Contrasting effects of IG20 and its splice isoforms, MADD and DENN-SV, on tumor necrosis factor alpha-induced apoptosis and activation of caspase-8 and -3.
We identified a novel cDNA (IG20) that is homologous to cDNAs encoding a protein differentially expressed in normal and neoplastic cells (DENN-SV) and human MADD (MAPK-activating death domain-containing protein). Furthermore, we show that the above variants most likely result from alternative splicing of a single gene. Functional analyses of these variants in permanently transfected HeLa cells revealed that IG20 and DENN-SV render them more susceptible or resistant to tumor necrosis factor alpha (TNF-alpha)-induced apoptosis, respectively. All variants tested could interact with TNF receptor 1 and activate ERK and nuclear factor kappaB. However, relative to control cells, only cells expressing IG20 showed enhanced TNF-alpha-induced activation of caspase-8 and -3, whereas cells expressing DENN-SV showed either reduced or no caspase activation. Transfection of these cells with a cDNA encoding CrmA maximally inhibited apoptosis in HeLa-IG20 cells. Our results show that IG20 can promote TNF-alpha-induced apoptosis and activation of caspase-8 and -3 and suggest that it may play a novel role in the regulation of the pleiotropic effects of TNF-alpha through alternative splicing.
Al-Zoubi
A M
AM
Department of Microbiology and Immunology, University of Illinois, 835 South Wolcott Ave., Chicago, IL 60612, USA.
Efimova
E V
EV
Kaithamana
S
S
Martinez
O
O
El-Idrissi
M El-A
Mel-A
Dogan
R E
RE
Prabhakar
B S
BS
D017398:Alternative Splicing; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002469:Cell Separation; D003001:Cloning, Molecular; D017931:DNA Primers / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins; D004789:Enzyme Activation; D005091:Exons; D005434:Flow Cytometry; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D020298:U937 Cells; D014764:Viral Proteins
D017931:DNA Primers; D018076:DNA, Complementary; D053418:Death Domain Receptor Signaling Adaptor Proteins; D020662:Guanine Nucleotide Exchange Factors; C105852:MADD protein, human; D016328:NF-kappa B; D020033:Protein Isoforms; D012333:RNA, Messenger; D015843:Serpins; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins; C074641:interleukin-1beta-converting enzyme inhibitor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases