From the Research Centre and.
the Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, China.
J Biol Chem. 2019 Apr 26;294(17):6871-6887. doi: 10.1074/jbc.RA118.005767. Epub 2019 Mar 1.
EPHB6 is a member of the erythropoietin-producing hepatocellular kinase (EPH) family and a receptor tyrosine kinase with a dead kinase domain. It is involved in blood pressure regulation and adrenal gland catecholamine (CAT) secretion, but several facets of EPHB6-mediated CAT regulation are unclear. In this study, using biochemical, quantitative RT-PCR, immunoblotting, and gene microarray assays, we found that EPHB6 up-regulates CAT biosynthesis in adrenal gland chromaffin cells (AGCCs). We observed that epinephrine content is reduced in the AGCCs from male Ephb6-KO mice, caused by decreased expression of tyrosine hydroxylase, the rate-limiting enzyme in CAT biosynthesis. We demonstrate that the signaling pathway from EPHB6 to tyrosine hydroxylase expression in AGCCs involves Rac family small GTPase 1 (RAC1), MAP kinase kinase 7 (MKK7), c-Jun N-terminal kinase (JNK), proto-oncogene c-Jun, activator protein 1 (AP1), and early growth response 1 (EGR1). On the other hand, signaling via extracellular signal-regulated kinase (ERK1/2), p38 mitogen-activated protein kinase, and ELK1, ETS transcription factor (ELK1) was not affected by EPHB6 deletion. We further report that EPHB6's effect on AGCCs was via reverse signaling through ephrin B1 and that EPHB6 acted in concert with the nongenomic effect of testosterone to control CAT biosynthesis. Our findings elucidate the mechanisms by which EPHB6 modulates CAT biosynthesis and identify potential therapeutic targets for diseases, such as hypertension, caused by dysfunctional CAT biosynthesis.
EPHB6 是促红细胞生成素产生肝细胞激酶 (EPH) 家族的成员，也是一种具有无激酶结构域的受体酪氨酸激酶。它参与血压调节和肾上腺儿茶酚胺 (CAT) 分泌，但 EPHB6 介导的 CAT 调节的几个方面尚不清楚。在这项研究中，我们使用生化、定量 RT-PCR、免疫印迹和基因微阵列分析，发现 EPHB6 上调肾上腺嗜铬细胞 (AGCC) 中的 CAT 生物合成。我们观察到 Ephb6-KO 雄性小鼠的 AGCC 中的肾上腺素含量减少，这是由于 CAT 生物合成的限速酶酪氨酸羟化酶的表达减少所致。我们证明，EPHB6 到 AGCC 中酪氨酸羟化酶表达的信号通路涉及 Rac 家族小 GTP 酶 1 (RAC1)、MAP 激酶激酶 7 (MKK7)、c-Jun N 末端激酶 (JNK)、原癌基因 c-Jun、激活蛋白 1 (AP1) 和早期生长反应 1 (EGR1)。另一方面，EPHB6 缺失对细胞外信号调节激酶 (ERK1/2)、p38 丝裂原激活蛋白激酶和 ELK1、ETS 转录因子 (ELK1) 的信号传递没有影响。我们进一步报告，EPHB6 对 AGCC 的作用是通过 Ephrin B1 的反向信号传递，并且 EPHB6 与睾酮的非基因组效应协同作用来控制 CAT 生物合成。我们的研究结果阐明了 EPHB6 调节 CAT 生物合成的机制，并确定了潜在的治疗靶点，例如由于 CAT 生物合成功能障碍引起的高血压等疾病。
