Studies on Cellular Nutrient Responses and Protein Degradation
type: CreativeWork
description: I have worked on two projects. The first project investigates mechanisms involved in cellular responses to amino acids. Amino-acid abundance promotes protein synthesis and cell growth via activation of the protein kinase mTOR, while amino-acid deprivation promotes protein degradation by autophagy. The heterodimeric G protein coupled receptor (GPCR) T1R1-T1R3 can act as an extracellular sensor for amino acids, promoting mTOR activity while repressing autophagy in cells. Quantitative PCR analysis revealed that T1R3 depletion increases mRNA expression of amino acid transporters as a compensatory mechanism induced by perceived starvation. The arrestin proteins can bind GPCRs to mediate their internalization or to facilitate downstream signaling. I tested the hypothesis that β-arrestin 2 might participate in regulation of mTOR activity and autophagy by amino acids. siRNA-mediated β-arrestin 2 depletion decreased T1R1-T1R3 protein expression, reduced mTOR activity and increased autophagy in different cell types. β-arrestin 2 loss increased phosphorylation of the MAP kinase ERK1/2, which may play a role in promoting autophagy. Taken together, these findings demonstrate a role for β-arrestin 2 in promoting mTOR activity and suppressing autophagy. The second project examined the role of different protein degradation pathways and an E3 ubiquitin ligase UBR5 in regulating the stability of the protein kinase WNK1, a key regulator of cellular ion homeostasis. Mutations that increase WNK1 protein expression cause familial hypertension, highlighting the importance of understanding the regulation of WNK1 protein expression. Cycloheximide chase experiments revealed that WNK1 degradation may be complex, as it does not follow simple exponential decay kinetics. Pharmacological inhibition of different protein degradation pathways showed that autophagy and the calpain system of non-lysosomal cysteine proteases, but not the proteasome, can promote WNK1 degradation. Inhibition of the prote…
abstract: I have worked on two projects. The first project investigates mechanisms involved in cellular responses to amino acids. Amino-acid abundance promotes protein synthesis and cell growth via activation of the protein kinase mTOR, while amino-acid deprivation promotes protein degradation by autophagy. The heterodimeric G protein coupled receptor (GPCR) T1R1-T1R3 can act as an extracellular sensor for amino acids, promoting mTOR activity while repressing autophagy in cells. Quantitative PCR analysis revealed that T1R3 depletion increases mRNA expression of amino acid transporters as a compensatory mechanism induced by perceived starvation. The arrestin proteins can bind GPCRs to mediate their internalization or to facilitate downstream signaling. I tested the hypothesis that β-arrestin 2 might participate in regulation of mTOR activity and autophagy by amino acids. siRNA-mediated β-arrestin 2 depletion decreased T1R1-T1R3 protein expression, reduced mTOR activity and increased autophagy in different cell types. β-arrestin 2 loss increased phosphorylation of the MAP kinase ERK1/2, which may play a role in promoting autophagy. Taken together, these findings demonstrate a role for β-arrestin 2 in promoting mTOR activity and suppressing autophagy. The second project examined the role of different protein degradation pathways and an E3 ubiquitin ligase UBR5 in regulating the stability of the protein kinase WNK1, a key regulator of cellular ion homeostasis. Mutations that increase WNK1 protein expression cause familial hypertension, highlighting the importance of understanding the regulation of WNK1 protein expression. Cycloheximide chase experiments revealed that WNK1 degradation may be complex, as it does not follow simple exponential decay kinetics. Pharmacological inhibition of different protein degradation pathways showed that autophagy and the calpain system of non-lysosomal cysteine proteases, but not the proteasome, can promote WNK1 degradation. Inhibition of the prote…
author: Ghosh, Anwesha
language: en
keywords: Autophagy, Intercellular Signaling Peptides and Proteins, TOR Serine-Threonine Kinases, Ubiquitin-Protein Ligases
date published: 2017-09-05T14:50:45Z
date modified: 2026-07-24T05:52:36Z
provider: University of Texas Southwestern Medical Center
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Texas Southwestern Medical Center

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2152.5/4204