Dynamic reciprocity: the role of annexin A2 in tissue integrity

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.

Knockdown of Hyaluronan synthase 2 suppresses liver fibrosis in mice via induction of transcriptomic changes similar to 4MU treatment

Hepatic fibrosis remains a significant clinical challenge due to ineffective treatments. 4-methylumbelliferone (4MU), a hyaluronic acid (HA) synthesis inhibitor, has proven safe in phase one clinical trials. In this study, we aimed to ameliorate liver fibrosis by inhibiting HA synthesis. We compared two groups of mice with CCl4-induced fibrosis, treated with 4-methylumbelliferone (4MU) and hyaluronan synthase 2 (HAS2) targeting siRNA (siHAS2). The administration of 4MU and siHAS2 significantly reduced collagen and HA deposition, as well as biochemical markers of hepatic damage induced by repeated CCl4 injections. The transcriptomic analysis revealed converging pathways associated with downstream HA signalling. 4MU- and siHAS2-treated fibrotic livers shared 405 upregulated and 628 downregulated genes. These genes were associated with xenobiotic and cholesterol metabolism, mitosis, endoplasmic reticulum stress, RNA processing, and myeloid cell migration. The functional annotation of differentially expressed genes (DEGs) in siHAS2-treated mice revealed attenuation of extracellular matrix-associated pathways. In comparison, in the 4MU-treated group, DEGs were related to lipid and bile metabolism pathways and cell cycle. These findings confirm that HAS2 is an important pharmacological target for suppressing hepatic fibrosis using siRNA.

Dynamic scRNA-seq of live human pancreatic slices reveals functional endocrine cell neogenesis through an intermediate ducto-acinar stage

Human pancreatic plasticity is implied from multiple single-cell RNA sequencing (scRNA-seq) studies. However, these have been invariably based on static datasets from which fate trajectories can only be inferred using pseudotemporal estimations. Furthermore, the analysis of isolated islets has resulted in a drastic underrepresentation of other cell types, hindering our ability to interrogate exocrine-endocrine interactions. The long-term culture of human pancreatic slices (HPSs) has presented the field with an opportunity to dynamically track tissue plasticity at the single-cell level. Combining datasets from same-donor HPSs at different time points, with or without a known regenerative stimulus (BMP signaling), led to integrated single-cell datasets storing true temporal or treatment-dependent information. This integration revealed population shifts consistent with ductal progenitor activation, blurring of ductal/acinar boundaries, formation of ducto-acinar-endocrine differentiation axes, and detection of transitional insulin-producing cells. This study provides the first longitudinal scRNA-seq analysis of whole human pancreatic tissue, confirming its plasticity in a dynamic fashion.

Recent Advances in Molecular and Cellular Functions of S100A10

S100A10 (p11, annexin II light chain, calpactin light chain) is a multifunctional protein with a wide range of physiological activity. S100A10 is unique among the S100 family members of proteins since it does not bind to Ca2+, despite its sequence and structural similarity. This review focuses on studies highlighting the structure, regulation, and binding partners of S100A10. The binding partners of S100A10 were collated and summarized.

Grouper annexin A2 affects RGNNV by regulating the host immune response

Annexin A2 (AnxA2) is ubiquitous in vertebrates and has been identified as a multifunctional protein participating in a series of biological processes, such as endocytosis, exocytosis, signal transduction, transcription regulation, and immune responses. However, the function of AnxA2 in fish during virus infection still remains unknown. In this study, we identified and characterized AnxA2 (EcAnxA2) in Epinephelus coioides. EcAnxA2 encoded a 338 amino acids protein with four identical annexin superfamily conserved domains, which shared high identity with other AnxA2 of different species. EcAnxA2 was widely expressed in different tissues of healthy groupers, and its expression was significantly increased in grouper spleen cells infected with red-spotted grouper nervous necrosis virus (RGNNV). Subcellular locatio n analyses showed that EcAnxA2 diffusely distributed in the cytoplasm. After RGNNV infection, the spatial distribution of EcAnxA2 was unaltered, and a few EcAnxA2 co-localized with RGNNV during the late stage of infection. Furthermore, overexpression of EcAnxA2 significantly increased RGNNV infection, and knockdown of EcAnxA2 reduced RGNNV infection. In addition, overexpressed EcAnxA2 reduced the transcription of interferon (IFN)-related and inflammatory factors, including IFN regulatory factor 7 (IRF7), IFN stimulating gene 15 (ISG15), melanoma differentiation related gene 5 (MDA5), MAX interactor 1 (Mxi1) laboratory of genetics and physiology 2 (LGP2), IFN induced 35 kDa protein (IFP35), tumor necrosis factor receptor-associated factor 6 (TRAF6) and interleukin 6 (IL-6). The transcription of these genes was up-regulated when EcAnxA2 was inhibited by siRNA. Taken together, our results showed that EcAnxA2 affected RGNNV infection by down-regulating the host immune response in groupers, which provided new insights into the roles of AnxA2 in fish during virus infection.

Protein Profiling in Human Papillomavirus-Associated Cervical Carcinogenesis: Cornulin as a Biomarker for Disease Progression

Nearly 90% of cervical cancers are linked to human papillomavirus (HPV). Uncovering the protein signatures in each histological phase of cervical oncogenesis provides a path to biomarker discovery. The proteomes extracted from formalin-fixed paraffin-embedded tissues of the normal cervix, HPV16/18-associated squamous intraepithelial lesion (SIL), and squamous cell carcinoma (SCC) were compared using liquid chromatography-mass spectrometry (LC-MS). A total of 3597 proteins were identified, with 589, 550, and 1570 proteins unique to the normal cervix, SIL, and SCC groups, respectively, while 332 proteins overlapped between the three groups. In the transition from normal cervix to SIL, all 39 differentially expressed proteins were downregulated, while all 51 proteins discovered were upregulated in SIL to SCC. The binding process was the top molecular function, while chromatin silencing in the SIL vs. normal group, and nucleosome assembly in SCC vs. SIL groups was the top biological process. The PI3 kinase pathway appears crucial in initiating neoplastic transformation, while viral carcinogenesis and necroptosis are important for cell proliferation, migration, and metastasis in cervical cancer development. Annexin A2 and cornulin were selected for validation based on LC-MS results. The former was downregulated in the SIL vs. normal cervix and upregulated in the progression from SIL to SCC. In contrast, cornulin exhibited the highest expression in the normal cervix and lowest in SCC. Although other proteins, such as histones, collagen, and vimentin, were differentially expressed, their ubiquitous expression in most cells precluded further analysis. Immunohistochemical analysis of tissue microarrays found no significant difference in Annexin A2 expression between the groups. Conversely, cornulin exhibited the strongest expression in the normal cervix and lowest in SCC, supporting its role as a tumor suppressor and potential biomarker for disease progression.

