Memmer Stefanie, Weil Sandra, Beyer Steffen, Zöller Tobias, Peters Eike, Hartmann Jessica, Steinle Alexander, Koch Joachim
From the Institute of Medical Microbiology and Hygiene, University of Mainz Medical Center, 55131 Mainz, Germany.
the Institute for Tumor Biology and Experimental Therapy, Georg-Speyer-Haus, 60596 Frankfurt am Main, Germany.
J Biol Chem. 2016 Dec 2;291(49):25427-25438. doi: 10.1074/jbc.M116.742981. Epub 2016 Oct 17.
The natural cytotoxicity receptor (NCR) NKp30 (CD337) is a key player for NK cell immunosurveillance of infections and cancer. The molecular details of ligand recognition and its connection to CD3ζ signaling remain unsolved. Here, we show that the stalk domain (KEHPQLGAGTVLLLR) of NKp30 is very sensitive to sequence alterations, as mutations lead to impaired ligand binding and/or signaling capacity. Surprisingly, the stalk domains of NKp30 and NKp46, another NCR employing CD3ζ for signaling, were not exchangeable without drastic deficiencies in folding, plasma membrane targeting, and/or ligand-induced receptor signaling. Further mutational studies, N-glycosylation mapping, and plasma membrane targeting studies in the absence and presence of CD3ζ suggest two interconvertible types of NCR-CD3ζ assemblies: 1) a signaling incompetent structural NKp30-CD3ζ complex and 2) a ligand-induced signaling competent NKp30-CD3ζ complex. Moreover, we propose that ligand binding triggers translocation of Arg-143 from the membrane interface into the membrane to enable alignment with oppositely charged aspartate residues within CD3ζ and activation of CD3ζ-signaling.
天然细胞毒性受体（NCR）NKp30（CD337）是NK细胞对感染和癌症进行免疫监视的关键分子。配体识别的分子细节及其与CD3ζ信号传导的联系仍未解决。在此，我们表明NKp30的柄部结构域（KEHPQLGAGTVLLLR）对序列改变非常敏感，因为突变会导致配体结合和/或信号传导能力受损。令人惊讶的是，NKp30和NKp46（另一种利用CD3ζ进行信号传导的NCR）的柄部结构域在折叠、质膜靶向和/或配体诱导的受体信号传导方面没有严重缺陷的情况下是不可互换的。在有无CD3ζ的情况下进行的进一步突变研究、N-糖基化图谱分析和质膜靶向研究表明，NCR-CD3ζ组装存在两种可相互转换的类型：1）信号传导无活性的结构型NKp30-CD3ζ复合物和2）配体诱导的信号传导有活性的NKp30-CD3ζ复合物。此外，我们提出配体结合触发Arg-143从膜界面转移到膜内，以便与CD3ζ内带相反电荷的天冬氨酸残基对齐并激活CD3ζ信号传导。
