Annexin XI co-localises with calcyclin in proliferating cells of the embryonic mouse testis

Annexin Animal Models-From Fundamental Principles to Translational Research

Routine manipulation of the mouse genome has become a landmark in biomedical research. Traits that are only associated with advanced developmental stages can now be investigated within a living organism, and the in vivo analysis of corresponding phenotypes and functions advances the translation into the clinical setting. The annexins, a family of closely related calcium (Ca²⁺)- and lipid-binding proteins, are found at various intra- and extracellular locations, and interact with a broad range of membrane lipids and proteins. Their impacts on cellular functions has been extensively assessed in vitro, yet annexin-deficient mouse models generally develop normally and do not display obvious phenotypes. Only in recent years, studies examining genetically modified annexin mouse models which were exposed to stress conditions mimicking human disease often revealed striking phenotypes. This review is the first comprehensive overview of annexin-related research using animal models and their exciting future use for relevant issues in biology and experimental medicine.

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.

Downregulation of Annexin A11 (ANXA11) Inhibits Cell Proliferation, Invasion, and Migration via the AKT/GSK-3β Pathway in Gastric Cancer

Background

Gastric cancer (GC) is one of the most common malignant tumors in the world and in China the incidence and mortality rates of gastric cancer are the second highest among all forms of cancer. Annexin A11 (ANXA11) is a member of the annexins family. Previous studies have shown that ANXA11 participates in many cellular functions and has significant influence on ovarian, breast, liver, and colorectal cancer. However, the expression and biological functions of ANXA11 in GC are still unknown.

Material/Methods

A total of 63 paired gastric cancer tissues and matched adjacent mucosa were used to measure the ANXA11 levels and its correlation with clinical characteristics. We carried out the biological functions and underlying mechanism study using SGC-7901and AGS cell lines.

Results

The expression of ANXA11 in cancer tissues was higher than in adjacent mucosa at mRNA and protein levels. In clinicopathological analysis, we found that increased expression of ANXA11 was significantly associated with tumor size, tumor infiltration, local lymph node metastasis, TNM staging, and vascular invasion. Small interfering RNA (siRNA) silencing of ANXA11 inhibits cell proliferation, colony formation, migration, and invasion through the AKT/GSK-3β pathway.

Conclusions

ANXA11 plays a critical role in regulating GC proliferation, migration, and invasion via the AKT/GSK-3β pathway, and can potentially be used as a prognostic factor and therapeutic target for gastric cancer patients.

ANXA11 regulates the tumorigenesis, lymph node metastasis and 5-fluorouracil sensitivity of murine hepatocarcinoma Hca-P cells by targeting c-Jun

Annexin A11 (Anxa11) is associated with various cancers. Using a pair of syngeneic murine hepatocarcinoma cells, Hca-P with ~25% and Hca-F with ~75% lymph node metastatic (LNM) potentials, we demonstrated Anxa11 involvement in hepatocarcinoma lymphatic metastasis. Here, ANXA11 acted as a suppressor for the tumorigenicity, LNM and 5-FU resistance of Hca-P via c-Jun. We constructed monoclonal Hca-P cell line with stable ANXA11 knockdown. Although Bax and Bcl-2 levels increased in shRNA-Anxa11-transfected Hca-P, ANXA11 downregulation showed no clear effect on Hca-P apoptosis. ANXA11 downregulation promoted in vitro migration and invasion capacities of Hca-P. In situ adhesion potential of Hca-P cells toward LN was significantly enhanced following ANXA11 downregulation. Consistently, ANXA11 downregulation promoted the in vivo tumor growth and LNM capacities of Hca-P cells. ANXA11 knockdown enhanced the chemoresistance of Hca-P cells specifically toward 5-FU instead of cisplatin. Its downregulation increased c-Jun (pSer73) and decreased c-Jun (pSer243) levels in Hca-P. c-Jun (pSer243) downregulation seemed to be only correlated with ANXA11 knockdown without the connection to 5-FU treatment. Interestingly, compared with scramble-Hca-P cells, the levels of c-Jun and c-Jun (pSer73) in shRNA-Anxa11-Hca-P cells were upregulated in the presences of 0.1 and 1.0 mg/L 5-FU. The levels changes from c-Jun and c-Jun (pSer73) in Hca-P cells showed a more obvious tendency with the combination of ANXA11 knockdown and 5-FU treatment. ANXA11 level regulates LNM and 5-FU resistance of Hca-P via c-Jun pathway. It might play an important role in hepatocarcinoma cell malignancy and be a therapeutic target for hepatocarcinoma.

