Biological Evaluation and Molecular Docking Studies of Novel 1,3,4-Oxadiazole Derivatives of 4,6-Dimethyl-2-sulfanylpyridine-3-carboxamide.

To date, chronic inflammation is involved in most main human pathologies such as cancer, and autoimmune, cardiovascular or neurodegenerative disorders. Studies suggest that different prostanoids, especially prostaglandin E2, and their own synthase (cyclooxygenase enzyme-COX) can promote tumor growth by activating signaling pathways which control cell proliferation, migration, apoptosis, and angiogenesis. Non-steroidal anti-inflammatory drugs (NSAIDs) are used, alongside corticosteroids, to treat inflammatory symptoms particularly in all chronic diseases. However, their toxicity from COX inhibition and the suppression of physiologically important prostaglandins limits their use. Therefore, in continuation of our efforts in the development of potent, safe, non-toxic chemopreventive compounds, we report herein the design, synthesis, biological evaluation of new series of Schiff base-type hybrid compounds containing differently substituted N-acyl hydrazone moieties, 1,3,4-oxadiazole ring, and 4,6-dimethylpyridine core. The anti-COX-1/COX-2, antioxidant and anticancer activities were studied. Schiff base 13, containing 2-bromobenzylidene residue inhibited the activity of both isoenzymes, COX-1 and COX-2 at a lower concentration than standard drugs, and its COX-2/COX-1 selectivity ratio was similar to meloxicam. Furthermore, the results of cytotoxicity assay indicated that all of the tested compounds exhibited potent anti-cancer activity against A549, MCF-7, LoVo, and LoVo/Dx cell lines, compared with piroxicam and meloxicam. Moreover, our experimental study was supported by density functional theory (DFT) and molecular docking to describe the binding mode of new structures to cyclooxygenase.

Proteasomes and antigen presentation: evidence that a KEKE motif does not promote presentation of the class I epitope SIINFEKL.

Previously we proposed that stretches of alternating Lys(K) and Glu(E) in polypeptides promote the expression of nearby sequences on Class I molecules [Realini, C., Rogers, S.W., Rechsteiner, M., 1994. KEKE motifs. Proposed roles in protein-protein association and presentation of peptides by MHC class I receptors. FEBS Lett. 348, 109-113]. As a test of the KEKE hypothesis we have employed osmotic lysis of pinosomes and transfection to introduce or express various ubiquitin peptide fusion proteins in the cytosol of wild type and PA28alphabetagamma- mouse embryo fibroblasts. KEKE or non-KEKE motifs were placed between ubiquitin and the OVA epitope SIINFEKL that was at or near the C-termini of the various fusion proteins. Measurements of surface Kb-SIINFEKL complexes using the monoclonal antibody 25.-D1.16 allowed us to assess the effects of upstream KEKE motifs and PA28 status on SIINFEKL surface presentation. KEKE motifs did not enhance presentation of the OVA epitope. However, our studies did confirm that PA28alphabeta is needed for efficient SIINFEKL surface expression when hsp90 is inhibited.

Structural and mechanistic studies of VPS4 proteins.

VPS4 ATPases function in multivesicular body formation and in HIV-1 budding. Here, we report the crystal structure of monomeric apo human VPS4B/SKD1 (hVPS4B), which is composed of five distinct elements: a poorly ordered N-terminal MIT domain that binds ESCRT-III substrates, large (mixed alpha/beta) and small (alpha) AAA ATPase domains that closely resemble analogous domains in the p97 D1 ATPase cassette, a three-stranded antiparallel beta domain inserted within the small ATPase domain, and a novel C-terminal helix. Apo hVPS4B and yeast Vps4p (yVps4p) proteins dimerized in solution, and assembled into larger complexes (10-12 subunits) upon ATP binding. Human and yeast adaptor proteins (LIP5 and yVta1p, respectively) bound the beta domains of the fully assembled hVPS4B and yVps4p proteins. We therefore propose that Vps4 proteins cycle between soluble, inactive low molecular weight complexes and active, membrane-associated double-ring structures that bind ATP and coassemble with LIP5/Vta1. Finally, HIV-1 budding was inhibited by mutations in a loop that projects into the center of the modeled hVPS4B rings, suggesting that hVPS4B may release the assembled ESCRT machinery by pulling ESCRT-III substrates up into the central pore.