TLR8-dependent TNF-(alpha) overexpression in Fanconi anemia group C cells.
Tumor necrosis factor alpha (TNF-alpha) production is abnormally high in Fanconi anemia (FA) cells and contributes to the hematopoietic defects seen in FA complementation group C-deficient (Fancc(-/-)) mice. Applying gene expression microarray and proteomic methods to studies on FANCC-deficient cells we found that genes encoding proteins directly involved in ubiquitinylation are overrepresented in the signature of FA bone marrow cells and that ubiquitinylation profiles of FA-C and complemented cells were substantially different. Finding that Toll-like receptor 8 (TLR8) was one of the proteins ubiquitinylated only in mutant cells, we confirmed that TLR8 (or a TLR8-associated protein) is ubiquitinylated in mutant FA-C cells and that TNF-alpha production in mutant cells depended upon TLR8 and the canonical downstream signaling intermediates interleukin 1 receptor-associated kinase (IRAK) and IkappaB kinase-alpha/beta. FANCC-deficient THP-1 cells and macrophages from Fancc(-/-) mice overexpressed TNF-alpha in response to TLR8 agonists but not other TLR agonists. Ectopically expressed FANCC point mutants were capable of fully complementing the mitomycin-C hypersensitivity phenotype of FA-C cells but did not suppress TNF-alpha overproduction. In conclusion, FANCC suppresses TNF-alpha production in mononuclear phagocytes by suppressing TLR8 activity and this particular function of FANCC is independent of its function in protecting the genome from cross-linking agents.
Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239, USA. vanderws@ohsu.edu
Scott M
SM
Vanderwerf
Johanna
J
Svahn
Susan
S
Olson
R Keaney
RK
Rathbun
Christina
C
Harrington
Jane
J
Yates
Winifred
W
Keeble
David C
DC
Anderson
Praveen
P
Anur
Noemi F
NF
Pereira
Daniela V
DV
Pilonetto
Ricardo
R
Pasquini
Grover C
GC
Bagby
D000818:Animals; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D005199:Fanconi Anemia / Q000235:genetics / Q000378:metabolism*; D052218:Fanconi Anemia Complementation Group C Protein / Q000172:deficiency / Q000235:genetics; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D047468:Immunoprecipitation; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051200:Toll-Like Receptor 8 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D054875:Ubiquitination / Q000502:physiology; D015854:Up-Regulation
D052218:Fanconi Anemia Complementation Group C Protein; D034741:RNA, Small Interfering; D051200:Toll-Like Receptor 8; D014409:Tumor Necrosis Factor-alpha