Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI.
Department of Internal Medicine/Division of Hematology/Oncology, University of Michigan Rogel Cancer Center, Ann Arbor, MI.
J Cell Biol. 2021 Jul 5;220(7). doi: 10.1083/jcb.202009179.
Myeloproliferative neoplasms (MPNs) are frequently driven by mutations within the C-terminal domain (C-domain) of calreticulin (CRT). CRTDel52 and CRTIns5 are recurrent mutations. Oncogenic transformation requires both mutated CRT and the thrombopoietin receptor (Mpl), but the molecular mechanism of CRT-mediated constitutive activation of Mpl is unknown. We show that the acquired C-domain of CRTDel52 mediates both Mpl binding and disulfide-linked CRTDel52 dimerization. Cysteine mutations within the novel C-domain (C400A and C404A) and the conserved N-terminal domain (N-domain; C163A) of CRTDel52 are required to reduce disulfide-mediated dimers and multimers of CRTDel52. Based on these data and published structures of CRT oligomers, we identify an N-domain dimerization interface relevant to both WT CRT and CRTDel52. Elimination of disulfide bonds and ionic interactions at both N-domain and C-domain dimerization interfaces is required to abrogate the ability of CRTDel52 to mediate cell proliferation via Mpl. Thus, MPNs exploit a natural dimerization interface of CRT combined with C-domain gain of function to achieve cell transformation.
骨髓增殖性肿瘤（MPNs）常由钙网织蛋白（CRT）C 末端结构域（C 域）内的突变驱动。CRTDel52 和 CRTIns5 是反复出现的突变。致癌转化需要突变的 CRT 和血小板生成素受体（Mpl），但 CRT 介导的 Mpl 组成性激活的分子机制尚不清楚。我们发现获得性 CRTDel52 的 C 域介导 Mpl 结合和二硫键连接的 CRTDel52 二聚体。CRTDel52 的新型 C 域（C400A 和 C404A）和保守的 N 端结构域（N 域；C163A）内的半胱氨酸突变，可减少二硫键介导的 CRTDel52 二聚体和多聚体。基于这些数据和 CRT 寡聚体的已发表结构，我们确定了与 WT CRT 和 CRTDel52 都相关的 N 域二聚体界面。消除 N 域和 C 域二聚体界面的二硫键和离子相互作用，可消除 CRTDel52 通过 Mpl 介导细胞增殖的能力。因此，MPNs 利用 CRT 的天然二聚体界面结合 C 域获得功能来实现细胞转化。
