Membrane Protein Transport in Photoreceptors

描述(申请人提供)：光感受器外节膜，最初的光子捕获启动光转导的位置，经历更新，在整个生命周期中每隔10天进行一次完全更换。对手机完整性的挑战与这篇文章有关 在光感受器的整个生命周期中，替换蛋白从内到外的生物合成输送。复杂的转运途径需要多种成分，如酰基结合蛋白、Rab GTP酶和中心素。这一应用将识别：i)参与膜蛋白囊泡运输的关键Rab GTP酶，以及ii)参与纤毛运输的中心蛋白。目标1将重点介绍Rab GTP酶在光感受器泡运输中的作用。RAB(脑内RAS类似物)蛋白是RAS超基因家族的成员，主要参与膜蛋白转运。目前已鉴定出70多种不同的Rab多肽。目的1a主要研究在非洲爪哇和果蝇模型中对光感受器运输具有重要作用的Rab8和Rab11亚型。令人惊讶的是，小鼠Rab8a/Rab11a双敲除并不产生缺陷的运输表型。因此，我们将重点关注密切相关的亚型，以确定负责膜蛋白组织和视紫红质运输的关键Rab蛋白。目的1b研究最近发现与隐性人类视锥/视杆细胞营养不良相关的Rab28基因。目的2将研究中心体蛋白的功能，称为“中心蛋白”，它是钙调素超家族的20kD EF-手钙结合蛋白(四个EF-手基序)。Centrins首先在单细胞绿藻中被描述，在那里它们与鞭毛基底器相关。光感受器中心蛋白(亚型1-4)位于睫状腔和基底体，在那里它们通过其T？γ亚基与转导蛋白结合。一种假说认为，中心素可能参与调节转导蛋白从外到内的转位，反之亦然。作为初步结果，我们发现Centin1是小鼠精子发生过程中核-基底体连接所必需的，Centin2调控ACIII和通道亚单位在嗅觉神经元中的运输。本研究的目的是确定与基底体和/或连接纤毛轴丝紧密相关的光感受器中心蛋白3和中心蛋白4的作用。我们希望建立视网膜变性综合征疾病的小鼠模型，例如Joubert或High-Loken综合征。

DESCRIPTION (provided by applicant): Photoreceptor outer segment membranes, the site of initial photon capture initiating phototransduction, undergo renewal with total replacement occurring at ten day intervals throughout life. A challenge to cellular integrity concerns the post biosynthetic delivery of replacement proteins from the inner, to the outer, segment over the lifetime of the photoreceptor. Complex trafficking pathways require multiple components, such as acyl-binding proteins, Rab GTPases and centrins. This application will identify: i) key Rab GTPases involved in vesicular transport of membrane protein, and ii) centrins participating in ciliary transport. Aim 1 will focus on Rab GTPases in photoreceptor vesicular transport. Rab (Ras analog in brain) proteins are members of the Ras supergene family involved mainly in membrane protein trafficking. More than 70 distinct Rab polypeptides have been identified. Aim 1a focuses on Rab8 and Rab11 isoforms which are known to be important for photoreceptor trafficking in Xenopus and Drosophila models. Surprisingly, a mouse Rab8a/Rab11a double knockout does not produce a defective trafficking phenotype. Therefore, we will focus on closely-related isoforms to identify key Rab proteins responsible for membrane protein organization and rhodopsin trafficking. Aim 1b investigates Rab28, shown recently associated with recessive human cone/rod dystrophy. Aim 2 will examine the function of centrosomal proteins, called "centrins," which are 20kD EF- hand calcium binding proteins (four EF-hand motifs) of the calmodulin superfamily. Centrins were first described in unicellular green algae where they are associated with the flagellar basal apparatus. Photoreceptor centrins (isoforms 1-4) are located in the ciliary lumen and basal body where they associate with transducin via its Tßγ-subunits. One hypothesis is that centrins may be involved in regulation of transducin translocation from the outer, to the inner, segment or vice-versa. As preliminary results, we found that centrin1 is required for the nucleus-basal body connection during mouse spermiogenesis, and centrin2 regulates trafficking of ACIII and channel subunits in olfactory sensory neurons. This aim seeks to identify the roles of photoreceptor centrin3 and centrin4 which associate strongly with the basal body and/or connecting cilium axoneme. We expect to generate mouse models of syndromic disease with retina degeneration, e.g., Joubert or Senior-Loken syndromes.