Annexin A11 knockdown inhibits in vitro proliferation and enhances survival of Hca-F cell via Akt2/FoxO1 pathway and MMP-9 expression

Annexin A11 (Anxa11), a Ca(2+)-regulated phospholipid-binding protein, is involved in cell apoptosis, differentiation, vesicle trafficking, cancer progression and autoimmune diseases. Previous study from our group indicated that Anxa11 was associated with lymphatic metastatic potential of murine hepatocarcinoma cells. Herein, we investigated the effects and action mechanism of Anxa11 knockdown on in vitro cell proliferation and apoptosis of Hca-F, a murine hepatocarcinoma cell with∼75% lymph node metastatic potential. Real-time PCR and western blotting assays indicated that Anxa11 was significantly downregulated in monoclonal Anxa11-shRNA-transfected Hca-F cells. Anxa11 knockdown in Hca-F suppressed its in vitro proliferation and cell apoptosis capacities. Following Anxa11 knockdown in Hca-F cells, Bax/Bcl-2 expression level ratio, Akt2 and FoxO1 (pSer319) expression levels as well as MMP-9 mRNA and active MMP-9 protein levels were significantly elevated in Hca-F cells. In conclusion, Annexin A11 knockdown inhibits the in vitro proliferation and cell apoptosis of Hca-F cell via Akt2/FoxO1 and/or MMP-9 expression pathway. Anxa11 might play an important role in hepatocarcinoma cell invasion and metastasis and hepatocarcinoma malignancy.

Annexin A11 in disease

Ubiquitously expressed in many cell types, annexin A11 (Anxa11) is a member of the multigene family of Ca(2+)-regulated phospholipid-dependent and membrane-binding annexin proteins. Studies have shown that Anxa11 plays an important role in cell division, Ca(2+) signaling, vesicle trafficking and apoptosis. The deregulation and mutation of Anxa11 are involved in systemic autoimmune diseases, sarcoidosis and the development, chemoresistance and recurrence of cancers. Malfunction of Anxa11 may lead to or enhance the metastasis, invasion and drug resistance of cancers through the platelet-derived growth factor receptor (PDGFR) pathway and/or the mitogen-activated protein kinase (MAPK)/p53 pathway. In a variety of diseases, Anxa11 is most commonly reported to function through interactions with apoptosis-linked gene-2 protein (ALG-2) and/or calcyclin (S100A6). Although it has been little studied, Anxa11 is a promising biomarker for the diagnosis, treatment and prognosis of certain diseases. In this review, the associations of Anxa11 with Ca(2+)-regulated exocytosis, cytokinesis, sex differentiation, autoimmune diseases, thrombolysis and cancers are summarized and interpreted.

Suppression of annexin A11 in ovarian cancer: implications in chemoresistance

Ovarian cancer patients treated with cisplatin-based chemotherapy often develop acquired cisplatin resistance and, consequently, cancer recurrence. We have previously reported that annexin A11 is associated with cisplatin resistance and related to tumor recurrence in ovarian cancer patients. In this study, we used small interfering RNA to suppress annexin A11 expression in ovarian cancer cells followed by various in vitro assays. We showed that knockdown of annexin A11 expression reduced cell proliferation and colony formation ability of ovarian cancer cells. Epigenetic silencing of annexin A11 conferred cisplatin resistance to ovarian cancer cells. Through a comprehensive time course study of cisplatin response in ovarian cancer cells with/without suppression of annexin A11 expression using whole-genome oligonucleotide microarrays, we identified a set of differentially expressed genes associated with annexin A11 expression and some patterns of gene expressions in response to cisplatin exposure. These identified genes/patterns were further validated by real-time polymerase chain reaction and immunoblot analysis. Many of them such as HMOX1, TGFBI, LY6D, S100P, EIF4EBP2, DHRS2, and PCSK9 have been involved in apoptosis, cell cycling/proliferation, cell adhesion/migration, transcription regulation, and signal transduction. In addition, immunohistochemistry analyses indicated that annexin A11 immunointensity inversely correlated with HMOX1 immunoreactivity in 142 ovarian cancer patients. In contrast to annexin A11, HMOX1 immunoreactivity positively correlated with in vitro cisplatin resistance in ovarian cancers. Collectively, annexin A11 is directly involved in cell proliferation and cisplatin resistance of ovarian cancer. Manipulation of annexin A11 and its associated genes may represent a novel therapeutic strategy in human ovarian cancers.

S100-annexin complexes--biology of conditional association

S100 proteins and annexins both constitute groups of Ca2+-binding proteins, each of which comprises more than 10 members. S100 proteins are small, dimeric, EF-hand-type Ca2+-binding proteins that exert both intracellular and extracellular functions. Within the cells, S100 proteins regulate various reactions, including phosphorylation, in response to changes in the intracellular Ca2+ concentration. Although S100 proteins are known to be associated with many diseases, exact pathological contributions have not been proven in detail. Annexins are non-EF-hand-type Ca2+-binding proteins that exhibit Ca2+-dependent binding to phospholipids and membranes in various tissues. Annexins bring different membranes into proximity and assist them to fuse, and therefore are believed to play a role in membrane trafficking and organization. Several S100 proteins and annexins are known to interact with each other in either a Ca2+-dependent or Ca2+-independent manner, and form complexes that exhibit biological activities. This review focuses on the interaction between S100 proteins and annexins, and the possible biological roles of these complexes. Recent studies have shown that S100-annexin complexes have a role in the differentiation of gonad cells and neurological disorders, such as depression. These complexes regulate the organization of membranes and vesicles, and thereby may participate in the appropriate disposition of membrane-associated proteins, including ion channels and/or receptors.

