl peptide receptor (FPR1, FPR2 and FPR3) expression and HTLV-1 proviral load (PVL) in peripheral blood cells were evaluated by real-time quantitative PCR (qPCR), and plasma AnxA1 levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

ANXA1 gene expression was increased in the AS group compared with the HAM/TSP and control groups, but the differences were not statistically significant. FPR1 gene expression was higher in patients with HTLV-1 than in controls (AS, p = 0.0032; HAM/TSP, p < 0.0001). Plasma AnxA1 levels were higher in the AS group than in the HAM/TSP group (p = 0.0045), and PVL was higher in patients with HAM/TSP than in AS individuals (p = 0.0162). The use of a combined ROC curve using Annexin 1 levels and proviral load significantly increased the sensitivity and specificity to predict progression to HAM/TSP (AUC = 0.851 and AUC = 0.937, respectively, to AUC = 1000).

CONCLUSIONS

Our results suggest that AnxA1 may be dysregulated in HAM/TSP patients. Serological detection of AnxA1 in association with proviral load may provide a prognostic biomarker for HTLV-1-associated neurodegenerative disease.

Identification of ANXA1 as a potential prognostic biomarker and correlating with immune infiltrates in colorectal cancer

BACKGROUND

ANXA1 is a calcium-dependent phospholipid-binding protein and is frequently associated with inflammation, cell proliferation and apoptosis. However, the relationship between ANXA1 and the prognosis of multiple tumours and tumour infiltrating immune cells remains unclear.

METHODS

Multivariate Cox proportional regression analysis was used for signature genes exploration in the basic of colon adenocarcinoma (COAD) RNA-sequence dataset obtained from TCGA, following the identification of 267 common differentially expressed genes, including ANXA1, among three expression profile datasets (GSE41328, GSE110224, and GSE113513). The differential expression of ANXA1 in different tumours and their corresponding normal tissues were evaluated through the Tumour Immune Estimation Resource (TIMER) and Oncomine database. Subsequently, we investigated the correlation between the expression level of ANXA1 and diverse panel of infiltrating immune cells and their related gene markers in colorectal cancer using correlation analysis in TIMER and GEPIA database.

RESULTS

The high expression of ANXA1 was demonstrated to be closely correlated with poor survival in patients with colorectal cancer. More importantly, we found that changes in ANXA1 expression showed a moderate to strong, and statistically significant, correlation with infiltrating levels of B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils and dendritic cells. By contrast, there are only weak correlations between ANXA1 expression and immune cell infiltration in ESCA and STAD. ANXA1 expression was considerably associated with various immune markers involving immune cell recruitment, polarization of tumour-associated macrophages, and T cell exhaustion.

CONCLUSION

ANXA1 is not only an independent risk factor in the prediction of the prognosis of colorectal cancer, but also a crucial regulator in immune cell infiltration. This study may shed light on the clinical value of ANXA1, especially in the areas of early diagnosis of colorectal cancer and therapeutic target discovery.

ANXA1 enhances tumor proliferation and migration by regulating epithelial-mesenchymal transition and IL-6/JAK2/STAT3 pathway in papillary thyroid carcinoma

Background: Annexin A1 (ANXA1) was discovered to show various effects during tumor initiation and development in a tumor-specific manner. However, the function of ANXA1 in papillary thyroid carcinoma (PTC) has not been reported. Methods: Bioinformatic analyses, RT-PCR and immunohistochemistry were employed to determine the ANXA1 expression level in PTC. Both gain- and loss-of-function studies, including CCK-8, EdU assay, transwell experiment and wound-healing assay were used to investigate the role of ANXA1 in PTC progression. GSEA enrichment analysis was utilized to explore the potential mechanisms of ANXA1 mediated downstream signaling, and ELISA, RT-PCR and western blot were used to confirm the relevance. Results: ANXA1 expression was prominently upregulated in PTC tumor tissues. Ectopic expression of ANXA1 expedited PTC cell proliferation, migration and invasion, whereas ANXA1 knockdown exhibited the opposing trends. Mechanistic investigations showed that ANXA1 regulated epithelial-mesenchymal transition (EMT) and activated the IL-6/JAK2/STAT3 pathway to contribute to PTC malignant behaviors. In particular, loss of ANXA1 retarded tumor burden and suppressed lung metastasis in vivo. Conclusions: In conclusion, our findings identified ANXA1 as a pivotal oncogene during PTC carcinogenesis and ANXA1 might function as a promising therapeutic target and prognostic marker for PTC.

