Deficiency of T2K leads to apoptotic liver degeneration and impaired NF-kappaB-dependent gene transcription.
Induction of NF-kappaB-dependent transcription requires phosphorylation and subsequent degradation of I-kappaB, an inhibitor of NF-kappaB, followed by nuclear translocation and DNA binding of NF-kappaB. Tumor necrosis factor receptor-associated factor 2 (TRAF2) plays a role in NF-kappaB activation in response to cytokines such as tumor necrosis factor alpha (TNFalpha). In this study, we purified and characterized a novel kinase (T2K, also known as TBK1 or NAK), which associates with TRAF2 and exhibits kinase activity towards I-kappaBalpha in vitro. The physiological function of T2K was investigated using T2K-deficient mice. Heterozygotes appear normal, but t2k(-/-) animals die at approximately E14.5 of massive liver degeneration and apoptosis. Never theless, hematopoietic progenitors from T2K-deficient fetal liver support normal lymphocyte development. Furthermore, t2k(-/-) embryonic fibroblasts and thymocytes do not display increased sensitivity to TNFalpha-induced apoptosis. In response to either TNFalpha or IL-1 induction, t2k(-/-) embryonic fibroblasts exhibit normal degradation of I-kappaB and kappaB-binding activity. However, NF-kappaB-directed transcription is dramatically reduced. These results demonstrate that, like I-kappaB kinase beta and the RelA subunit of NF-kappaB, T2K is critical in protecting embryonic liver from apoptosis. However, T2K has a unique role in the activation of NF-kappaB-directed transcription, apparently independent of I-kappaB degradation and NF-kappaB DNA binding.
Bonnard
M
M
Amgen Institute, Ontario Cancer Institute and the Department of Medical Biophysics, University of Toronto, 620 University Avenue, Toronto, Ontario, Canada.
Mirtsos
C
C
Suzuki
S
S
Graham
K
K
Huang
J
J
Ng
M
M
Itié
A
A
Wakeham
A
A
Shahinian
A
A
Henzel
W J
WJ
Elia
A J
AJ
Shillinglaw
W
W
Mak
T W
TW
Cao
Z
Z
Yeh
W C
WC
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D015139:Blotting, Southern; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D018390:Gene Targeting; D017930:Genes, Reporter; D005838:Genotype; D006579:Heterozygote; D051550:I-kappa B Kinase; D020287:In Situ Nick-End Labeling; D007375:Interleukin-1 / Q000494:pharmacology; D008025:Ligases / Q000378:metabolism; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000096:biosynthesis* / Q000235:genetics*; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D047992:TNF Receptor-Associated Factor 2; D013950:Thymus Gland / Q000166:cytology; D013997:Time Factors; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D007375:Interleukin-1; D016328:NF-kappa B; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D011994:Recombinant Proteins; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; C498588:Tbk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases