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J. Virol., Apr 1997, 2830-2837, Vol 71, No. 4
T Dimitrov, P Krajcsi, TW Hermiston, AE Tollefson, M Hannink and WS Wold
We have reported that three adenovirus (Ad) proteins, named E3-
10.4K/14.5K, E3-14.7K, and E1B-19K, independently inhibit tumor necrosis
factor (TNF)-induced apoptosis in Ad-infected cells. E3- 10.4K/14.5K and
E3-14.7K also inhibit TNF-induced release of arachidonic acid (AA).
TNF-induced apoptosis and AA release are thought to require TNF-activation
of the 85-kDa cytosolic phospholipase A2 (cPLA2). cPLA2 normally exists in
a latent form in the cytosol; it is activated by phosphorylation by
mitogen-activated protein kinase, and in the presence of agents that
mobilize intracellular Ca2+, cPLA2 translocates to membranes where it
cleaves AA from membrane phospholipids. We now report that TNF induces
translocation of cPLA2 from the cytosol to membranes in Ad-infected human
A549 cells and that E3-10.4K/14.5K but not E3-14.7K or E1B-19K is required
to inhibit TNF- induced translocation of cPLA2. Ad infection also inhibited
TNF-induced release of AA. Under the same conditions, Ad infection did not
inhibit TNF-induced phosphorylation of cPLA2 or TNF activation of NFkappaB.
Ad infection also inhibited cPLA2 translocation in response to the Ca2+
ionophore A23187 and to cycloheximide, but this inhibition did not require
E3-10.4K/14.5K. Ad infection did not inhibit cPLA2 translocation in
response to interleukin-1beta or platelet-derived growth factor. We propose
that E3-10.4K/14.5K inhibits TNF-induced AA release and apoptosis by
directly or indirectly inhibiting TNF-induced translocation of cPLA2 from
the cytosol to membranes. AA formed by cPLA2 can be metabolized to
prostaglandins, leukotrienes, and lipoxyns, molecules that amplify
inflammation. E3-10.4K/14.5K probably functions in Ad infections to inhibit
both TNF-induced apoptosis and inflammation.
Copyright © 1997, American Society for Microbiology
Adenovirus E3-10.4K/14.5K protein complex inhibits tumor necrosis factor-induced translocation of cytosolic phospholipase A2 to membranes
Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, Missouri 63104, USA.
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