Protein interactions between surface annexin A2 and S100A10 mediate adhesion of breast cancer cells to microvascular endothelial cells

Annexin A2 (AnxA2) and S100A10 are known to form a molecular complex. Using fluorescence-based binding assays, we show that both proteins are localised on the cell surface, in a molecular form that allows mutual interaction. We hypothesized that binding between these proteins could facilitate cell-cell interactions. For cells that express surface S100A10 and surface annexin A2, cell-cell interactions can be blocked by competing with the interaction between these proteins. Thus an annexin A2-S100A10 molecular bridge participates in cell-cell interactions, revealing a hitherto unexplored function of this protein interaction.

Annexin A2 promotes the migration and invasion of human hepatocellular carcinoma cells in vitro by regulating the shedding of CD147-harboring microvesicles from tumor cells

It has been reported that Annexin A2 (ANXA2) is up-regulated in hepatocellular carcinoma (HCC), but the roles of ANXA2 in the migration and invasion of HCC cells have not been determined. In this study, we found that ANXA2-specific siRNA (si-ANXA2) significantly inhibited the migration and invasion of HCC cells co-cultured with fibroblasts in vitro. In addition, the production of MMP-2 by fibroblasts cultured in supernatant collected from si-ANXA2-transfected HCC cells was notably down-regulated. ANXA2 was also found to be co-localized and co-immunoprecipitated with CD147. Further investigation revealed that the expression of ANXA2 in HCC cells affected the shedding of CD147-harboring membrane microvesicles, acting as a vehicle for CD147 in tumor-stromal interactions and thereby regulating the production of MMP-2 by fibroblasts. Together, these results suggest that ANXA2 enhances the migration and invasion potential of HCC cells in vitro by regulating the trafficking of CD147-harboring membrane microvesicles.

[The expression and function of annexin A2 in the course of retinal angiogenesis of mouse]

OBJECTIVE

To study the production and the role of annexin A2 (ANXA2) in the process of retinal neovascularization of mouse.

METHODS

Experimental study. C57BL/6J mice were classified into four groups:normal group (80 mice), oxygen induced retinopathy (OIR) mock group (80 mice) , siANXA2 group (transfected with siRNA target ANXA2) (50 mice) , and siANXA2_M group (50 mice) .Stretched preparation of retina after angiography was used to observe the morphology change of retinal neovascularization from 12 to 30 days after birth in normal group and OIR mock group, and real-time PCR was used to test the expression of ANXA2 in these days. On 17 days old, the mRNA and protein production of vascular endothelial growth factor (VEGF)-α, matrix metalloproteinase (MMP)-2, MMP-9, and tissue inhibitor of metalloproteinase (TIMP)-2 in 4 groups were assessed by real-time PCR and Western blot. The results of all factors among four groups were analyzed by one way ANOVA and SNK-q test.

RESULTS

The retinal neovascularization of siANXA2 group in 17 days old was more regular than that in OIR mock group. The production of ANXA2 in mouse retina was associated with the stage of retinal neovascularization. The expression of ANXA2 was in high level when neovessels grew and in low level when neovessels stopped growing. The mRNA expressions of ANXA2,VEGF-α, MMP-2, MMP-9 and TIMP-2 showed statistical difference among 4 groups (F = 8.122-74.009, P < 0.05) . Significant statistics difference was found in multiple comparison:the expressions of VEGF-α (0.22 ± 0.04), MMP-2 (11.08 ± 1.28), MMP-9 (4.64 ± 0.38) in OIR mock group were significantly higher than that in normal group (0.16 ± 0.02, 2.18 ± 1.39, 1.17 ± 0.25) (SNK-q test: P < 0.01).In siANXA2 group, the productions of VEGF-α (0.02 ± 0.01), MMP-2 (2.21 ± 0.42) , MMP-9 (1.33 ± 0.10) were significantly lower than that in OIR mock group (SNK-q test: P < 0.01). The mRNA expression of TIMP-2 (0.59 ± 0.15) in OIR mock group was significantly lower than that in normal group (1.35 ± 0.01) (SNK-q test: P < 0.05). In siANXA2 group, the production of TIMP-2 was higher than that in OIR mock group (SNK-q test: P < 0.05). The results of Western blot were similar to that in real-time PCR.

CONCLUSIONS

ANXA2 is overexpressed in oxygen-induced retinal neovascularization in a mouse model. The overexpression of ANXA2 may affect the expression of proangiogenic factors. ANXA2 may involve in the development of the retinal neovascularization. The production of ANXA2 may be inhibited by siRNA. ANXA2 maybe a new target for inhibition of retinal neovascularization.

