A major lipid raft protein raftlin modulates T cell receptor signaling and enhances th17-mediated autoimmune responses.
The membrane microdomains known as lipid rafts have been shown to act as platforms for the initiation of various receptor signals. Through proteomic analysis, we have identified a novel protein termed Raftlin (raft-linking protein) as a major protein in lipid rafts. To determine the physiological and immunological functions of Raftlin in mammals, we generated Raftlin-deficient mice, as well as Raftlin-transgenic (Tg) mice. Although Raftlin was originally identified in B cells, we observe no severe abnormalities in the B cells of these mice, presumably due to a high expression of Raftlin-homologue (Raftlin-2). T cells, in contrast, expressed a substantial amount of Raftlin but no Raftlin-2. In Raftlin-deficient mice, T cell-dependent Ab production was reduced, and experimental autoimmune encephalomyelitis, a Th17-dependent autoimmune disease model, was ameliorated. In Raftlin-Tg mice, in contrast, Ab production was enhanced and experimental autoimmune encephalomyelitis was more severe. Cytokine production, especially that of IL-17, was reduced in Raftlin-deficient T cells, while it was enhanced in Raftlin-Tg T cells. We found that these changes were associated with the strength of the TCR-mediated signals. Importantly, localization of Lck protein in the lipid rafts was enhanced by Raftlin overexpression and reduced by Raftlin deficiency. These data indicate that Raftlin modulates TCR signals and is necessary for the fine-tuning of T cell-mediated immune responses.
Saeki
Kazuko
K
Division of Molecular and Cellular Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
Fukuyama
Satoru
S
Ayada
Toranoshin
T
Nakaya
Mako
M
Aki
Daisuke
D
Takaesu
Giichi
G
Hanada
Toshikatsu
T
Matsumura
Yumiko
Y
Kobayashi
Takashi
T
Nakagawa
Ryusuke
R
Yoshimura
Akihiko
A
D000818:Animals; D001249:Asthma / Q000276:immunology / Q000378:metabolism; D015139:Blotting, Southern; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000276:immunology / Q000378:metabolism; D020381:Interleukin-17 / Q000096:biosynthesis / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D021962:Membrane Microdomains / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000378:metabolism
D020381:Interleukin-17; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell