蛋白运输对感光细胞的正常功能至关重要，蛋白运输异常最终会导致视网膜变性。已知感光细胞内异戊二烯化蛋白运输到外节段需要PDEδ的帮助，而脂酰化蛋白的运输则受UNC119的调节。 最近的体外实验表明，ARL2和ARL3这两个小G蛋白能促进异戊二烯化蛋白从PDEδ解离，而ARL3还能促使脂酰化蛋白从UNC119解离。为验证ARL2和ARL3参与调节感光细胞内膜蛋白运输，我们将制备感光细胞特异 的Arl2和Arl3基因敲除的小鼠并研究基因敲除对感光细胞内膜蛋白运输定位的影响。另有研究表明视网膜色素变性Rp2基因编码的蛋白是ARL3的GAP蛋白， 我们将分析Rp2基因缺失对小鼠感光细胞内膜蛋白运输定位的影响，确定RP2视网膜色素变性的病理机制。最后，我们将纯化鉴定参与ARL2和ARL3调节膜蛋白运输的的鸟苷酸交换因子GEF。完成本研究课题将增进我们对光细胞内的膜蛋白运输机制以及RP2病理机理的了解。

Intracellular protein trafficking is a key aspect for maintaining proper function of photoreceptors. Deregulation of protein trafficking caused by gene mutations leads to retinal degeneration. Previously we discovered that transport of isoprenylated proteins to photoreceptor outer segments is regulated by an isoprenyl binding protein PDEδ, while that of acylated proteins by an acyl binding protein UNC119. Recent in vitro experiments indicated that ARL2 and ARL3 facilitate release of isoprenylated proteins from PDEδ, and ARL3 also promotes dissociation of acylated proteins from UNC119. In order to test the in vivo role of ARL2 and ARL3 in regulating transport of membrane proteins, we plan to generate photoreceptor-specific knockout mice of Arl2 and Arl3 gene,respectively, and analyze trafficking and targeting of membrane proteins within mice lacking Arl2 or Arl3. Additionally, other evidence showed that the Retinitis Pigmentosa 2 gene encodes the GAP protein of ARL3. We will determine the disease mechanism of Retinitis Pigmentosa 2 by investigating membrane protein trafficking in Rp2 gene-deficient photoreceptors. In the end, we will purify and characterize the guanine exchange factors of ARL2 and ARL3 involved in regulating protein transport in photoreceptors. Completion of the experiments in this proposal will improve our understanding of the function of ARL2, ARL3, and their related proteins in regulating membrane trafficking in photoreceptors as well as the pathological mechanism of the RP2 disease.