Isolation and identification of extracellular matrix proteins from oil-based CASPERized mouse brains for matrisomal analysis

The extracellular matrix (ECM) components present within all tissues and organs help to maintain the cytoskeletal architecture and tissue morphology. Although the ECM plays a role in cellular events and signaling pathways, it has not been well studied due its insolubility and complexity. Brain tissue has a higher cell density and weaker mechanical strength than other tissues in the body. When removing cells using a general decellularization method to produce scaffolds and obtain ECM proteins, various problems must be considered because tissues are easily damaged. To retain the brain shape and ECM components, we performed decellularization in combination with polymerization. We immersed mouse brains in oil for polymerization and decellularization via O-CASPER (Oil-based Clinically and Experimentally Applicable Acellular Tissue Scaffold Production for Tissue Engineering and Regenerative Medicine) and then isolated ECM components using sequential matrisome preparation reagents (SMPRs), namely, RIPA, PNGase F, and concanavalin A. Adult mouse brains were preserved with our decellularization method. Western blot and LC-MS/MS analyses revealed that ECM components, including collagen and laminin, were isolated efficiently from decellularized mouse brains using SMPRs. Our method will be useful to obtain matrisomal data and perform functional studies using adult mouse brains and other tissues.

Structures of annexin A2-PS DNA complexes show dominance of hydrophobic interactions in phosphorothioate binding

The introduction of phosphorothioate (PS) linkages to the backbone of therapeutic nucleic acids substantially increases their stability and potency. It also affects their interactions with cellular proteins, but the molecular mechanisms that underlie this effect are poorly understood. Here, we report structural and biochemical studies of interactions between annexin A2, a protein that does not possess any known canonical DNA binding domains, and phosphorothioate-modified antisense oligonucleotides. We show that a unique mode of hydrophobic interactions between a sulfur atom of the phosphorothioate group and lysine and arginine residues account for the enhanced affinity of modified nucleic acid for the protein. Our results demonstrate that this mechanism of interaction is observed not only for nucleic acid-binding proteins but can also account for the association of PS oligonucleotides with other proteins. Using the anomalous diffraction of sulfur, we showed that preference for phosphorothioate stereoisomers is determined by the hydrophobic environment around the PS linkage that comes not only from protein but also from additional structural features within the ASO such as 5-Me groups on cytosine nucleobases.

Persistent Properties of a Subpopulation of Cancer Cells Overexpressing the Hedgehog Receptor Patched

Despite the development of new therapeutic strategies, cancer remains one of the leading causes of mortality worldwide. One of the current major challenges is the resistance of cancers to chemotherapy treatments inducing metastases and relapse of the tumor. The Hedgehog receptor Patched (Ptch1) is overexpressed in many types of cancers. We showed that Ptch1 contributes to the efflux of doxorubicin and plays an important role in the resistance to chemotherapy in adrenocortical carcinoma (ACC), a rare cancer which presents strong resistance to the standard of care chemotherapy treatment. In the present study, we isolated and characterized a subpopulation of the ACC cell line H295R in which Ptch1 is overexpressed and more present at the cell surface. This cell subpopulation is more resistant to doxorubicin, grows as spheroids, and has a greater capability of clonogenicity, migration, and invasion than the parental cells. Xenograft experiments performed in mice and in ovo showed that this cell subpopulation is more tumorigenic and metastatic than the parental cells. These results suggest that this cell subpopulation has cancer stem-like or persistent cell properties which were strengthened by RNA-seq. If present in tumors from ACC patients, these cells could be responsible for therapy resistance, relapse, and metastases.

Comprehensive quantitative characterization of the human term amnion proteome

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We report an unprecedented quantitative high coverage of the human amnion proteome.

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We identified novel proteins that hold great promise for understanding fetal membrane biology.

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Together, this comprehensive proteome provides a basis for the evaluation of pre-term or diseased fetal membranes.

The loss of fetal membrane (FM) integrity and function at an early time point during pregnancy can have devastating consequences for the fetus and the newborn. However, biomaterials for preventive sealing and healing of FMs are currently non-existing, which can be partly attributed to the current fragmentary knowledge of FM biology. Despite recent advances in proteomics analysis, a robust and comprehensive description of the amnion proteome is currently lacking. Here, by an optimized protein sample preparation and offline fractionation before liquid chromatography coupled to mass spectrometry (LC-MS) analysis, we present a characterization of the healthy human term amnion proteome, which covers more than 40% of the previously reported transcripts in similar RNA sequencing datasets and, with more than 5000 identifications, greatly outnumbers previous reports. Together, beyond providing a basis for the study of compromised and preterm ruptured FMs, this comprehensive human amnion proteome is a stepping-stone for the development of novel healing-inducing biomaterials. The proteomic dataset has been deposited in the ProteomeXchange Consortium with the identifier PXD019410.

Clinical Limitations of Tissue Annexin A2 Level as a Predictor of Postoperative Overall Survival in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second common cause of cancer-related death in Taiwan. Tumor recurrence is frequently observed in HCC patients receiving surgical resection, resulting in unsatisfactory overall survival (OS). Therefore, it is pivotal to identify effective prognostic makers, so that intensive surveillance or adjuvant treatments can be applied to predictively unfavorable patients. Previous studies indicated that Annexin A2 (ANXA2) was an effective prognostic marker in several cancers, including HCC. However, the prognostic value of ANXA2 in Taiwanese HCC patients remains unclear, where a great proportion of patients had chronic hepatitis B with liver cirrhosis. Here, ANXA2 was highly expressed in HCC tissues compared with para-neoplastic noncancerous tissues. Furthermore, high ANXA2 expression in HCC tissues independently predicted shorter OS. In subgroup analysis, however, ANXA2 expression could not effectively predict OS in the following subgroups: female, age > 65 years old, Child–Pugh classification B, hepatitis B virus surface antigen negative or anti-hepatitis C antibody positive, alcoholism, tumor number >1, presence of micro- or macrovascular invasion, absence of capsule, non-cirrhosis and high alpha-fetoprotein. In conclusion, ANXA2 expression in HCC tissues could predict postoperative OS. However, the predictive value was limited in patients with specific clinical conditions.

Dephosphorylation of annexin A2 by protein phosphatase 1 regulates endothelial cell barrier

Annexin A2 (ANXA2) is a multifunctional protein expressed in nearly all human tissues and cell types, playing a role in various signaling pathways. It is subjected to phosphorylation, but no specific protein phosphatase has been identified in its posttranslational regulation yet. Using pull-down assay followed by liquid chromatography-mass spectrometry analysis we found that ANXA2 interacts with TIMAP (TGF-beta-inhibited membrane-associated protein) in pulmonary artery endothelial cells. TIMAP is highly expressed in endothelial cells, where it acts as a regulatory and targeting subunit of protein phosphatase 1 (PP1). TIMAP plays an important role in the regulation of the endothelial barrier maintenance through the dephosphorylation of its several substrate proteins. In the present work, phosphorylation of Ser25 side chain in ANXA2 by protein kinase C (PKC) was shown both in vivo and in vitro. Phosphorylation level of ANXA2 at Ser25 increased greatly by inhibition of PP1 and by depletion of its regulatory subunit, TIMAP, implying a role of this PP1 holoenzyme in the dephosphorylation of ANXA2. Immunofluorescence staining and subcellular fractionations revealed a diffuse subcellular localization for the endogenous ANXA2, but phospho-Ser25 ANXA2 was mainly detected in the membrane. ANXA2 depletion lowered the basal endothelial barrier and inhibited cell migration, but had no significant effect on cell proliferation or viability. ANXA2 depleted cells failed to respond to PMA treatment, indicating an intimately involvement of phospho-ANXA2 in PKC signaling. Moreover, phosphorylation of ANXA2 disrupted its interaction with S100A10 suggesting a phosphorylation dependent multiple regulatory role of ANXA2 in endothelial cells. Our results demonstrate the pivotal role of PKC-ANXA2-PP1 pathway in endothelial cell signaling, especially in barrier function and cell migration.

