Annexins-a family of proteins with distinctive tastes for cell signaling and membrane dynamics

Multi-Omic Analysis Reveals Astrocytic Annexin-A2 as Critical for Network-Level Circadian Timekeeping in the Suprachiasmatic Nucleus

The mammalian suprachiasmatic nucleus (SCN) orchestrates daily (circadian) rhythms of physiology and behavior by broadcasting timing cues generated autonomously by its mutually reinforcing network of ~10,000 neurons and ~3000 astrocytes. Although astrocytic control of extracellular glutamate and GABA has been implicated in driving circadian oscillations in SCN gene expression and neuronal activity, the full scale of the network-level signaling mechanisms is unknown. To understand better how this astrocyte-neuron network operates, we adopted a multi-omics approach, first using SILAC-based mass spectrometry to generate an SCN proteome where ~7% of identified proteins were circadian. This circadian proteome was analyzed bioinformatically alongside existing single-cell RNAseq transcriptomic data to identify the cell-types and processes to which they contribute. This highlighted "S100 protein binding," tracked to astrocytes, and revealed annexin-A2 (Anxa2) as an astrocyte-enriched circadian protein for further investigation. We show that Anxa2 and its partner S100a10 are co-expressed and enriched in SCN astrocytes. We also show that pharmacological disruption of their association acutely and reversibly dysregulated the circadian cycle of astrocytic calcium levels and progressively compromised SCN neuronal oscillations. Anxa2 and S100a10 interaction therefore constitutes an astrocytic cellular signaling axis that regulates circadian neuronal excitability and ultimately SCN network coherence necessary for circadian timekeeping.

Revisiting the role of Annexins in membrane trafficking

Ever since their discovery five decades ago, annexins have been implicated in membrane-related events along endo- and exocytic pathways. Over the years, structural, biochemical and cell imaging studies have revealed that annexins facilitate the organization of membrane domains to allow the formation of tight interactions between membranes destined to fuse. Yet, a comprehensive understanding that would elucidate the molecular characteristics, specific pathways and modes of action in relation to membrane trafficking events for all 12 human annexins is still lacking. By and large, annexins are considered cytosolic proteins that bind to acidic membrane phospholipids upon Ca²⁺ elevation. However, as extended Ca²⁺ stores in the ER, mitochondria and lysosomes continuously exchange Ca²⁺ with the cytosol, significant amounts of annexins remain in contact with membranes for the majority of their intracellular lifespan. Hence, how annexins sense and respond to subcellular Ca2+ fluctuations in a dynamic manner and how this influences their localized lipid-binding preferences and functions still needs further clarification. This review examines earlier and recent observations that highlight the involvement of annexins in membrane traffic at the crossroads of endo- and exocytic pathways. The role of annexins in those less known facets such as membrane contact site formation, membrane repair, exosome biology and membrane-less compartments including annexins as RNA-binding proteins will also be discussed. Together, these new avenues strongly imply that annexins serve as important regulators of membrane trafficking.

Annexin A2 is a potential membrane protein target of cobra venom cytotoxin

Cytotoxin (CTX), a three-finger toxin in cobra venoms, is known to cause cytotoxicity, though inconclusive mechanisms are reported. This study discovered the potential cell membrane protein target of CTX using crosslinking differential mass spectrometry. Among 89 proteins identified, annexin A2-CTX was the most stable binding complex with high binding affinity at the nanomolar scale. The findings provide insights into further investigation of the possible internationalisation pathways of CTX through interaction with annexin A2 in mediating cytotoxicity.

Annexin A3 Represses Endothelial Permeability and Inflammation During Sepsis via Actin Cytoskeleton Modulation

Increased endothelial permeability and a dysregulated inflammatory response play key roles in organ damage in sepsis. The role of annexin A3 (ANXA3) in regulating endothelial permeability and inflammation during sepsis is explored using ANXA3 knockout mice and primary human umbilical vein endothelial cells (HUVECs). The absence of ANXA3 exacerbated sepsis outcomes, including increased mortality, lung injury, leukocyte infiltration, and vascular permeability. ANXA3 is highly expressed in endothelial cells and its loss results in the formation of cytoskeletal stress fibers and a decrease in the expression of the junction proteins zonula occludens (Zo)-1, vascular endothelial (VE)-cadherin, and claudin 5, leading to increase permeability. ANXA3 knockdown also upregulates E-selectin (CD62E) expression through the phosphorylation of activating transcription factor 2 (ATF2), which increases monocyte adhesion in HUVECs after LPS stimulation. Inhibiting actin polymerization reverse these effects. Thus, ANXA3 stabilizes the actin cytoskeleton, playing a protective role in endothelial dysfunction during sepsis.

Precise Oligomer Organization Enhanced Electrostatic Interactions for Efficient Cell Membrane Binding

Efficient binding of cell membranes onto nanomaterials is essential for biomedical applications such as diagnostics and cellular engineering. We find that fine control over oligomer orientation led to enhanced electrostatic interactions with the cell membrane and improved cell membrane capture. Specifically, we designed polycation oligomers incorporating positively charged imidazole heads and alkyl tails synthesized through the reversible addition-fragmentation chain transfer (RAFT) reaction. These oligomers spontaneously self-assemble through head-to-head π-π interactions, and their spatial arrangement markedly accelerates the interaction with negatively charged cell membranes. Experimental results indicate that these oriented oligomers produce a large decrease in the time required to kill bacteria compared to unmodified nanostructures (3 min versus 100 min). This is attributed to locally concentrated electrostatic attraction, which enhances the attraction between nanostructures and negatively charged cell surfaces. Our findings suggest that molecular orientation control could be a promising approach to enhancing interactions between biomaterials and live cells.

Annexin A6 membrane repair protein protects against amyloid-induced dystrophic neurites and tau phosphorylation in Alzheimer's disease model mice

In Alzheimer's disease, accumulation of amyloid-β (Aβ) peptide is thought to cause formation of neurofibrillary tangles composed of hyperphosphorylated tau protein, which correlates with neuronal loss and cognitive impairment, but the mechanism linking Aβ and tau pathologies is unknown. Dystrophic neurites, which surround Aβ plaques and accumulate phosphorylated tau and other proteins, may play a role in seeding and spreading of pathologic tau. Here, we investigate the novel hypothesis that improved membrane repair capacity decreases dystrophic neurite formation by protecting axons from Aβ-induced membrane damage. Using a ratiometric calcium sensor and a FRET-based calpain cleavage sensor, we demonstrate that dystrophic neurites in 5XFAD mice have elevated resting calcium levels and calpain activity because of putative membrane damage. Annexin A6, a plasma membrane repair in muscle and neurons, is present at plasma membrane of neurons and dystrophic neurites in murine and human brains. Overexpression of annexin A6 in brains of 5XFAD mice decreased size and quantity of dystrophic neurites and accumulation of phospho-tau181, an early biomarker of amyloid pathology. Phospho-tau231, another early amyloid biomarker, and phosphorylated of tau kinases, c-jun N-terminal kinase (JNK) and Calmodulin Kinase II (CaMKII) accumulate in dystrophic neurites in the brains of amyloid pathology mice and humans with AD, suggesting that dystrophic neurites are sites of active tau phosphorylation. Overexpression of dominant-negative annexin A6 in 5XFAD mice increased dystrophic neurites and phospho-tau181. Intracerebral injection of recombinant annexin A6 in 5XFAD and APP-NLGF knock-in mice resulted in localization of recombinant A6 to membranes of dystrophic neurites, suggesting therapeutic potential of recombinant annexin A6 for AD. In conclusion, dystrophic neurites have Aβ-induced membrane damage characterized by calcium elevation, calpain activation, and accumulation of tau kinases and phosphorylated tau. Overexpression of annexin A6 reduces dystrophic neurites and phospho-tau accumulation, suggesting that annexin A6-mediated membrane repair may represent a novel therapeutic approach for AD.

ANXA1 promotes intrahepatic cholangiocarcinoma proliferation and growth by regulating glutamine metabolism through GOT1 stabilization

BACKGROUND

Intrahepatic cholangiocarcinoma (ICC) is a malignant tumor with a poor prognosis, marked by a postoperative recurrence rate of 50-60% and a 5-year survival rate of 8-30%. Abnormal tumor metabolism, particularly, amino acid metabolism, plays a key role in malignant progression. However, the molecular mechanisms linking amino acid metabolism to ICC progression remain unclear.

METHODS

Bioinformatics was used to identity the key amino acid metabolism related gene in ICC, qRT-PCR, western blotting and immunohistochemical (IHC) were used to detect the expression of ANXA1 in normal tissues or ICC tissues and cells at mRNA and protein levels. The effects of ANXA1 on the proliferation ability of ICC in vitro and in vivo were investigated using CCK8, cloning formation experiment, EdU, IHC, nude mice subcutaneous tumorigenesis model. Immunoprecipitation, mass spectrometry analysis, protein ubiquitin level detection test, immunofluorescence co-localization, and redox stress metabolite detection test were used to explore the metabolism-related regulatory mechanism of ANXA1.

RESULTS

we employed bioinformatics analysis to classify ICC into metabolic subgroups with distinct prognoses and identified the associated biomarker Annexin A1(ANXA1), whose high expression is correlated with poor prognosis and promotes ICC development. Mass spectrometry analysis revealed that ANXA1 interacts with the key enzyme in glutamine metabolism, glutamic-oxaloacetic transaminase 1(GOT1). Through in vitro and in vivo experiments, overexpressed ANXA1 stabilizes GOT1 by recruiting the deubiquitinase USP5. This stabilization enhances glutamine uptake, as well as the production of aspartate and glutamate, which in turn reduces oxidative stress, thereby promoting tumor cell growth. Moreover, knockdown of ANXA1 combined with glutamine uptake inhibition significantly suppressed ICC cell proliferation and Inhibited subcutaneous tumor formation and growth.

CONCLUSIONS

These results suggest that the ANXA1/USP5/GOT1 axis promotes glutamine metabolism and ICC proliferation and growth. Inhibiting ANXA1 alongside glutamine uptake inhibition offers a promising strategy for treating ICC.

Annexin A2 Contributes to Release of Extracellular Vimentin in Response to Inflammation

Vimentin, an abundant intracellular cytoskeletal protein, is secreted into the extracellular space, where it can amplify tissue destruction in inflammatory diseases. The mechanisms by which inflammation promotes the release of extracellular vimentin (ECV) are not defined. In human subjects, we found > twofold higher levels of ECV in gingival crevicular fluid from periodontitis sites with inflammation compared with healthy sites. In cultures of human gingival fibroblasts (hGFs) treated with 1% serum or IL-1β (10 ng/mL) to model tissue injury or inflammation, respectively, we found that 1% serum increased ECV release > 11-fold while IL-1β further enhanced release 17-fold. Mass spectrometry of vimentin immunoprecipitates identified Annexin A2 (AnxA2), a Ca2+-dependent phospholipid-binding protein, as a potential binding protein of ECV, which was confirmed by immunoprecipitation of cultured hGFs and immunostaining of inflamed human gingiva. IL-1β treatment enhanced the abundance of AnxA2 and vimentin in membrane fractions prepared by sucrose gradients of hGF lysates. IL-1β increased colocalization of ECV and AnxA2 at the outer aspect of the plasma membrane of intact hGFs. Knockdown of AnxA2 with siRNA or inhibition of the unconventional secretory pathway reduced ECV release from hGFs. These findings indicate that the production of ECV by hGFs in response to inflammation is mediated by an AnxA2-dependent, unconventional secretory pathway that may play a role in amplification of the inflammatory response.

