Complex Negative Regulation of TLR9 by Multiple Proteolytic Cleavage Events.
Complex Negative Regulation of TLR9 by Multiple Proteolytic Cleavage Events.
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多重蛋白水解裂解事件对 TLR9 的复杂负调控。
DOI：
10.4049/jimmunol.1502357
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发表时间：
2016-08-15
期刊：
影响因子：
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通讯作者：
Leifer CA
中科院分区：
文献类型：
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作者：
Sinha SS;Cameron J;Brooks JC;Leifer CA
Toll样受体9（TLR 9）是一种先天性免疫受体，对识别宿主和外源DNA都很重要。提出的防止对宿主DNA的过度应答的机制是需要内体中TLR 9的蛋白水解切割以产生受体的成熟形式（TLR 9471 -1032）。我们先前描述了在胞外域的质膜区域中的另一个裂解事件，其产生了显性负性形式的TLR 9。因此，至少有两个独立的切割事件调节TLR 9。在这里，我们调查是否TLR 9的N-末端片段可以负责成熟或负调节形式的调节。我们表明，TLR 9471 -1032，对应于蛋白水解切割的形式，本身不起作用。此外，N-末端片段（TLR 91 -440）的共表达、铰链区（TLR 9441 -1032）的包含或UNC 93 B1的过表达不能挽救活性，后者对于TLR 9的运输和切割是关键的。TLR 91 -440与全长TLR 9和TLR 9471 -1032共免疫沉淀，但不拯救天然糖基化模式，因此不适当的运输可能解释了TLR 9471 -1032无功能的原因。最后，我们表明TLR 9471 -1032也是TLR 9信号传导的显性负调节因子。总之，这些数据提供了一个新的视角，通过蛋白水解裂解调节TLR 9的复杂性，并提供了通过这种受体抑制活性的潜在方法，这可能会抑制自身免疫性炎症。
Toll like receptor 9 (TLR9) is an innate immune receptor important for recognizing DNA, both of host and foreign origin. A mechanism proposed to prevent excessive response to host DNA is the requirement for proteolytic cleavage of TLR9 in endosomes to generate a mature form of the receptor (TLR9471-1032). We previously described another cleavage event in the juxtamembrane region of the ectodomain that generated a dominant negative form of TLR9. Thus, there are at least two independent cleavage events that regulate TLR9. Here we investigated whether an N-terminal fragment of TLR9 could be responsible for regulation of the mature- or negative regulatory-form. We show that TLR9471-1032, corresponding to the proteolytically cleaved form, does not function on its own. Furthermore, activity is not rescued by co-expression of the N-terminal fragment (TLR91-440), inclusion of the hinge region (TLR9441-1032) or overexpression of UNC93B1, the latter of which is critical for trafficking and cleavage of TLR9. TLR91-440 co-immunoprecipitates with full-length TLR9 and TLR9471-1032, but does not rescue the native glycosylation pattern, thus inappropriate trafficking likely explains why TLR9471-1032 is nonfunctional. Lastly, we show that TLR9471-1032 is also a dominant negative regulator of TLR9 signaling. Together these data provide a new perspective on the complexity of TLR9 regulation by proteolytic cleavage and offer potential ways to inhibit activity through this receptor, which may dampen autoimmune inflammation.