The annexin A2-S100A10 heterotetramer (AIIt) is a multifunctional Ca 2؉ -dependent, phospholipid-binding, and F-actin-binding phosphoprotein composed of two annexin A2 subunits and two S100A10 subunits. It was reported previously that oxidative stress from exogenous hydrogen peroxide or generated in response to tumor necrosis factor-␣ results in the glutathionylation of Cys 8 of annexin A2. In this study, we demonstrate that AIIt is an oxidatively labile protein whose level of activity is regulated by the redox status of its sulfhydryl groups. Oxidation of AIIt by diamide resulted in a timeand concentration-dependent loss of the ability of AIIt to interact with phospholipid liposomes and F-actin. The inhibitory effect of diamide on the activity of AIIt was partially reversed by dithiothreitol. In addition, incubation of AIIt with diamide and GSH resulted in the glutathionylation of AIIt in vitro. Mass spectrometry established the incorporation of 2 mol of GSH/mol of annexin A2 subunit at Cys 8 and Cys 132 . Glutathionylation potentiated the inhibitory effects of diamide on the activity of AIIt. Furthermore, AIIt could be deglutathionylated by glutaredoxin (thiol transferase). Thus, we show for the first time that AIIt can undergo functional reactivation by glutaredoxin, therefore establishing that AIIt is regulated by reversible glutathionylation.The molecular mechanisms by which the cell alleviates oxidative stress and achieves redox homeostasis are still a matter of considerable debate. However, the modulation of the thiol disulfide status of critical cysteine residues on proteins is being recognized as a critical mechanism of oxidative signal transduction as well as a cellular response to protect key regulatory molecules from oxidative insult (1-3). Recent evidence suggests that the reversible covalent modification of cysteine residues by the tripeptide glutathione (␥-Glu-Cys-Gly) plays a significant role in the antioxidant network of the cells and is involved in regulating individual aspects of cellular function (3, 4). Although proteins can bind cysteine, GSH, and homocysteine to generate mixed disulfides, GSH is the dominant ligand, as it occurs in the cell at concentrations between 1 and 10 mM (5, 6). S-Glutathionylation has been shown to alter the function of a number of discrete proteins under oxidant stress (7,8). Furthermore, the formation of a mixed disulfide with glutathione precludes the irreversible oxidation of the cysteine thiol to a sulfinic or sulfonic acid and enables reactivation of the protein by cellular thioreductases.Annexins compose a large multigene family of water-soluble proteins that can bind to negatively charged phospholipids and cellular membranes in a Ca 2ϩ -dependent fashion (9 -11). The annexin family is structurally characterized by two domains: a highly conserved ␣-helical protein core consisting of four 70-amino acid repeats (eight repeats in the case of annexin VI) and a variable N-terminal segment (12). Annexin A2 is unique among the annexins, for its N-terminal tail poss...

Annexin II heterotetramer (AIIt) is a Ca 2؉-and phospholipid-binding protein that consists of two copies of a p36 and p11 subunit. AIIt regulates the production and autoproteolysis of plasmin at the cell surface. In addition to its role as a key cellular protease, plasmin also plays a role in angiogenesis as the precursor for antiangiogenic proteins. Recently we demonstrated that the primary antiangiogenic plasmin fragment, called A 61 (Lys -Lys 468) was released from cultured cells. In the present study we report for the first time that AIIt possesses an intrinsic plasmin reductase activity. AIIt stimulated the reduction of the plasmin Cys 462-Cys 541 bond in a time-and concentration-dependent manner, which resulted in the release of A 61 from plasmin. Mutagenesis of p36 C334S and either p11 C61S or p11 C82S inactivated the plasmin reductase activity of the isolated subunits, suggesting that specific cysteinyl residues participated in the plasmin reductase activity of each subunit. Furthermore, we demonstrated that the loss of AIIt from the cell surface of HT1080 cells transduced with a retroviral vector encoding p11 antisense dramatically reduced the cellular production of A 61 from plasminogen. This is the first demonstration that AIIt regulates the cellular production of the antiangiogenic plasminogen fragment, A 61 .Angiostatin was originally identified in the urine of mice bearing Lewis lung carcinoma as a 38-kDa proteolytically derived fragment of plasminogen which encompassed the first four kringle domains (Lys 78 -Ala 440 ). Angiostatin was shown to be a potent antiangiogenic protein that inhibited the growth of human and murine carcinomas and also induced dormancy in their metastases. Angiostatin was also characterized as a specific antiangiogenic protein that blocked microvascular endothelial cell proliferation but not the proliferation of nonendothelial cells (1).It is now apparent that angiostatin is a member of a family of antiangiogenic plasminogen fragments (AAPFs).1 Physiologically relevant AAPFs include a 38-kDa AAPF isolated from the conditioned media of tumor-infiltrating macrophages (2) and AAPFs of 48, 42, and 50 kDa present in macrophage-conditioned media (3). Other AAPFs include a 50-kDa AAPF isolated from the conditioned media of human prostate carcinoma PC-3 cells (4, 5) and AAPFs of 66, 60, and 57 kDa detected in the conditioned media of HT1080 and Chinese hamster ovary cells (6). Because the carboxyl terminus of most of these AAPFs was not determined, the exact primary sequence of most of the AAPFs is not known. Two distinct pathways for the formation of AAPFs have been identified. First, certain proteinases can directly cleave plasminogen into AAPFs. These proteinases include metalloelastase, gelatinase B (matrix metalloproteinase-9), stromelysin-1 (matrix metalloproteinase-3), matrilysin (matrix metalloproteinase-7), cathepsin D, and prostate-specific antigen (7-11). The source of these proteinases may be tumor-infiltrating macrophages (2) or the cancer cells themselves. For example...

No abstract

No abstract

The synthesis of Ru2(μ-O2CR)4(μ´-O2CR) (1), R = -CH2(CH2)6CH=CH(CH2)5CH3, has been achieved and characterization using elemental analysis and FTIR and UV-Vis spectroscopies undertaken. Strong evidence for a hexagonal discotic mesophase has been found using differential scanning calorimetry, variable-temperature polarizing optical microscopy, and X-ray powder diffraction. A solid to liquid crystal transition was found upon heating at 128°C and the mesophase is found to persist to room temperature upon cooling from 150°C. This is the first report of room temperature mesomorphism in a mixed-valent metallomesogen. Key words: ruthenium carboxylate, liquid crystal, metallomesogen, mixed valence, polymer.

-Tetrahydrodipicolinic acid 1, a key intermediate of diaminopimelate metabolism has been prepared in 6 steps and 23% overall yield from -allylglycine 4. The key step during this synthesis involves a base mediated cyclisation ofshow this one pot transformation involves four steps; base elimination of toluene-p-sulfinic acid, intramolecular nucleophilic attack of the 6-benzyloxycarbonylamino group on the resulting imine, followed by hydrolysis of the esters and elimination of benzyl carbamate under acidic work-up to give the cyclic enamine 9.

[reaction: see text] Vinylogous amides 5 and 6 have been synthesized from L-propargyl glycine and tested against diaminopimelate (DAP) enzymes involved in bacterial lysine biosynthesis. Both are reversible inhibitors of DAP D-dehydrogenase and DAP epimerase with IC(50) values in the 500 microM range. Compound 5 shows competitive inhibition against the L-dihydrodipicolinate (DHDP) reductase with a K(i) value of 32 microM, which is comparable to the planar dipicolinate 16 (K(i) = 26 microM), the best known inhibitor of the enzyme.

No abstract