Annexin A2 system in human biology: cell surface and beyond

Annexin A2 (A2) is a multicompartmental, multifunctional protein that orchestrates a growing spectrum of biologic processes. At the endothelial cell surface, A2 and S100A10 (p11) form a heterotetramer, which accelerates tissue plasminogen activator-dependent activation of the fibrinolytic protease, plasmin. In antiphospholipid syndrome, anti-A2 antibodies are associated with clinical thrombosis, whereas overexpression of A2 in acute promyelocytic leukemia promotes hyperfibrinolytic bleeding. A2 is upregulated in hypoxia, and mice deficient in A2 are resistant to oxygen-induced retinal neovascularization, suggesting a role for A2 in human retinal vascular proliferation. In solid malignancies, the (A2•p11)(2) tetramer may promote cancer cell invasion, whereas in multiple myeloma A2 enables malignant plasmacyte growth and predicts prognosis. In the central nervous system, the p11 enables membrane insertion of serotonin receptors that govern mood. In the peripheral nervous system, p11 directs sodium channels to the plasma membrane, enabling pain perception. In cerebral cortex neurons, A2 stabilizes the microtubule-associated tau protein, which, when mutated, is associated with frontotemporal dementia. In inflammatory dendritic cells, A2 maintains late endosomal/lysosomal membrane integrity, thus modulating inflammasome activation and cytokine secretion in a model of aseptic arthritis. Together, these findings suggest an emerging, multifaceted role for A2 in human health and disease.

ANXA2 remodels the microstructures of caco2 cells

ANXA2 was reported as a multiple tumors relevant gene expressed excessively in many tumor tissue types, especially in the cancers from digestion system, and its aberrant expression enhances the malignant properties of cancer cells. We suppose that the microstructure heterogeneity is important to maintain the malignancy of cancer cells, and excessive ANXA2 expression enhance the malignancy by remodeling the microstructures of cancer cells. To validate the proposal, the ANXA2-/-caco2 cell line was generated and the changes of the microstructures in the ANXA2 deleted and wild type caco2 cells were observed under fluorescence microscope, laser scanning confocal microscope and electron microscope. We found that ANXA2 deletion induced the pseudopodia shorted and spared, non-stained areas increased, mitochondria decreased, and the expression and polymerization of F-actin and β-tubulin changed. By the findings above, it is firstly reported in this paper that the ANXA2 excessive expression induces the significant changes of the microstructures in cancer cells. Combining our previous data together, our results indicate that ANXA2 excessive expression enhances the malignancy of cancers partially by remodeling the cell microstructures.

Proteomic biomarkers of type 2 diabetes mellitus risk in women with polycystic ovary syndrome

Women with polycystic ovary syndrome (PCOS) are at increased risk of developing insulin resistance and type 2 diabetes mellitus (T2DM). In this study, we attempted to list the proteomic biomarkers of PCOS and T2DM that have been published in the literature so far. We identified eight common biomarkers that were differentially expressed in both women with PCOS and T2DM when compared with healthy controls. These include pyruvate kinase M1/M2, apolipoprotein A-I, albumin, peroxiredoxin 2, annexin A2, α-1-B-glycoprotein, flotillin-1 and haptoglobin. These biomarkers could help improve our understanding of the links between PCOS and T2DM and could be potentially used to identify subgroups of women with PCOS at increased risk of T2DM. More studies are required to further evaluate the role these biomarkers play in women with PCOS and T2DM.

Plasminogen receptors and their role in the pathogenesis of inflammatory, autoimmune and malignant disease

Plasminogen is the proenzyme of plasmin, the key protease of the fibrinolytic system, but its role is not limited to fibrinolysis regulation. Plasminogen binds not only to fibrin, but also to different receptors on cell surfaces, including the heterotetrameric complex Annexin A2-S100A10, enolase-1, histone H2B and the plasminogen receptor Plg-R(KT) . These receptors localize plasmin generation to the cell surface and provide a broad spectrum of reactions including proteolytic activity, cell migration and recruitment as well as signaling pathway activation. These plasminogen-binding proteins are involved in both physiologic and pathologic processes such as inflammation, thrombosis and cancer. Thus, plasminogen is at the center of a complex tightly controlled and regulated system where plasminogen-binding proteins have a crucial role, suggesting new therapeutic and diagnostic strategies. This review will discuss currently available information on plasminogen receptors, particularly their mechanisms of action and their roles in inflammatory, autoimmune and malignant disease.