Computational insights into the role of calcium ions in protein–glycosaminoglycan systems

The prediction power of computational methodologies for studying the role of ions in protein–glycosaminoglycan interactions was critically assessed.

Clinical Significance of Annexin A2 Expression in Breast Cancer Patients

Simple Summary

Annexin A2 (AnxA2) is a Ca⁺⁺-dependent phospholipid-binding protein that is involved in invasion and metastasis of breast cancer. However, the expression of AnxA2 in breast cancer patients has not been reported. Here, we show that the expression of AnxA2 was high in tumor tissues and serum samples of breast cancer patients compared to non-cancer patients. The high expression of serum AnxA2 in breast cancer was associated with tumor grade and poor survival. The expression and diagnostic value of serum AnxA2 was high in triple-negative breast cancer (TNBC) subtypes and associated with the phosphorylation of AnxA2 at tyrosine 23. Overall, this study highlights the diagnostic and prognostic significance of AnxA2 in breast cancer.

Abstract

Increasing evidence suggests that AnxA2 contributes to invasion and metastasis of breast cancer. However, the clinical significance of AnxA2 expression in breast cancer has not been reported. The expression of AnxA2 in cell lines, tumor tissues, and serum samples of breast cancer patients were analyzed by immunoblotting, immunohistochemistry, and enzyme-linked immunosorbent assay, respectively. We found that AnxA2 was significantly upregulated in tumor tissues and serum samples of breast cancer patients compared with normal controls. The high expression of serum AnxA2 was significantly associated with tumor grades and poor survival of the breast cancer patients. Based on molecular subtypes, AnxA2 expression was significantly elevated in tumor tissues and serum samples of triple-negative breast cancer (TNBC) patients compared with other breast cancer subtypes. Our analyses on breast cancer cell lines demonstrated that secretion of AnxA2 is associated with its tyrosine 23 (Tyr23) phosphorylation in cells. The expression of non-phosphomimetic mutant of AnxA2 in HCC1395 cells inhibits its secretion from cells compared to wild-type AnxA2, which further suggest that Tyr23 phosphorylation is a critical step for AnxA2 secretion from TNBC cells. Our analysis of AnxA2 phosphorylation in clinical samples further confirmed that the phosphorylation of AnxA2 at Tyr23 was high in tumor tissues of TNBC patients compared to matched adjacent non-tumorigenic breast tissues. Furthermore, we observed that the diagnostic value of serum AnxA2 was significantly high in TNBC compared with other breast cancer subtypes. These findings suggest that serum AnxA2 concentration could be a potential diagnostic biomarker for TNBC patients.

Biological and physical approaches on the role of piplartine (piperlongumine) in cancer

Chronic inflammation provides a favorable microenvironment for tumorigenesis, which opens opportunities for targeting cancer development and progression. Piplartine (PL) is a biologically active alkaloid from long peppers that exhibits anti-inflammatory and antitumor activity. In the present study, we investigated the physical and chemical interactions of PL with anti-inflammatory compounds and their effects on cell proliferation and migration and on the gene expression of inflammatory mediators. Molecular docking data and physicochemical analysis suggested that PL shows potential interactions with a peptide of annexin A1 (ANXA1), an endogenous anti-inflammatory mediator with therapeutic potential in cancer. Treatment of neoplastic cells with PL alone or with annexin A1 mimic peptide reduced cell proliferation and viability and modulated the expression of MCP-1 chemokine, IL-8 cytokine and genes involved in inflammatory processes. The results also suggested an inhibitory effect of PL on tubulin expression. In addition, PL apparently had no influence on cell migration and invasion at the concentration tested. Considering the role of inflammation in the context of promoting tumor initiation, the present study shows the potential of piplartine as a therapeutic immunomodulator for cancer prevention and progression.

