Toll-like receptor 4 (TLR4) mediates lipopolysaccharide (LPS) signaling in a variety of cell types. MD-2 is associated with the extracellular domain of TLR4 and augments TLR4-dependent LPS responses in vitro. We show here that MD-2−/− mice do not respond to LPS, do survive endotoxic shock but are susceptible to Salmonella typhimurium infection. We found that in MD-2−/− embryonic fibroblasts, TLR4 was not able to reach the plasma membrane and predominantly resided in the Golgi apparatus, whereas TLR4 was distributed at the leading edge surface of cells in wild-type embryonic fibroblasts. Thus, MD-2 is essential for correct intracellular distribution and LPS-recognition of TLR4.
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We thank R. Horai, K. Fukudome and T. Furuta for technical suggestions; and P. W. Kincade and D. R. Liddicoat for helpful comments on the manuscript. Supported by Special Coordination Funds of the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government (Monbukagakusho); the Uehara Memorial Foundation; the Yamanouchi Foundation for Research on Metabolic Disorders; Mitsubishi Pharma; and Sankyo.
The authors declare no competing financial interests.
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Nagai, Y., Akashi, S., Nagafuku, M. et al. Essential role of MD-2 in LPS responsiveness and TLR4 distribution. Nat Immunol 3, 667–672 (2002). https://doi.org/10.1038/ni809
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