Biochemistry, Biophysics, and Structural Biology Commons^™

Determining The Existence And Regulation Of Microlipophagy In Primary Brown And White Adipocytes, Sara C. Arenas De Leon

Biomedical Sciences ETDs

Lipids are one of life’s four main macromolecules and provide essential functions to cells.

The degradation of lipid droplets and mobilization of lipids occurs through lipolysis. Emerging evidence demonstrates evidence of a selective form of autophagy in lipolysis. The process of microlipophagy has only recently been described, and many features of its regulation are still poorly understood. Our recent study showed that inhibiting mammalian target of rapamycin complex 1 (mTORC1) pathway by depletion of Raptor in adipocytes led to an influx of lysosomes and accumulation of lipid droplets within lysosome. Here, we expand on these previous findings. We were able …

Gene Expression Regulation In The Mouse Liver By Mechanistic Target Of Rapamycin Complexes I And Ii, Anthony Poluyanoff

Masters Theses

The mechanistic target of rapamycin (mTOR) is a key serine/threonine protein kinase that functions in complexes mTORC1 and mTORC2. mTORC1, originally discovered due to its sensitivity towards the mTOR inhibitor rapamycin, responds to extracellular growth factor signaling, WNT signaling, and nutrient abundance via glucose and amino acid-triggered signaling. Downstream effectors of mTORC1 include autophagy, mitochondrial metabolic function, protein synthesis, and ribosome biogenesis. mTORC2, initially discovered as a rapamycin-insensitive complex of mTOR, responds to insulin, growth factor signaling, and inflammatory signaling such as tumor necrosis factor-alpha, with its downstream effectors being Akt, a key serine/threonine kinase that functions in cell division …

Nutrient Sensing Pathways Mediating Igfbp1 Phosphorylation In Fgr, Shapnil Bhuiyan

Electronic Thesis and Dissertation Repository

Impairment of fetal oxygen levels and nutrient delivery contributes to fetal growth restriction (FGR), which affects 20% of pregnancies. Such cellular stress induces hepatic Insulin-like Growth Factor Binding Protein 1 (IGFBP1) phosphorylation, which sequesters Insulin-like Growth Factor 1 (IGF-I) and markedly reduces fetal growth signaling. IGFBP1 hyperphosphoryaltion in hypoxia is mediated through the mTOR signaling pathway and through the Amino Acid Response (AAR) pathway during amino acid deprivation. Hypoxia stimulates upstream mTORC1 regulators, AMPK and REDD1 which are well-established upstream regulators of one of the two mTOR complexes, mTORC1. The molecular mechanisms by which upstream mTORC1-driven processes regulate IGFBP1 phosphorylation …

The Role Of Ifrd1 In The Recruitment And Function Of Reserve Stem Cells In Regeneration And Cancer, Mark Anthony Lewis

Arts & Sciences Electronic Theses and Dissertations

Mature cells can reprogram into a proliferative, progenitor-like state to repair tissue following injury and inflammation. Differentiated cells in diverse tissues can become proliferative via a dedicated, evolutionarily conserved program we termed paligenosis. We detailed how paligenosis occurs, in both gastric chief and pancreatic acinar cells, in a step-wise manner that involves: 1) autodegradation of mature cell components; 2) re-expression of progenitor genes; 3) re-entry into the cell cycle. This process is governed by mTORC1, a fundamental cellular energy sensor and regulator of protein translation. Blocking mTORC1 permitted autophagy and metaplastic gene induction but blocked cell cycle re-entry at S-phase. …

Pas Kinase And Tor, Controllers Of Cell Growth And Proliferation, Brooke Jasmyn Cozzens

Theses and Dissertations

Nutrient sensing kinases lie at the heart of cellular health and homeostasis, allowing cells to quickly adapt to changing environments. Target of Rapamycin (TOR) and PAS kinase (PASK, or PASKIN) are two such nutrient kinases, conserved from yeast to man. In yeast, these kinases each have paralogs. The two TOR paralogs in yeast mimic the mammalian TORC1 and TORC2 complexes, except both Tor1 and Tor2 may contribute to TORC1 or TORC2 function. The two PAS kinase paralogs are paired with the TOR paralogs, meaning that both Psk1 and Psk2 regulate TORC1, while Psk2 suppresses a temperature-sensitive allele of Tor2. Herein …

Characterization Of Notch1 And Pi3k-Pten-Akt/Mtor Pathway Interaction In Head And Neck Squamous Cell Carcinoma, Kyriante' Henry

Dissertations & Theses (Open Access)

Head and neck squamous cell carcinoma (HNSCC) affects various mucosal sites of the upper aerodigestive tract, including the nasal and oral cavities, the nasopharynx, and the oropharynx. More than five hundred thousand new cases of HNSCC occurred in 2011 alone, with 50,000 reported cases in the United States. This trend made HNSCC the seventh most common non-skin cancer worldwide (Ferlay et al., 2015). Although significant epidemiological and pathological advancements have been made, survival rates have not improved much over the last 40 years, leaving a mortality rate that remains at approximately 50%. An unbiased drug screen demonstrated that HNSCC cell …

Solving The Structure Of The Raptor-Cct Complex, Grant Ludlam, Barry Willardson

Journal of Undergraduate Research

The protein Raptor is an essential component of the mechanistic target of rapamycin (mTOR) cell signaling complex 1 (mTORC1) (1). The mTORC1 complex is a master regulator of cell growth, making it a high-priority target in cancer and inflammation research (2). Before Raptor can be assembled into the mTORC1, it is first folded by the chaperone protein cytosolic chaperonin containing TCP1 (CCT). CCT is composed of two rings of 8 different subunits, which together form a barrel shape. CCT substrates are folded in the 85 Å wide folding cavity inside the barrel.

