Cell
Volume 147, Issue 4, 11 November 2011, Pages 868-880
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Article
CD14 Controls the LPS-Induced Endocytosis of Toll-like Receptor 4

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Summary

The transport of Toll-like Receptors (TLRs) to various organelles has emerged as an essential means by which innate immunity is regulated. While most of our knowledge is restricted to regulators that promote the transport of newly synthesized receptors, the regulators that control TLR transport after microbial detection remain unknown. Here, we report that the plasma membrane localized Pattern Recognition Receptor (PRR) CD14 is required for the microbe-induced endocytosis of TLR4. In dendritic cells, this CD14-dependent endocytosis pathway is upregulated upon exposure to inflammatory mediators. We identify the tyrosine kinase Syk and its downstream effector PLCγ2 as important regulators of TLR4 endocytosis and signaling. These data establish that upon microbial detection, an upstream PRR (CD14) controls the trafficking and signaling functions of a downstream PRR (TLR4). This innate immune trafficking cascade illustrates how pathogen detection systems operate to induce both membrane transport and signal transduction.

Highlights

► CD14 is a receptor for LPS that promotes TLR4 endocytosis and interferon expression ► CD14-induced endocytosis occurs independently of TLR4 signaling ► CD14-induced endocytosis is an ITAM-mediated process dependent on Syk and PLCg2 ► Mature dendritic cells exhibit enhanced CD14-dependent responses to bacteria

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These authors contributed equally to this work