Date of Award
J. Todd Blankenship
Intracellular protein trafficking, GTPase
Intracellular protein trafficking is the movement of membrane-bound organelles to and from requisite locations within the cell. Small GTPases are a critical component to the spatiotemporal accuracy of intracellular trafficking pathways as they determine the specificity and direction of organelle transport. There exists over 150 small GTPases categorized into 5 sub-families and are employed across all cell types. Despite their universal expression and relevance to cellular function, small GTPases remain incompletely understood across tissue types. In various instances, the trafficking pathway of a particular Rab in one cell type may belong to a completely disparate pathway in another cell type. Rab27 has been shown to traffic melanosomes in epithelial tissue, however, in endothelium, Rab27 has been linked to the trafficking of an endothelial specific vesicle known as the Weibel-Palade body (WPB). However, information is lacking as to whether Rab27 trafficking is applicable to sprouting angiogenesis. Rab35 is a well-studied Rab involved in a broad spectrum of cellular functions, including cytokinesis, cell migration, and cell polarity across tissue types. Surprisingly, Rab35 lacks investigation in endothelial cells. Like Rab35, Arf6 is also well-studied and implicated in several different cellular functions. It is most associated with cytoskeletal rearrangements, cell migration and endocytosis. Some Arf6 data exists in endothelial cells, but information is lacking on its role in sprouting angiogenesis and lumen formation. Rab8 is reported to traffic cargo exiting the trans-Golgi network bound for the apical membrane. The relevance of Rab8 to apical trafficking in endothelium remains unknown. Our data agrees that Rab27 is linked to the WPB pathway, and it is WPB cargo, Angiopoietin-2, that causes the hyper-sprouting phenotype observed in the absence of Rab27. In our hands, Rab35 does impact a range of endothelial cell processes. The extensive effects Rab35 induces is due to Rab35’s regulation of the actin cytoskeleton. We found that Arf6 also regulates the actin cytoskeleton but is critical to the management of transmembrane proteins important for sprouting angiogenesis and lumen formation. Finally, our results show that Rab8 is indeed important to apical trafficking in endothelium, independent of the WPB pathway. Together, these investigations provide insight to the divergent trafficking patterns of small GTPases in endothelium.
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Francis, Caitlin, "Small GTPase Regulated Intracellular Protein Trafficking in Endothelium" (2023). Electronic Theses and Dissertations. 2172.
Received from ProQuest
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