Overexpression of adenovirus E3-11.6K protein induces cell killing by both caspase-dependent and caspase-independent mechanisms.
Recent studies have shown enhanced antitumor efficacy with adenoviruses that either lack E1B-19K or overexpress E3-11.6K (also known as adenoviral death protein). E1B-19K is a well-characterized anti-apoptotic protein, and viruses with E1B-19K deletions show increased cytopathicity. However, the mechanism of cell killing by E3-11.6K, which plays an important role in killing infected cells and virion release, is not well characterized. To understand the mechanism of cell killing following E3-11.6K overexpression, we constructed a recombinant adenovirus, Ad-ME, by introducing viral major late promoter upstream of the E3-11.6K sequence. Similar to the E1B-19K-deleted virus, E1B/19K-, Ad-ME induced cell death to a greater extent than the wild-type virus. Cell shrinkage, membrane blebbing, activation of caspases 3 and 9, cleavage of poly(ADP-ribose)polymerase (PARP), DNA degradation, and ratio of ADP to ATP in Ad-ME-infected cells indicated that apoptosis contributes to cell death following E3-11.6K overexpression. However, the levels of activation of caspases 3 and 9 were lower in cells infected with Ad-ME compared to those infected with E1B/19K-. Furthermore, cell killing by Ad-ME was not effectively inhibited by Z-VAD-FMK, a general caspase inhibitor. Taken together, our results suggest both caspase-dependent and caspase-independent mechanisms of cell killing due to overexpression of E3-11.6K.
Zou
Aihua
A
Canji, Inc., San Diego, CA 92128, USA.
Atencio
Isabella
I
Huang
Whei-Mei
WM
Horn
Mark
M
Ramachandra
Murali
M
D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism*; D017503:Adenovirus E3 Proteins / Q000096:biosynthesis* / Q000235:genetics; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D003588:Cytopathogenic Effect, Viral; D006801:Humans; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis
D017503:Adenovirus E3 Proteins; D011994:Recombinant Proteins; C099609:adenovirus death protein, Adenovirus; D020169:Caspases