Deficiency of KIF15 contributes to oxaliplatin-induced cold hypersensitivity by limiting annexin A2 and enhancing TRPA1 localization in DRG neuronal membrane

Effective treatments for oxaliplatin-induced cold hypersensitivity remain a significant clinical challenge, primarily due to gaps in our understanding of the underlying pathophysiology. Our previous studies have indicated that kinesin-12 (KIF15) is expressed in neurons, suggesting its potential involvement in neurodevelopment and neuronal plasticity. However, its role in mediating chemotherapy-induced pain in primary sensory neurons has not yet been reported. In this study, we found that KIF15-knockout (Kif15-KO) mice showed an increase in cold sensitivity, with this heightened cold hypersensitivity being dependent on the accumulation of the TRP ankyrin 1 (TRPA1) channel on the cell membrane. We further demonstrated that in a model of oxaliplatin-induced peripheral neuropathy (OIPN), KIF15 expression was markedly reduced, coinciding with an increase in TRPA1 membrane localization and a physical interaction between KIF15 and Annexin A2 in peripheral sensory neurons. This suggests a mechanistic link where the loss of KIF15 disrupts the function of Annexin A2, enhancing the localization of TRPA1 on the cell membrane of dorsal root ganglion (DRG) neurons, thereby contributing to cold hypersensitivity. Our results offer a new understanding of the molecular mechanisms underlying chemotherapy-induced cold hypersensitivity, highlighting KIF15 as a key regulator and a potential therapeutic target for conditions like OIPN.

Annexin, a Protein for All Seasons: From Calcium Dependent Membrane Metabolism to RNA Recognition

Annexins are a protein family well known to bind to phospholipids in a calcium-dependent way. They are involved in several different crucial cellular processes such as cell division, calcium signaling, membrane repair, vesicle trafficking, and apoptosis. Although RNA binding for some members of the family was reported long ago, it was only recently that it was shown that a common feature of the family is also the ability to bind RNA, a discovery that has added significantly to our perception of the cellular role of these proteins. In the present review, we discuss the properties of annexins under an updated light and the current knowledge on the RNA binding properties of annexins. We then focus specifically on annexin A11, because this is a less characterized member of the family but, at the same time, a potentially important component of the mRNA transport machinery in neurons. We hope to offer to the reader a more complete picture of the annexins' binding properties and new tools to evaluate the multifaceted functions of this important protein family.

Computational, crystallographic, and biophysical characterizations provide insights into calcium and phosphate binding by human annexin A4

The members of the annexin family are proteins involved in important biological processes that share a common propensity, mediated by the binding of calcium, to interact with membranes. Despite the remarkable amount of literature reports on these proteins several aspects of their functionality remain obscure. Considering the importance of the pH in modulating annexin activities, we here reassessed the pH dependency (range 4.6-7.4) of the binding of the calcium by human annexin A4 (hAnxA4) and determined its structure from crystals obtained in acidic conditions at nearly atomic resolution in media containing different calcium concentrations. The interactions of calcium ions with hAnxA4 were studied using isothermal titration calorimetry measurements and molecular dynamics simulations. Present solution data corroborate and quantify the pH dependence of the binding of calcium to hAnxA4. Moreover, crystallographic structures provide a clear ranking of the metal affinity of the hAnxA4 calcium binding sites. These findings have been extended by performing computational studies that provide information on the binding affinity of the different calcium sites that are in good agreement with the crystallographic data. Crystallographic data highlight the occurrence of unexpected clusterings of positively charged arginine residues that can cooperate for the binding of the phospholipid phosphate moieties. These crystallographic data integrated with molecular dynamics simulations provide an atomic-level description of the local conformational changes associated with calcium release and upload. Interestingly, docking analyses demonstrate the optimal juxtaposition of these arginine residues and calcium ions to correctly anchor phosphatidylserine.

Total proteome and calcium-binding proteins from human breast milk: Exploring the impact of tobacco smoke exposure and environmental factors

This study integrates proteome analysis of human breast milk (HBM) from a homogeneous group of mothers who are of similar age and live in the same geographical area, along with an analysis of essential and potentially toxic elements in HBM in relation to lifestyle and environmental factors. This preliminary proteomic study, which examined 11 samples of HBM from lactating women, identified a total of 1619 proteins across all samples, revealing significant differences in proteomes influenced by lactation stages, parity, and exposure to tobacco smoke. The pilot study aimed to explore the feasibility of correlating certain proteins with several elements, considered as indicators of tobacco smoke and environmental influences on HBM. Notably, a clear and significant correlation was found between altered calcium content in HBM and the proteome fraction associated with calcium-binding proteins. The findings suggest that all analyzed factors impact the HBM proteome and the activity of certain enzymes.

Annexin A: Cell Death, Inflammation, and Translational Medicine

The annexin superfamily proteins, a family of calcium-dependent phospholipid-binding proteins, are involved in a variety of Ca²+-regulated membrane events. Annexin A, expressed in vertebrates, has been implicated in a variety of regulated cell death (RCD) pathways, including apoptosis, autophagy, pyroptosis, ferroptosis, and neutrophil extracellular trap-induced cell death (NETosis). Given that inflammation is a key driver of cell death, the roles of Annexin A in inflammation have been extensively studied. In this review, we discuss the regulatory roles of Annexin A in RCD and inflammation, the development of related targeted therapies in translational medicine, and the application of animal models to study these processes. We also analyze current challenges and discuss future directions for improved diagnostic and therapeutic strategies.