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.

Annexin A2 Expression in the Aerogenous Spread of Pulmonary Invasive Mucinous Adenocarcinoma with Gastric Lineage

Spread through air spaces (STAS) is a unique form of lung cancer progression associated with a worse prognosis. However, the mechanisms underlying STAS and the associated proteins remain unclear. Annexin A2 (ANX A2), which is a membrane-binding protein involved in cell adhesion, is known to promote cancer invasion. In this report, we describe the immunohistochemical analysis of ANX A2 expression in an invasive mucinous adenocarcinoma (IMAC) resected from a 63-year-old man in whom the tumor cells had detached from the alveolar wall and exhibited STAS. At the detachment site, we observed cytoplasmic ANX A2 positivity on the basal side and in the exfoliative gap, as well as reduced collagen IV positivity expression. This biomarker pattern suggested an IMAC with gastric lineage. We hypothesize that ANX A2 is secreted from the basal sides of tumor cells and induces tumor cell detachment by degrading the basement membrane. A further comparison of this case with an IMAC with nongastric lineage suggested the following probabilities: (1) ANX A2 likely contributes to STAS in a manner that is dependent on its subcellular localization. (2) Both the subcellular localization of ANX A2 and the detachment site depend on tumor cell characteristics, including the biomarker immunophenotype.

High glucose induces phosphorylation and oxidation of mitochondrial proteins in renal tubular cells: A proteomics approach

Mitochondrial dysfunction has been thought to play roles in the pathogenesis of diabetic nephropathy (DN). However, precise mechanisms underlying mitochondrial dysfunction in DN remained unclear. Herein, mitochondria were isolated from renal tubular cells after exposure to normal glucose (5.5 mM glucose), high glucose (25 mM glucose), or osmotic control (5.5 mM glucose + 19.5 mM mannitol) for 96 h. Comparative proteomic analysis revealed six differentially expressed proteins among groups that were subsequently identified by tandem mass spectrometry (nanoLC-ESI-ETD MS/MS) and confirmed by Western blotting. Several various types of post-translational modifications (PTMs) were identified in all of these identified proteins. Interestingly, phosphorylation and oxidation were most abundant in mitochondrial proteins whose levels were exclusively increased in high glucose condition. The high glucose-induced increases in phosphorylation and oxidation of mitochondrial proteins were successfully confirmed by various assays including MS/MS analyses. Moreover, high glucose also increased levels of phosphorylated ezrin, intracellular ATP and ROS, all of which could be abolished by a p38 MAPK inhibitor (SB239063), implicating a role of p38 MAPK-mediated phosphorylation in high glucose-induced mitochondrial dysfunction. These data indicate that phosphorylation and oxidation of mitochondrial proteins are, at least in part, involved in mitochondrial dysfunction in renal tubular cells during DN.

Heat Shock Protein 90 Chaperone Regulates the E3 Ubiquitin-Ligase Hakai Protein Stability

The E3 ubiquitin-ligase Hakai binds to several tyrosine-phosphorylated Src substrates, including the hallmark of the epithelial-to-mesenchymal transition E-cadherin, and signals for degradation of its specific targets. Hakai is highly expressed in several human cancers, including colon cancer, and is considered as a drug target for cancer therapy. Here, we report a link between Hakai and the heat shock protein 90 (Hsp90) chaperone complex. Hsp90 participates in the correct folding of its client proteins, allowing them to maintain their stability and activity. Hsp90 inhibitors specifically interfere with the association with its Hsp90 client proteins, and exhibit potent anti-cancer properties. By immunoprecipitation, we present evidence that Hakai interacts with Hsp90 chaperone complex in several epithelial cells and demonstrate that is a novel Hsp90 client protein. Interestingly, by overexpressing and knocking-down experiments with Hakai, we identified Annexin A2 as a Hakai-regulated protein. Pharmacological inhibition of Hsp90 with geldanamycin results in the degradation of Hakai in a lysosome-dependent manner. Interestingly, geldanamycin-induced Hakai degradation is accompanied by an increased expression of E-cadherin and Annexin A2. We also show that geldanamycin suppresses cell motility at least in part through its action on Hakai expression. Taken together, our results identify Hakai as a novel Hsp90 client protein and shed light on the regulation of Hakai stability. Our results open the possibility to the potential use of Hsp90 inhibitors for colorectal cancer therapy through its action on Hakai client protein of Hsp90.

Annexin A2 Expression in Aerogenous Metastasis of Pulmonary Invasive Mucinous Adenocarcinoma: A Case Report including Immunohistochemical Analysis

Aerogenous metastasis (AM) is a form of lung cancer that spreads in a unique fashion, but its mechanisms are still unclear. Annexin A2 (ANX A2), a membrane-binding protein, promotes cancer invasion and is involved in cell adhesion and polarity. The relationship between ANX A2 and cancers with poor stromal invasion capacity has not been studied. We immunohistochemically analyzed ANX A2 expression in AM observed in a patient with pulmonary invasive mucinous adenocarcinoma. In the primary site, ANX A2 immunopositivity on the cell-cell borders weakened as tumor cells projected and separated into alveolar spaces. In AM, tumor cell aggregates with ANX A2 immunopositivity near the surface and within the cytoplasm attached to alveolar epithelial cells, then engulfed them and formed a protrusion. As tumor cell aggregates adhered to the alveolar wall and formed a single layer, cytoplasmic ANX A2-positive products accumulated in the lateral sides of the tumor cells and exhibited distinct membranous positivity. These results indicated that ANX A2 near the tumor cell surface was related to alveolar wall attachment. Furthermore, the translocation of cytoplasmic ANX A2 to cell-cell borders changed cell morphology, adhesion, and polarity restoration.

High levels of ANXA2 are characteristic of malignant salivary gland tumors

OBJECTIVE

Malignant salivary gland tumors (MSGTs) present different phenotypic characteristics and various clinical outcomes, which proved to be a diagnostic challenge. Considering the heterogeneity of MSGT, this study aims to identify molecule related to the nature of MSGT.

METHODS

For screening, proteomic analysis comparing MSGT with pleomorphic adenoma (PA) and salivary gland was performed. The MSGT-associated protein which presented in the higher number in the Gene Expression Omnibus (GEO) database was selected. To validate the data, immunohistochemistry (IHC) was performed in 14 patients with PA, 22 patients with MSGT, and 14 controls.

RESULTS

16 proteins were associated with MSGT. ANXA2 was the primary protein, according to GEO database analyses. ANXA2 was most expressed in the cell membrane. However, some ANXA2 staining was also observed in the cytoplasm and nucleus. ANXA2 was highly expressed in MSGT in comparison with control. Also, ANXA2 has a higher expression in adenocarcinoma not otherwise specified (ANOS) and myoepithelial carcinoma (MC) in comparison with PA.

