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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Figure 1

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A PEST sequence regulates the cell surface expression and function of AB...
A PEST sequence regulates the cell surface expression and function of ABCA1. (a) Schematic model of ABCA1 showing the location and amino acid sequence of the PEST sequence in mouse (m), human (h), and chicken (c). The PEST score is +16.42, as determined by PESTfind. (b) Levels of total (bottom) and cell surface (top, biotinylated) ABCA1 and ABCA1delPEST in transiently transfected HEK293 cells. (c, f, and g) DNA dose-dependent ABCA1-mediated and ABCA1delPEST-mediated cellular cholesterol efflux (c), phospholipid efflux (f), and apoA-I cell association (g). (d) Total cellular ABCA1 protein mass as determined by quantitative Western blotting in the cholesterol efflux assay. (e) Cholesterol efflux efficiency determined by percentage efflux normalized for total cellular ABCA1 protein mass. (h) Levels of total (bottom) and ubiquitinated (top) ABCA1 and ABCA1delPEST in HEK293 cells incubated with or without lactacystin (20 μM) for 3 hours. The data are representative of two experiments (c and e–h, triplicate; d, duplicate) or three experiments (b, duplicate and triplicate) with similar results.