The relevance of calcium-binding domains to promoting activities of annexin A2 in calcium oxalate stone formation

Annexin A2 (ANXA2) is a Ca2+-binding protein involved in kidney stone disease (KSD) but with unclear mechanism. Herein, five Ca2+-binding domains of ANXA2 were mutated by substituting glutamic acid (E) at positions 53rd (domain I), 96th (domain II) and 247th (domain IV), and aspartic acid (D) at positions 162nd (domain III) and 322nd (domain V) with alanine (A). Recombinant ANXA2 wide type (WT) and mutants (E53A, E96A, D162A, E247A and D322A) were constructed, produced, purified and subjected to multiple crystal and functional assays. Crystal assays revealed that ANXA2 WT increased calcium oxalate monohydrate (COM) crystal size during crystallization and enhanced growth and crystal-cell adhesion phases compared with blank and negative controls. However, crystals exposed to all ANXA2 mutants had comparable or slightly lower parameters compared with controls. Although ANXA2 WT did not affect crystal aggregation, its mutants still showed a lower degree of crystal aggregation. Immunofluorescence staining and Ca2+-binding assay demonstrated that ANXA2 WT had the greatest affinity to COM crystals and free Ca2+ ions, whereas all the mutants showed lower affinity. Taken together, all five Ca2+-binding domains are relevant to the promoting activities of ANXA2 in COM stone formation by interacting with COM crystal surfaces and free Ca2+ ions.

Anxa10 and neuropathic pain: Insights into dysregulation of endoplasmic reticulum-mitochondria contact tethering complex and therapeutic potential

The stability of membrane contact sites is critically dependent on Endoplasmic Reticulum mitochondria contact tethering complexes (EMCTCs), and dysregulation of these sites has been implicated in neuropathic diseases. In this study, we examined the role of Annexin A10 (Anxa10), a calcium-dependent protein, in neuropathic pain by investigating its influence on EMCTCs dysregulation. Using RNA sequencing, western blotting, and behavioral assays, we observed that spared nerve injury (SNI)-induced neuropathic pain significantly increased Anxa10 expression levels within the spinal dorsal horn (SDH) of mice. By employing cell-specific gene regulation via the Cre/loxp system, we utilized loxp-modified adeno-associated virus vectors to modulate Anxa10 expression in GAD2-Cre (inhibitory neurons), vGlut2-Cre (excitatory neurons), and Fos-Cre (activity-induced neurons) transgenic mice. Our results demonstrated that specific down-regulation of Anxa10 in excitatory neurons within the SDH alleviated neuropathic pain, whereas up-regulation of Anxa10, regardless of cell type, induced spontaneous pain in mice. Ultrastructural analysis of the endoplasmic reticulum (ER) and mitochondria, as well as double immunofluorescence staining, revealed that downregulation of Anxa10 mitigated the SNI-induced reduction in ER-mitochondrial distance. Additionally, it attenuated the SNI-induced upregulation of key components of EMCTCs, including IP3R, GRP75, and VDAC1, while preventing the SNI-induced downregulation of NCX3 expression. Furthermore, we formulated and validated the hypothesis that SGK1 and PI3K are positioned downstream of Anxa10. The up-regulation of Anxa10 compromised mitochondrial integrity and disrupted mitochondrial networks, ultimately leading to elevated oxidative stress. Collectively, these findings suggest that Anxa10 represents a promising therapeutic target for correcting EMCTCs dysregulation and mitigating neuropathic pain.

Aggregation-induced emission-based fluorescent probes for cellular microenvironment detection

The cellular microenvironment exerts a pivotal regulatory influence on cell survival, function, and behavior. Dynamic analysis and detection of the cellular microenvironment can promptly elucidate changes in cellular microenvironmental information, uncover the pathogenesis of diseases associated with aberrant microenvironments, and aid in predicting disease risk and monitoring disease progression. Aggregation-induced emission (AIE) fluorescent molecules possess unique AIE characteristics and offer significant advantages in imaging and sensing cellular microenvironments. In this review, we present a profile of the remarkable progress achieved in utilizing AIE fluorescent molecules for detecting cellular microenvironments in recent years. We particularly focus on AIE fluorescent probes applied in imaging key parameters of the cellular microenvironment, including pH, viscosity, polarity, and temperature, as well as in analyzing critical biological components of the microenvironment, such as gas signal molecules, metal ions, redox state, and proteins. We underscore the design principles, detection mechanisms, sensing performance, and biological applications of these fluorescent probes. Furthermore, we address the current challenges confronting this field and provide prospects for the future development of AIE probes used for microenvironment detection. We trust that this review will inspire researchers to develop more precise and sensitive AIE fluorescent probes for the detection of cellular microenvironments.

Extracellular vesicles in cancer´s communication: messages we can read and how to answer

Extracellular vesicles (EVs) are emerging as critical mediators of intercellular communication in the tumor microenvironment (TME), profoundly influencing cancer progression. These nano-sized vesicles, released by both tumor and stromal cells, carry a diverse cargo of proteins, nucleic acids, and lipids, reflecting the dynamic cellular landscape and mediating intricate interactions between cells. This review provides a comprehensive overview of the biogenesis, composition, and functional roles of EVs in cancer, highlighting their significance in both basic research and clinical applications. We discuss how cancer cells manipulate EV biogenesis pathways to produce vesicles enriched with pro-tumorigenic molecules, explore the specific contributions of EVs to key hallmarks of cancer, such as angiogenesis, metastasis, and immune evasion, emphasizing their role in shaping TME and driving therapeutic resistance. Concurrently, we submit recent knowledge on how the cargo of EVs can serve as a valuable source of biomarkers for minimally invasive liquid biopsies, and its therapeutic potential, particularly as targeted drug delivery vehicles and immunomodulatory agents, showcasing their promise for enhancing the efficacy and safety of cancer treatments. By deciphering the intricate messages carried by EVs, we can gain a deeper understanding of cancer biology and develop more effective strategies for early detection, targeted therapy, and immunotherapy, paving the way for a new era of personalized and precise cancer medicine with the potential to significantly improve patient outcomes.