Proteome of the Triatomine Digestive Tract: From Catalytic to Immune Pathways; Focusing on Annexin Expression

Rhodnius prolixus, Panstrongylus megistus, Triatoma infestans, and Dipetalogaster maxima are all triatomines and potential vectors of the protozoan Trypanosoma cruzi responsible for human Chagas' disease. Considering that the T. cruzi's cycle occurs inside the triatomine digestive tract (TDT), the analysis of the TDT protein profile is an essential step to understand TDT physiology during T. cruzi infection. To characterize the protein profile of TDT of D. maxima, P. megistus, R. prolixus, and T. infestans, a shotgun liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach was applied in this report. Most proteins were found to be closely related to metabolic pathways such as gluconeogenesis/glycolysis, citrate cycle, fatty acid metabolism, oxidative phosphorylation, but also to the immune system. We annotated this new proteome contribution gathering it with those previously published in accordance with Gene Ontology and KEGG. Enzymes were classified in terms of class, acceptor, and function, while the proteins from the immune system were annotated by reference to the pathways of humoral response, cell cycle regulation, Toll, IMD, JNK, Jak-STAT, and MAPK, as available from the Insect Innate Immunity Database (IIID). These pathways were further subclassified in recognition, signaling, response, coagulation, melanization and none. Finally, phylogenetic affinities and gene expression of annexins were investigated for understanding their role in the protection and homeostasis of intestinal epithelial cells against the inflammation.

Autoantibodies to tumor-associated antigens in lung cancer diagnosis

Lung cancer (LC) accounts for the majority of cancer-related deaths worldwide. Although screening the high-risk population by low-dose CT (LDCT) has reduced mortality, the cost and high false positivity rate has prevented its general diagnostic use. As such, better and more specific minimally invasive biomarkers are needed in general and for early LC detection, specifically. Autoantibodies produced by humoral immune response to tumor-associated antigens (TAA) are emerging as a promising noninvasive biomarker for LC. Given the low sensitivity of any one single autoantibody, a panel approach could provide a more robust and promising strategy to detect early stage LC. In this review, we summarize the background of TAA autoantibodies (TAAb) and the techniques currently used for identifying TAA, as well as recent findings of LC specific antigens and TAAb. This review provides guidance toward the development of accurate and reliable TAAb as immunodiagnostic biomarkers in the early detection of LC.

Recent Advances in Liver Cancer Stem Cells: Non-coding RNAs, Oncogenes and Oncoproteins

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies worldwide, with high morbidity, relapse, metastasis and mortality rates. Although liver surgical resection, transplantation, chemotherapy, radiotherapy and some molecular targeted therapeutics may prolong the survival of HCC patients to a certain degree, the curative effect is still poor, primarily because of tumor recurrence and the drug resistance of HCC cells. Liver cancer stem cells (LCSCs), also known as liver tumor-initiating cells, represent one small subset of cancer cells that are responsible for disease recurrence, drug resistance and death. Therefore, understanding the regulatory mechanism of LCSCs in HCC is of vital importance. Thus, new studies that present gene regulation strategies to control LCSC differentiation and replication are under development. In this review, we provide an update on the latest advances in experimental studies on non-coding RNAs (ncRNAs), oncogenes and oncoproteins. All the articles addressed the crosstalk between different ncRNAs, oncogenes and oncoproteins, as well as their upstream and downstream products targeting LCSCs. In this review, we summarize three pathways, the Wnt/β-catenin signaling pathway, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway, and interleukin 6/Janus kinase 2/signal transducer and activator of transcription 3 (IL6/JAK2/STAT3) signaling pathway, and their targeting gene, c-Myc. Furthermore, we conclude that octamer 4 (OCT4) and Nanog are two important functional genes that play a pivotal role in LCSC regulation and HCC prognosis.

Mechanisms of Insecticidal Action of Metarhizium anisopliae on Adult Japanese Pine Sawyer Beetles (Monochamus alternatus)

Pine wilt disease, caused by Bursaphelenchus xylophilus (pine wood nematode), leads to severe environmental and economic damage. Here, we report the results of experiments on the biological control of pine wilt disease through termination of the insect vector of the nematode and the mechanism of the insecticidal action of Metarhizium anisopliae JEF-279 against Monochamus alternatus (Japanese pine sawyer). A combined treatment with a fungal conidia suspension and a fungal protease-containing culture filtrate caused 75.8% mortality of the insect vector. Additionally, the presence of destruxins was confirmed in the dead Japanese pine sawyer adults, and half of the 10 protein spots in proteomic analysis were identified as an actin related to muscle contraction. Based on proteomic and microscopic analyses, the infection cycle of the Japanese pine sawyer by M. anisopliae JEF-279 was inferred to proceed in the following sequence: (1) host adhesion and germination, (2) epicuticle degradation, (3) growth as blastospore, (4) killing by various fungal toxins (insecticidal metabolites), (5) immune response as defense mechanism, and (6) hyphal extrusion and conidiation. Consequently, the combined fungal conidia suspension and protease-containing culture filtrate treatment may be applied as an insecticidal agent, and flaccid paralysis is likely a major mechanism underlying the insecticidal action of M. anisopliae JEF-279 on host insects.

Annexin A2 gene interacting with viral matrix protein to promote bovine ephemeral fever virus release

Bovine ephemeral fever virus (BEFV) causes bovine ephemeral fever, which can produce considerable economic damage to the cattle industry. However, there is limited experimental evidence regarding the underlying mechanisms of BEFV. Annexin A2 (AnxA2) is a calcium and lipid-conjugated protein that binds phospholipids and the cytoskeleton in a Ca²⁺-dependent manner, and it participates in various cellular functions, including vesicular trafficking, organization of membrane domains, and virus proliferation. The role of the AnxA2 gene during virus infection has not yet been reported. In this study, we observed that AnxA2 gene expression was up-regulated in BHK-21 cells infected with the virus. Additionally, overexpression of the AnxA2 gene promoted the release of mature virus particles, whereas BEFV replication was remarkably inhibited after reducing AnxA2 gene expression by using the small interfering RNA (siRNA). For viral proteins, overexpression of the Matrix (M) gene promotes the release of mature virus particles. Moreover, the AnxA2 protein interaction with the M protein of BEFV was confirmed by GST pull-down and co-immunoprecipitation assays. Experimental results indicate that the C-terminal domain (268-334 aa) of AxnA2 contributes to this interaction. An additional mechanistic study showed that AnxA2 protein interacts with M protein and mediates the localization of the M protein at the plasma membrane. Furthermore, the absence of the AnxA2-V domain could attenuate the effect of AnxA2 on BEFV replication. These findings can contribute to elucidating the regulation of BEFV replication and may have implications for antiviral strategy development.

36-kDa Annexin A3 Isoform Negatively Modulates Lipid Storage in Clear Cell Renal Cell Carcinoma Cells

The adipocyte-like morphology of clear cell renal cell carcinoma (ccRCC) cells results from a grade-dependent neutral lipid accumulation; however, the molecular mechanism and role in renal cancer progression have yet to be clarified. ccRCC shows a gene expression signature consistent with adipogenesis, and the phospholipid-binding protein annexin A3 (AnxA3), a negative regulator of adipocyte differentiation, is down-regulated in RCC and shows a differential expression pattern for two isoforms of 36 and 33 kDa. Using primary cell cultures and cell lines, we investigated the involvement of AnxA3 isoforms in lipid storage modulation of ccRCC cells. We found that the increased accumulation of lipids into ccRCC cells correlated with a decrease of the 36/33 isoform ratio. Treatment with adipogenic medium induced a significant increment of lipid storage in ccRCC cells that had a low 36-kDa AnxA3 expression and 36/33 ratio. The 36-kDa AnxA3 silencing in ccRCC cells increased lipid storage induced by adipogenic medium. These data suggest that 36-kDa AnxA3 negatively modulates the response to adipogenic treatment and may act as negative regulator of lipid storage in ccRCC cells. The subcellular distribution of AnxA3 in the cellular endocytic compartment suggests its involvement in modulation of vesicular trafficking, and it might serve as a putative mechanism of lipid storage regulation in ccRCC cells, opening novel translational outcomes.

