N-myristoylation regulates the axonal distribution of the Fragile X-related protein FXR2P
N-myristoylation regulates the axonal distribution of the Fragile X-related protein FXR2P
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DOI：
10.1016/j.mcn.2014.08.003
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发表时间：
2014-09-01
影响因子：
3.5
通讯作者：
Fallon, Justin R.
中科院分区：
文献类型：
--
作者：
Stackpole, Emily E.;Akins, Michael R.;Fallon, Justin R.
脆性X综合征是由脆性X智力低下蛋白（FMRP）功能丧失引起的遗传性智力残疾和自闭症的主要原因。FMRP是一种RNA结合蛋白，调节体树突区室中的局部蛋白质合成。然而，新的证据也表明FMRP在轴突和突触前功能中的重要作用。特别地，FMRP及其同源物FXR 2 P在轴突上和突触前定位于脑中称为脆性X颗粒（FXG）的离散内源性结构。FXR 2 P是所有FXG的组分，并且对于FMRP到这些结构的轴突和突触前定位是必需的。因此，我们试图确定和表征调控其轴突定位的FXR 2 P的结构特征。序列分析显示，FXR 2 P具有FMRP中不存在的共有N-末端豆蔻酰化序列（MGXXXS）。使用点击化学与野生型和unmyristoylatable G2 A突变体，我们证明，FXR 2 P是N-豆蔻酰化甘氨酸2，建立它作为一种脂质修饰的RNA结合蛋白。为了研究FXR 2 P N-豆蔻酰化在神经元中的作用，我们产生了荧光标记的野生型和不可豆蔻酰化的FXR 2 P（分别为WT和G2 A），并在原代皮质培养物中表达它们。FXR 2 P（WT）和FXR 2 P（G2 A）均以相等的总体水平表达，并且能够形成含FMRP的轴突颗粒。然而，FXR 2 P（WT）颗粒主要限于近端轴突节段，而不可肉豆蔻酰化的FXR 2 PG 2A形成的颗粒定位在整个轴突轴，包括在生长锥。这些研究表明，N-末端豆蔻酰化的RNA结合蛋白FXR 2 P调节其定位在轴突乔木。此外，由于FMRP定位在轴突结构域内需要其与FXR 2 P的关联，这些发现表明FXR 2 P脂质修饰是FMRP轴突和突触前分布的控制点。(C)2014爱思唯尔公司All rights reserved.
Fragile X syndrome, the leading cause of inherited intellectual disability and autism, is caused by loss of function of Fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that regulates local protein synthesis in the somatodendritic compartment. However, emerging evidence also indicates important roles for FMRP in axonal and presynaptic functions. In particular, FMRP and its homologue FXR2P localize axonally and presynaptically to discrete endogenous structures in the brain termed Fragile X granules (FXGs). FXR2P is a component of all FXGs and is necessary for the axonal and presynaptic localization of FMRP to these structures. We therefore sought to identify and characterize structural features of FXR2P that regulate its axonal localization. Sequence analysis reveals that FXR2P harbors a consensus N-terminal myristoylation sequence (MGXXXS) that is absent in FMRP. Using click chemistry with wild type and an unmyristoylatable G2A mutant we demonstrate that FXR2P is N-myristoylated on glycine 2, establishing it as a lipid-modified RNA binding protein. To-investigate the role of FXR2P N-myristoylation in neurons we generated fluorescently tagged wild type and unmyristoylatable FXR2P (WT and G2A, respectively) and expressed them in primary cortical cultures. Both FXR2P(WT) and FXR2P(G2A) are expressed at equivalent overall levels and are capable of forming FMRP-containing axonal granules. However, FXR2P(WT) granules are largely restricted to proximal axonal segments while granules formed with unmyristoylatable FXR2PG2A are localized throughout the axonal arbor, including in growth cones. These studies indicate that N-terminal myristoylation of the RNA binding protein FXR2P regulates its localization within the axonal arbor. Moreover, since FMRP localization within axonal domains requires its association with FXR2P, these findings suggest that FXR2P lipid modification is a control point for the axonal and presynaptic distribution of FMRP. (C) 2014 Elsevier Inc. All rights reserved.