Photoreceptor cell degeneration in D. melanogaster

描述(申请人提供)：在视觉系统中，光的光子激活视紫红质启动了一系列称为光转导级联的事件。通过调节蛋白arrestin与视紫红质的结合，在一个水平上实现了级联的失活。视紫红质和arrestin之间通常短暂的相互作用在某些遗传背景下是稳定的，其中arrestin保持未磷酸化的形式。视紫红质和arrestin之间这些稳定的复合体的积累是光感受器细胞凋亡和视网膜变性的直接媒介。光感受器细胞退化的第一步是视紫红质/arrestin复合体通过受体介导的内吞作用内化到细胞体中。视紫红质在光感受器细胞质内聚集成不可溶的聚集体。这定义了一条新的凋亡信号通路，该通路与许多果蝇突变体的视网膜退化有关。有趣的是，在几种不同形式的常染色体显性遗传性视网膜色素变性中，已经观察到视紫红质和arrestin之间稳定的复合体。此外，许多神经元退行性疾病的特点是蛋白质复合体在细胞内积聚，这表明这可能是一种常见的凋亡机制，用于各种疾病。 为了进一步研究这一新的细胞凋亡途径，将采用三种实验方法。1)。我们将确定arrestin和AP2异构体之间的相互作用是否是视紫红质内吞所必需的。2)。我们将研究视紫红质和arrestin的内体运输在激活细胞死亡中的作用。3)。将进行遗传筛选，以分离参与这一新的凋亡信号通路的基因产物。涉及视紫红质/arrestin复合体形成和细胞死亡机制的基因产物将被识别和表征。

DESCRIPTION (provided by applicant): In the visual system, the activation of rhodopsin by a photon of light initiates a chain of events referred to as the phototransduction cascade. The inactivation of the cascade at one level is achieved by the binding of the regulatory protein arrestin to rhodopsin. The normally transient interaction between rhodopsin and arrestin is stabilized in certain genetic backgrounds where arrestin remains in the unphosphorylated form. The accumulation of these stable complexes between rhodopsin and arrestin are direct mediators of photoreceptor cell apoptosis and retinal degeneration. The initial step in photoreceptor cell degeneration is the internalization of the rhodopsin/arrestin complexes into the cell body via receptor-mediated endocytosis. The rhodopsin accumulates in insoluble aggregates within the photoreceptor cytoplasm. This defines a novel apoptotic signaling pathway that is responsible for retinal degeneration in a number of Drosophila mutants. Interestingly, in several different forms of autosomal dominant retinitis pigmentosa stable complexes between rhodopsin and arrestin have been observed. Moreover, many neuronal degenerative disorders are characterized by the intracellular accumulation of protein complexes, suggesting that this may be a common apoptotic mechanism that is used in a wide variety of diseases. In an effort to further characterize this novel apoptotic pathway three experimental approaches will be undertaken. 1). We will determine if an interaction between arrestin and the AP2 heterotetramer is essential for rhodopsin endocytosis. 2). We will examine the role of endosomal trafficking of rhodopsin and arrestin in the activation of cell death. 3). A genetic screen will be conducted to isolate gene products involved in this novel apoptotic signaling pathway. Gene products involved in coupling rhodopsin/arrestin complex formation with the cell death machinery will be identified and characterized.