Annexin XI is associated with cisplatin resistance and related to tumor recurrence in ovarian cancer patients

PURPOSE

Ovarian cancer patients treated with cisplatin-based chemotherapy often develop acquired cisplatin resistance and, consequently, cancer recurrence. The precise nature of chemoresistance remains unclear. In this study, a protein identified to be associated with cisplatin resistance in ovarian cancer cells was investigated in ovarian cancer tissues to address its clinical significance.

EXPERIMENTAL DESIGN

Antibody microarrays were used to identify proteins consistently differentially expressed across three pairs of cisplatin-sensitive and cisplatin-resistant ovarian cancer cell lines. Immunoblotting was used to confirm observed alteration of protein expression. The protein expression was further evaluated by immunohistochemical staining using tissue microarrays containing various human normal and malignant tissues and 164 surgical specimens derived from primary and recurrent ovarian cancer patients who underwent primary debulking surgery followed by standard chemotherapeutic regimen.

RESULTS

Annexin XI was down-regulated in all three cisplatin-resistant cell lines as compared with their parent cells. Annexin XI expression was observed in the majority of human normal organs and decreased in some of the most common human malignancies. The expression level of Annexin XI in first recurrent ovarian cancers was much lower than that in primary ovarian cancers (P = 0.0004). Increased Annexin XI immunoreactivity in ovarian cancers seemed to prolong the disease-free interval of patients (P = 0.03). Annexin XI immunoreactivity inversely correlated with in vitro cisplatin resistance in ovarian cancers (P = 0.01).

CONCLUSION

Decreased expression of Annexin XI is characteristic for cisplatin-resistant cancer cells and may contribute to tumor recurrence. Annexin XI may be a potential marker for chemoresistance and earlier recurrence of ovarian cancer patients.

Insights into S100 target specificity examined by a new interaction between S100A11 and annexin A2

S100 proteins are a group of EF-hand calcium-signaling proteins, many of which interact with members of the calcium- and phospholipid-binding annexin family of proteins. This calcium-sensitive interaction enables two neighboring membrane surfaces, complexed to different annexin proteins, to be brought into close proximity for membrane reorganization, using the S100 protein as a bridging molecule. S100A11 and S100A10 are two members of the S100 family found to interact with the N-termini of annexins A1 and A2, respectively. Despite the high degree of structural similarity between these two complexes and the sequences of the peptides, earlier studies have shown that there is little or no cross-reactivity between these two S100s and the annexin peptides. In the current work the specificity and the affinity of the interaction of the N-terminal sequences of annexins A1 and A2 with Ca2+-S100A11 were investigated. Through the use of alanine-scanning peptide array experiments and NMR spectroscopy, an approximate 5-fold tighter interaction was identified between Ca2+-S100A11 and annexin A2 (approximately 3 microM) compared to annexin A1 (approximately 15 microM). Chemical shift mapping revealed that the binding site for annexin A2 on S100A11 was similar to that observed for the annexin A1 but with distinct differences involving the C-terminus of the annexin A2 peptide. In addition, kinetic measurements based on NMR titration data showed that annexin A2 binding to Ca2+-S100A11 occurs at a comparable rate (approximately 120 s(-1)) to that observed for membrane fusion processes such as endo- and exocytosis.

Calcium-dependent and -independent interactions of the S100 protein family

The S100 proteins comprise at least 25 members, forming the largest group of EF-hand signalling proteins in humans. Although the proteins are expressed in many tissues, each S100 protein has generally been shown to have a preference for expression in one particular tissue or cell type. Three-dimensional structures of several S100 family members have shown that the proteins assume a dimeric structure consisting of two EF-hand motifs per monomer. Calcium binding to these S100 proteins, with the exception of S100A10, results in an approx. 40 degrees alteration in the position of helix III, exposing a broad hydrophobic surface that enables the S100 proteins to interact with a variety of target proteins. More than 90 potential target proteins have been documented for the S100 proteins, including the cytoskeletal proteins tubulin, glial fibrillary acidic protein and F-actin, which have been identified mostly from in vitro experiments. In the last 5 years, efforts have concentrated on quantifying the protein interactions of the S100 proteins, identifying in vivo protein partners and understanding the molecular specificity for target protein interactions. Furthermore, the S100 proteins are the only EF-hand proteins that are known to form both homo- and hetero-dimers, and efforts are underway to determine the stabilities of these complexes and structural rationales for their formation and potential differences in their biological roles. This review highlights both the calcium-dependent and -independent interactions of the S100 proteins, with a focus on the structures of the complexes, differences and similarities in the strengths of the interactions, and preferences for homo- compared with hetero-dimeric S100 protein assembly.