Molecular Mechanisms Linking Amino Acid (Leucine) Deprivation To Igfbp-1 Hyperphosphorylation In Fetal Growth Restriction, Niyati M. Malkani

Electronic Thesis and Dissertation Repository

In this study, we explore the molecular mechanisms linking amino acid (leucine) deprivation to IGFBP-1 hyperphosphorylation in vitro. During pregnancy, a maladaptive fetal response to in utero amino acid deprivation leads to Fetal Growth Restriction (FGR). FGR infants display elevated phosphorylated IGFBP-1, which is associated with decreased IGF-I bioavailability. Leucine deprivation inhibits mechanistic target of rapamycin (mTOR) signaling and stimulates the amino acid response (AAR). Using HepG2 cells, a model for fetal hepatocytes, we demonstrate that in leucine deprivation, the AAR modulates total and phosphorylated IGFBP-1 while mTOR mediates total IGFBP-1 secretion only. We also reveal that protein kinases …

The Endosomal Sorting Complex Required For Transport Pathway Mediates Chemokine Receptor Cxcr4 Akt Signaling By Promoting Lysosomal Degradation Of Mtor Antagonist Deptor, Rita Ramkaran Verma

Dissertations

The chemokine receptor CXCR4 is a member of the G protein-coupled receptor (GPCR) family. The cognate ligand for CXCR4 is the C-X-C chemokine known as CXCL12. The CXCL12/CXCR4 signaling axis is essential for a number of developmental processes including organogenesis, vascularization of the GI tract and hematopoiesis. Dysregulated CXCR4 signaling is also implicated in a variety of pathological conditions such as WHIM (Warts, Hypogammaglobunemia, Infections and myelokathexis) syndrome, cardiovascular disease and cancer. Despite its role in several pathologies, the molecular mechanisms mediating CXCR4 signaling are not completely understood. Upon CXCL12 binding to CXCR4, several signaling pathways are activated including the …

Regulation Of Igfbp-1 Phosphorylation In Hypoxia Via Mtor Signaling, Ian Damerill

Electronic Thesis and Dissertation Repository

In this study, we provide novel evidence for a role of fetal liver mTOR signaling in regulating IGF-I bioavailability by modulating IGFBP-1 phosphorylation due to hypoxia – a key factor in the development of reduced fetal growth in utero. We utilized HepG2 cells in vitro and demonstrated a link between mTOR inhibition and hypoxia-induced IGFBP-1 phosphorylation. Using a biological assay for IGF-I receptor autophosphorylation, we demonstrated a functional significance for hypoxia-induced IGFBP-1 phosphorylation in reducing IGF-I bioactivity in vitro. Further, we have implicated a mechanistic link to increased CK2 activity within this regulation. We demonstrate that mTOR inhibition …

Pi3k- And Mtor-Dependent Mechanisms Of Lapatinib Resistance And Resulting Therapeutic Opportunities, Samuel Brady

Dissertations & Theses (Open Access)

Breast cancers with HER2 amplification represent 20-25% of breast cancer cases and are frequently responsive to the HER2 kinase inhibitor lapatinib, but generally for only short duration. We aimed to understand how breast cancers with HER2 amplification become resistant to lapatinib, in order to identify potential therapies that can overcome lapatinib resistance. To establish lapatinib resistance models we treated three HER2+ breast cancer cell lines with lapatinib for several months until they became lapatinib-resistant. We then compared lapatinib-sensitive (parental) cells with their lapatinib-resistant (LapR) counterparts to identify changes conferring lapatinib resistance. We found that activation of PI3K, specifically the p110α …

Lipid Dependence In Ras-Driven Tumors, Darin Salloum

Dissertations, Theses, and Capstone Projects

Over past decade, metabolic alterations in cancer cells have received a substantial amount of interest. It had been established that cancer cells undergo a significant amount of metabolic alterations, and some of these alterations are similar to those in normal highly proliferative cells. However, it is becoming more apparent that many of the metabolic alterations are specific to particular oncogenic signaling pathways. Although altered metabolic machinery makes cancer cells more efficient at promoting growth when nutrients are supplied at the sufficient amounts, the dependency of cancer cells on particular metabolic reprogramming deems cancer cells susceptible to disruptions within metabolic network. …

Metabolic Checkpoints In Cancer Cell Cycle, Mahesh Saqcena

Dissertations, Theses, and Capstone Projects

Growth factors (GFs) as well as nutrient sufficiency regulate cell division in metazoans. The vast majority of mutations that contribute to cancer are in genes that regulate progression through the G1 phase of the cell cycle. A key regulatory site in G1 is the growth factor-dependent Restriction Point (R), where cells get permissive signals to divide. In the absence of GF instructions, cells enter the quiescent G0 state. Despite fundamental differences between GF signaling and nutrient sensing, they both have been confusingly referred to as R and therefore by definition considered to be a singular event in G1. Autonomy from …