Annexin 1 is present in different molecular forms in rat cerebral cortex

Identification of two phosphorylation sites essential for annexin A1 in blood-brain barrier protection after experimental intracerebral hemorrhage in rats

Annexin A1 has been reported to exert a blood-brain barrier protection. This study was designed to examine the role of annexin A1 in intracerebral hemorrhage-induced blood-brain barrier dysfunction. A collagenase intracerebral hemorrhage model was performed in adult male Sprague Dawley rats. First, a possible relationship between annexin A1 and intracerebral hemorrhage pathology was confirmed by a loss of annexin A1 in the cerebrovascular endothelium and serum of intracerebral hemorrhage rats, and the rescue effects of i.v. administration of human recombinant annexin A1 in vivo and annexin A1 overexpression in vitro on the barrier function of brain microvascular endothelial cells exposed to intracerebral hemorrhage stimulus. Second, we found that intracerebral hemorrhage significantly increased the phosphorylation ratio of annexin A1 at the serine/threonine residues. Finally, based on site-specific mutagenesis, we identified two phosphorylation sites (a) annexin A1 phosphorylation at threonine 24 is required for its interaction with actin cytoskeleton, and (b) phosphorylation at serine27 is essential for annexin A1 secretion, both of which were essential for maintaining cytoskeleton integrity and paracellular permeability. In conclusion, annexin A1 prevents intracerebral hemorrhage-induced blood-brain barrier dysfunction in threonine 24 and serine27 phosphorylation-dependent manners. Annexin A1 phosphorylation may be a self-help strategy in brain microvascular endothelial cells after intracerebral hemorrhage; however, that was almost completely abolished by the intracerebral hemorrhage-induced loss of annexin A1.

Heparin affinity purification of extracellular vesicles

Extracellular vesicles (EVs) are lipid membrane vesicles released by cells. They carry active biomolecules including DNA, RNA, and protein which can be transferred to recipient cells. Isolation and purification of EVs from culture cell media and biofluids is still a major challenge. The most widely used isolation method is ultracentrifugation (UC) which requires expensive equipment and only partially purifies EVs. Previously we have shown that heparin blocks EV uptake in cells, supporting a direct EV-heparin interaction. Here we show that EVs can be purified from cell culture media and human plasma using ultrafiltration (UF) followed by heparin-affinity beads. UF/heparin-purified EVs from cell culture displayed the EV marker Alix, contained a diverse RNA profile, had lower levels of protein contamination, and were functional at binding to and uptake into cells. RNA yield was similar for EVs isolated by UC. We were able to detect mRNAs in plasma samples with comparable levels to UC samples. In conclusion, we have discovered a simple, scalable, and effective method to purify EVs taking advantage of their heparin affinity.

Annexin 1: a glucocorticoid-inducible protein that modulates inflammatory pain

Annexin 1, a glucocorticoid (GC)-inducible protein, can play an important role via formyl peptide receptor like 1 (FPR2/ALX, also known as FPRL1) in inflammatory pain modulation. The aim of this review is to analyze different lines of evidence for the role of ANXA1 with different mechanisms on inflammatory pain and describe the profile of ANXA1 as a potential analgesic. A Medline (PUBMED) search using the terms 'Annexin 1 distribution OR expression, FPR2/ALX distribution OR expression, Annexin 1 AND pain, Annexin 1 AND FPR2/ALX AND pain' was performed. Articles with a publication date up to Nov. 1st, 2012 were included. The antinociception of ANXA1 has been evaluated in diverse pain models. It has been suggested that ANXA1 may exerts its action via: (1) inhibiting vital cytokines involved in pain transmission, (2) inhibiting neutrophil accumulation through preventing transendothelial migration via an interaction with formyl peptide receptors, (3) facilitating tonic opioid release from neutrophil in inflammatory site, (4) interrupting the peripheral nociceptive transmission by suppressing neuronal excitability. In general, ANXA1 is a potential mediator for anti-nociception and the role with its receptor constitute attractive targets for developing anesthesia and analgesic drugs, and their interaction may prove to be a useful strategy to treat inflammatory pain.

