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The Toll‐like receptor 2 (TLR2) ligand FSL‐1 is internalized via the clathrin‐dependent endocytic pathway triggered by CD14 and CD36 but not by TLR2
Author(s) -
Shamsul Haque M.,
Hasebe Akira,
Iyori Mitsuhiro,
Ohtani Makoto,
Kiura Kazuto,
Zhang Diya,
Totsuka Yasunori,
Shibata Ken ichiro
Publication year - 2010
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1111/j.1365-2567.2009.03232.x
Subject(s) - clathrin , internalization , endocytosis , microbiology and biotechnology , endocytic cycle , tlr2 , caveolae , toll like receptor , transfection , biology , receptor , dynamin , chemistry , cell culture , innate immune system , signal transduction , biochemistry , tlr4 , genetics
Summary Little is known of how Toll‐like receptor (TLR) ligands are processed after recognition by TLRs. This study was therefore designed to investigate how the TLR2 ligand FSL‐1 is processed in macrophages after recognition by TLR2. FSL‐1 was internalized into the murine macrophage cell line, RAW264.7. Both chlorpromazine and methyl‐β‐cyclodextrin, which inhibit clathrin‐dependent endocytosis, reduced FSL‐1 uptake by RAW264.7 cells in a dose‐dependent manner but nystatin, which inhibits caveolae‐ and lipid raft‐dependent endocytosis, did not. FSL‐1 was co‐localized with clathrin but not with TLR2 in the cytosol of RAW264.7 cells. These results suggest that internalization of FSL‐1 is clathrin dependent. In addition, FSL‐1 was internalized by peritoneal macrophages from TLR2‐deficient mice. FSL‐1 was internalized by human embryonic kidney 293 cells transfected with CD14 or CD36 but not by the non‐transfected cells. Also, knockdown of CD14 or CD36 in the transfectants reduced FSL‐1 uptake. In this study, we suggest that (i) FSL‐1 is internalized into macrophages via a clathrin‐dependent endocytic pathway, (ii) the FSL‐1 uptake by macrophages occurs irrespective of the presence of TLR2, and (iii) CD14 and CD36 are responsible for the internalization of FSL‐1.