Type
Text
Type
Dissertation
Advisor
Brown, Deborah | Zong, We-xing | Lin, Richard | Czaplinski, Kevin | Yue, Zhenyu.
Date
2015-12-01
Keywords
autophagy, endocytosis, mTOR, PI 3-kinase, Rab7, Vps34 | Molecular biology
Department
Department of Biochemistry and Cell Biology.
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/76918
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
Vps34 is the sole member of the Class III phosphoinositide 3-kinases (PI3Ks) identified in mammals thus far. It phosphorylates phosphatidylinositol (PI) to generate PI(3)P on intracellular membranes. Previous work has suggested that Vps34 is important for the protein degradation pathways of autophagy and endocytosis, as well as nutrient-induced mTOR signaling. However, due to the pluripotent nature of available PI3K inhibitors, a clear understanding of the functions of mammalian Vps34 remains to be illustrated. To investigate the precise role of Vps34 in these processes, I have generated and characterized mice with conditional genetic ablation of Vps34. Mice with liver or heart-specific deletion of Vps34 suffer from organ enlargement, excess lipid accumulation and organ dysfunction. Mice and embryonic fibroblasts (MEFs) lacking Vps34 are completely deficient in autophagy and instead accumulate intracellular aggregates. Vps34-deficient MEFs display a growth defect and dramatically reduced amino acid-induced mTOR signaling. In addition, while it is widely believed that Vps34 controls the early stages of endocytosis, I find that early endosome functions such as transferrin recycling and EEA1 recruitment are not affected by Vps34 knockout. This is attributed to a compensatory increase of Rab5-GTP which is sufficient to support these early endosome functions. Furthermore, I find that Vps34 is essential for late endocytic functions like cargo degradation and endosome morphology. Interestingly, the deletion of Vps34 leads to a dramatic increase in Rab7-GTP levels. In the absence of Vps34, the Rab7 GTPase activating protein Armus, which limits Rab7 activity, loses its correct intracellular localization. Increased Rab7-GTP levels in Vps34 knockout cells translate to increased effector RILP recruitment, which may enhance v-ATPase activity and cause intracellular vacuolization as well as failure of endosome-lysosome fusion. These results solidify our understanding of the role of mammalian Vps34 in autophagy and uncover a previously unappreciated role for Vps34 in maintaining late endosome functions via the regulation of Rab7. | 115 pages
Recommended Citation
Jaber, Nadia, "Class III phosphoinositide 3-kinase Vps34 in autophagy, endocytosis, and nutrient-induced signaling" (2015). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 2791.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/2791