Zooming into the Dark Side of Human Annexin-S100 Complexes: Dynamic Alliance of Flexible Partners

Annexins and S100 proteins form two large families of Ca²⁺-binding proteins. They are quite different both structurally and functionally, with S100 proteins being small (10–12 kDa) acidic regulatory proteins from the EF-hand superfamily of Ca²⁺-binding proteins, and with annexins being at least three-fold larger (329 ± 12 versus 98 ± 7 residues) and using non-EF-hand-based mechanism for calcium binding. Members of both families have multiple biological roles, being able to bind to a large cohort of partners and possessing a multitude of functions. Furthermore, annexins and S100 proteins can interact with each other in either a Ca²⁺-dependent or Ca²⁺-independent manner, forming functional annexin-S100 complexes. Such functional polymorphism and binding indiscrimination are rather unexpected, since structural information is available for many annexins and S100 proteins, which therefore are considered as ordered proteins that should follow the classical “one protein–one structure–one function” model. On the other hand, the ability to be engaged in a wide range of interactions with multiple, often unrelated, binding partners and possess multiple functions represent characteristic features of intrinsically disordered proteins (IDPs) and intrinsically disordered protein regions (IDPRs); i.e., functional proteins or protein regions lacking unique tertiary structures. The aim of this paper is to provide an overview of the functional roles of human annexins and S100 proteins, and to use the protein intrinsic disorder perspective to explain their exceptional multifunctionality and binding promiscuity.

Emerging Cancer Epigenetic Mechanisms Regulated by All-Trans Retinoic Acid

All-trans retinoic acid (RA), which is the dietary bioactive derivative obtained from animal (retinol) and plant sources (beta-carotene), is a physiological lipid signal of both embryonic and postembryonic development. During pregnancy, either RA deficiency or an excessive RA intake is teratogenic. Too low or too high RA affects not only prenatal, but also postnatal, developmental processes such as myelopoiesis and mammary gland morphogenesis. In this review, we mostly focus on emerging RA-regulated epigenetic mechanisms involving RA receptor alpha (RARA) and Annexin A8 (ANXA8), which is a member of the Annexin family, as well as ANXA8 regulatory microRNAs (miRNAs). The first cancer showing ANXA8 upregulation was reported in acute promyelocytic leukemia (APL), which induces the differentiation arrest of promyelocytes due to defective RA signaling caused by RARA fusion genes as the PML-RARA gene. Over the years, ANXA8 has also been found to be upregulated in other cancers, even in the absence of RARA fusion genes. Mechanistic studies on human mammary cells and mammary glands of mice showed that ANXA8 upregulation is caused by genetic mutations affecting RARA functions. Although not all of the underlying mechanisms of ANXA8 upregulation have been elucidated, the interdependence of RA-RARA and ANXA8 seems to play a relevant role in some normal and tumorigenic settings.

Doxorubicin-Conjugated Innovative 16-mer DNA Aptamer-Based Annexin A1 Targeted Anti-Cancer Drug Delivery

