Bacterial CpG-DNA and lipopolysaccharides activate Toll-like receptors at distinct cellular compartments

作者：Parviz Ahmad‐Nejad, Hans Häcker, Mark Rutz, Stefan Bauer, R. Martin Vabulas, Hermann Wagner · 发表于：European Journal of Immunology · 年份：2002 · DOI：10.1002/1521-4141(200207)32:7<1958::aid-immu1958>3.0.co;2-u · 被引用次数：716 · 研究领域：Immune Response and Inflammation、Neonatal and Maternal Infections、Neonatal Respiratory Health Research

Recognition by innate immune cells of the pathogen associated molecular patterns (PAMP) lipopolysaccharide (LPS) from Gram-negative bacteria and bacterial CpG-DNA depends on Toll-like receptor4 (TLR4) and TLR9, respectively. To define differences in the response to these distinct PAMP we compared a key intracellular event, namely recruitment of myeloid differentiation marker 88 (MyD88) to the respective PAMP-initiated TLR signaling. Using MyD88-GFP fusion protein expressing macrophages we demonstrate that LPS and CpG-DNA trigger signaling from two different cellular locations: theformer at the cell membrane and the latter at the lysosomal compartment. While LPS does not require endocytosis to functionally associate with the membrane expressed TLR4/MD2 complex, internalization and endosomal maturation is conditional for CpG-DNA to activate TLR9. In support of these data TLR9 is not localized at the cell surface, but intracellularily. These data stress the need to characterize individual TLR at the very beginning of signal initiation in order to understand their diverse biological functions.