NKG2D discriminates diverse ligands through selectively mechano‐regulated ligand conformational changes. (16th December 2021)

• Record Type: Journal Article
• Authors: Fan, Juan; Shi, Jiawei; Zhang, Yong; Liu, Junwei; An, Chenyi; Zhu, Huaying; Wu, Peng; Hu, Wei; Qin, Rui; Yao, Danmei; Shou, Xin; Xu, Yibing; Tong, Zhou; Wen, Xue; Xu, Jianpo; Zhang, Jin; Fang, Weijia; Lou, Jizhong; Yin, Weiwei; Chen, Wei
• Is Part Of: EMBO journal. Volume 41:Number 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-16
• Subjects: conformational changes -- ligand discrimination -- mechanical regulation -- NKG2D; Molecular biology -- Periodicals; 572.805
• DOI: 10.15252/embj.2021107739
• Languages: English
• ISSNs: 0261-4189

Abstract

Abstract: Stimulatory immune receptor NKG2D binds diverse ligands to elicit differential anti‐tumor and anti‐virus immune responses. Two conflicting degeneracy recognition models based on static crystal structures and in‐solution binding affinities have been considered for almost two decades. Whether and how NKG2D recognizes and discriminates diverse ligands still remain unclear. Using live‐cell‐based single‐molecule biomechanical assay, we characterized the in situ binding kinetics of NKG2D interacting with different ligands in the absence or presence of mechanical force. We found that mechanical force application selectively prolonged NKG2D interaction lifetimes with the ligands MICA and MICB, but not with ULBPs, and that force‐strengthened binding is much more pronounced for MICA than for other ligands. We also integrated steered molecular dynamics simulations and mutagenesis to reveal force‐induced rotational conformational changes of MICA, involving formation of additional hydrogen bonds on its binding interface with NKG2D, impeding MICA dissociation under force. We further provided a kinetic triggering model to reveal that force‐dependent affinity determines NKG2D ligand discrimination and its downstream NK cell activation. Together, our results demonstrate that NKG2D has a discrimination power to recognize different ligands, which depends on selective mechanical force‐induced ligand conformational changes. SYNOPSIS: NKG2D is able to discriminate different ligands. Its discrimination power is fulfilled by physical restrictions of two‐dimensional plasma membrane and by conformational changes of ligands selectively induced by mechanical force. Mechanical force selectively prolongs NKG2D/MICs bond lifetimes, amplifying their differences with those of NKG2D/ULBPs bonds. Mechanical force induces conformational changes of MIC ligands but not ULBPs to form new interactions with NKG2D. In situ force‐dependent binding affinity of NKG2D interacting with its ligands provides the power for NKG2D to discriminate different ligands. Abstract : Force‐induced alterations of ligand affinity and conformation allow immune receptor NKG2D to recognize different ligands and trigger distinct signaling responses for downstream natural killer cell activation.