Structure of a C-terminal AHNAK peptide in a 1:2:2 complex with S100A10 and an acetylated N-terminal peptide of annexin A2

AHNAK, a large 629 kDa protein, has been implicated in membrane repair, and the annexin A2-S100A10 heterotetramer [(p11)(2)(AnxA2)(2))] has high affinity for several regions of its 1002-amino-acid C-terminal domain. (p11)(2)(AnxA2)(2) is often localized near the plasma membrane, and this C2-symmetric platform is proposed to be involved in the bridging of membrane vesicles and trafficking of proteins to the plasma membrane. All three proteins co-localize at the intracellular face of the plasma membrane in a Ca(2+)-dependent manner. The binding of AHNAK to (p11)(2)(AnxA2)(2) has been studied previously, and a minimal binding motif has been mapped to a 20-amino-acid peptide corresponding to residues 5654-5673 of the AHNAK C-terminal domain. Here, the 2.5 Å resolution crystal structure of this 20-amino-acid peptide of AHNAK bound to the AnxA2-S100A10 heterotetramer (1:2:2 symmetry) is presented, which confirms the asymmetric arrangement first described by Rezvanpour and coworkers and explains why the binding motif has high affinity for (p11)(2)(AnxA2)(2). Binding of AHNAK to the surface of (p11)(2)(AnxA2)(2) is governed by several hydrophobic interactions between side chains of AHNAK and pockets on S100A10. The pockets are large enough to accommodate a variety of hydrophobic side chains, allowing the consensus sequence to be more general. Additionally, the various hydrogen bonds formed between the AHNAK peptide and (p11)(2)(AnxA2)(2) most often involve backbone atoms of AHNAK; as a result, the side chains, particularly those that point away from S100A10/AnxA2 towards the solvent, are largely interchangeable. While the structure-based consensus sequence allows interactions with various stretches of the AHNAK C-terminal domain, comparison with other S100 structures reveals that the sequence has been optimized for binding to S100A10. This model adds new insight to the understanding of the specific interactions that occur in this membrane-repair scaffold.

Genotoxic agents promote the nuclear accumulation of annexin A2: role of annexin A2 in mitigating DNA damage

Annexin A2 is an abundant cellular protein that is mainly localized in the cytoplasm and plasma membrane, however a small population has been found in the nucleus, suggesting a nuclear function for the protein. Annexin A2 possesses a nuclear export sequence (NES) and inhibition of the NES is sufficient to cause nuclear accumulation. Here we show that annexin A2 accumulates in the nucleus in response to genotoxic agents including gamma-radiation, UV radiation, etoposide and chromium VI and that this event is mediated by the nuclear export sequence of annexin A2. Nuclear accumulation of annexin A2 is blocked by the antioxidant agent N-acetyl cysteine (NAC) and stimulated by hydrogen peroxide (H₂O₂), suggesting that this is a reactive oxygen species dependent event. In response to genotoxic agents, cells depleted of annexin A2 show enhanced phospho-histone H2AX and p53 levels, increased numbers of p53-binding protein 1 nuclear foci and increased levels of nuclear 8-oxo-2′-deoxyguanine, suggesting that annexin A2 plays a role in protecting DNA from damage. This is the first report showing the nuclear translocation of annexin A2 in response to genotoxic agents and its role in mitigating DNA damage.

Relationship between the inflammatory molecular profile of breast carcinomas and distant metastasis development

Inflammatory conditions may promote tumor progression and aggressiveness. In previous reports, we found a group of breast cancer tumors characterized by metalloprotease-11 (MMP-11) expression by intratumoral mononuclear inflammatory cells (MICs), which was associated with distant metastasis development. Thus, in the present study we evaluated the relationship between MMP-11 expression by MICs, distant metastasis development, and a wide panel of inflammatory factors in breast carcinoma. In an initial approach, we analyzed 65 factors associated with tumor progression and inflammation, in a tumor population classified in good or bad prognosis, based on MMP-11 expression by intratumoral MICs. The most differentially expressed factors were then analyzed in a wider tumor population classified according to MMP-11 expression by MICs and also according to metastasis development. These analyses were carried out by Real-time PCR. The results showed that of the 65 starting factors analyzed, those related with MMP-11 expression by MICs were: IL-1, −5, −6, −8, −17, −18, MMP-1, TIMP-1, ADAM-8, −10, −15, −23, ADAMTS-1, −2, −15, Annexin A2, IFNβ, Claudin-3, CCL-3, MyD88, IRAK-4 and NFκB. Of them, factors more differentially expressed between both groups of tumors were IL-1, IL-5, IL-6, IL-17, IFNβ and NFκB. Thereafter, we confirmed in the wider tumor population, that there is a higher expression of those factors in tumors infiltrated by MMP-11 positive MICs. Altogether these results indicate that tumors developing worse prognosis and identified by MMP-11 expression by intratumoral MICs, shows an up-regulation of inflammatory-related genes.