Overexpression of annexin a1 induced by terephthalic acid calculi in rat bladder cancer

Prolonged cell proliferation in response to irritation by bladder calculi can evoke malignant transformation of the urothelium. However, the molecular mechanisms responsible for calculi-associated bladder carcinogenesis are unknown. We compared the protein expression pattern of rat bladder transitional cell carcinomas (TCCs) induced by terephthalic acid with that of normal bladder tissues using 2-DE. Comparative analysis of the respective spot patterns on 2-DE showed 146 spots that were markedly changed in TCC samples. Subsequently, 56 of the variant protein spots were identified by MALDI-TOF MS. Among them, overexpression of annexin a1 (ANNA1) in rat TCCs was confirmed by Western blotting and real-time RT-PCR analysis. Immunohistochemical staining revealed that ANNA1, usually a cytoplasmic protein in normal urothelium, was translocated to the nucleus in rat bladder cancer cells. In contrast to the animal studies, examination of human clinical specimens showed that ANNA1 expression was reduced in TCC compared to normal urothelium. The expression of ANNA1 was inversely related to the level of differentiation of TCC. Our data suggest that overexpression of ANNA1 is involved in bladder carcinogenesis induced by bladder calculi and that translocation of the protein may be partly responsible for the effect. ANNA1 may serve as a new marker of differentiation for the histopathological grading of human TCC.

Nuclear annexin II negatively regulates growth of LNCaP cells and substitution of ser 11 and 25 to glu prevents nucleo-cytoplasmic shuttling of annexin II

BACKGROUND

Annexin II heavy chain (also called p36, calpactin I) is lost in prostate cancers and in a majority of prostate intraepithelial neoplasia (PIN). Loss of annexin II heavy chain appears to be specific for prostate cancer since overexpression of annexin II is observed in a majority of human cancers, including pancreatic cancer, breast cancer and brain tumors. Annexin II exists as a heterotetramer in complex with a protein ligand p11 (S100A10), and as a monomer. Diverse cellular functions are proposed for the two forms of annexin II. The monomer is involved in DNA synthesis. A leucine-rich nuclear export signal (NES) in the N-terminus of annexin II regulates its nuclear export by the CRM1-mediated nuclear export pathway. Mutation of the NES sequence results in nuclear retention of annexin II.

RESULTS

Annexin II localized in the nucleus is phosphorylated, and the appearance of nuclear phosphorylated annexin II is cell cycle dependent, indicating that phosphorylation may play a role in nuclear entry, retention or export of annexin II. By exogenous expression of annexin II in the annexin II-null LNCaP cells, we show that wild-type annexin II is excluded from the nucleus, whereas the NES mutant annexin II localizes in both the nucleus and cytoplasm. Nuclear retention of annexin II results in reduced cell proliferation and increased doubling time of cells. Expression of annexin II, both wild type and NES mutant, causes morphological changes of the cells. By site-specific substitution of glutamic acid in the place of serines 11 and 25 in the N-terminus, we show that simultaneous phosphorylation of both serines 11 and 25, but not either one alone, prevents nuclear localization of annexin II.

CONCLUSION

Our data show that nuclear annexin II is phosphorylated in a cell cycle-dependent manner and that substitution of serines 11 and 25 inhibit nuclear entry of annexin II. Aberrant accumulation of nuclear annexin II retards proliferation of LNCaP cells.

"In vitro" phosphorylation of annexin 2 heterotetramer by protein kinase C. Comparative properties of the unphosphorylated and phosphorylated annexin 2 on the aggregation and fusion of chromaffin granule membranes

Heterotetrameric annexin 2 phosphorylated "in vitro" by rat brain protein kinase C is purified and obtained devoid of unphosphorylated protein; it contains 2 mol of phosphate/mol of heterotetramer. The aggregative and binding properties of the phosphorylated annexin 2 toward purified chromaffin granules are compared with those of the unphosphorylated annexin 2. Annexin 2 binds to chromaffin granules with high affinity. Phosphorylation of annexin 2 decreases the affinity of this binding without affecting the maximum binding capacity. The binding curves are strongly cooperative. It is suggested that a surface oligomerization of the proteins may take place upon binding. Besides, phosphorylation of annexin 2 is followed by a dissociation of the light chains from the heavy chains in the heterotetramer. Whereas annexin 2 induces the aggregation of chromaffin granules at microM calcium concentration, the phosphorylated annexin 2 does not induce aggregation at any concentration of calcium either at pH 6 or 7. The phosphorylation of annexin 2 by protein kinase C, MgATP, and 12-O-tetradecanoylphorbol-13-acetate on chromaffin granules induces a fusion of chromaffin granules membranes observed in electron microscopy. The fusion requires the activation of protein kinase C by 12-O-tetradecanoylphorbol-13-acetate. Given these results and since annexin 2 is phosphorylated by protein kinase C under stimulation of chromaffin cells, it is suggested that phosphorylated annexin 2 may be implicated in the fusion step during exocytosis of chromaffin granules.