CONCLUSION

In conclusion, this study demonstrated that MSGT presented higher levels of ANXA2 in comparison with normal salivary glands. Also, ANXA2 might be interesting as a molecular marker of ANOS and MS.

ANXA2Tyr23 and FLNASer2152 phosphorylation associate with poor prognosis in hepatic carcinoma revealed by quantitative phosphoproteomics analysis

Hepatoma is one of the most common malignant tumors, and most patients have very poor prognosis. Early prediction and intervention of the hepatoma recurrence/metastasis are the most effective way to improve the patients' clinical outcomes. Here, we used isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative phospho-proteomics approach to identify biomarkers associated with hepatoma recurrence/metastasis in hepatoma cell lines with increasing metastasis ability. In total, 75 phosphorylated peptides corresponding to 60 phosphoproteins were significantly dysregulated and the participated biological processes of these phosphoproteins were tightly associated with tumor metastasis. Further signaling pathway analysis revealed that key signaling pathways which play crucial roles in cancer metastasis have been significantly over activated in the highly metastatic cells. Furthermore, the phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 were validated to be significantly up regulated in the high-metastatic cells comparing with the low-metastatic cells. By further investigation the clinical significance of the phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 in large-scale clinical samples, revealed that the over phosphorylation of FLNA^Ser2152 and ANXA2^Tyr23 were associated with poor prognosis and might be potential prognostic biomarkers for the primary hepatoma. When FLNA^Ser2152 combined with ANXA2^Tyr23, it had a better prognostic value for both OS and TTR.

Annexin A2 in Virus Infection

Viral life cycles consist of three main phases: (1) attachment and entry, (2) genome replication and expression, and (3) assembly, maturation, and egress. Each of these steps is intrinsically reliant on host cell factors and processes including cellular receptors, genetic replication machinery, endocytosis and exocytosis, and protein expression. Annexin A2 (AnxA2) is a membrane-associated protein with a wide range of intracellular functions and a recurrent host factor in a variety of viral infections. Spatially, AnxA2 is found in the nucleus and cytoplasm, vesicle-bound, and on the inner and outer leaflet of the plasma membrane. Structurally, AnxA2 exists as a monomer or in complex with S100A10 to form the AnxA2/S100A10 heterotetramer (A2t). Both AnxA2 and A2t have been implicated in a vast array of cellular functions such as endocytosis, exocytosis, membrane domain organization, and translational regulation through RNA binding. Accordingly, many discoveries have been made involving AnxA2 in viral pathogenesis, however, the reported work addressing AnxA2 in virology is highly compartmentalized. Therefore, the purpose of this mini review is to provide information regarding the role of AnxA2 in the lifecycle of multiple epithelial cell-targeting viruses to highlight recurrent themes, identify discrepancies, and reveal potential avenues for future research.

The prognostic value of S100A10 expression in cancer

S100A10, a member of the S100 protein family, commonly forms a heterotetrameric complex with Annexin A2. This is essential for the generation of cellular plasmin from plasminogen, which leads to a cascade of molecular events crucial for tumor progression. S100A10 upregulation has been reported in a number of cancers, suggesting that it may have potential as a prognostic biomarker, as well as predicting sensitivity to anticancer drugs. This review evaluates the direct and indirect relationships between S100A10 and cancer progression by investigating its role in cancer. Research papers published on PubMed and Google Scholar between 2007–2017 were collated and reviewed. We concluded that S100A10 affects the development of the hallmarks of cancer as explained by Hanahan and Weinberg in 2011, most notably by activating the invasion and metastasis of cancer cells. However, further studies are required to explore the underlying biological mechanisms of S100A10.

Heterotetrameric annexin A2/S100A10 (A2t) is essential for oncogenic human papillomavirus trafficking and capsid disassembly, and protects virions from lysosomal degradation

Human papillomavirus (HPV) entry into epithelial cells is independent of canonical endocytic pathways. Upon interaction with host cells, HPV establishes infection by traversing through an endocytic pathway that is clathrin- and caveolin-independent, but dependent on the annexin A2/S100A10 heterotetramer (A2t). We examined the contribution of monomeric annexin A2 (AnxA2) vs. A2t in HPV infection and endocytosis, and further characterized the role of these molecules in protein trafficking. We specifically show that cell surface A2t is not required for HPV attachment, and in the absence of A2t virion internalization remains clathrin-independent. Without A2t, viral progression from early endosomes to multivesicular endosomes is significantly inhibited, capsid uncoating is dramatically reduced, and lysosomal degradation of HPV is accelerated. Furthermore, we present evidence that AnxA2 forms a complex with CD63, a known mediator of HPV trafficking. Overall, the observed reduction in infection is less significant in the absence of S100A10 alone compared to full A2t, supporting an independent role for monomeric AnxA2. More broadly, we show that successful infection by multiple oncogenic HPV types is dependent on A2t. These findings suggest that A2t is a central mediator of high-risk HPV intracellular trafficking post-entry and pre-viral uncoating.

Annexin A2 Mediates the Localization of Measles Virus Matrix Protein at the Plasma Membrane

Annexins are a family of structurally related proteins that bind negatively charged membrane phospholipids in a Ca²⁺-dependent manner. Annexin A2 (AnxA2), a member of this family, has been implicated in a variety of cellular functions, including the organization of membrane domains, vesicular trafficking, and cell-cell adhesion. AnxA2 generally forms a heterotetrameric complex with a small Ca²⁺-binding protein, S100A10. Measles virus (MV), a member of the family Paramyxoviridae, is an enveloped virus with a nonsegmented negative-strand RNA genome. Knockdown of AnxA2 greatly reduced MV growth in cells without affecting its entry and viral RNA production. In MV-infected, AnxA2 knockdown cells, the expression level of the matrix (M) protein, but not other viral proteins, was reduced compared with that in control cells, and the distribution of the M protein at the plasma membrane was decreased. The M protein lines the inner surface of the envelope and plays an important role in virus assembly by connecting the nucleocapsid to the envelope proteins. The M protein bound to AnxA2 independently of AnxA2's phosphorylation or its association with S100A10 and was colocalized with AnxA2 within cells. Truncation of the N-terminal 10 amino acid residues, but not the N-terminal 5 residues, compromised the ability of the M protein to interact with AnxA2 and localize at the plasma membrane. These results indicate that AnxA2 mediates the localization of the MV M protein at the plasma membrane by interacting with its N-terminal region (especially residues at positions 6 to 10), thereby aiding in MV assembly.IMPORTANCE MV is an important human pathogen, still claiming ∼100,000 lives per year despite the presence of effective vaccines, and it causes occasional outbreaks even in developed countries. Replication of viruses largely relies on the functions of host cells. Our study revealed that the reduction of the host protein annexin A2 compromises the replication of MV within the cell. Further studies demonstrated that annexin A2 interacts with the MV M protein and mediates the localization of the M protein at the plasma membrane where MV particles are formed. The M protein lines the inner surface of the MV envelope membrane and plays a role in MV particle formation. Our results provide useful information for the understanding of the MV replication process and potential development of antiviral agents.