Extracellular release of annexin II from pancreatic cancer cells and resistance to anticancer drug-induced apoptosis by supplementation of recombinant annexin II

OBJECTIVES

Extracellular microenvironment plays crucial roles in the development of cancers and chemoresistance. Pancreatic carcinoma is resistant to almost all chemotherapeutic agents. In this study, we identified annexin II in the medium from pancreatic cancer cells as a protein released into the extracellular environment.

METHODS

Medium from 5-hour cultures of various cancer cells was collected. Proteins in the medium were detected by molecular mass analysis and immunoblotting. Anticancer drug sensitivity of cells preincubated with or without recombinant annexin II (rANX II) was measured using crystal violet assay and colony survival assay. Apoptosis-related molecules were analyzed by immunoblotting.

RESULTS

Recombinant ANX II supplementation in the medium confers resistance to anticancer drugs, including cisplatin, 5-fluorouracil, and gemcitabine, in MiaPaCa-2 and AsPC-1 cells. In MiaPaCa-2 cells, rANX II supplementation resulted in suppression of caspase-3 activation associated with increased Bcl-2/Bax ratios. Suppression of cisplatin-induced cell death by rANX II supplementation was canceled by inhibitors of phosphatidylinositol 3-kinase and mitogen-activated protein kinase kinase signal pathways.

CONCLUSIONS

The current study is the first report to demonstrate that supplementation of rANX II in the medium increased resistance to anticancer drugs in pancreatic cancer cells. Recombinant ANX II exerts cell death-suppressive function by antagonizing cisplatin-induced apoptosis.

[Annexin A2 expression in intestinal mucosa of patients with inflammatory bowel disease and its clinical implications]

OBJECTIVE

To explore the role of annexin A2 (ANXA2) expression in the intestinal mucosa in the pathogenesis of inflammatory bowel disease (IBD).

METHODS

Intestinal or colonic mucosal biopsy samples were obtained from 54 patients with ulcerative colitis (UC), 37 with Crohn's disease (CD), and 15 healthy control subjects. Immunohistochemistry was employed to examine the expression of ANXA2 in the intestinal mucosa, and mRNA expression of ANXA2 was detected using real-time PCR.

RESULTS

Immunohistochemistry showed a ANXA2 positivity rate of 83.3% (45/54) in patients with UC, 27.0% (10/37) in patients with CD, and 53.3% (8/15) in the control subjects. ANXA2 expression in the intestinal or colonic mucosa was significantly up-regulated in patients with UC compared with the patients with CD and healthy control subjects, but was significantly lower in patients with CD than in the healthy controls (P<0.05). The expression levels of ANXA2 were strongly associated with the severity of clinical manifestations and the histopathological grades of UC (P<0.05). Compared with the healthy controls and patients with CD, patients with UC showed a significantly increased ANXA2 mRNA expression level in the inflamed mucosa of UC (P<0.05).

CONCLUSION

ANXA2 can serve as a marker for differential diagnosis of IBD, and its up-regulated expression is closely related to the pathogenesis of UC.

Annexin A2 and A5 serve as new ligands for C1q on apoptotic cells

C1q is the initiator of the classical complement pathway and opsonizes apoptotic cells to facilitate phagocytosis. Deficiency of C1q is the strongest known risk factor for development of systemic lupus erythematosus (SLE), which appears to be related to ensuing impaired clearance of apoptotic material. The objective of the current study was to investigate new ligands for C1q on the surface of apoptotic cells. We revealed that the two phospholipid-binding proteins annexin A2 and A5 are, beside DNA, significant C1q ligands. We furthermore, demonstrated that C1q binds directly to histones exposed on the surface of dying cells but we did not detect significant interaction with phosphatidylserine. The complement inhibitors C4b-binding protein and factor H also interact with dying cells, most likely to decrease complement activation beyond the level of C3 to allow noninflammatory clearance. Despite the fact that C4b-binding protein, factor H, and C1q share some ligands on dying cells, we showed that these three proteins did not compete with one another for binding to apoptotic cells. We additionally demonstrated that the way in which apoptosis is induced influenced both the degree of apoptosis and the binding of C1q. The knowledge, that annexin A2 and A5 act as ligands for C1q on apoptotic cells, sheds new light on the pathophysiology of autoimmune diseases.

Reciprocal regulation of annexin A2 and EGFR with Her-2 in Her-2 negative and herceptin-resistant breast cancer

Alternative survival pathways are commonly seen to be upregulated upon inhibition of receptor tyrosine kinases (RTK), including Her-2. It is established that treatment with Herceptin leads to selective overexpression and activation of epidermal growth factor receptor (EGFR) and Src which further contributes to oncogenesis in Herceptin resistant and triple negative breast cancer (TNBC) patients. Here, we show a co-regulated upregulation in the expression of Annexin A2 (AnxA2), a known substrate of Src and one of the regulators of EGFR receptor endocytosis, in Herceptin resistant and Her-2 negative breast cancer. Immunohistochemical expression analysis revealed a reciprocal regulation between Her-2 and AnxA2 in breast cancer clinical samples as well as in cell lines as confirmed by protein and RNA analysis. The siRNA and Herceptin mediated downregulation/inhibition of Her-2 in Her-2 amplified cells induced AnxA2 expression and membrane translocation. In this study we report a possible involvement of AnxA2 in maintaining constitutively activated EGFR downstream signaling intermediates and hence in cell proliferation, migration and viability. This effect was consistent in Herceptin resistant JIMT-1 cells as well as in Her-2 negative breast cancer. The siRNA mediated AnxA2 downregulation leads to increased apoptosis, decreased cell viability and migration. Our studies further indicate the role of AnxA2 in EGFR-Src membrane bound signaling complex and ligand induced activation of downstream signaling pathways. Targeting this AnxA2 dependent positive regulation of EGFR signaling cascade may be of therapeutic value in Her-2 negative breast cancer.

The S100A10 subunit of the annexin A2 heterotetramer facilitates L2-mediated human papillomavirus infection

Mucosotropic, high-risk human papillomaviruses (HPV) are sexually transmitted viruses that are causally associated with the development of cervical cancer. The most common high-risk genotype, HPV16, is an obligatory intracellular virus that must gain entry into host epithelial cells and deliver its double stranded DNA to the nucleus. HPV capsid proteins play a vital role in these steps. Despite the critical nature of these capsid protein-host cell interactions, the precise cellular components necessary for HPV16 infection of epithelial cells remains unknown. Several neutralizing epitopes have been identified for the HPV16 L2 minor capsid protein that can inhibit infection after initial attachment of the virus to the cell surface, which suggests an L2-specific secondary receptor or cofactor is required for infection, but so far no specific L2-receptor has been identified. Here, we demonstrate that the annexin A2 heterotetramer (A2t) contributes to HPV16 infection and co-immunoprecipitates with HPV16 particles on the surface of epithelial cells in an L2-dependent manner. Inhibiting A2t with an endogenous annexin A2 ligand, secretory leukocyte protease inhibitor (SLPI), or with an annexin A2 antibody significantly reduces HPV16 infection. With electron paramagnetic resonance, we demonstrate that a previously identified neutralizing epitope of L2 (aa 108-120) specifically interacts with the S100A10 subunit of A2t. Additionally, mutation of this L2 region significantly reduces binding to A2t and HPV16 pseudovirus infection. Furthermore, downregulation of A2t with shRNA significantly decreases capsid internalization and infection by HPV16. Taken together, these findings indicate that A2t contributes to HPV16 internalization and infection of epithelial cells and this interaction is dependent on the presence of the L2 minor capsid protein.

Annexin A2 is a natural extrahepatic inhibitor of the PCSK9-induced LDL receptor degradation

Proprotein convertase subtilisin/kexin-9 (PCSK9) enhances the degradation of hepatic low-density lipoprotein receptor (LDLR). Deletion of PCSK9, and loss-of-function mutants in humans result in lower levels of circulating LDL-cholesterol and a strong protection against coronary heart disease. Accordingly, the quest for PCSK9 inhibitors has major clinical implications. We have previously identified annexin A2 (AnxA2) as an endogenous binding partner and functional inhibitor of PCSK9. Herein, we studied the relevance of AnxA2 in PCSK9 inhibition and lipid metabolism in vivo. Plasma analyses of AnxA2(-/-) mice revealed: i) a ∼1.4-fold increase in LDL-cholesterol without significant changes in VLDLs or HDLs, and ii) a ∼2-fold increase in circulating PCSK9 levels. Western blotting and immunohistochemistry of AnxA2(-/-) tissues revealed that the LDLR was decreased by ∼50% in extrahepatic tissues, such as adrenals and colon. We also show that AnxA2-derived synthetic peptides block the PCSK9≡LDLR interaction in vitro, and adenoviral overexpression of AnxA2 in mouse liver increases LDLR protein levels in vivo. These results suggest that AnxA2 acts as an endogenous regulator of LDLR degradation, mostly in extrahepatic tissues. Finally, we identified an AnxA2 coding polymorphism, V98L, that correlates with lower circulating levels of PCSK9 thereby extending our results on the physiological role of AnxA2 in humans.

