Structure and Function of Natural Killer Cell Receptors

描述(申请人提供)：在进化过程中，病毒已经发展出一系列机制来逃避免疫系统的监视，包括产生模拟宿主分子的诱骗蛋白，以避免异体识别。小鼠巨细胞病毒(MCMV)基因组编码MHC I类分子m157，它与抑制性NK细胞受体Ly49I结合。M157蛋白显示在感染MCMV的细胞表面，以防止NK细胞攻击。我们将对抑制性受体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细胞遇到靶细胞表面的m157诱骗分子，就会激活NK细胞。这种相互作用通过杀死受感染的细胞来保护宿主免受病毒感染。我们将进行研究，以了解激活受体Ly49H与MCMV蛋白M157相互作用的生物物理和结构基础。此外，MCMV以某种方式改变感染细胞上表达的MHC I类分子H-2Dk，诱导携带激活Ly49P受体的NK细胞杀伤目标细胞。为了了解这一机制的本质，“修饰的自我”抵抗病原体感染，我们将确定激活受体Ly49P的晶体结构与H-2Dk负载病毒或自体多肽的复合体。KLRG1是一种在人和小鼠体内发现的凝集素样受体，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与其同源配体黏附分子N-、R-和E-钙粘蛋白的结合性质并确定其晶体结构。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方面发挥了作用。我们预计，拟议的研究将确定NK细胞受体与病毒(M157)和宿主(MHC I类，钙粘素)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。这项研究将主要在阿根廷布宜诺斯艾利斯大学与埃米利奥·马尔基奥迪博士合作进行，作为NIH补助金R01 AI047990-07的延伸(Mariuzza；7/1/2004-6/30/2009)。目前有30多亿人患有巨细胞病毒(CMV，疱疹病毒科)感染。病毒和宿主机制共同进化，使这两个人在大多数受感染的人中能够以相互容忍的关系生活，但病毒在新生儿和免疫受损的成年人中是致病的。自然杀伤(NK)细胞在对各种病毒感染或恶性细胞的先天免疫反应中起着核心作用。NK细胞的功能受与特定配体相互作用的激活和抑制受体之间的动态平衡调节。这项建议的目的是获得关于小鼠NK细胞受体与病毒或宿主配体相互作用的结构性见解，这些配体在病毒感染过程中调节NK细胞的功能。这些知识可能有助于开发基于NK细胞杀伤活性调节的病毒感染治疗的新策略。

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.