Raftlin is involved in the nucleocapture complex to induce poly(I:C)-mediated TLR3 activation.
The double-stranded RNA analog, poly(I:C), extracellularly activates both the endosomal Toll-like receptor (TLR) 3 and the cytoplasmic RNA helicase, melanoma differentiation-associated gene 5, leading to the production of type I interferons (IFNs) and inflammatory cytokines. The mechanism by which extracellular poly(I:C) is delivered to TLR3-positive organelles and the cytoplasm remains to be elucidated. Here, we show that the cytoplasmic lipid raft protein, Raftlin, is essential for poly(I:C) cellular uptake in human myeloid dendritic cells and epithelial cells. When Raftlin was silenced, poly(I:C) failed to enter cells and induction of IFN-β production was inhibited. In addition, cellular uptake of B-type oligodeoxynucleotide that shares its uptake receptor with poly(I:C) was suppressed in Raftlin knockdown cells. Upon poly(I:C) stimulation, Raftlin was translocated from the cytoplasm to the plasma membrane where it colocalized with poly(I:C), and thereafter moved to TLR3-positive endosomes. Thus, Raftlin cooperates with the uptake receptor to mediate cell entry of poly(I:C), which is critical for activation of TLR3.
Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo 060-8638, Japan.
Ayako
A
Watanabe
Megumi
M
Tatematsu
Kazuko
K
Saeki
Sachiko
S
Shibata
Hiroaki
H
Shime
Akihiko
A
Yoshimura
Chikashi
C
Obuse
Tsukasa
T
Seya
Misako
M
Matsumoto
D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D003713:Dendritic Cells / Q000166:cytology / Q000378:metabolism*; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D020868:Gene Silencing; D057809:HEK293 Cells; D006801:Humans; D007369:Interferon Inducers / Q000494:pharmacology*; D016899:Interferon-beta / Q000096:biosynthesis / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000166:cytology / Q000378:metabolism*; D011070:Poly I-C / Q000494:pharmacology*; D051196:Toll-Like Receptor 3 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*
D007369:Interferon Inducers; D008565:Membrane Proteins; C476398:RFTN1 protein, human; C495344:TLR3 protein, human; C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3; D016899:Interferon-beta; D011070:Poly I-C
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