Oligomerized Ced-4 kills budding yeast through a caspase-independent mechanism.
In Caenorhabdtis elegans, Ced-3, Ced-4, and Ced-9 are components of a cell suicide program. Ced-4 facilitates the proteolytic activation of the caspase, Ced-3, while Ced-9 opposes Ced-3/Ced-4 killing. To examine the interactions among these proteins they were expressed in Saccharomyces cerevisiae. Ced-3 and Ced-4 were lethal when expressed alone, revealing an intrinsic Ced-4 killing activity. Coexpression of Ced-9 blocked Ced-3- and Ced-4-induced killing, showing Ced-9 can independently antagonize the action of both proteins. Ced-3- but not Ced-4-toxicity was attenuated by coexpression of the caspase inhibitors, CrmA and p35. Thus, besides its Ced-3- and Ced-9-dependent action in C. elegans, Ced-4 has an additional Ced-9-dependent, Ced-3-independent killing mechanism in yeast. Two-hybrid analysis confirmed that Ced-4 formed heteromers with Ced-9. In addition, Ced-4 formed homomers and mutation of its nucleoside triphosphate binding motif eliminated both homomerization and cell killing. We suggest the caspase-independent lethality of Ced-4 in yeast is mediated by a Ced-4 homomer.
Tao
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Department of Developmental Neurobiology, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, Tennessee, 38105-2794, USA.
Walke
D W
DW
Morgan
J I
JI
D000818:Animals; D051017:Apoptosis Regulatory Proteins; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D005804:Genes, Lethal; D015801:Helminth Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051034:Inhibitor of Apoptosis Proteins; D051379:Mice; D009154:Mutation; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009705:Nucleosides / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D015843:Serpins / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014170:Transformation, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D051020:bcl-X Protein
D051017:Apoptosis Regulatory Proteins; C494812:Bcl2l1 protein, mouse; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; D061945:Caspase Inhibitors; C089224:Ced-4 protein, C elegans; C087233:Ced-9 protein, C elegans; D015801:Helminth Proteins; D051034:Inhibitor of Apoptosis Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D009705:Nucleosides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D015843:Serpins; D014764:Viral Proteins; D051020:bcl-X Protein; C086430:inhibitor of apoptosis, Nucleopolyhedrovirus; C074641:interleukin-1beta-converting enzyme inhibitor; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; C089223:ced-3 protein, C elegans