Authors
Egri, Shawn B.Faculty Advisor
Kuang ShenAcademic Program
InterdisciplinaryUMass Chan Affiliations
Program in Molecular MedicineDocument Type
Doctoral DissertationPublication Date
2023-03-10Keywords
GTPase-Activating ProteinBiochemistry
Structural Biology
Cell Growth
mTORC1
Nutrient Sensing
Signaling
GTPase
Cancer
Biology
Single Particle Cryo-EM
Metadata
Show full item recordAbstract
In order to initiate cellular growth, a cell must weigh its nutrient availability against its anabolic needs. A critical pathway responsible for this process is the mechanistic target of rapamycin complex 1 (mTORC1) pathway. mTORC1 is a serine threonine protein kinase complex that will phosphorylate its downstream substrates in order to promote anabolic reactions. mTORC1 activity is dependent upon the Rag GTPase heterodimer. In the presence of amino acids, the Rags will activate mTORC1 by promoting its translocation to the lysosomal surface. In contrast, amino acid withdrawal results in mTORC1 inactivation. In order to ensure faithful mTORC1 signaling, the nucleotide loading state of the Rag GTPase is tightly regulated. In this thesis, we combine biochemical and biophysical approaches to investigate the molecular mechanism of how the nucleotide loading state of the Rag GTPase subunits are regulated. First, we characterized a conserved interdomain hydrogen bond within the Rag GTPases that is responsible for maintaining the GDP-bound state of the subunits. Elimination of this hydrogen bond abolishes the ability of the Rag GTPase to maintain its functional state, resulting in dysregulated mTORC1 signaling. Second, we utilize cryo-EM to describe the molecular mechanism of how GATOR1, a potent negative regulator of the mTORC1 pathway, modulates the nucleotide loading state of the Rag subunits in response to nutrient deprivation. These results reveal the molecular details of how the Rag GTPases are regulated in response to changes in amino acid availability, and furthermore how disruptions to those mechanisms can lead to dysregulation of the mTORC1 signaling pathway.DOI
10.13028/pbfs-dm43Permanent Link to this Item
http://hdl.handle.net/20.500.14038/51921Rights
Copyright © 2023 EgriDistribution License
https://creativecommons.org/licenses/by/4.0/ae974a485f413a2113503eed53cd6c53
10.13028/pbfs-dm43