Aptamers are small, functional single-stranded DNA or RNA oligonucleotides that bind to their targets with high affinity and specificity. Experimentally, aptamers are selected by the systematic evolution of ligands by exponential enrichment (SELEX) method. Here, we have used rational drug designing and bioinformatics methods to design the aptamers, which involves three different steps. First, finding a probable aptamer-binding site, and second, designing the recognition and structural parts of the aptamers by generating a virtual library of sequences, selection of specific sequence via molecular docking, molecular dynamics (MD) simulation, binding energy calculations, and finally evaluating the experimental affinity. Following this strategy, a 16-mer DNA aptamer was designed for Annexin A1 (ANXA1). In a direct binding assay, DNA1 aptamer bound to the ANXA1 with dissociation constants value of 83 nM. Flow cytometry and fluorescence microscopy results also showed that DNA1 aptamer binds specifically to A549, HepG2, U-87 MG cancer cells that overexpress ANXA1 protein, but not to MCF7 and L-02, which are ANXA1 negative cells. We further developed a novel system by conjugating DNA1 aptamer with doxorubicin and its efficacy was studied by cellular uptake and cell viability assay. Also, anti-tumor analysis showed that conjugation of doxorubicin with aptamer significantly enhances targeted therapy against tumors while minimizing overall adverse effects on mice health.

Annexin-A1 promotes RIG-I-dependent signaling and apoptosis via regulation of the IRF3-IFNAR-STAT1-IFIT1 pathway in A549 lung epithelial cells

Within the last century, millions of lives have been lost to the four major Influenza pandemics. These influenza pandemics were all caused by Influenza Type A viruses (IAV) through their ability to undergo antigenic drifts and shifts. A greater understanding of IAV and host–pathogen interactions is required to develop effective therapeutics against future outbreaks. Annexin A1 (ANXA1) is a phospholipid binding, calcium-dependent protein known to play essential roles in multiple cellular functions including inflammation, proliferation, migration, and apoptosis. ANXA1 was previously shown to enhance apoptosis after IAV infection. The current study explores the role of ANXA1 in IAV infection of A549 lung epithelial cells further in the context of RIG-I-dependent signaling using A549 and Crispr/Cas9 ANXA1 deleted (A549∆ANXA1) cells. ANXA1 was found to enhance the expression of a cytoplasmic RNA sensor, RIG-I basally and post-infection. RIG-I activation by 5′ppp-RNA in A549 lung epithelial cell induces apoptotic cell death, which is inhibited when ANXA1 is deleted, and reversed when ANXA1 is re-expressed. RIG-I activation by 5′ppp-RNA stimulates the production of IFNβ from lung epithelial cells to the same extent as monocytic cells, albeit very late after infection at 48–72 h, through IRF3 and STAT1 activation. ANXA1 deletion delays the phosphorylation of IRF3 and STAT1, leading to lower expression of interferon-stimulated genes, such as IFIT1, and silencing IFIT1 inhibited RIG-I-induced cell death. In all, these results suggest that ANXA1 plays a regulatory role in RIG-I signaling and cell death in A549 lung epithelial cells.

RNA-Sequencing-Based Transcriptomic Analysis Reveals a Role for Annexin-A1 in Classical and Influenza A Virus-Induced Autophagy

Influenza viruses have been shown to use autophagy for their survival. However, the proteins and mechanisms involved in the autophagic process triggered by the influenza virus are unclear. Annexin-A1 (ANXA1) is an immunomodulatory protein involved in the regulation of the immune response and Influenza A virus (IAV) replication. In this study, using clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 (CRISPR associated protein 9) deletion of ANXA1, combined with the next-generation sequencing, we systematically analyzed the critical role of ANXA1 in IAV infection as well as the detailed processes governing IAV infection, such as macroautophagy. A number of differentially expressed genes were uniquely expressed in influenza A virus-infected A549 parental cells and A549 ∆ANXA1 cells, which were enriched in the immune system and infection-related pathways. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway revealed the role of ANXA1 in autophagy. To validate this, the effect of mechanistic target of rapamycin (mTOR) inhibitors, starvation and influenza infection on autophagy was determined, and our results demonstrate that ANXA1 enhances autophagy induced by conventional autophagy inducers and influenza virus. These results will help us to understand the underlying mechanisms of IAV infection and provide a potential therapeutic target for restricting influenza viral replication and infection.

