Date Approved

6-2017

Document Type

Thesis

Degree Name

Master of Science, Molecular Pathology and Immunology

Department

Molecular Biology

College

Graduate School of Biomedical Sciences

First Advisor

Salvatore Caradonna, PhD

Committee Member 1

Grant Gallagher, PhD

Committee Member 2

Scott Gygax, PhD

Committee Member 3

Joseph T. Nickels, PhD

Subject(s)

Metabolic Syndrome, Coenzymes, Transferases, Acyl Coenzyme A, Sterol O-Acyltransferase

Disciplines

Cell Biology | Endocrine System Diseases | Laboratory and Basic Science Research | Medicine and Health Sciences | Molecular Biology | Nutritional and Metabolic Diseases

Abstract

Metabolic Syndrome (MetS) is a combination of risk factors that can over time increase the probability of developing diseases, including cardiovascular disease, type 2 diabetes, non-alcoholic fatty liver disease (NAFLD), and non-alcoholic steatohepatitis (NASH). Acyl-coenzyme-A: cholesterol O-acyl transferase related enzyme required for viability-1, abbreviated as Arv1, is an evolutionarily conserved putative lipid binding protein. Several studies have implicated hArv1 as a critical regulator of lipid transport and trafficking.

Recent work using an Arv1 knock out (KO) mouse model have established a clear link between Arv1 function and the progression of MetS and NAFLD/NASH [unpublished data] [1]. Overall, studies show that KO animals exhibit a reduction in body weight, have less blood circulating cholesterol, are more glucose tolerant and insulin sensitive, and show severely reduced signs of NASH.

Little is known about whether Arv1 binds lipids directly and if it is involved in their transport in any way. Here, we explored whether Arv1 could bind lipid, and if so what was its lipid specificity for binding. Moreover, we undertook a structure/function approach to define the critical residues within the hArv1 homology domain (AHD) required for function. Homogeneous time resolved fluorescence (HTRF) assays were used to assess the interactions between Arv1 and specific phospholipids. We found that hArv1 directly binds to phosphatidylglycerol (PG), phosphatidic acid (PA), cardiolipin (CL) and hosphatidylserine (PS) with decreasing affinity. Using site directed mutagenesis, we identified specific residues that are required for AHD lipid binding. Overall, we have verified that the AHD of Arv1 does have lipid binding activity. Moreover, we have defined critical residues within the AHD that are required for this binding. Understanding the molecular basis for Arv1 lipid binding will further our understanding of how hArv1 may be contributing to the initiation and/or progression of MetS related diseases.

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