Protein phosphorylation and its role in the regulation of Annexin A2 function

BACKGROUND

Annexin A2 (AnxA2) is a multifunctional protein involved in endocytosis, exocytosis, membrane domain organisation, actin remodelling, signal transduction, protein assembly, transcription and mRNA transport, as well as DNA replication and repair.

SCOPE OF REVIEW

The current knowledge of the role of phosphorylation in the functional regulation of AnxA2 is reviewed. To provide a more comprehensive treatment of this topic, we also address in depth the phosphorylation process in general and discuss its possible conformational effects. Furthermore, we discuss the apparent limitations of the methods used to investigate phosphoproteins, as exemplified by the study of AnxA2.

MAJOR CONCLUSIONS

AnxA2 is subjected to complex regulation by post-translational modifications affecting its cellular functions, with Ser11, Ser25 and Tyr23 representing important phosphorylation sites. Thus, Ser phosphorylation of AnxA2 is involved in the recruitment and docking of secretory granules, the regulation of its association with S100A10, and sequestration of perinuclear, translationally inactive mRNP complexes. By contrast, Tyr phosphorylation of AnxA2 regulates its role in actin dynamics and increases its association with endosomal compartments. Modification of its three main phosphorylation sites is not sufficient to discriminate between its numerous functions. Thus, fine-tuning of AnxA2 function is mediated by the joint action of several post-translational modifications.

GENERAL SIGNIFICANCE

AnxA2 participates in malignant cell transformation, and its overexpression and/or phosphorylation is associated with cancer progression and metastasis. Thus, tight regulation of AnxA2 function is an integral aspect of cellular homeostasis. The presence of AnxA2 in cancer cell-derived exosomes, as well as the potential regulation of exosomal AnxA2 by phosphorylation or other PTMs, are topics of great interest.

Vimentin Modulates Infectious Internalization of Human Papillomavirus 16 Pseudovirions

Human papillomavirus (HPV) infection is the most common viral infection of the reproductive tract, with virtually all cases of cervical cancer being attributable to infection by oncogenic HPVs. However, the exact mechanism and receptors used by HPV to infect epithelial cells are controversial. The current entry model suggests that HPV initially attaches to heparan sulfate proteoglycans (HSPGs) at the cell surface, followed by conformational changes, cleavage by furin convertase, and subsequent transfer of the virus to an as-yet-unidentified high-affinity receptor. In line with this model, we established an in vitro infection system using the HSPG-deficient cell line pgsD677 together with HPV16 pseudovirions (HPV16-PsVs). While pgsD677 cells were nonpermissive for untreated HPV16-PsVs, furin cleavage of the particles led to a substantial increase in infection. Biochemical pulldown assays followed by mass spectrometry analysis showed that furin-precleaved HPV16-PsVs specifically interacted with surface-expressed vimentin on pgsD677 cells. We further demonstrated that both furin-precleaved and uncleaved HPV16-PsVs colocalized with surface-expressed vimentin on pgsD677, HeLa, HaCaT, and NIKS cells, while binding of incoming viral particles to soluble vimentin protein before infection led to a substantial decrease in viral uptake. Interestingly, decreasing cell surface vimentin by small interfering RNA (siRNA) knockdown in HeLa and NIKS cells significantly increased HPV16-PsV infectious internalization, while overexpression of vimentin had the opposite effect. The identification of vimentin as an HPV restriction factor enhances our understanding of the initial steps of HPV-host interaction and may lay the basis for the design of novel antiviral drugs preventing HPV internalization into epithelial cells.IMPORTANCE Despite HPV being a highly prevalent sexually transmitted virus causing significant disease burden worldwide, particularly cancer of the cervix, cell surface events preceding oncogenic HPV internalization are poorly understood. We herein describe the identification of surface-expressed vimentin as a novel molecule not previously implicated in the infectious internalization of HPV16. Contrary to our expectations, vimentin was found to act not as a receptor but rather as a restriction factor dampening the initial steps of HPV16 infection. These results importantly contribute to our current understanding of the molecular events during the infectious internalization of HPV16 and open a new direction in the development of alternative drugs to prevent HPV infection.

An osteogenesis/angiogenesis-stimulation artificial ligament for anterior cruciate ligament reconstruction

To solve the poor healing of polyethylene terephthalate (PET) artificial ligament in bone tunnel, copper-containing bioactive glass (Cu-BG) nanocoatings on PET artificial ligaments were successfully prepared by pulsed laser deposition (PLD). It was hypothesized that Cu-BG coated PET (Cu-BG/PET) grafts could enhance the in vitro osteogenic and angiogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) and in vivo graft-bone healing after anterior cruciate ligament (ACL) reconstruction in a goat model. Scanning electron microscope and EDS mapping analysis revealed that the prepared nanocoatings had uniform element distribution (Cu, Ca, Si and P) and nanostructure. The surface hydrophilicity of PET grafts was significantly improved after depositing Cu-BG nanocoatings. The in vitro study displayed that the Cu-BG/PET grafts supported the attachment and proliferation of rBMSCs, and significantly promoted the expression of HIF-1α gene, which up-regulated the osteogenesis-related genes (S100A10, BMP2, OCN) and angiogenesis-related genes (VEGF) in comparison with PET or BG coated PET (BG/PET) grafts which do not contain Cu element. Meanwhile, Cu-BG/PET grafts promoted the bone regeneration at the graft-host bone interface and decreased graft-bone interface width, thus enhancing the bonding strength as well as angiogenesis (as indicated by CD31 expression) in the goat model as compared with BG/PET and pure PET grafts. The study demonstrates that the Cu-containing biomaterials significantly promote osteogenesis and angiogenesis in the repair of bone defects of large animals and thus offering a promising method for ACL reconstruction by using Cu-containing nanobioglass modified PET grafts.

STATEMENT OF SIGNIFICANCE

It remains a significant challenge to develop an artificial graft with distinct osteogenetic/angiogenetic activity to enhance graft-bone healing for ligament reconstruction. To solve these problems, copper-containing bioactive glass (Cu-BG) nanocoatings on PET artificial ligaments were successfully prepared by pulsed laser deposition (PLD). It was found that the prepared Cu-BG/PET grafts significantly stimulated the proliferation and osteogenic/angiogenic differentiation of bone marrow stromal cells (BMSCs) through activating HIF-1α/S100A10/Ca²⁺ signal pathway. The most important is that the in vivo bone-forming ability of Cu-containing biomaterials was, for the first time, elucidated in a large animal model, revealing the enhanced capacity of osteogenesis and angiogenesis with incorporation of bioactive Cu element. It is suggested that the copper-containing biomaterials significantly promote osteogenesis and angiogenesis in large animal defects and thus offering a promising method for ACL reconstruction by using Cu-containing nanobioglass modification of PET grafts, paving the way to apply Cu-containing biomaterials for tissue engineering and regenerative medicine.

Complex Roles of Annexin A2 in Host Blood-Brain Barrier Invasion by Cryptococcus neoformans

INTRODUCTION

Fungal transversal across the brain microvascular endothelial cells (BMECs) is the essential step for the development of cryptococcal meningoencephalitis. Annexin A2 (AnxA2) is an important signaling protein involved in several intracellular processes such as membrane trafficking, endocytosis, and exocytosis.

