ABSTRACT Elevated plasma cholesterol, triglycerides and metabolic complications such as obesity are among the most important risk factors for cardiovascular disease (CVD). Understanding the factors and mechanisms that regulate plasma low-density lipoprotein (LDL) cholesterol levels is of the utmost importance. Increasing hepatic LDL receptor (LDLR) expression leads to increased uptake of LDL cholesterol from the circulation, and has been a successful therapeutic strategy for treating CVD and dyslipidemia. Here, we identify a novel gene that regulates hepatic LDLR and plasma LDL cholesterol levels that is also a locus for LDL-C levels in human Genome-wide Association Studies. In extensive preliminary data, we show that overexpression and silencing (using antisense oligonucleotides, ASOs) of the candidate gene in vivo also alters plasma total and LDL cholesterol levels, and reciprocally regulates the LDLR, suggesting the mechanism of action is directly through targeting the LDLR. In Specific Aim 1 we will determine the molecular mechanism and structural requirements of the regulation of LDLR protein expression and plasma LDL cholesterol levels. In Specific Aim 2, we will use complimentary in vivo gain- and loss-of-function models, including tissue-specific knockout mice and ASOs, to determine the therapeutic potential of specific ASO silencing agents in a relevant disease model of atherosclerosis. In the current proposal we describe a novel post-translational pathway that modulates plasma cholesterol homeostasis. Our findings identify a novel post- translational regulation that can be targeted with ASO silencing agents and therefore has significant therapeutic potential.