Keratin attenuates tumor necrosis factor-induced cytotoxicity through association with TRADD.
Keratin 8 and 18 (K8/18) are the major components of intermediate filament (IF) proteins of simple or single-layered epithelia. Recent data show that normal and malignant epithelial cells deficient in K8/18 are nearly 100 times more sensitive to tumor necrosis factor (TNF)-induced cell death. We have now identified human TNF receptor type 1 (TNFR1)-associated death domain protein (TRADD) to be the K18-interacting protein. Among IF proteins tested in two-hybrid systems, TRADD specifically bound K18 and K14, type I (acidic) keratins. The COOH-terminal region of TRADD interacted with the coil Ia of the rod domain of K18. Endogenous TRADD coimmunoprecipitated with K18, and colocalized with K8/18 filaments in human mammary epithelial cells. Overexpression of the NH2 terminus (amino acids 1-270) of K18 containing the TRADD-binding domain as well as overexpression of K8/18 in SW13 cells, which are devoid of keratins, rendered the cells more resistant to killing by TNF. We also showed that overexpressed NH2 termini of K18 and K8/18 were associated with endogenous TRADD in SW13 cells, resulting in the inhibition of caspase-8 activation. These results indicate that K18 may sequester TRADD to attenuate interactions between TRADD and activated TNFR1 and moderate TNF-induced apoptosis in simple epithelial cells.
Inada
H
H
Division of Biochemistry, Aichi Cancer Center Research Institute, Aichi 464-8681, Japan.
Izawa
I
I
Nishizawa
M
M
Fujita
E
E
Kiyono
T
T
Takahashi
T
T
Momoi
T
T
Inagaki
M
M
D015250:Aclarubicin / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D007382:Intermediate Filaments / Q000378:metabolism; D007633:Keratins / Q000235:genetics / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D047990:TNF Receptor-Associated Factor 1; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D009353:Zinostatin / Q000494:pharmacology
D011506:Proteins; D016271:Proto-Oncogene Proteins c-myc; D018124:Receptors, Tumor Necrosis Factor; D011993:Recombinant Fusion Proteins; D047990:TNF Receptor-Associated Factor 1; D014409:Tumor Necrosis Factor-alpha; D007633:Keratins; D015250:Aclarubicin; D009353:Zinostatin; D017239:Paclitaxel