AIM

To investigate the roles and mechanism of AnxA2 during cryptococcal transversal of BMECs.

RESULTS

Cryptococcus neoformans infection initiated upregulation of AnxA2 in mouse BMECs. Blockade with anti-AnxA2 antibody led to a reduction in fungal transcytosis activity but no change in its adhesion efficiency. Intriguingly, AnxA2 depletion caused a significant increase in fungal association activity but had no effect on their transcytosis. AnxA2 suppression resulted in marked reduction in its partner protein S100A10, and S100A10 suppression in BMECs significantly reduced the cryptococcal transcytosis efficiency. Furthermore, AnxA2 dephosphorylation at Tyr23 and dephosphorylation of downstream cofilin were required for cryptococcal transversal of BMECs, both of which might be primarily involved in the association of C. neoformans with host cells.

CONCLUSIONS

Our work indicated that AnxA2 played complex roles in traversal of C. neoformans across host BMECs, which might be dependent on downstream cofilin to inhibit fungal adhesion but rely on its partner S100A10 to promote cryptococcal transcytosis.

Post-translational modifications of Annexin A2 are linked to its association with perinuclear nonpolysomal mRNP complexes

Various post‐translational modifications (PTMs) regulate the localisation and function of the multifunctional protein Annexin A2 (AnxA2). In addition to its various tasks as a cytoskeletal‐ and membrane‐associated protein, AnxA2 can function as a trans‐acting protein binding to cis‐acting sequences of specific mRNAs. In the present study, we have examined the role of Ser25 phosphorylation in subcellular localisation of AnxA2 and its interaction with mRNP complexes. Subcellular fractionation and confocal microscopy of rat neuroendocrine PC12 cells showed that Ser25‐phosphorylated AnxA2 (pSer25AnxA2) is absent from the nucleus and mainly localised to the perinuclear region, evidently associating with both membranes and cytoskeletal elements. Perinuclear targeting of AnxA2 was abolished by inhibition of protein kinase C activity, which resulted in cortical enrichment of the protein. Although oligo(dT)‐affinity purification of mRNAs revealed that pSer25AnxA2 associates with nonpolysomal, translationally inactive mRNP complexes, it displayed only partial overlap with a marker of P‐bodies. The phosphorylated protein is present as high‐molecular‐mass forms, indicating that it contains additional covalent PTMs, apparently triggered by its Ser25 phosphorylation. The subcellular distributions of these forms clearly differ from the main form of AnxA2 and are also distinct from that of Tyr23‐phosphorylated AnxA2. Immunoprecipitation verified that these high‐molecular‐mass forms are due to ubiquitination and/or sumoylation. Moreover, these results indicate that Ser25 phosphorylation and ubiquitin/SUMO1 conjugation of AnxA2 promote its association with nonpolysomal mRNAs, providing evidence of a possible mechanism to sequester a subpopulation of mRNAs in a translationally inactive and transport competent form at a distinct subcellular localisation.

Harnessing 3D models of mammary epithelial morphogenesis: An off the beaten path approach to identify candidate biomarkers of early stage breast cancer

Regardless of the etiological factor, an aberrant morphology is the common hallmark of ductal carcinoma in situ (DCIS), which is a highly heterogeneous disease. To test if critical core morphogenetic mechanisms are compromised by different mutations, we performed proteomics analysis of five mammary epithelial HME1 mutant lines that develop a DCIS-like morphology in three dimensional (3D) culture. Here we show first, that all HME1 mutant lines share a common protein signature highlighting an inverse deregulation of two annexins, ANXA2 and ANXA8. Either ANXA2 downregulation or ANXA8 upregulation in the HME1 cell context are per se sufficient to confer a 3D DCIS-like morphology. Seemingly, different mutations impinged on a common mechanism that differentially regulates the two annexins. Second, we show that ANXA8 expression is significantly higher in DCIS tissue samples versus normal breast tissue and atypical ductal hyperplasia (ADH). Apparently, ANXA8 expression is significantly more upregulated in ER-negative versus ER-positive cases, and significantly correlates with tumor stage, grade and positive lymph node. Based on our study, 3D mammary morphogenesis models can be an alternate/complementary strategy for unraveling new DCIS mechanisms and biomarkers.

Dysferlin function in skeletal muscle: Possible pathological mechanisms and therapeutical targets in dysferlinopathies

Mutations in the dysferlin gene are linked to a group of muscular dystrophies known as dysferlinopathies. These myopathies are characterized by progressive atrophy. Studies in muscle tissue from dysferlinopathy patients or dysferlin-deficient mice point out its importance in membrane repair. However, expression of dysferlin homologous proteins that restore sarcolemma repair function in dysferlinopathy animal models fail to arrest muscle wasting, therefore suggesting that dysferlin plays other critical roles in muscle function. In the present review, we discuss dysferlin functions in the skeletal muscle, as well as pathological mechanisms related to dysferlin mutations. Particular focus is presented related the effect of dysferlin on cell membrane related function, which affect its repair, vesicle trafficking, as well as Ca(2+) homeostasis. Such mechanisms could provide accessible targets for pharmacological therapies.

Extracellular vesicles released from cells exposed to reactive oxygen species increase annexin A2 expression and survival of target cells exposed to the same conditions

Annexin A2 (AnxA2) is present in multiple cellular compartments and interacts with numerous ligands including calcium, proteins, cholesterol, negatively charged phospholipids and RNA. These interactions are tightly regulated by its post-translational modifications. The levels of AnxA2 and its Tyr23 phosphorylated form (pTyr23AnxA2) are increased in many cancers and the protein is involved in malignant cell transformation, metastasis and angiogenesis. Our previous studies of rat pheochromocytoma (PC12) cells showed that reactive oxygen species (ROS) induce rapid, simultaneous and transient dephosphorylation of nuclear AnxA2, most likely associating with PML bodies, while AnxA2 associated with F-actin at the cell cortex undergoes Tyr23 phosphorylation. The pTyr23AnxA2 in the periphery of the cells is incorporated into intraluminal vesicles of multivesicular endosomes and subsequently released to the extracellular space. We show here that extracellular vesicles (EVs) from cells exposed to ROS prime untreated PC12 cells to better tolerate subsequent oxidative stress, thus enhancing their survival. There is an increase in the levels of pTyr23AnxA2 and AnxA2 in the primed cells, suggesting that AnxA2 is involved in their survival. This increase is due to an upregulation of AnxA2 expression both at the transcriptional and translational levels after relatively short term (2 h) exposure to primed EVs.

