【求助】请教一个很白痴很基础的问题：到底什么是soluble receptor？

读了很多文献，直接上来就开始说XXX受体的亚型中存在可溶性受体……是我文献没读够吧，但是我还是晕晕的搞不清楚概念。请老师们指点一下！
对于配体来说，到底decoy receptor，soluble receptor，和soluble decoy receptor，有什么区别？谢谢！:I

这段话不知是否有助于理解这个概念：

The concept of a ‘receptive substance’ (or receptor) was first formulated by Langley, and subsequently by Ehrlich, at the start of the 20th century . The definition of a receptor implies binding of a ligand, usually with high affinity and specificity, and the elicitation of a cellular response to that ligand. Studies conducted in the early 1990s suggested that the type II interleukin-1 receptor (IL-1RII) binds IL-1 but is not part of a signaling receptor complex. Evidence suggests that IL-1RII, in transmembrane or soluble (sIL-1RII) form, acts as a molecular trap for the agonist, functioning as a negative regulator of the IL-1 system . The decoy receptor paradigm therefore describes a receptor capable of recognizing its ligand (e.g. IL-1) with high affinity and specificity, but which is structurally incapable of signaling

这类受体只有配体结合域，没有跨膜结构，也没有传导信号的结构域。它们有信号肽，被分泌到细胞外，以可溶形式存在。在细胞外它们高亲和力与细胞因子等配体结合，中和配体的功能，也被叫做decoy receptor。如楼上说的IL-1RII。利用这种现象可以把受体的配体结合域克隆出来，做成dominant negative mutant形式。从而抑制该受体的信号传导。

Decoy receptor:
Soluble secreted proteins derived from cytokine receptors. They lack transmembrane and intracellular domains and may be the products of splice isoforms or obtained by proteolytic cleavage (see also: receptor shedding). Such proteins may function as extracellular antagonists to signaling by cytokines.

A decoy receptor, or sink receptor , is a receptor that binds a ligand, inhibiting it from binding to its normal receptor. For instance, the receptor VEGFR-1 can prevent vascular endothelial growth factor (VEGF) from binding to the VEGFR-2.

Decoy receptor:
Soluble secreted proteins derived from cytokine receptors. They lack transmembrane and intracellular domains and may be the products of splice isoforms or obtained by proteolytic cleavage (see also: receptor shedding). Such proteins may function as extracellular antagonists to signaling by cytokines.

A decoy receptor, or sink receptor , is a receptor that binds a ligand, inhibiting it from binding to its normal receptor. For instance, the receptor VEGFR-1 can prevent vascular endothelial growth factor (VEGF) from binding to the VEGFR-2.

明白了！其实三者是一样的。谢谢各位老师！