Dys-regulated phosphatidylserine externalization as a cell intrinsic immune escape mechanism in cancer

The negatively charged aminophospholipid, phosphatidylserine (PS), is typically restricted to the inner leaflet of the plasma membrane under normal, healthy physiological conditions. PS is irreversibly externalized during apoptosis, where it serves as a signal for elimination by efferocytosis. PS is also reversibly and transiently externalized during cell activation such as platelet and immune cell activation. These events associated with physiological PS externalization are tightly controlled by the regulated activation of flippases and scramblases. Indeed, improper regulation of PS externalization results in thrombotic diseases such as Scott Syndrome, a defect in coagulation and thrombin production, and in the case of efferocytosis, can result in autoimmunity such as systemic lupus erythematosus (SLE) when PS-mediated apoptosis and efferocytosis fails. The physiological regulation of PS is also perturbed in cancer and during viral infection, whereby PS becomes persistently exposed on the surface of such stressed and diseased cells, which can lead to chronic thrombosis and chronic immune evasion. In this review, we summarize evidence for the dysregulation of PS with a main focus on cancer biology and the pathogenic mechanisms for immune evasion and signaling by PS, as well as the discussion of new therapeutic strategies aimed to target externalized PS. We posit that chronic PS externalization is a universal and agnostic marker for diseased tissues, and in cancer, likely reflects a cell intrinsic form of immune escape. The continued development of new therapeutic strategies for targeting PS also provides rationale for their co-utility as adjuvants and with immune checkpoint therapeutics.

Clinical Scaleup of Humanized AnnA1 Antibody Yielded Unexpected High Reticuloendothelial (RES) Uptake in Mice

BACKGROUND/OBJECTIVES

A mouse antibody directed against truncated Annexin A1 showed high tumor retention in pre-clinical cancer models and was approved by the National Cancer Institute Experimental Therapeutics (NExT) program for humanization and large batch cGMP production for toxicology and clinical trials. In this process, a contractor for Leidos accidentally produced a mutated version of humanized AnnA1 (hAnnA1-mut) with a single nucleotide deletion in the terminal Fc coding region that increased the translated size by eight amino acids with random alterations in the final twenty-four amino acids. We investigated the tissue distribution of hAnnA1-mut, hAnnA1, mAnnA1, and isotope-matched human IgG1 under various injection and conjugation conditions with C57BL/6, FVB, and BALB/c nude mice strains.

METHODS

Biodistribution studies were performed 24 h after injection of Tc-99m-HYNIC radiolabeled antibodies (purity > 98%). Non-reducing gel electrophoresis studies were conducted with IR680 labeled antibodies incubated with various mouse sera.

RESULTS

Our results showed that Tc-99m-HYNIC-hAnnA1 had low spleen and liver retention not statistically different from Tc-99m-HYNIC-IgG1 and Tc-99m-HYNIC-mAnnA1, with corresponding higher blood levels; however, Tc-99m-HYNIC-hAnnA1-mut had high levels in the spleen and liver with differences identified among the mouse strains, radiolabeling conditions, and injection routes. Histopathology showed no morphological change in the liver or spleen from any conditions. Gel electrophoresis showed an upward shift of hAnnA1-mut, consistent with the binding of blood serum protein.

CONCLUSIONS

The changes in the Fc region of hAnnA1-mut led to higher liver and spleen uptake, suggesting the antibody's recognition by the innate immune system (likely complement protein binding) and subsequent clearance. Future clinical translation using hAnnA1 and other antibodies needs to limit protein modifications that could drastically reduce blood clearance.

Tomato-derived extracellular vesicles increase intestinal zinc transportation by potentially down-regulating the expression of the metallothionein family

Extracellular vesicles (EVs) have the ability to regulate physiological and pathological processes across species and have been shown to be present in plants. Tomatoes are one of the most widespread vegetables on the market and exhibit a broad range of health-promoting effects, including antioxidant and anti-inflammatory properties. However, little is known about the bioactivity of tomato-derived EVs. Here, we isolated EVs from tomatoes and explored their gene regulatory potential using array-based transcriptomics. Interestingly, using a differentiated Caco-2 monolayer model, tomato-derived EVs were shown to upregulate the transportation of zinc, which may involve the down-regulation of metallothionein proteins (MTs). Differentiated Caco-2 cells internalized tomato-derived EVs. Post-EV treatment the relative expression levels of MT-related mRNAs within the cells decreased by approximately threefold, accompanied by an approximately twofold reduction in intracellular zinc concentration. Additionally, the amount of secreted zinc in the basolateral medium increased by approximately threefold. Moreover, tomato-derived EV regulation of MT gene expression occurred only in differentiated epithelial cells. This effect was observed in differentiated Caco-2 and HIEC-6 cells, whereas no impact was seen on the MT gene in undifferentiated cells. This mechanistic study uniquely demonstrates the bioactivity of tomato-derived EVs, and for the first time, reveals the ability of plant-derived EVs to modify zinc regulation across the intestinal epithelia. This further suggests the potential of plant-derived EVs as functional food supplements in the future.