Overexpression of annexin A2 is associated with abnormal ubiquitination in breast cancer

Abnormal expression of annexin A2 contributes to metastasis and infiltration of cancer cells. To elucidate the cause of abnormal expression of annexin A2, Western blotting, immunoproteomics and immunohistochemical staining were performed to analyze differentially ubiquitinated proteins between fresh breast cancer tissue and its adjacent normal breast tissue from five female volunteers. We detected an ubiquitinated protein that was up-regulated in the cancer tissue, which was further identified as annexin A2 by mass spectrometry. These results suggest that abnormal ubiquitination and/or degradation of annexin A2 may lead to presence of annexin A2 at high level, which may further promote metastasis and infiltration of the breast cancer cells.

A novel pathway for human endothelial cell activation by antiphospholipid/anti-β2 glycoprotein I antibodies

Antiphospholipid Abs (APLAs) are associated with thrombosis and recurrent fetal loss. These Abs are primarily directed against phospholipid-binding proteins, particularly β(2)GPI, and activate endothelial cells (ECs) in a β(2)GPI-dependent manner after binding of β(2)GPI to EC annexin A2. Because annexin A2 is not a transmembrane protein, the mechanisms of APLA/anti-β(2)GPI Ab-mediated EC activation are uncertain, although a role for a TLR4/myeloid differentiation factor 88-dependent pathway leading to activation of NF-κB has been proposed. In the present study, we confirm a critical role for TLR4 in anti-β(2)GPI Ab-mediated EC activation and demonstrate that signaling through TLR4 is mediated through the assembly of a multiprotein signaling complex on the EC surface that includes annexin A2, TLR4, calreticulin, and nucleolin. An essential role for each of these proteins in cell activation is suggested by the fact that inhibiting the expression of each using specific siRNAs blocked EC activation mediated by APLAs/anti-β(2)GPI Abs. These results provide new evidence for novel protein-protein interactions on ECs that may contribute to EC activation and the pathogenesis of APLA/anti-β(2)GPI-associated thrombosis and suggest potential new targets for therapeutic intervention in antiphospholipid syndrome.

Expression of cytoskeleton and energetic metabolism-related proteins at human abdominal aortic aneurysm sites

OBJECTIVE

The purpose of this study was to evaluate the expression of proteins related to cytoskeleton and energetic metabolism at abdominal aortic aneurysm (AAA) sites using proteomics. Several remodeling-related mechanisms have been associated with AAA formation but less is known about the expression of proteins associated with cytoskeleton and energetic metabolism in AAAs.

METHODS

AAA samples (6.73 ± 0.40 cm size) were obtained from 13 patients during elective aneurysm repair. Control abdominal aortic samples were obtained from 12 organ donors. Proteins were analyzed using two-dimensional electrophoresis and mass spectrometry.

RESULTS

The expression of filamin was increased in the AAA site compared to control abdominal aortic samples while microfibril-associated glycoprotein-4 isotype 1, annexin A5 isotype 1, and annexin A2 were reduced compared with control abdominal aortic samples. Reduction in expression level of energetic metabolism-associated proteins such as triosephosphate isomerase, glyceraldehyde 3-phosphate dehydrogenase, and cytosolic aldehyde dehydrogenase was also observed in AAAs compared to controls. Reduction of triosephosphate isomerase expression was also observed by Western blot, which was accompanied by diminished triosephosphate isomerase activity. At the AAA site, pyruvate dehydrogenase expression was reduced and the content of both lactate and pyruvate was increased with respect to controls without changes in lactate dehydrogenase activity.

CONCLUSIONS

The present results suggest that an anaerobic metabolic state may be favored further to reduce the expression of cytoskeleton-related proteins. The better knowledge of molecular mechanism involved in AAAs may favor development of new clinical strategies.

[The expression and clinical significance of Annexin II in clear-cell renal cell carcinoma]

AIM

To discuss the difference of annexinII expression between the Clear-Cell Renal Cell Carcinoma(ccRCC) and the corresponding normal renal tissues, and to reveal the clinical significance of Annexin II expression in ccRCC.

