MHC I级
主要组织相容性复合体
生物
MHC限制
细胞生物学
受体
CD1型
自然杀伤细胞
细胞毒性T细胞
抗原
自然杀伤性T细胞
CD8型
免疫学
生物化学
体外
作者
Erin J. Adams,Z. Sean Juo,Rayna Venook,Martin J. Boulanger,Hisashi Arase,Lewis L. Lanier,K. Christopher Garcia
标识
DOI:10.1073/pnas.0703735104
摘要
Natural killer (NK) cells express activating and inhibitory receptors that, in concert, survey cells for proper expression of cell surface major histocompatibility complex (MHC) class I molecules. The mouse cytomegalovirus encodes an MHC-like protein, m157, which is the only known viral antigen to date capable of engaging both activating (Ly49H) and inhibitory (Ly49I) NK cell receptors. We have determined the 3D structure of m157 and studied its biochemical and cellular interactions with the Ly49H and Ly49I receptors. m157 has a characteristic MHC-fold, yet possesses several unique structural features not found in other MHC class I-like molecules. m157 does not bind peptides or other small ligands, nor does it associate with beta(2)-microglobulin. Instead, m157 engages in extensive intra- and intermolecular interactions within and between its domains to generate a compact minimal MHC-like molecule. m157's binding affinity for Ly49I (K(d) approximately 0.2 microM) is significantly higher than that of classical inhibitory Ly49-MHC interactions. Analysis of viral escape mutations on m157 that render it resistant to NK killing reveals that it is likely to be recognized by Ly49H in a binding mode that differs from Ly49/MHC-I. In addition, Ly49H+ NK cells can efficiently lyse RMA cells expressing m157, despite the presence of native MHC class I. Collectively, our results show that m157 represents a structurally divergent form of MHC class I-like proteins that directly engage Ly49 receptors with appreciable affinity in a noncanonical fashion.
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