Structure and Function of Natural Killer Cell Receptors

描述（由申请人提供）：在进化过程中，病毒已经发展出一系列逃避免疫系统监视的机制，包括产生模拟宿主分子的诱饵蛋白，以避免自我识别。小鼠巨细胞病毒（MCMV）基因组编码MHC i类分子m157，该分子与抑制性NK细胞受体Ly49I结合。m157蛋白显示在mcmv感染细胞的表面，以阻止NK细胞的攻击。我们将对抑制受体Ly49I与病毒蛋白m157的相互作用进行生物物理和结构研究。免疫系统通过激活NK受体（如Ly49H）进行反击，一旦NK细胞在靶细胞表面遇到m157诱饵分子，就会激活NK细胞。这种相互作用通过杀死被感染的细胞来保护宿主免受病毒感染。我们将开展研究，了解激活受体Ly49H与MCMV蛋白m157相互作用的生物物理和结构基础。此外，MCMV以某种方式修饰在感染细胞上表达的MHC I类分子H-2Dk，诱导携带活化Ly49P受体的NK细胞杀死靶细胞。为了理解这种机制的本质，即“修饰自我”抵抗病原体感染，我们将确定激活受体Ly49P与装载病毒或自身肽的H-2Dk复合物的晶体结构。KLRG1是人类和小鼠中发现的一种凝集素样受体，是一种在病毒感染过程中过度表达的抑制性NK细胞和CD8+ T细胞受体。我们将分析KLRG1与其同源配体（粘附分子N-， R-和E-cadherin）配合物的结合特性并确定其晶体结构。klrg1 -钙粘蛋白相互作用被认为在杀死病毒感染和转移的癌细胞中发挥作用。我们期望所提出的研究将定义NK细胞受体与病毒（m157）和宿主（MHC类I，钙粘蛋白）配体相互作用的分子基础，这些配体在病毒感染过程中调节NK细胞的活性。本研究将主要在阿根廷布宜诺斯艾利斯大学与Emilio Malchiodi博士合作进行，作为NIH资助R01 AI047990-07的延伸（Mariuzza; 7/1/2004-6/30/2009）。今天，有超过30亿人感染巨细胞病毒（CMV，疱疹病毒科）。病毒和宿主机制已共同进化，使大多数感染者能够相互容忍，但该病毒在新生儿和免疫功能低下的成年人中具有致病性。自然杀伤（NK）细胞在先天免疫应答多种病毒感染或恶性细胞中发挥核心作用。NK细胞的功能是由激活和抑制受体与特定配体相互作用的动态平衡调节的。本提案的目标是获得在病毒感染过程中调节NK细胞功能的小鼠NK细胞受体与病毒或宿主配体相互作用的结构见解。这些知识可能有助于开发基于NK细胞溶细胞活性调节的治疗病毒感染的新策略。

DESCRIPTION (provided by applicant): During evolution viruses have developed an array of mechanisms to escape surveillance by the immune system, including production of decoy proteins that mimic the host's molecules for the purpose of avoiding nonself recognition. The murine cytomegalovirus (MCMV) genome codes for an MHC class I-like molecule, m157, which binds the inhibitory NK cell receptor Ly49I. The m157 protein is displayed on the surface of MCMV-infected cells to prevent NK cell attack. We will carry out biophysical and structural studies of the interaction of the inhibitory receptor Ly49I with the viral protein m157. The immune system counterattacks with activating NK receptors, such as Ly49H, that activate NK cells once they encounter m157 decoy molecules on the surface of target cells. This interaction protects the host against viral infection by killing the infected cell. We will conduct research to understand the biophysical and structural basis for the interaction of the activating receptor Ly49H with the MCMV protein m157. In addition, MCMV somehow modifies the MHC class I molecule H-2Dk expressed on an infected cell in a manner that induces NK cells carrying the activating Ly49P receptor to kill the target cell. To understand the nature of this mechanism, whereby "modified self" resists a pathogen infection, we will determine the crystal structures of the activating receptor Ly49P in complex with H-2Dk loaded with viral or self peptides. KLRG1, a lectin-like receptor found in both human and mouse, is an inhibitory NK cell and CD8+ T cell receptor over-expressed during viral infection. We will analyze the binding properties and determine the crystal structure of KLRG1 in complex with its cognate ligands, the adhesion molecules N-, R- and E-cadherin. The KLRG1-cadherin interaction is believed to play a role in the killing of virally infected and metastatic cancer cells. We expect that the proposed studies will define the molecular basis for the interaction of NK cell receptors with both viral (m157) and host (MHC class I, cadherins) ligands that regulate NK cell activity during the course of viral infections. This research will be done primarily in Argentina at the University of Buenos Aires in collaboration with Dr. Emilio Malchiodi, as an extension of NIH Grant R01 AI047990-07 (Mariuzza; 7/1/2004-6/30/2009). More than 3 billion people today live with cytomegalovirus (CMV, Herpesviridae) infection. Viral and host mechanisms have coevolved to enable the pair to live in a mutually tolerant relationship in most infected individuals, but the virus is pathogenic in neonatal life and in adults who are immunocompromised. Natural killer (NK) cells play a central role in innate immune responses to a variety of virally infected or malignant cells. NK cell function is regulated by a dynamic balance between activating and inhibitory receptors that interact with specific ligands. The goal of this proposal is to obtain structural insights into the interaction of murine NK cell receptors with viral or host ligands that regulate NK cell function during the course of viral infections. Such knowledge may contribute to the development of new strategies for the treatment of viral infections based on modulation of NK cell cytolytic activity.