betadex and benzyloxycarbonylvalyl-alanyl-aspartyl-fluoromethyl-ketone

Viral infection activates a host's cellular phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, which is involved in cell differentiation, growth, survival, and apoptosis. To elucidate molecular mechanisms in the pathogenesis of Newcastle disease virus (NDV), we demonstrated that NDV transiently activates the PI3K/Akt pathway in chicken cells at an early phase of infection. Its activation was observed as early as 15 min post-infection and gradually weakened after 24 h. Incubating cells with a PI3K inhibitor, LY294002 or wortmannin, prior to NDV infection decreased NDV progeny yields and suppressed Akt phosphorylation at early times post-infection. Akt activation is triggered by NDV-GM or NDV-F48E9 and is abolished by methyl β-cyclodextrin and chlorpromazine. Treatment following NDV-La Sota infection had no obvious effect. However, inhibiting PI3K activation promoted apoptotic responses during an early stage of NDV infection. The pan caspase inhibitor ZVAD-FMK mitigated the reduction in Akt phosphorylation by inhibiting PI3K activation, which indicates the signaling pathway promotes cell survival and, in turn, facilitates viral replication. By suppressing premature apoptosis upon NDV infection, the PI3K/Akt pathway enhances the anti-apoptotic response.

Topics: Amino Acid Chloromethyl Ketones; Androstadienes; Animals; Apoptosis; beta-Cyclodextrins; Blotting, Western; Cell Line; Cells, Cultured; Chick Embryo; Chickens; Chlorpromazine; Chromones; Enzyme Inhibitors; Fibroblasts; Host-Pathogen Interactions; Morpholines; Newcastle disease virus; Phosphatidylinositol 3-Kinase; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Proto-Oncogene Proteins c-akt; Signal Transduction; Virus Replication; Wortmannin

Binding of either ligand or agonistic antibodies to the death receptor CD95 (APO-1/Fas) induces the formation of the death-inducing signaling complex (DISC). We now show that signal initiation of CD95 in type I cells can be further separated into at least four distinct steps. (i) The first step is ligand-induced formation of CD95 microaggregates at the cell surface. (ii) The second step is recruitment of FADD to form a DISC. This step is dependent on actin filaments. (iii) The third step involves formation of large CD95 surface clusters. This event is positively regulated by DISC-generated caspase 8. (iv) The fourth step is internalization of activated CD95 through an endosomal pathway. The latter step is again dependent on the presence of actin filaments. The data indicate that the signal initiation by CD95 is a complex process actively regulated at various levels, providing a number of new drug targets to specifically modulate CD95 signaling.

Topics: Actin Cytoskeleton; Adaptor Proteins, Signal Transducing; Amino Acid Chloromethyl Ketones; Animals; Anti-Bacterial Agents; Apoptosis; beta-Cyclodextrins; Bridged Bicyclo Compounds, Heterocyclic; Carrier Proteins; Caspase 8; Caspase 9; Caspase Inhibitors; Caspases; Cell Line; Cell Membrane; Cyclodextrins; Endocytosis; fas Receptor; Fas-Associated Death Domain Protein; Filipin; Fluorescent Dyes; Humans; Ionophores; Ligands; Lymphocytes; Membrane Microdomains; Membrane Potentials; Microscopy, Fluorescence; Mitochondria; Models, Biological; Nystatin; Receptor Aggregation; Signal Transduction; Thiazoles; Thiazolidines