Human S100A10 plays a crucial role in the acquisition of the endometrial receptivity phenotype

In assisted reproduction, about 30% of embryo implantation failures are related to inadequate endometrial receptivity. To identify molecules involved in endometrial receptivity acquisition, we investigated, using a SELDI-TOF approach, the protein expression profile of early-secretory and mid-secretory endometrium samples. Among the proteins upregulated in mid-secretory endometrium, we investigated the function of S100A10 in endometrial receptivity and implantation process. S100A10 was expressed in epithelial and stromal cells of the endometrium of fertile patients during the implantation windows. Conversely, it was downregulated in the mid-secretory endometrium of infertile patients diagnosed as non-receptive. Transcriptome analysis of human endometrial epithelial and stromal cells where S100A10 was silenced by shRNA revealed the deregulation of 37 and 256 genes, respectively, related to components of the extracellular matrix and intercellular connections. Functional annotations of these deregulated genes highlighted alterations of the leukocyte extravasation signaling and angiogenesis pathways that play a crucial role during implantation. S100A10 silencing also affected the migration of primary endometrial epithelial and stromal cells, decidualization and secretory transformation of primary endometrial stromal cells and epithelial cells respectively, and promoted apoptosis in serum-starved endometrial epithelial cells. Our findings identify S100A10 as a player in endometrial receptivity acquisition.

Annexin A2-dependent actin bundling promotes secretory granule docking to the plasma membrane and exocytosis

Annexin A2, a calcium-, actin-, and lipid-binding protein involved in exocytosis, mediates the formation of lipid microdomains required for the structural and spatial organization of fusion sites at the plasma membrane. To understand how annexin A2 promotes this membrane remodeling, the involvement of cortical actin filaments in lipid domain organization was investigated. 3D electron tomography showed that cortical actin bundled by annexin A2 connected docked secretory granules to the plasma membrane and contributed to the formation of GM1-enriched lipid microdomains at the exocytotic sites in chromaffin cells. When an annexin A2 mutant with impaired actin filament-bundling activity was expressed, the formation of plasma membrane lipid microdomains and the number of exocytotic events were decreased and the fusion kinetics were slower, whereas the pharmacological activation of the intrinsic actin-bundling activity of endogenous annexin A2 had the opposite effects. Thus, annexin A2-induced actin bundling is apparently essential for generating active exocytotic sites.

DAMPs and influenza virus infection in ageing

Influenza A virus (IAV) is a serious global health problem worldwide due to frequent and severe outbreaks. IAV causes significant morbidity and mortality in the elderly population, due to the ineffectiveness of the vaccine and the alteration of T cell immunity with ageing. The cellular and molecular link between ageing and virus infection is unclear and it is possible that damage associated molecular patterns (DAMPs) may play a role in the raised severity and susceptibility of virus infections in the elderly. DAMPs which are released from damaged cells following activation, injury or cell death can activate the immune response through the stimulation of the inflammasome through several types of receptors found on the plasma membrane, inside endosomes after endocytosis as well as in the cytosol. In this review, the detriment in the immune system during ageing and the links between influenza virus infection and ageing will be discussed. In addition, the role of DAMPs such as HMGB1 and S100/Annexin in ageing, and the enhanced morbidity and mortality to severe influenza infection in ageing will be highlighted.

Annexin A2 silencing enhances apoptosis of human umbilical vein endothelial cells in vitro

OBJECTIVE

To study the effects of inhibited Annexin A2 (ANXA2) on human umbilical vein endothelial cells (HUVECs) in vitro.

METHODS

Short hairpin RNA (shRNA) targeting ANXA2 was designed and cloned into double marked lentivirial vector GV248 for RNAi to generate the recombinant expression plasmids, which were stably transfected into HUVECs. The protein and mRNA expression levels of ANXA2 were analyzed by western blotting and real-time polymerase chain reaction, respectively. Cell proliferation (cell counting kit-8 assay), apoptosis (flow cytometry analysis), the expression (western blotting) and the activity of caspases (enzyme-linked immunosorbent assay) were used to assess the effects of silencing ANXA2 on HUVECs in vitro.

RESULTS

The plasmids to express ANXA2-specific shRNA were constructed and were infected into HUVEC resulting in the stably transfected experimental (ANXA2-shRNA), control (control-shRNA) and mock (no plasmid) cell lines, which were verified with western blot and real-time PCR. HUVEC/ANXA2-shRNA showed an inhibition rate 91.89% of ANXA2 expression compared to the mock HUVEC. ANXA2 silencing cell strain obviously presented a lower cell proliferation activity compared to the control and mock HUVECs, with an inhibition rate 82.35% on day 7 in vitro. FACS analysis indicated that the HUVEC/ANXA2-shRNA cells undergoing apoptosis increased by 102.61% compared to the mock HUVECs (P < 0.01). Moreover, the activity levels of caspase-3, caspase-8 and caspase-9 in HUVEC/ANXA2-shRNA cells were increased and the activated cleaved caspase-3, cleaved caspase-8 and cleaved caspase-9 were upregulated evidently compared with that of the control and mock HUVECs by 56.29%, 89.59% and 144.58% (P < 0.01).

CONCLUSIONS

shRNA-mediated silencing of ANXA2 could not only be able to suppress HUVECs proliferation but to upregulate the enzyme activity of caspases, which bring to an increase of cell apoptosis. This work suggested that ANXA2 may represent a useful target of future molecular therapies.

Annexin A2 Acts as an Adhesion Molecule on the Endometrial Epithelium during Implantation in Mice

To determine the function of Annexin A2 (Axna2) in mouse embryo implantation in vivo, experimental manipulation of Axna2 activities was performed in mouse endometrial tissue in vivo and in vitro. Histological examination of endometrial tissues was performed throughout the reproduction cycle and after steroid treatment. Embryo implantation was determined after blockage of the Axna2 activities by siRNA or anti-Axna2 antibody. The expression of Axna2 immunoreactivies in the endometrial luminal epithelium changed cyclically in the estrus cycle and was upregulated by estrogen. After nidatory estrogen surge, there was a concentration of Axna2 immunoreactivities at the interface between the implanting embryo and the luminal epithelium. The phenomenon was likely to be induced by the implanting embryos as no such concentration of signal was observed in the inter-implantation sites and in pseudopregnancy. Knockdown of Axna2 by siRNA reduced attachment of mouse blastocysts onto endometrial tissues in vitro. Consistently, the number of implantation sites was significantly reduced after infusion of anti-Axna2 antibody into the uterine cavity. Steroids and embryos modulate the expression of Axna2 in the endometrial epithelium. Axna2 may function as an adhesion molecule during embryo implantation in mice.

A novel role of annexin A2 in human type I collagen gene expression

The fibrillar collagen scaffold of the extracellular matrix provides a structural framework for cells in tissues and regulates intercellular communication; its disregulation has been associated with tumour development and progression. Previous work has shown that expression of type I collagen, the most abundant mammalian extracellular matrix protein, is decreased in chemically or virally transformed cells. This negative regulation could be mapped to a proximal COL1A2 promoter element spanning a CME (Collagen Modulating Element) site in SV40‐transformed human fibroblasts (SV‐WI38) that binds an unknown repressing protein. By magnetic bead pull‐down, we observed a multi‐protein complex bound to the CME with preference for single‐stranded over conventional double‐stranded DNA. MALDI‐TOF mass spectrometry of the CME‐binding protein complex revealed involvement of nuclear annexin A2 (AnxA2) which was increased in SV40‐transformed cells. Further EMSA analysis demonstrated that AnxA2 did not directly bind to the DNA but stabilised the complex and led to an increase in protein binding to the CME in SV‐WI38 but not untransformed WI38 cells. Knockdown of AnxA2 by siRNA increased type I collagen production in both WI38 and SV‐WI38 cells; however, these effects were not mediated at the transcriptional level. Rather, our data indicate a novel functional role of AnxA2 in the negative post‐transcriptional regulation of type I collagen synthesis in human fibroblasts. In SV40‐transformed cells, AnxA2 is accumulated at the proximal COL1A2 promoter region, suggesting close association with the transcriptional machinery that possibly facilitates binding to the emerging mRNA, eventually contributing to overall repression of type I collagen protein synthesis. J. Cell. Biochem. 116: 408–417, 2015. © 2014 The Authors. Journal of Cellular Biochemistry published by Wiley Periodicals, Inc.

