Understanding Photoreceptor Trafficking Pathways to the Outer Segment

 描述(申请人提供)：视觉的第一步发生在视网膜，光被光感受器细胞的外层捕捉。这种感光细胞器的独特之处在于，它是一种改良的初级纤毛，由一组参与视觉信号转导的特殊蛋白质组成。这些蛋白质是在细胞体中合成的，并使用离散的细胞内运输机制输送到外节。这些运输机制对光感受器的发育和一般维持至关重要，因为外节是一个动态的结构，必须不断更新。在指导阶段I将完成三个正在进行的、相互关联的项目，这些项目解决如何建立细胞内贩运机制以及外部片段稳定所需的机制。首先，我将破译视紫红质的特征及其运输途径是如何对外节形成所必需的。其次，我将通过分析一个杆状特异的Arf4基因敲除小鼠来确定Arf4参与视紫红质运输到外节的范围。最后，我将识别和提炼编码在外段蛋白质中的活性靶向结构域。这种综合的方法将有助于我过渡到独立的阶段，在这个阶段，我建议阐明信号蛋白是如何在视盘和外节的质膜亚域之间分离的。我的建议对于理解遗传性视网膜退行性变背后的病理生物学过程具有广泛的意义，许多遗传性视网膜退行性变是由影响蛋白质运输到光感受器外段的突变引起的。

 DESCRIPTION (provided by applicant): The first step of vision takes place in the retina where light is captured by the outer segment of photoreceptor cells. This light-sensing organelle is unique in that it is a modified primary cilium that is composed of a specialized group of proteins involved in visual signal transduction. These proteins are synthesized in the cell soma and use discrete intracellular trafficking mechanisms to be delivered to the outer segment. These trafficking mechanisms are critical for development and general maintenance of photoreceptors, as the outer segment is a dynamic structure that must be continuously renewed. During the mentored phase I will complete three ongoing, interconnected projects that address how intracellular trafficking mechanisms are established and required for outer segment stability. First, I will decipher how the features of rhodopsin and its trafficking pathway are necessary for outer segment formation. Second, I will determine the scope of Arf4 involvement in rhodopsin trafficking to outer segments by analyzing a rod-specific Arf4 knockout mouse. Finally, I will identify and refine active targeting domains encoded within proteins localized in the outer segment. This comprehensive approach will facilitate my transition to the independent phase, in which I propose to elucidate how signaling proteins are segregated between the disc and the plasma membrane subdomains of the outer segment. My proposal has broad implications for understanding the pathobiological processes underlying cases of inherited retinal degenerations, many of which are caused by mutations affecting protein trafficking to the photoreceptor outer segment.