Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
J Cell Sci. 2009 Oct 15;122(Pt 20):3780-90. doi: 10.1242/jcs.048397. Epub 2009 Sep 29.
X-linked recessive Emery-Dreifuss muscular dystrophy (EDMD) is caused by loss of emerin, a nuclear-membrane protein with roles in nuclear architecture, gene regulation and signaling. Phosphoproteomic studies have identified 13 sites of tyrosine phosphorylation in emerin. We validated one study, confirming that emerin is hyper-tyrosine-phosphorylated in Her2-overexpressing cells. We discovered that non-receptor tyrosine kinases Src and Abl each phosphorylate emerin and a related protein, LAP2beta, directly. Src phosphorylated emerin specifically at Y59, Y74 and Y95; the corresponding triple Y-to-F (;FFF') mutation reduced tyrosine phosphorylation by approximately 70% in vitro and in vivo. Substitutions that removed a single hydroxyl moiety either decreased (Y19F, Y34, Y161F) or increased (Y4F) emerin binding to BAF in cells. Y19F, Y34F, Y161F and the FFF mutant also reduced recombinant emerin binding to BAF from HeLa lysates, demonstrating the involvement of both LEM-domain and distal phosphorylatable tyrosines in binding BAF. We conclude that emerin function is regulated by multiple tyrosine kinases, including Her2, Src and Abl, two of which (Her2, Src) regulate striated muscle. These findings suggest roles for emerin as a downstream effector and ;signal integrator' for tyrosine kinase signaling pathway(s) at the nuclear envelope.
X 连锁隐性先天性肌营养不良症（EDMD）是由核膜蛋白 emerin 的缺失引起的，该蛋白在核结构、基因调控和信号转导中发挥作用。磷酸蛋白质组学研究已经鉴定出 emerin 中的 13 个酪氨酸磷酸化位点。我们验证了一项研究，证实 Her2 过表达细胞中的 emerin 呈高酪氨酸磷酸化状态。我们发现非受体酪氨酸激酶 Src 和 Abl 均可直接磷酸化 emerin 和相关蛋白 LAP2β。Src 特异性地在 emerin 的 Y59、Y74 和 Y95 处磷酸化 emerin；相应的三重 Y 到 F（FFF'）突变使体外和体内的酪氨酸磷酸化减少了约 70%。去除单个羟基的取代（Y19F、Y34、Y161F）要么降低（Y19F、Y34）要么增加（Y4F）了 emerin 在细胞中与 BAF 的结合。Y19F、Y34F、Y161F 和 FFF 突变体也降低了来自 HeLa 裂解物的重组 emerin 与 BAF 的结合，证明了 LEM 结构域和远端可磷酸化的酪氨酸都参与了 BAF 的结合。我们得出结论，emerin 的功能受多种酪氨酸激酶调节，包括 Her2、Src 和 Abl，其中两种（Her2、Src）调节横纹肌。这些发现表明 emerin 作为核膜上酪氨酸激酶信号通路的下游效应子和信号整合子发挥作用。