METHODS

Western blotting was used to detect the expression of Annexin II in 29 samples of fresh ccRCC and the corresponding normal renal tissues. Annexin II expression was examined in 120 samples of paraffin-embedding ccRCC and the corresponding normal renal tissues using immunohistochemistry. Correlations with Annexin IIexpression and clinic-pathological parameters were analyzed.

RESULTS

There was expression of Annexin II in both ccRCC and the corresponding normal renal tissues. In ccRCC tissues, the total levels of Annexin II proteins were significantly higher than that in the corresponding normal renal tissues (P<0.01). The positive rate of AnnexinII expression in immunohistochemistry was 67.5% in the ccRCC tissues, existing significant difference compared with the corresponding normal renal tissues (P<0.01). Expression of Annexin II in ccRCC mainly showed membranous staining. Annexin II expression level was positively correlated with TNM stage (P<0.05), histology grade (P<0.05), renal capsule infiltration (P<0.01) and distant metastasis (P<0.01) of ccRCC. Moreover, Annexin II expression level was significantly correlated with ccRCC patients'5-years survival rate(P<0.01).

CONCLUSION

Overexpression of AnnexinII in the ccRCC is closely correlated with the ccRCC development. It may play an important role in the process of ccRCC invasion and metastasis.

Efficient nanoparticle mediated sustained RNA interference in human primary endothelial cells

Endothelium forms an important target for drug and/or gene therapy since endothelial cells play critical roles in angiogenesis and vascular functions and are associated with various pathophysiological conditions. RNA mediated gene silencing presents a new therapeutic approach to overcome many such diseases, but the major challenge of such an approach is to ensure minimal toxicity and effective transfection efficiency of short hairpin RNA (shRNA) to primary endothelial cells. In the present study, we formulated shAnnexin A2 loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles which produced intracellular small interfering RNA (siRNA) against Annexin A2 and brought about the downregulation of Annexin A2. The per cent encapsulation of the plasmid within the nanoparticle was found to be 57.65%. We compared our nanoparticle based transfections with Lipofectamine mediated transfection, and our studies show that nanoparticle based transfection efficiency is very high (~97%) and is more sustained compared to conventional Lipofectamine mediated transfections in primary retinal microvascular endothelial cells and human cancer cell lines. Our findings also show that the shAnnexin A2 loaded PLGA nanoparticles had minimal toxicity with almost 95% of cells being viable 24 h post-transfection while Lipofectamine based transfections resulted in only 30% viable cells. Therefore, PLGA nanoparticle based transfection may be used for efficient siRNA transfection to human primary endothelial and cancer cells. This may serve as a potential adjuvant treatment option for diseases such as diabetic retinopathy, retinopathy of prematurity and age related macular degeneration besides various cancers.

Antibody-directed neutralization of annexin II (ANX II) inhibits neoangiogenesis and human breast tumor growth in a xenograft model

Activation of the fibrinolytic pathway has long been associated with human breast cancer. Plasmin is the major end product of the fibrinolytic pathway and is critical for normal physiological functions. The mechanism by which plasmin is generated in breast cancer is not yet fully described. We previously identified annexin II (ANX II), a fibrinolytic receptor, in human breast tumor tissue samples and observed a strong positive correlation with advanced stage cancer (Sharma et al., 2006a). We further demonstrated that tissue plasminogen activator (tPA) binds to ANX II in invasive breast cancer MDA-MB231cells, which leads to plasmin generation (Sharma et al., 2010). We hypothesize that ANX II-dependent plasmin generation in breast tumor is necessary to trigger the switch to neoangiogenesis, thereby stimulating a more aggressive cancer phenotype. Our immunohistochemical studies of human breast tumor tissues provide compelling evidence of a strong positive correlation between ANX II expression and neoangiogenesis, and suggest that ANX II is a potential target to slow or inhibit breast tumor growth by inhibiting neoangiogenesis. We now report that administration of anti-ANX II antibody potently inhibits the growth of human breast tumor in a xenograft model. Inhibition of tumor growth is at least partly due to attenuation of neoangiogenic activity within the tumor. In vitro studies demonstrate that anti-ANX II antibody inhibits angiogenesis on three dimensional matrigel cultures by eliciting endothelial cell (EC) death likely due to apoptosis. Taken together, these data suggest that selective disruption of the fibrinolytic activity of ANX II may provide a novel strategy for specific inhibition of neoangiogenesis in human breast cancer.

