NEGATIVE SIGNALLING BY KILLER CELL INHIBITORY RECEPTORS

人类自然杀伤（NK）细胞表现出独特的活化机制，其主要由抑制性受体（包括杀伤细胞抑制性受体（KIR））调节。 KIR是主要的NK细胞受体，其结合经典的主要组织相容性复合物I类分子（MHC-I）和抑制NK细胞活化的负性信号。 KIR阴性信号传导的一个组成部分是蛋白酪氨酸磷酸酶SHP-1向受体胞质结构域内的磷酸化酪氨酸残基的募集。 SHP-1如何发挥作用以抑制NK细胞活化，以及其他信号效应分子是否也在此过程中发挥作用仍有待确定。我们最近发现，蛋白酪氨酸激酶（PTK），Csk，也可以结合酪氨酸磷酸化的KIR。 通过KIR的Csk募集为我们未来的研究提供了一个令人兴奋的基础，因为该PTK具有独特的能力磷酸化Src家族受体近端PTK上的调节酪氨酸残基并终止其活性。这种新的负信号机制尚未被确定为任何抑制性受体，我们假设，Csk招聘提供KIR的能力，在早期阶段抑制蛋白酪氨酸磷酸化介导的激活事件。额外的数据支持我们的假设，即KIR上两个单独的酪氨酸磷酸化位点的磷酸化状态直接调节效应酶结合谱和功能结果。我们建议测试我们的假设有三个具体的目标：（1）生物化学特征的Csk招聘KIR及其对Src家族的PTKs的影响，（2）以确定功能的贡献Csk招聘KIR抑制NK细胞活化，和（3）表征的作用，个别KIR酪氨酸抑制信号反应。这些研究将大大有助于我们了解KIR介导的负信号的机制。 更好地理解主要调节NK细胞活化的机制最终应允许开发治疗方法，以有利地操纵其在癌症、病毒感染和预防组织移植排斥的治疗中的功能。

Human natural killer (NK) cells exhibit a unique activation mechanism that is dominantly regulated by inhibitory receptors, including Killer Cell Inhibitory Receptors (KIR). KIR are the major NK cell receptors that bind classical major histocompatibility complex class I molecules (MHC-I) and transduce negative signals that restrain NK cell activation. A component of KIR negative signalling is recruitment of the protein tyrosine phosphatase SHP-1 to phosphorylated tyrosine residues within the receptor cytoplasmic domain. How SHP-1 functions to inhibit NK cell activation and whether additional signalling effector molecules also play roles in this process remain to be established. We have recently discovered that the protein tyrosine kinase (PTK), Csk, can also bind to tyrosine phosphorylated KIR. Csk recruitment by KIR provides an exciting basis for our future studies, since this PTK has the unique capacity to phosphorylate the regulatory tyrosine residues on receptor proximal PTKs of the Src family and terminate their activity. Such a novel negative signalling mechanism has not yet been identified for any inhibitory receptor, and we hypothesize that Csk recruitment provides KIR with capacity to dampen protein tyrosine phosphorylation-mediated activation events at an early stage. Additional data supports our hypothesis that phosphorylation status of the two individual tyrosine phosphorylation sites on KIR directly regulates effector enzyme binding profiles and functional outcomes. We propose to test our hypotheses with three specific aims: (1) to biochemically characterize Csk recruitment to KIR and its impact on PTKs of the Src family, (2) to determine the functional contributions of Csk recruitment on KIR inhibition of NK cell activation, and (3) to characterize the roles of the individual KIR tyrosines on inhibitory signalling responses. These studies will contribute substantially to our understanding of the mechanisms of KIR-mediated negative signalling. A better understanding of the mechanisms that dominantly regulate NK cell activation should ultimately allow for the development of therapeutic methods to beneficially manipulate their functions in therapies for cancer, viral infection, and prevention of tissue transplant rejection.