The main objective of Project 1 (""""""""Function and Regulation of GPIHBP1 in Lipid Metabolism"""""""") is to define the function of glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) in plasma triglyceride metabolism and in the regulation of fuel delivery to adipose tissue and muscle. This objective is closely aligned with the overall objectives of this PPG, which are to elucidate the basic mechanisms of triglyceride metabolism and adipogenesis, focusing on newly discovered molecules and pathways that are regulated by PPARy. Gpihbpl-deficient mice have severe chylomicronemia, even on a low-fat diet, with plasma triglyceride levels as high as 5000 mg/dl. GPIHBP1 is located on the luminal surface of endothelial cells of heart, muscle, and fat, where lipolysis of plasma triglycerides occurs. Expression of GPIHBP1 in cultured cells confers the ability to bind both lipoprotein lipase (LpL) and chylomicrons, suggesting that GPIHBP1 is a key platform for the lipolytic processing of chylomicrons along the luminal face of capillaries. Although GPIHBP1 is clearly important for the lipolysis of triglyceride-rich lipoproteins, many issues regarding the biological function of GPIHBP1 have not been explored. We have not yet examined the impact of different diets on lipid and glucose metabolism in Gpihbpl-deficient mice, nor do we know why Gpihbpl - deficient mice are protected from diet-induced obesity. Also, the molecular basis for chylomicron and LpL binding to GPIHBP1 is unknown?in particular whether the highly negatively charged domain in GPIHBP1 interacts with positively charged """"""""heparin-binding"""""""" domains in LpL and various apolipoproteins within chylomicrons (e.g., apo-E, apo-B, and apo-AV). Finally, Gpihbpl is highly regulated by fasting and refeeding and by PPARy, but the molecular basis for this regulation has not been defined.
In Specific Aim 1, we will further define the metabolic abnormalities in Gpihbpl-deficient mice.
In Specific Aim 2, we will identify the structural domains of GPIHBP1 required for the binding of LpL and chylomicrons and define the apolipoproteins that mediate the binding of chylomicrons (and other lipoprotein fractions) to Gpihbpl-transfected cells.
In Specific Aim 3, we will define the tissue pattern of Gpihbpl expression and changes in Gpihbpl expression with PPARy agonists and different metabolic conditions.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Program Projects (P01)
Project #
5P01HL090553-03
Application #
8115984
Study Section
Heart, Lung, and Blood Initial Review Group (HLBP)
Project Start
Project End
Budget Start
2010-07-01
Budget End
2011-06-30
Support Year
3
Fiscal Year
2010
Total Cost
$474,394
Indirect Cost
Name
University of California Los Angeles
Department
Type
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
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Rajbhandari, Prashant; Thomas, Brandon J; Feng, An-Chieh et al. (2018) IL-10 Signaling Remodels Adipose Chromatin Architecture to Limit Thermogenesis and Energy Expenditure. Cell 172:218-233.e17
He, Cuiwen; Hu, Xuchen; Weston, Thomas A et al. (2018) Macrophages release plasma membrane-derived particles rich in accessible cholesterol. Proc Natl Acad Sci U S A 115:E8499-E8508
Kristensen, Kristian K; Midtgaard, Søren Roi; Mysling, Simon et al. (2018) A disordered acidic domain in GPIHBP1 harboring a sulfated tyrosine regulates lipoprotein lipase. Proc Natl Acad Sci U S A 115:E6020-E6029
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He, Cuiwen; Weston, Thomas A; Jung, Rachel S et al. (2018) NanoSIMS Analysis of Intravascular Lipolysis and Lipid Movement across Capillaries and into Cardiomyocytes. Cell Metab 27:1055-1066.e3
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Beigneux, Anne P; Miyashita, Kazuya; Ploug, Michael et al. (2017) Autoantibodies against GPIHBP1 as a Cause of Hypertriglyceridemia. N Engl J Med 376:1647-1658
Zhang, Li; Rajbhandari, Prashant; Priest, Christina et al. (2017) Inhibition of cholesterol biosynthesis through RNF145-dependent ubiquitination of SCAP. Elife 6:

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