Identification of estrogen response element in the aquaporin-2 gene that mediates estrogen-induced cell migration and invasion in human endometrial carcinoma

BACKGROUND

Accumulating evidence suggests that aquaporins (AQP) can facilitate cell migration, invasion, and proliferation in tumor development in addition to water transport.

OBJECTIVE

The aim of this study was to examine AQP2 expression in the endometrial tissues from patients with endometrial carcinoma (EC) and determine the roles and mechanisms of AQP2 in estrogen-related cell migration, invasion, adhesion, and proliferation of Ishikawa (IK) cells.

APPROACH

AQP2 expression levels were measured in human endometrial cells and estradiol (E(2))-treated IK cells, and the estrogen-response element was identified. After blocking down and up-regulating the endogenous expression of AQP2 in IK cells, cell morphology, capacity for invasion, migration and adhesion, and expression markers of membrane/cytoskeleton were analyzed.

RESULTS

AQP2 was expressed in endometrial tissues from patients with EC and endometriosis, both of which are estrogen-dependent diseases. In IK cells, E(2) dose-dependently increased AQP2 expression, which was blocked by the estrogen receptor inhibitor ICI182780. An estrogen-response element was identified in the AQP2 promoter. E(2) significantly increased the migration, invasion, adhesion, and proliferation of IK cells. AQP2 knockdown attenuated E(2)-enhanced migration, invasion, and adhesion. AQP2 knockdown reduced not only the E(2)-enhanced expression of F-actin and annexin-2 but also the E(2)-induced alteration of cell morphology. Moreover, higher expression levels of F-actin and annexin-2 were detected in the endometrial tissues from patients with EC.

CONCLUSIONS

AQP2 mediates E(2)-enhanced migration, invasion, and adhesion through alteration of F-actin and annexin-2 expression and reorganization of F-actin, and inhibition of AQP may be a potential method for antitumor therapy.

Cochlin induced TREK-1 co-expression and annexin A2 secretion: role in trabecular meshwork cell elongation and motility

Fluid flow through large interstitial spaces is sensed at the cellular level, and mechanistic responses to flow changes enables expansion or contraction of the cells modulating the surrounding area and brings about changes in fluid flow. In the anterior eye chamber, aqueous humor, a clear fluid, flows through trabecular meshwork (TM), a filter like region. Cochlin, a secreted protein in the extracellular matrix, was identified in the TM of glaucomatous patients but not controls by mass spectrometry. Cochlin undergoes shear induced multimerization and plays a role in mechanosensing of fluid shear. Cytoskeletal changes in response to mechanosensing in the ECM by cochlin will necessitate transduction of mechanosensing. TREK-1, a stretch activated outward rectifying potassium channel protein known to act as mechanotransducer was found to be expressed in TM. Cochlin expression results in co-expression of TREK-1 and filopodia formation. Prolonged cochlin expression results in expression and subsequent secretion of annexin A2, a protein known to play a role in cytoskeletal remodeling. Cochlin interacts with TREK-1 and annexin A2. Cochlin-TREK-1 interaction has functional consequences and results in changes in cell shape and motility. Annexin A2 expression and secretion follows cochlin-TREK-1 syn-expression and correlates with cell elongation. Thus cytoskeleton changes in response to fluid shear sensed by cochlin are further mediated by TREK-1 and annexin A2.

The targeting of plasmalemmal ceramide to mitochondria during apoptosis

Ceramide is a key lipid mediator of cellular processes such as differentiation, proliferation, growth arrest and apoptosis. During apoptosis, ceramide is produced within the plasma membrane. Although recent data suggest that the generation of intracellular ceramide increases mitochondrial permeability, the source of mitochondrial ceramide remains unknown. Here, we determine whether a stress-mediated plasmalemmal pool of ceramide might become available to the mitochondria of apoptotic cells. We have previously established annexin A1—a member of a family of Ca²⁺ and membrane-binding proteins—to be a marker of ceramide platforms. Using fluorescently tagged annexin A1, we show that, upon its generation within the plasma membrane, ceramide self-associates into platforms that subsequently invaginate and fuse with mitochondria. An accumulation of ceramide within the mitochondria of apoptotic cells was also confirmed using a ceramide-specific antibody. Electron microscopic tomography confirmed that upon the formation of ceramide platforms, the invaginated regions of the plasma membrane extend deep into the cytoplasm forming direct physical contacts with mitochondrial outer membranes. Ceramide might thus be directly transferred from the plasma membrane to the mitochondrial outer membrane. It is conceivable that this “kiss-of-death” increases the permeability of the mitochondrial outer membrane thereby triggering apoptosis.