The Molecular Biology of Placental Transport of Calcium to the Human Foetus

From fertilisation to delivery, calcium must be transported into and within the foetoplacental unit for intracellular signalling. This requires very rapid, precisely located Ca2+ transfers. In addition, from around the eighth week of gestation, increasing amounts of calcium must be routed directly from maternal blood to the foetus for bone mineralisation through a flow-through system, which does not impact the intracellular Ca2+ concentration. These different processes are mediated by numerous membrane-sited Ca2+ channels, transporters, and exchangers. Understanding the mechanisms is essential to direct interventions to optimise foetal development and postnatal bone health and to protect the mother and foetus from pre-eclampsia. Ethical issues limit the availability of human foetal tissue for study. Our insight into the processes of placental Ca2+ handling is advancing rapidly, enabled by developing genetic, analytical, and computer technology. Because of their diverse sources, the reports of new findings are scattered. This review aims to pull the data together and to highlight areas of uncertainty. Areas needing clarification include trafficking, membrane expression, and recycling of channels and transporters in the placental microvilli; placental metabolism of vitamin D in gestational diabetes and pre-eclampsia; and the vascular effects of increased endothelial Orai expression by pregnancy-specific beta-1-glycoproteins PSG1 and PSG9.

Knocking-down annexin A3 suppresses inflammation, oxidative stress, apoptosis, and endoplasmic reticulum stress to attenuate sepsis-induced acute kidney injury in HK2 cells

Objective

Sepsis-induced acute kidney injury (AKI) is considered as a life-threatening complication of sepsis. The purpose of this study is to clarify the involvement of annexin A3 (ANXA3) in sepsis-related AKI.

Material and Methods

Lipopolysaccharide (LPS) was used to establish a cell model based on HK2 cells. ANXA3 expression was quantified through quantitative real-time polymerase chain reaction. Cell proliferative capacities were assessed through 5-ethynyl-2'-deoxyuridine proliferation, cell counting kit-8, and colony formation experiments. Flow cytometry was utilized to analyze apoptotic cells. Inflammatory and oxidative stress indicators were measured by employing corresponding commercial assay kits. Endoplasmic reticulum (ER) stress markers were quantified through western blot analysis.

Results

ANXA3 levels were significantly elevated in HK2 cells treated with LPS and in serum samples obtained from patients with AKI and sepsis (P < 0.001). LPS treatment exacerbated cellular damage, leading to increased ER and oxidative stresses, apoptosis, and inflammation, whereas knocking down ANXA3 significantly reversed these changes (P < 0.001).

Conclusion

Interference with ANXA3 protected HK2 cells from LPS-induced cell injury through inhibiting inflammation, oxidative stress, apoptosis, and ER stress.

Annexin- and calcium-regulated priming of legume root cells for endosymbiotic infection

Legumes establish endosymbioses with arbuscular mycorrhizal (AM) fungi or rhizobia bacteria to improve mineral nutrition. Symbionts are hosted in privileged habitats, root cortex (for AM fungi) or nodules (for rhizobia) for efficient nutrient exchange. To reach these habitats, plants form cytoplasmic cell bridges, key to predicting and guiding fungal hyphae or rhizobia-filled infection thread (IT) root entry. However, the underlying mechanisms are poorly studied. Here we show that unique ultrastructural changes and calcium (Ca2+) spiking signatures, closely associated with Medicago truncatula Annexin 1 (MtAnn1) accumulation, accompany rhizobia-related bridge formation. Loss of MtAnn1 function in M. truncatula affects Ca2+ spike amplitude, cytoplasmic configuration and rhizobia infection efficiency, consistent with a role of MtAnn1 in regulating infection priming. MtAnn1, which evolved in species establishing intracellular symbioses, is also AM-symbiosis-induced and required for proper arbuscule formation. Together, we propose that MtAnn1 is part of an ancient Ca2+-regulatory module for transcellular endosymbiotic infection.

ANXA4 restricts HBV replication by inhibiting autophagic degradation of MCM2 in chronic hepatitis B

BACKGROUND

Hepatitis B virus (HBV) is an enveloped DNA virus that causes chronic hepatitis B (CHB) infection. Annexin, a Ca2+-activated protein, is widely expressed in various organs and tissues and has potential utility in disease diagnosis and treatment. However, the relationship between the annexin family and CHB remains unclear.

METHODS

Clinical samples from hepatitis patients and donors or healthy individuals were collected. Transcriptome sequencing in CHB liver tissues and HBV-infected cells were performed. HepG2.2.15 cells with the full-length HBV genome and HBV-infected HepG2-NTCP cell models were established. HBV-infected mouse model was constructed and adeno-associated virus was utilized.

RESULTS

ANXA4 expression was elevated during CHB infection. ANXA4 knockdown promoted HBV replication and aggravated liver injury, while ANXA4 overexpression alleviated that. Mechanistically, autophagy pathway was activated by ANXA4 deficiency, promoting autophagic degradation of minichromosome maintenance complex component 2 (MCM2). MCM2 inhibition activated HBV replication, while MCM2 overexpression attenuated ANXA4 deficiency-induced HBV replication and liver injury. Clinically, the expression of hepatitis B viral protein was negatively correlated with the ANXA4 levels, and CHB patients with high ANXA4 levels (> 8 ng/ml) showed higher sensitivity to interferon therapy.

CONCLUSIONS

ANXA4 functions as a protective factor during HBV infection. ANXA4 expression is elevated under HBV attack to restrict HBV replication by inhibiting autophagic degradation of MCM2, thereby alleviating liver injury and suppressing the CHB infection process. ANXA4 also enhances the sensitivity of CHB patients to interferon therapy. Therefore, ANXA4 is expected to be a new target for CHB treatment and prognostic evaluation.

Self-Assembly at Curved Biointerfaces

Most of the biological interfaces are curved. Understanding the organizational structures and interaction patterns at such curved biointerfaces is therefore crucial not only for deepening our comprehension of the principles that govern life processes but also for designing and developing targeted drugs aimed at diseased cells and tissues. Despite the considerable efforts dedicated to this area of research, our understanding of curved biological interfaces is still limited. Many aspects of these interfaces remain elusive, presenting both challenges and opportunities for further exploration. In this review, we summarize the structural characteristics of biological interfaces found in nature, the current research status of materials associated with curved biointerfaces, and the theoretical advancements achieved to date. Finally, we outline future trends and challenges in the theoretical and technological development of curved biointerfaces. By addressing these challenges, people could bridge the knowledge gap and unlock the full potential of curved biointerfaces for scientific and technological advancements, ultimately benefiting various fields and improving human health and well-being.

