TLR2 is mobilized into an apical lipid raft receptor complex to signal infection in airway epithelial cells
Grace Soong, … , Robert Adamo, Alice Prince
Grace Soong, … , Robert Adamo, Alice Prince
Published May 15, 2004
Citation Information: J Clin Invest. 2004;113(10):1482-1489. https://doi.org/10.1172/JCI20773.
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Article Immunology

TLR2 is mobilized into an apical lipid raft receptor complex to signal infection in airway epithelial cells

Abstract

Toll-like receptors (TLRs) mediate host responses to bacterial gene products. As the airway epithelium is potentially exposed to many diverse inhaled bacteria, TLRs involved in defense of the airways must be broadly responsive, available at the exposed apical surface of the cells, and highly regulated to prevent activation following trivial encounters with bacteria. We demonstrate that TLR2 is enriched in caveolin-1–associated lipid raft microdomains presented on the apical surface of airway epithelial cells after bacterial infection. These receptor complexes include myeloid differentiation protein (MyD88), interleukin-1 receptor–activated kinase-1, and TNF receptor–associated factor 6. The signaling capabilities of TLR2 are amplified through its association with the asialoganglioside gangliotetraosylceramide (Galβ1,2GalNAcβ1,4Galβ1,4Glcβ1,1Cer), which has receptor function itself for many pulmonary pathogens. Ligation of either TLR2 or asialoGM1 by ligands with specificity for either receptor, by Pseudomonas aeruginosa, or by Staphylococcus aureus stimulates IL-8 production through activation of NF-κB, as mediated by TLR2 and MyD88. Thus, TLR2 in association with asialo-glycolipids presented within the context of lipid rafts provides a broadly responsive signaling complex at the apical surfaces of airway cells to initiate the host response to potential bacterial infection.

Authors

Grace Soong, Bharat Reddy, Sach Sokol, Robert Adamo, Alice Prince

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Figure 1

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Distribution of asialoGM1, TLR2, and TLR4 in infected airway cells. (A) ...
Distribution of asialoGM1, TLR2, and TLR4 in infected airway cells. (A) Confocal microscopy was used to image monolayers of polarized 16HBE cells transfected with Flag epitope–tagged TLR2 or TLR4 and stimulated with P. aeruginosa PAO1. z-sections treated with anti-Flag labeled with TRITC (red) and with anti-asialoGM1 labeled with FITC (green) are shown. AsialoGM1 (aGM1) is apical and colocalizes with TLR2 (yellow) in discrete clusters along the apical surface of the monolayers. TLR4 is more diffuse, and colocalization with asialoGM1 is not appreciable. (B) Human airway cells in primary culture isolated from nasal polyps from a CF patient and stimulated with P. aeruginosa PAO1 were stained for asialoGM1 labeled with TRITC and TLR2 labeled with FITC and show abundant colocalization of these receptors.