E1B 19,000-molecular-weight protein interacts with and inhibits CED-4-dependent, FLICE-mediated apoptosis.
Genetic studies of the nematode Caenorhabditis elegans (C. elegans) have identified several important components of the cell death pathway, most notably CED-3, CED-4, and CED-9. CED-4 directly interacts with the Bcl-2 homologue CED-9 (or the mammalian Bcl-2 family member Bcl-xL) and the caspase CED-3 (or the mammalian caspases ICE and FLICE). This trimolecular complex of CED-4, CED-3, and CED-9 is functional in that CED-9 inhibits CED-4 from activating CED-3 and thereby inhibits apoptosis in heterologous systems. The E1B 19,000-molecular weight protein (E1B 19K) is a potent apoptosis inhibitor and the adenovirus homologue of Bcl-2-related apoptosis inhibitors. Since E1B 19K and Bcl-xL have functional similarity, we determined if E1B 19K interacts with CED-4 and regulates CED-4-dependent caspase activation. Binding analysis indicated that E1B 19K interacts with CED-4 in a Saccharomyces cerevisiae two-hybrid assay, in vitro, and in mammalian cell lysates. The subcellular localization pattern of CED-4 was dramatically changed by E1B 19K, supporting the theory of a functional interaction between CED-4 and E1B 19K. Whereas expression of CED-4 alone could not induce cell death, coexpression of CED-4 and FLICE augmented cell death induction by FLICE, which was blocked by expression of E1B 19K. Even though E1B 19K did not prevent FLICE-induced apoptosis, it did inhibit CED-4-dependent, FLICE-mediated apoptosis, which suggested that CED-4 was required for E1B 19K to block FLICE activation. Thus, E1B 19K functions through interacting with CED-4, and presumably a mammalian homologue of CED-4, to inhibit caspase activation and apoptosis.
Han
J
J
Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, New Jersey 08854, USA.
Wallen
H D
HD
Nuñez
G
G
White
E
E
D017501:Adenovirus E1B Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D006367:HeLa Cells; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008970:Molecular Weight; D016296:Mutagenesis; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D012441:Saccharomyces cerevisiae; D013347:Subcellular Fractions; D051028:bcl-2-Associated X Protein
D017501:Adenovirus E1B Proteins; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; C089224:Ced-4 protein, C elegans; D015801:Helminth Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505528:Casp8 protein, rat; C506435:Casp9 protein, rat; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases