The KBTBD6/7-DRD2 axis regulates pituitary adenoma sensitivity to dopamine agonist treatment
The KBTBD6/7-DRD2 axis regulates pituitary adenoma sensitivity to dopamine agonist treatment
复制标题
KBTBD6/7-DRD2 轴调节垂体腺瘤对多巴胺激动剂治疗的敏感性
DOI：
10.1007/s00401-020-02180-4
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发表时间：
2020-06-22
影响因子：
12.7
通讯作者：
Wu, Zhe Bao
中科院分区：
文献类型：
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作者：
Liu, Yan Ting;Liu, Fang;Wu, Zhe Bao
垂体腺瘤（PA）是最常见的颅内肿瘤之一，约40%的PA是泌乳素瘤。多巴胺激动剂（DA），如卡麦角林（CAB），已成功用于治疗泌乳素瘤。多巴胺2型受体（DRD 2）的表达决定了DA的治疗效果，但DRD 2调节的分子机制尚未完全了解。在这项研究中，我们首先证明了DRD 2经历了蛋白酶体介导的降解。我们进一步采用酵母双杂交系统，并确定了kelch重复和BTB（POZ）结构域包含7（KBTBD 7），一个底物接头的CUL 3-RING泛素（Ub）连接酶复合物，作为DRD 2相互作用蛋白。KBTBD 6/7在5个泛素化位点（K221、K226、K241、K251和K258）与DRD 2直接相互作用并泛素化DRD 2。CAB是一种高亲和力DRD 2激动剂，可诱导DRD 2内化，细胞质DRD 2在KBTBD 6/7的控制下通过遍在蛋白化降解，其活性减弱了CAB介导的对AKT/mTOR途径的抑制。使用CRISPR-Cas9技术产生KBTBD 7敲除（KO）小鼠，其中与WT小鼠相比，DRD 2蛋白的静态水平在脑垂体、丘脑和心脏中升高。KBTBD 6/7与DRD 2在垂体瘤中的表达呈负相关。此外，KBTBD 7在多巴胺耐药的泌乳素瘤中高度表达，但在多巴胺敏感的泌乳素瘤中表达水平较低。KBTBD 6/7的敲除使MMQ细胞和原代垂体瘤细胞对CAB处理敏感。相反，KBTBD 7过表达增加了雌激素诱导的原位大鼠泌乳素瘤模型的CAB抵抗。总之，我们的研究结果揭示了DRD 2蛋白降解的新机制，并表明KBTBD 6/7-DRD 2轴调节PA对DA治疗的敏感性。因此，KBTBD 6/7可能成为垂体瘤的一个有前途的治疗靶点。
Pituitary adenoma (PA) is one of the most common intracranial tumors, and approximately 40% of all PAs are prolactinomas. Dopamine agonists (DAs), such as cabergoline (CAB), have been successfully used in the treatment of prolactinomas. The expression of dopamine type 2 receptor (DRD2) determines the therapeutic effect of DAs, but the molecular mechanisms of DRD2 regulation are not fully understood. In this study, we first demonstrated that DRD2 underwent proteasome-mediated degradation. We further employed the yeast two-hybrid system and identified kelch repeat and BTB (POZ) domain containing 7 (KBTBD7), a substrate adaptor for the CUL3-RING ubiquitin (Ub) ligase complex, as a DRD2-interacting protein. KBTBD6/7 directly interacted with, and ubiquitinated DRD2 at five ubiquitination sites (K221, K226, K241, K251, and K258). CAB, a high-affinity DRD2 agonist, induced DRD2 internalization, and cytoplasmic DRD2 was degraded via ubiquitination under the control of KBTBD6/7, the activity of which attenuated CAB-mediated inhibition of the AKT/mTOR pathway. KBTBD7 knockout (KO) mice were generated using the CRISPR-Cas9 technique, in which the static level of DRD2 protein was elevated in the pituitary gland, thalamus, and heart, compared to that of WT mice. Consistently, the expression of KBTBD6/7 was negatively correlated with that of DRD2 in human pituitary tumors. Moreover, KBTBD7 was highly expressed in dopamine-resistant prolactinomas, but at low levels in dopamine-sensitive prolactinomas. Knockdown of KBTBD6/7 sensitized MMQ cells and primary pituitary tumor cells to CAB treatment. Conversely, KBTBD7 overexpression increased CAB resistance of estrogen-induced in situ rat prolactinoma model. Together, our findings have uncovered the novel mechanism of DRD2 protein degradation and shown that the KBTBD6/7-DRD2 axis regulates PA sensitivity to DA treatment. KBTBD6/7 may thus become a promising therapeutic target for pituitary tumors.