A PEST sequence in ABCA1 regulates degradation by calpain protease and stabilization of ABCA1 by apoA-I
Nan Wang, … , David L. Silver, Alan R. Tall
Nan Wang, … , David L. Silver, Alan R. Tall
Published January 1, 2003
Citation Information: J Clin Invest. 2003;111(1):99-107. https://doi.org/10.1172/JCI16808.
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Article Cardiology

A PEST sequence in ABCA1 regulates degradation by calpain protease and stabilization of ABCA1 by apoA-I

Abstract

Cholesterol-loaded macrophage foam cells are a central component of atherosclerotic lesions. ABCA1, the defective molecule in Tangier disease, mediates the efflux of phospholipids and cholesterol from cells to apoA-I, reversing foam cell formation. In ABCA1, we identified a sequence rich in proline, glutamic acid, serine, and threonine (PEST sequence) that enhances the degradation of ABCA1 by calpain protease and thereby controls the cell surface concentration and cholesterol efflux activity of ABCA1. In an apparent positive feedback loop, apoA-I binds ABCA1, promotes lipid efflux, inhibits calpain degradation, and leads to increased levels of ABCA1. ApoA-I infusion also increases ABCA1 in vivo. These studies reveal a novel mode of regulation of ABCA1 by PEST sequence–mediated calpain proteolysis that appears to be reversed by apolipoprotein-mediated phospholipid efflux. Inhibition of ABCA1 degradation by calpain could represent a novel therapeutic approach to increasing macrophage cholesterol efflux and decreasing atherosclerosis.

Authors

Nan Wang, Wengen Chen, Patrick Linsel-Nitschke, Laurent O. Martinez, Birgit Agerholm-Larsen, David L. Silver, Alan R. Tall

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ApoA-I and apoE increase ABCA1 protein in mouse primary hepatocytes and ...
ApoA-I and apoE increase ABCA1 protein in mouse primary hepatocytes and macrophages. (a) Time course of the effect of apoA-I (10 μg/ml) on ABCA1 protein levels in mouse peritoneal macrophages pretreated overnight with 50 μg/ml acetyl-LDL and LXR/RXR ligands 22(R)-hydroxycholesterol and 9-cis retinoic acid (RA) (both 10 μM). (b) Cell surface biotinylated ABCA1 levels in macrophages after 3 hours of incubation with 10 μg/ml apoA-I. (c) ABCA1 levels in primary mouse hepatocytes incubated for 3 hours with 10 μg/ml apoA-I. (d) Effects of apoA-I (10 μg/ml) on ABCA1 levels in macrophages treated with or without acetyl-LDL (AcLDL) and LXR/RXR ligands. (e) Dose response of apoE3 effect (3 hours’ incubation) on ABCA1 protein levels in mouse peritoneal macrophages pretreated with acetyl-LDL, 22(R)-hydroxycholesterol, and 9-cis retinoic acid. (f) ABCA1 levels in mouse peritoneal macrophages after 3 hours of incubation with or without apoE3 (10 μg/ml). (g) ABCA1, W590S-ABCA1, and ABCA1delPEST protein levels in HEK293 cells after 3 hours of incubation with or without apoE3. The data are representative of two (a, b, e, and g) or three (c, d, and f) experiments with similar results.