Toll-like receptors (TLRs) are key pathogen sensors of the immune system. Their activation results in the production of cytokines, chemokines, and costimulatory molecules that are crucial for innate and adaptive immune responses. In recent years, specific (sub)-cellular location and timing of TLR activation have emerged as parameters for defining the signaling outcome and magnitude. To study the subtlety of this signaling, we here report a new molecular tool to control the activation of TLR2 via “click-to-release”-chemistry. We conjugated a bioorthogonal trans-cyclooctene (TCO) protecting group via solid support to a critical position within a synthetic TLR2/6 ligand to render the compound unable to initiate signaling. The TCO-group could then be conditionally removed upon addition of a tetrazine, resulting in restored agonist activity and TLR2 activation. This approach was validated on RAW264.7 macrophages and various murine primary immune cells as well as human cell line systems, demonstrating that TCO-caging constitutes a versatile approach for generating chemically controllable TLR2 agonists.

中文翻译：

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通过反式环辛烯笼状配体有条件地控制人TLR2的活性。

Toll样受体（TLR）是免疫系统的关键病原体传感器。它们的激活导致细胞因子，趋化因子和共刺激分子的产生，这对于先天性和适应性免疫反应至关重要。近年来，TLR激活的特定（亚）细胞位置和时机已成为定义信号转导结果和强度的参数。为了研究这种信号的微妙之处，我们在这里报告了一种新的分子工具，可通过“点击释放”化学方法控制TLR2的激活。我们通过固体支持物将生物正交的反式环辛烯（TCO）保护基偶联到合成TLR2 / 6配体中的关键位置，使该化合物无法启动信号传导。然后可以在加入四嗪后有条件地除去TCO-基团，导致激动剂活性恢复和TLR2激活。该方法已在RAW264.7巨噬细胞和各种鼠类原代免疫细胞以及人类细胞系上得到验证，证明TCO笼蔽是产生化学可控TLR2激动剂的通用方法。