Tenascin-C from the tissue microenvironment promotes muscle stem cell self-renewal through Annexin A2

Skeletal muscle tissue self-repair occurs through the finely timed activation of resident muscle stem cells (MuSC). Following perturbation, MuSC exit quiescence, undergo myogenic commitment, and differentiate to regenerate the injured muscle. This process is coordinated by signals present in the tissue microenvironment, however the precise mechanisms by which the microenvironment regulates MuSC activation are still poorly understood. Here, we identified Tenascin-C (TnC), an extracellular matrix (ECM) glycoprotein, as a key player in promoting of MuSC self-renewal and function. We show that fibro-adipogenic progenitors (FAPs) are the primary cellular source of TnC during muscle repair, and that MuSC sense TnC signaling through cell the surface receptor Annexin A2. We provide in vivo evidence that TnC is required for efficient muscle repair, as mice lacking TnC exhibit a regeneration phenotype of premature aging. We propose that the decline of TnC in physiological aging contributes to inefficient muscle regeneration in aged muscle. Taken together, our results highlight the pivotal role of TnC signaling during muscle repair in healthy and aging skeletal muscle.

Integrative Human Genetic and Cellular Analysis of the Pathophysiological Roles of AnxA2 in Alzheimer's Disease

Alzheimer's disease (AD) is an intractable and progressive neurodegenerative disease. Amyloid beta (Aβ) aggregation is the hallmark of AD. Aβ induces neurotoxicity through a variety of mechanisms, including interacting with membrane receptors to alter downstream signaling, damaging cellular or organelle membranes, interfering with protein degradation and synthesis, and inducing an excessive immune-inflammatory response, all of which lead to neuronal death and other pathological changes associated with AD. In this study, we extracted gene expression profiles from the GSE5281 and GSE97760 microarray datasets in the GEO (Gene Expression Omnibus) database, as well as from the Human Gene Database. We identified differentially expressed genes in the brain tissues of AD patients and healthy persons. Through GO, KEGG, and ROC analyses, annexin A2 (AnxA2) was identified as a putative target gene. Notably, accumulating evidence suggests that intracellular AnxA2 is a key regulator in various biological processes, including endocytosis, transmembrane transport, neuroinflammation, and apoptosis. Thus, we conducted a series of cell biology experiments to explore the biological function of AnxA2 in AD. The results indicate that AnxA2 gene knockdown primarily affects oxidative phosphorylation, cell cycle, AD, protein processing in the endoplasmic reticulum, SNARE interactions in vesicular transport, and autophagy. In SH-SY5Y cells secreting Aβ42, AnxA2 gene knockdown exacerbated Aβ42-induced cytotoxicity, including cell death, intracellular ROS levels, and neuronal senescence, altered cell cycle, and reduced ATP levels, suggesting its critical role in mitochondrial function maintenance. AnxA2 gene knockdown also exacerbated the inhibitory effect of Aβ42 on cell migration. AnxA2 overexpression reduced the inflammatory response induced by Aβ42, while its absence increased pro-inflammatory and decreased anti-inflammatory responses. Furthermore, AnxA2 gene knockdown facilitated apoptosis and decreased autophagy. These results indicated potential pathophysiological roles of AnxA2 in AD.

"Dictionary of immune responses" reveals the critical role of monocytes and the core target IRF7 in intervertebral disc degeneration

Background

Intervertebral disc degeneration (IDD) is widely regarded as the primary contributor to low back pain(LBP). As an immune-privileged organ, upon the onset of IDD, various components of the nucleus pulposus (NP) are exposed to the host's immune system, accumulating cytokines. Cytokines facilitate intercellular communication within the immune system, induce immune cells polarisation, and exacerbate oxidative stress in IDD.

Methods

Machine learning was used to identify crucial immune cells. Subsequently, Immune Response Enrichment Analysis (IREA) was conducted on the key immune cells to determine their cytokine responses and polarisation states in IDD. "CellChat" package facilitated the analysis of cell-cell communication. Differential gene expression analysis, PPI network, GO and KEGG pathway enrichment analysis, GSVA, co-expressed gene analysis and key gene-related networks were also performed to explore hub genes and their associated functions. Lastly, the differential expression and functions of key genes were validated through in vitro and in vivo experiments.

Results

Through multiple machine learning methods, monocytes were identified as the crucial immune cells in IDD, exhibiting significant differentiation capacity. IREA revealed that monocytes in IDD polarize into an IFN-a1 and IFN-b enriched Mono-a state, potentially intensifying inflammation. Cell-cell communication analysis uncovered alteration in ANNEXIN pathway and a reduction in CXCL signaling between macrophages and monocytes, suggesting immune response dysregulation. Furthermore, ten algorithms identified three hub genes. Both experiments conducted in vitro and in vivo have conclusively shown that IRF7 serves as a crucial target for the treatment of IDD, and its knockdown alleviates IDD. Eight small-molecule drugs were predicted to have therapeutic potential for IDD.

Conclusion

These findings offer a multidimensional understanding of the pathogenesis of IDD, pinpointing monocytes and key genes as potential diagnostic and therapeutic targets. They provide novel insights into potential diagnostic and therapeutic targets for IDD.