Annexin A4 inhibits sulfatide-induced activation of coagulation factor XII

BACKGROUND

Factor XII (FXII) is a plasma serine protease that initiates the intrinsic pathway of blood coagulation upon contact with anionic substances, such as the sulfated glycolipid sulfatide. Annexins (ANXs) have been implicated in the regulation of the blood coagulation reaction by binding to anionic surfaces composed of phospholipids and sulfated glycoconjugates, but their physiological importance is only partially understood.

OBJECTIVE

To test the hypothesis that ANXs are involved in suppressing the intrinsic pathway initiated by sulfatide, we examined the effect of eight recombinant ANX proteins on the intrinsic coagulation reaction and their sulfatide binding activities.

METHODS

Recombinant ANXs were prepared in Escherichia coli expression systems and their anticoagulant effects on the intrinsic pathway initiated by sulfatide were examined using plasma clotting assay and chromogenic assay. ANXA4 active sites were identified by alanine scanning and fold deletion in the core domain.

RESULTS AND CONCLUSIONS

We found that ANXA3, ANXA4, and ANXA5 strongly inhibited sulfatide-induced plasma coagulation. Wild-type and mutated ANXA4 were used to clarify the molecular mechanism involved in inhibition. ANXA4 inhibited sulfatide-induced auto-activation of FXII to FXIIa and the conversion of its natural substrate FXI to FXIa but showed no effect on the protease activity of FXIIa or FXIa. Alanine scanning showed that substitution of the Ca2+ -binding amino acid residue in the fourth fold of the core domain of ANXA4 reduced anticoagulant activity, and deletion of the entire fourth fold of the core domain resulted in complete loss of anticoagulant activity.

ER-luminal [Ca2+] regulation of InsP3 receptor gating mediated by an ER-luminal peripheral Ca2+-binding protein

Modulating cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) by endoplasmic reticulum (ER)-localized inositol 1,4,5-trisphosphate receptor (InsP₃R) Ca²⁺-release channels is a universal signaling pathway that regulates numerous cell-physiological processes. Whereas much is known regarding regulation of InsP₃R activity by cytoplasmic ligands and processes, its regulation by ER-luminal Ca²⁺ concentration ([Ca²⁺]_ER) is poorly understood and controversial. We discovered that the InsP₃R is regulated by a peripheral membrane-associated ER-luminal protein that strongly inhibits the channel in the presence of high, physiological [Ca²⁺]_ER. The widely-expressed Ca²⁺-binding protein annexin A1 (ANXA1) is present in the nuclear envelope lumen and, through interaction with a luminal region of the channel, can modify high-[Ca²⁺]_ER inhibition of InsP₃R activity. Genetic knockdown of ANXA1 expression enhanced global and local elementary InsP₃-mediated Ca²⁺ signaling events. Thus, [Ca²⁺]_ER is a major regulator of InsP₃R channel activity and InsP₃R-mediated [Ca²⁺]_i signaling in cells by controlling an interaction of the channel with a peripheral membrane-associated Ca²⁺-binding protein, likely ANXA1.

Extracellular-Ca2+-Induced Decrease in Small Molecule Electrotransfer Efficiency: Comparison between Microsecond and Nanosecond Electric Pulses

Electroporation—a transient electric-field-induced increase in cell membrane permeability—can be used to facilitate the delivery of anticancer drugs for antitumour electrochemotherapy. In recent years, Ca²⁺ electroporation has emerged as an alternative modality to electrochemotherapy. The antitumor effect of calcium electroporation is achieved as a result of the introduction of supraphysiological calcium doses. However, calcium is also known to play a key role in membrane resealing, potentially altering the pore dynamics and molecular delivery during electroporation. To elucidate the role of calcium for the electrotransfer of small charged molecule into cell we have performed experiments using nano- and micro-second electric pulses. The results demonstrate that extracellular calcium ions inhibit the electrotransfer of small charged molecules. Experiments revealed that this effect is related to an increased rate of membrane resealing. We also employed mathematical modelling methods in order to explain the differences between the CaCl₂ effects after the application of nano- and micro-second duration electric pulses. Simulation showed that these differences occur due to the changes in transmembrane voltage generation in response to the increase in specific conductivity when CaCl₂ concentration is increased.