Regulation of the Host Antiviral State by Intercellular Communications

Viruses usually induce a profound remodeling of host cells, including the usurpation of host machinery to support their replication and production of virions to invade new cells. Nonetheless, recognition of viruses by the host often triggers innate immune signaling, preventing viral spread and modulating the function of immune cells. It conventionally occurs through production of antiviral factors and cytokines by infected cells. Virtually all viruses have evolved mechanisms to blunt such responses. Importantly, it is becoming increasingly recognized that infected cells also transmit signals to regulate innate immunity in uninfected neighboring cells. These alternative pathways are notably mediated by vesicular secretion of various virus- and host-derived products (miRNAs, RNAs, and proteins) and non-infectious viral particles. In this review, we focus on these newly-described modes of cell-to-cell communications and their impact on neighboring cell functions. The reception of these signals can have anti- and pro-viral impacts, as well as more complex effects in the host such as oncogenesis and inflammation. Therefore, these “broadcasting” functions, which might be tuned by an arms race involving selective evolution driven by either the host or the virus, constitute novel and original regulations of viral infection, either highly localized or systemic.

Interaction of human tumor viruses with host cell surface receptors and cell entry

Currently, seven viruses, namely Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpes virus (KSHV), high-risk human papillomaviruses (HPVs), Merkel cell polyomavirus (MCPyV), hepatitis B virus (HBV), hepatitis C virus (HCV) and human T cell lymphotropic virus type 1 (HTLV-1), have been described to be consistently associated with different types of human cancer. These oncogenic viruses belong to distinct viral families, display diverse cell tropism and cause different malignancies. A key to their pathogenicity is attachment to the host cell and entry in order to replicate and complete their life cycle. Interaction with the host cell during viral entry is characterized by a sequence of events, involving viral envelope and/or capsid molecules as well as cellular entry factors that are critical in target cell recognition, thereby determining cell tropism. Most oncogenic viruses initially attach to cell surface heparan sulfate proteoglycans, followed by conformational change and transfer of the viral particle to secondary high-affinity cell- and virus-specific receptors. This review summarizes the current knowledge of the host cell surface factors and molecular mechanisms underlying oncogenic virus binding and uptake by their cognate host cell(s) with the aim to provide a concise overview of potential target molecules for prevention and/or treatment of oncogenic virus infection.

BMP9 Crosstalk with the Hippo Pathway Regulates Endothelial Cell Matricellular and Chemokine Responses

Endoglin is a type III TGFβ auxiliary receptor that is upregulated in endothelial cells during angiogenesis and, when mutated in humans, results in the vascular disease hereditary hemorrhagic telangiectasia (HHT). Though endoglin has been implicated in cell adhesion, the underlying molecular mechanisms are still poorly understood. Here we show endoglin expression in endothelial cells regulates subcellular localization of zyxin in focal adhesions in response to BMP9. RNA knockdown of endoglin resulted in mislocalization of zyxin and altered formation of focal adhesions. The mechanotransduction role of focal adhesions and their ability to transmit regulatory signals through binding of the extracellular matrix are altered by endoglin deficiency. BMP/TGFβ transcription factors, SMADs, and zyxin have recently been implicated in a newly emerging signaling cascade, the Hippo pathway. The Hippo transcription coactivator, YAP1 (yes-associated protein 1), has been suggested to play a crucial role in mechanotransduction and cell-cell contact. Identification of BMP9-dependent nuclear localization of YAP1 in response to endoglin expression suggests a mechanism of crosstalk between the two pathways. Suppression of endoglin and YAP1 alters BMP9-dependent expression of YAP1 target genes CCN1 (cysteine-rich 61, CYR61) and CCN2 (connective tissue growth factor, CTGF) as well as the chemokine CCL2 (monocyte chemotactic protein 1, MCP-1). These results suggest a coordinate effect of endoglin deficiency on cell matrix remodeling and local inflammatory responses. Identification of a direct link between the Hippo pathway and endoglin may reveal novel mechanisms in the etiology of HHT.

Extending the limits of quantitative proteome profiling with data-independent acquisition and application to acetaminophen-treated three-dimensional liver microtissues

The data-independent acquisition (DIA) approach has recently been introduced as a novel mass spectrometric method that promises to combine the high content aspect of shotgun proteomics with the reproducibility and precision of selected reaction monitoring. Here, we evaluate, whether SWATH-MS type DIA effectively translates into a better protein profiling as compared with the established shotgun proteomics.

We implemented a novel DIA method on the widely used Orbitrap platform and used retention-time-normalized (iRT) spectral libraries for targeted data extraction using Spectronaut. We call this combination hyper reaction monitoring (HRM). Using a controlled sample set, we show that HRM outperformed shotgun proteomics both in the number of consistently identified peptides across multiple measurements and quantification of differentially abundant proteins. The reproducibility of HRM in peptide detection was above 98%, resulting in quasi complete data sets compared with 49% of shotgun proteomics.

Utilizing HRM, we profiled acetaminophen (APAP)¹-treated three-dimensional human liver microtissues. An early onset of relevant proteome changes was revealed at subtoxic doses of APAP. Further, we detected and quantified for the first time human NAPQI-protein adducts that might be relevant for the toxicity of APAP. The adducts were identified on four mitochondrial oxidative stress related proteins (GATM, PARK7, PRDX6, and VDAC2) and two other proteins (ANXA2 and FTCD).

Our findings imply that DIA should be the preferred method for quantitative protein profiling.

Dynamic reciprocity between cells and their microenvironment in reproduction

Dynamic reciprocity (DR) refers to the ongoing, bidirectional interaction between cells and their microenvironment, specifically the extracellular matrix (ECM). The continuous remodeling of the ECM exerts mechanical force on cells and modifies biochemical mediators near the cell membrane, thereby initiating cell-signaling cascades that produce changes in gene expression and cell behavior. Cellular changes, in turn, affect the composition and organization of ECM components. These continuous interactions are the fundamental principle behind DR, and its critical role throughout development and adult tissue homeostasis has been extensively investigated. While DR in the mammary gland has been well described, we provide direct evidence that similar dynamic interactions occur in other areas of reproductive biology as well. In order to establish the importance of DR in the adaptive functioning of the female reproductive tract, we present our most current understanding of DR in reproductive tissues, exploring the mammary gland, ovary, and uterus. In addition to explaining normal physiological function, investigating DR may shed new light into pathologic processes that occur in these tissues and provide an exciting opportunity for novel therapeutic intervention.