The human glioblastoma SF268 cell line was used to investigate the induction of apoptosis by the 3C protease of enterovirus 71 (EV71). Transient expression in these cells of the wild-type 3C protein encoded by EV71 induced morphological alterations typical of apoptosis, including generation of apoptotic bodies. Degradation of cellular DNA in nucleosomes was also observed. When two of the amino acids in the catalytic motif of 3C were changed by mutagenesis, the 3C protein not only lost its proteolytic activity, but also its ability to induce apoptosis in the SF268 cells. Twenty-four hours after 3C transfection, poly(ADP-ribose) polymerase, a DNA repair enzyme, was cleaved, indicating that caspases were activated by the expression of EV71 3C. The 3C-induced apoptosis was blocked by the caspase inhibitors DEVD-fmk and VAD-fmk. Our findings suggest that the proteolytic activity of 3C triggers apoptosis in the SF268 cells through a mechanism involving caspase activation and that this apoptotic pathway may play an important role in the pathogenesis of EV71 infection.

Insect cells have been widely utilized as hosts for the production of numerous glycoproteins through the baculovirus expression system (1, 2). Native insect cell glycoproteins also serve as models for developmental processes in eucaryotes (3, 4). While the structure, synthesis, and function of oligosaccharides in mammalian glycoproteins are well characterized, information on the carbohydrate structures and processing pathways present in insect cells is limited and sometimes contradictory (5-7). The oligosaccharides in glycoproteins can play critical roles in cellular targeting, structural stability, resistance to proteolysis, immunogenicity, and circulatory halflife (8, 9). With insects representing more than half of the animal species classified (5), there is a need to obtain more information on the carbohydrate structures and processing of glycoproteins from insect cells.Many initial studies of N-glycans in insect cell-derived heterologous glycoproteins indicated the presence of only high mannose-type or short truncated, paucimannosidic oligosaccharides, 1 sometimes containing L-fucosyl 2 residues (6, 7). These observations confirmed the earlier studies of endogenous insect cell glycoproteins which were similarly found to lack complex carbohydrate structures (10 -12). It was presumed that insect cells did not possess the capacity to synthesize complex-type oligosaccharides since the levels of sialyl-, galactosyl-, and N-acetylglucosamine transferases were found to be insignificant (12).In contrast, studies with the recombinant human plasminogen indicated that insect cells could synthesize complex Nlinked oligosaccharides (13). Several more recent studies on homologous glycoproteins also have indicated that certain insect cell lines can synthesize hybrid and complex oligosaccharides. Honeybee venom phospholipase A 2 (PLA 2 ) 3 was found to

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Background: Endothelial-to-mesenchymal transition (EndoMT) can provide a source of cancer-associated fibroblasts which contribute to desmoplasia of many malignancies including pancreatic ductal adenocarcinoma (PDAC). We investigated the clinical relevance of EndoMT in PDAC, and explored its underlying mechanism and therapeutic implication. Methods: Expression levels of 29 long non-coding RNAs were analyzed from the cells undergoing EndoMT, and an EndoMT index was proposed to survey its clinical associations in the PDAC patients of The Cancer Genome Atlas database. The observed clinical correlation was further confirmed by a mouse model inoculated with EndoMT cellsinvolved PDAC cell grafts. In vitro co-culture with EndoMT cells or treatment with the conditioned medium were performed to explore the underlying mechanism. Because secreted HSP90α was involved, anti-HSP90α antibody was evaluated for its inhibitory efficacy against the EndoMT-involved PDAC tumor. Results: A combination of low expressions of LOC340340, LOC101927256, and MNX1-AS1 was used as an EndoMT index. The clinical PDAC tissues with positive EndoMT index were significantly correlated with T4-staging and showed positive for M2-macrophage index. Our mouse model and in vitro cell-culture experiments revealed that HSP90α secreted by EndoMT cells could induce macrophage M2-polarization and more HSP90α secretion to promote PDAC tumor growth. Furthermore, anti-HSP90α antibody showed a potent therapeutic efficacy against the EndoMT and M2-macrophages-involved PDAC tumor growth. Conclusions: EndoMT cells can secrete HSP90α to harness HSP90α-overproducing M2-type macrophages to promote PDAC tumor growth, and such effect can be targeted and abolished by anti-HSP90α antibody.

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The synthesis and structure-activity relationship studies of novel indole derivatives as peroxisome proliferator-activated receptor (PPAR) agonists are reported. Indole, a drug-like scaffold, was studied as a core skeleton for the acidic head part of PPAR agonists. The structural features (acidic head, substitution on indole, and linker) were optimized first, by keeping benzisoxazole as the tail part, based on binding and functional activity at PPARgamma protein. The variations in the tail part, by introducing various heteroaromatic ring systems, were then studied. In vitro evaluation led to identification of a novel series of indole compounds with a benzisoxazole tail as potent PPAR agonists with the lead compound 14 (BPR1H036) displaying an excellent pharmacokinetic profile in BALB/c mice and an efficacious glucose lowering activity in KKA(y) mice. Structural biology studies of 14 showed that the indole ring contributes strong hydrophobic interactions with PPARgamma and could be an important moiety for the binding to the protein.

Infection of Trichoplusia ni (BTI-TN5B1-4) insect cells with a baculovirus coding for immunoglobulin G resulted in significant intracellular insolubility of the immunoglobulin chains. In order to increase the immunoglobulin solubility, the chaperone BiP was coexpressed in the insect cells using a separate baculovirus vector. This heterologous BiP was observed to associate with immunoglobulin chains in vivo and enhance the level of soluble intracellular and secreted IgG obtained from T.ni. Pulse chase studies indicated that the heterologous BiP increased the level of soluble nascent immunoglobulin chains and assembly intermediates to suggest that BiP is acting as a true molecular chaperone. The effect of heterologous BiP became more significant with time post-infection as secreted IgG levels increased by 90% after 3.4 days of baculovirus infection. Even following the treatment of cells with tunicamycin, BiP coexpression still enhanced immunoglobulin solubility and secretion to indicate that BiP does not function specifically to retain unglycosylated proteins in the endoplasmic reticulum. Thus, coexpression of a molecular chaperone may be used to enhance cellular productivity and protein secretion provided that the chaperone is involved with post-translational processing and significant protein aggregation is observed.

We provide the first evidence for the role of ACSL4 in enterovirus replication organelle formation. Moreover, both enteroviruses and coronaviruses induce ferroptosis via ACSL4. These findings establish a novel regulatory mechanism for viral replication. The inhibition of ACSL4 by ferroptosis inhibitors can reduce viral yields of enteroviruses and coronaviruses, including SARS-CoV-2, implying that ACSL4-mediated ferroptosis is a promising therapeutic target for viral diseases.