Apolipoprotein (apo) E plays critical roles in lipid and lipoprotein metabolism both extracellularly and intracellularly. Recent studies in our laboratories have shown that internalized apoE may be spared from degradation and recycled, a process that would enable apoE to impact cellular functions. It is the objective of this grant to define the mechanisms of apoE recycling and resecretion and to start addressing its physiologic relevance. This proposal will test the working hypothesis that a fraction of internalized apoE is spared degradation in the cell and recycled, providing a mechanism whereby a protein that is critical for many biological processes can maximize its impact on cellular functions. This hypothesis will be tested through the following specific aims:
Specific Aim #1. To determine if apoE recycling is dependent upon cellular entry point or the lipoprotein particle with which apoE is associated. These studies will test the hypothesis that the disposition of internalized apoE and the potential for recycling are dependent on the particle on which apoE resides and the point of entry into the cell.
Specific Aim #2. To define the intracellular trafficking pathway of recycling apoE. These studies will test the hypothesis that apoE recycles through the secretory pathway, specifically through the Golgi apparatus.
Specific Aim #3. To define the physiologic relevance of apoE recycling. These studies will test the hypothesis that recycling provides a pathway for apoE to impact cellular functions, specifically lipid and lipoprotein metabolism, secretion-capture, and cholesterol efflux. These studies will primarily focus on apoE recycling by the hepatocyte, but will also expand to the macrophage, a cell type for which the impact of apoE recycling on function may be of great relevance to atherogenesis.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL068114-04
Application #
6757895
Study Section
Special Emphasis Panel (ZRG1-SSS-T (01))
Program Officer
Wassef, Momtaz K
Project Start
2001-09-11
Project End
2006-12-31
Budget Start
2004-07-01
Budget End
2006-12-31
Support Year
4
Fiscal Year
2004
Total Cost
$302,000
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Pathology
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
Braun, Nicole A; Mohler, Peter J; Weisgraber, Karl H et al. (2006) Intracellular trafficking of recycling apolipoprotein E in Chinese hamster ovary cells. J Lipid Res 47:1176-86
Hasty, Alyssa H; Plummer, Michelle R; Weisgraber, Karl H et al. (2005) The recycling of apolipoprotein E in macrophages: influence of HDL and apolipoprotein A-I. J Lipid Res 46:1433-9
Dove, Dwayne E; Su, Yan Ru; Zhang, Wenwu et al. (2005) ACAT1 deficiency disrupts cholesterol efflux and alters cellular morphology in macrophages. Arterioscler Thromb Vasc Biol 25:128-34
Gruen, Marnie L; Plummer, Michelle R; Zhang, Wenwu et al. (2005) Persistence of high density lipoprotein particles in obese mice lacking apolipoprotein A-I. J Lipid Res 46:2007-14
Fazio, Sergio; Linton, MacRae F (2004) Unique pathway for cholesterol uptake in fat cells. Arterioscler Thromb Vasc Biol 24:1538-9
Farkas, Monica H; Weisgraber, Karl H; Shepherd, Virginia L et al. (2004) The recycling of apolipoprotein E and its amino-terminal 22 kDa fragment: evidence for multiple redundant pathways. J Lipid Res 45:1546-54
Farkas, Monica H; Swift, Larry L; Hasty, Alyssa H et al. (2003) The recycling of apolipoprotein E in primary cultures of mouse hepatocytes. Evidence for a physiologic connection to high density lipoprotein metabolism. J Biol Chem 278:9412-7