Defining non-transcriptional innate immune responses to bacterial endotoxin

描述(申请人提供)：这项建议的目标是定义一种新的信号转导途径，它由细菌脂多糖(LPS)激活，但不需要Toll样受体4(TLR4)的信号。虽然TLR4被广泛认为控制对内毒素的转录反应，但它在控制即时(非转录)反应中的作用尚不清楚。这种反应的例子包括内吞、吞噬、自噬和酪氨酸磷酸化。内毒素如何触发这些活动在很大程度上是未知的，但我们已经发现，非转录反应控制着经典定义的对内毒素的转录反应。了解微生物产品是如何激活不同的信号转导通路的，可能会使药物的设计能够针对通路的子集进行治疗。我们的建议是基于我们最近的发现，即内毒素通过一个不需要TLR4信号的过程诱导TLR4的内吞作用。相反，TLR4是由内毒素结合蛋白CD14激活的内吞途径的货物。虽然TLR4不直接进行自身的内吞作用，但这一过程对于TLR4从内吞体内诱导TRIF依赖的信号转导是必不可少的。我们发现了一种不需要TLR4信号的对内毒素的反应，因为这种受体被认为介导了对内毒素(也称为内毒素)的所有反应。在这项拨款申请中，我们建议1)确定CD14依赖的内吞作用的新的胞浆调节因子，2)确定CD14依赖的内吞作用所需的细胞外相互作用，以及3)确定CD14依赖的内吞作用在巨噬细胞和致病性耶尔森菌之间的接触中的重要性。总而言之，这项工作将为控制对内毒素的非转录反应的方式提供重要的见解。

DESCRIPTION (provided by applicant): The goal of this proposal is to define a novel signal transduction pathway that is activated by bacterial lipopolysaccharide (LPS), but does not require signaling by Toll-like Receptor 4 (TLR4). While TLR4 is widely recognized to control transcriptional responses to LPS, its role in controlling immediate (non-transcriptional) responses is less clear. Examples of such responses include endocytosis, phagocytosis, autophagy and tyrosine phosphorylation. How LPS triggers these activities is largely unknown, but we have discovered that non-transcriptional responses control the classically-defined transcriptional responses to LPS. Understanding how microbial products activate distinct signal transduction pathways may permit the design of drugs that can target a subset of pathways therapeutically. Our proposal is founded on our recent discovery that LPS-induces the endocytosis of TLR4 by a process that does not require TLR4 signaling. Rather TLR4 is cargo for an endocytosis pathway that is activated by the LPS-binding protein CD14. While TLR4 does not direct its own endocytosis, this process is essential for TLR4 to induce TRIF-dependent signal transduction from endosomes. Our discovery of a response to LPS that does not require TLR4 signaling is important, as this receptor is thought to mediate all responses to LPS (also known as endotoxin). In this grant application, we propose to 1) identify new cytosolic regulators of CD14-dependent endocytosis, 2) identify the extracellular interactions that are needed for CD14-dependent endocytosis, and 3) identify the importance of CD14-dependent endocytosis in encounters between macrophages and pathogenic Yersinia. Collectively, this work will provide important insight into the means by which non-transcriptional responses to LPS are controlled.