Date of Graduation
School of Medicine
Microbiology, Immunology, and Cell Biology
Photoreceptor cells are specialized neurons optimized for the capture of light and the signal transduction to downstream cells that provides vision. Proper photoreceptor cell function depends heavily on efficient regulation of protein-protein interactions both during development and in the adult retina. Despite years of research on photoreceptor development and protein trafficking, the components vital to these processes are poorly understood. Interestingly, there are a number of small GTPases, which act as molecular switches, that are believed to play a role in regulating such interactions throughout the process of ciliogenesis, OS formation and protein trafficking. However, research into the role of these proteins in photoreceptor cells is in its infancy. Moreover, there are a growing number of discoveries linking small GTPases with photoreceptor mediated disease, such as ARL6, ARL2, ARL3, and RAB28. In this work I characterize the role of the small GTPases, ARL2 and ARL3, in the regulation of photoreceptor cell protein trafficking and OS development. In order to study these proteins in vivo, we utilized site-direct mutagenesis and transgenesis to create multiple animal models. Through these models, we have discovered that ARL2 and ARL3 serve different primary functions in vivo despite their high sequence similarity and sharing a number of binding partners. In Chapter 1 of this dissertation, we discuss the potential mechanisms and key players of photoreceptor cell ciliary development and protein trafficking. In Chapter 2, data is presented from the first animal model we generated expressing dominant active ARL3-Q71L. We further propose a mechanistic model for the role of ARL3 in prenylated protein trafficking in photoreceptor cells in which it acts to displace lipid modified cargo at the cilium. Chapter 3 focuses on data obtained from our dominant active ARL2-Q70L transgenic animal model. Here we discuss the potential role for ARL2 in ciliogenesis and OS formation in photoreceptor cells highlighting the novel observation that proper ARL2 function is necessary for cilia localization and axonemal extension. Finally, in Chapter 4 we discuss the data obtained during my dissertation and strategies to fill the gaps in knowledge that remain concerning the role of these small GTPases in photoreceptor cells. This work provides a strong foundation for the mechanisms of ARL2 and ARL3 action in photoreceptor cells. Complete elucidation of the components involved in photoreceptor protein trafficking and OS formation will provide the data necessary to generate novel therapeutics targeting the pathways underlying photoreceptor mediated blinding disease.
Wright, Zachary C., "Complex Regulation of Protein Trafficking and Photoreceptor Cell Development by Small GTPases" (2016). Graduate Theses, Dissertations, and Problem Reports. 6979.