Yuji Kondo, Kazutaka Ikeda, Noriyo Tokuda, Chiaki Nishitani, Umeharu Ohto, Sachiko Akashi-Takamura, Yasutomo Ito, Makoto Uchikawa, Yoshio Kuroki, Ryo Taguchi, Kensuke Miyake, Qing Zhang, Keiko Furukawa, Koichi Furukawa
Proceedings of the National Academy of Sciences of the United States of America 2013 Mar 19Although endogenous ligands for Toll-like receptor (TLR)4-myeloid differentiation factor 2 (MD2) have not been well-understood, we here report that a globo-series glycosphingolipid, globotetraosylceramide (Gb4), attenuates the toxicity of lipopolysaccharides (LPSs) by binding to TLR4-MD-2. Because α1,4-galactosyltransferase (A4galt)-deficient mice lacking globo-series glycosphingolipids showed higher sensitivity to LPS than wild-type mice, we examined mechanisms by which globo-series glycosphingolipids attenuate LPS toxicity. Cultured endothelial cells lacking A4galt showed higher expression of LPS-inducible genes upon LPS treatment. In turn, introduction of A4galt cDNA resulted in the neo expression of Gb4, leading to the reduced expression of LPS-inducible genes. Exogenous Gb4 induced similar effects. As a mechanism for the suppressive effects of Gb4 on LPS signals, specific binding of Gb4 to the LPS receptor TLR4-MD-2 was demonstrated by coprecipitation of Gb4 with recombinant MD-2 and by native PAGE. A docking model also supported these data. Taken together with colocalization of TLR4-MD-2 with Gb4 in lipid rafts after LPS stimulation, it was suggested that Gb4 competes with LPS for binding to TLR4-MD-2. Finally, administration of Gb4 significantly protected mice from LPS-elicited mortality. These results suggest that Gb4 is an endogenous ligand for TLR4-MD-2 and is capable of attenuating LPS toxicity, indicating the possibility for its therapeutic application in endotoxin shock.
Yuji Kondo, Kazutaka Ikeda, Noriyo Tokuda, Chiaki Nishitani, Umeharu Ohto, Sachiko Akashi-Takamura, Yasutomo Ito, Makoto Uchikawa, Yoshio Kuroki, Ryo Taguchi, Kensuke Miyake, Qing Zhang, Keiko Furukawa, Koichi Furukawa. TLR4-MD-2 complex is negatively regulated by an endogenous ligand, globotetraosylceramide. Proceedings of the National Academy of Sciences of the United States of America. 2013 Mar 19;110(12):4714-9
PMID: 23471986
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