Comparative analysis of formyl peptide receptor 1 and formyl peptide receptor 2 reveals shared and preserved signalling profiles

BACKGROUND AND PURPOSE

The pattern recognition receptors, formyl peptide receptors, FPR1 and FPR2, are G protein-coupled receptors that recognize many different pathogen- and host-derived ligands. While FPR1 conveys pro-inflammatory signals, FPR2 is linked with pro-resolving outcomes. To analyse how the two very similar FPRs exert opposite effects in modulating inflammatory responses despite their high homology, a shared expression profile on immune cells and an overlapping ligand repertoire, we questioned whether the signalling profile differs between these two receptors.

EXPERIMENTAL APPROACH

We deduced EC50 and Emax values for synthetic, pathogen-derived and host-derived peptide agonists for both FPR1 and FPR2 and analysed them within the framework of biased signalling. We furthermore investigated whether FPR isoform-specific agonists affect the ex vivo lifespan of human neutrophils.

KEY RESULTS

The FPRs share a core signature across signalling pathways. Whereas the synthetic WKYMVm and formylated peptides acted as potent agonists at FPR1, and at FPR2, only WKYMVm was a full agonist. Natural FPR2 agonists, irrespective of N-terminal formylation, displayed lower activity ratios, suggesting an underutilized signalling potential of this receptor. FPR2 agonism did not counteract LPS-induced neutrophil survival, indicating that FPR2 activation per se is not linked with a pro-resolving function.

CONCLUSION AND IMPLICATIONS

Activation of FPR1 and FPR2 by a representative agonist panel revealed a lack of a receptor-specific signalling texture, challenging assumptions about distinct inflammatory profiles linked to specific receptor isoforms, signalling patterns or agonist classes. These conclusions are restricted to the specific agonists and signalling pathways examined.

Exploring the anticancer mechanism of cardiac glycosides using proteome integral solubility alteration approach

BACKGROUND AND AIMS

Cardiac glycosides (CGs), traditionally used for heart failure, have shown potential as anti-cancer agents. This study aims to explore their multifaceted mechanisms in cancer cell biology using proteome integral solubility alteration (PISA), focusing on the interaction with key proteins implicated in cellular metabolism and mitochondrial function.

METHODS

We conducted lysate-based and intact-cell PISA assays on cancer cells treated with CGs (Digoxin, Digitoxin, Ouabain) to analyze protein solubility changes. This was followed by mass spectrometric analysis and bioinformatics to identify differentially soluble proteins (DSPs). Molecular docking simulations were performed to predict protein-CG interactions. Public data including gene expression changes upon CG treatment were re-analyzed for validation.

RESULTS

The PISA assays revealed CGs' broad-spectrum interactions, particularly affecting proteins like PKM2, ANXA2, SLC16A1, GOT2 and GLUD1. Molecular docking confirmed stable interactions between CGs and these DSPs. Re-analysis of public data supported the impact of CGs on cancer metabolism and cell signaling pathways.

CONCLUSION

Our findings suggest that CGs could be repurposed for cancer therapy by modulating cellular processes. The PISA data provide insights into the polypharmacological effects of CGs, warranting further exploration of their mechanisms and clinical potential.

Analysis of Sigma-1 Receptor Antagonist BD1047 Effect on Upregulating Proteins in HIV-1-Infected Macrophages Exposed to Cocaine Using Quantitative Proteomics

HIV-1 infects monocyte-derived macrophages (MDM) that migrate into the brain and secrete virus and neurotoxic molecules, including cathepsin B (CATB), causing cognitive dysfunction. Cocaine potentiates CATB secretion and neurotoxicity in HIV-infected MDM. Pretreatment with BD1047, a sigma-1 receptor antagonist, before cocaine exposure reduces HIV-1, CATB secretion, and neuronal apoptosis. We aimed to elucidate the intracellular pathways modulated by BD1047 in HIV-infected MDM exposed to cocaine. We hypothesized that the Sig1R antagonist BD1047, prior to cocaine, significantly deregulates proteins and pathways involved in HIV-1 replication and CATB secretion that lead to neurotoxicity. MDM culture lysates from HIV-1-infected women treated with BD1047 before cocaine were compared with untreated controls using TMT quantitative proteomics, bioinformatics, Lima statistics, and pathway analyses. Results demonstrate that pretreatment with BD1047 before cocaine dysregulated eighty (80) proteins when compared with the infected cocaine group. We found fifteen (15) proteins related to HIV-1 infection, CATB, and mitochondrial function. Upregulated proteins were related to oxidative phosphorylation (SLC25A-31), mitochondria (ATP5PD), ion transport (VDAC2-3), endoplasmic reticulum transport (PHB, TMED10, CANX), and cytoskeleton remodeling (TUB1A-C, ANXA1). BD1047 treatment protects HIV-1-infected MDM exposed to cocaine by upregulating proteins that reduce mitochondrial damage, ER transport, and exocytosis associated with CATB-induced neurotoxicity.

New Therapeutic Strategies in Retinal Vascular Diseases: A Lipid Target, Phosphatidylserine, and Annexin A5-A Future Theranostic Pairing in Ophthalmology

Despite progress in the management of patients with retinal vascular and degenerative diseases, there is still an unmet clinical need for safe and effective therapeutic options with novel mechanisms of action. Recent mechanistic insights into the pathogenesis of retinal diseases with a prominent vascular component, such as retinal vein occlusion (RVO), diabetic retinopathy (DR) and wet age-related macular degeneration (AMD), may open up new treatment paradigms that reach beyond the inhibition of vascular endothelial growth factor (VEGF). Phosphatidylserine (PS) is a novel lipid target that is linked to the pathophysiology of several human diseases, including retinal diseases. PS acts upstream of VEGF and complement signaling pathways. Annexin A5 is a protein that targets PS and inhibits PS signaling. This review explores the current understanding of the potential roles of PS as a target and Annexin A5 as a therapeutic. The clinical development status of Annexin A5 as a therapeutic and the potential utility of PS-Annexin A5 as a theranostic pairing in retinal vascular conditions in particular is described.