Phosphorylation by protein kinase C stabilizes ABCG1 and increases cholesterol efflux

Taro Watanabe; Noriyuki Kioka; Kazumitsu Ueda; Michinori Matsuo

doi:10.1093/jb/mvz039

Phosphorylation by protein kinase C stabilizes ABCG1 and increases cholesterol efflux

J Biochem. 2019 Oct 1;166(4):309-315. doi: 10.1093/jb/mvz039.

Authors

Taro Watanabe¹, Noriyuki Kioka¹, Kazumitsu Ueda^{1

2}, Michinori Matsuo^{1

3}

Affiliations

¹ Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
² Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan.
³ Department of Food and Nutrition, Faculty of Home Economics, Kyoto Women's University, Kyoto, Japan.

PMID: 31111899
DOI: 10.1093/jb/mvz039

Abstract

ATP-binding cassette protein G1 (ABCG1) plays an important role in eliminating excess cholesterol from macrophages and in the formation of high-density lipoprotein (HDL), which contributes to the prevention and regression of atherosclerosis. The post-translational regulation of ABCG1 remains elusive, although phosphorylation by protein kinase A destabilizes ABCG1 proteins. We examined the phosphorylation of ABCG1 using HEK293 and Raw264.7 cells. ABCG1 phosphorylation was enhanced by treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA), a protein kinase C (PKC) activator. PKC activation by TPA increased ABCG1 protein levels and promoted ABCG1-dependent cholesterol efflux to HDL. This activity was suppressed by Go6976, a PKCα/βI inhibitor, suggesting that PKC activation stabilizes ABCG1. To confirm this, the degradation rate of ABCG1 was analysed; ABCG1 degradation was suppressed upon PKC activation, suggesting that PKC phosphorylation regulates ABCG1 levels. To confirm this involvement, we co-expressed ABCG1 and a constitutively active form of PKCα in HEK cells. ABCG1 was increased upon co-expression. These results suggest that PKC-mediated phosphorylation, probably PKCα, stabilizes ABCG1, consequently increasing ABCG1-mediated cholesterol efflux, by suppressing ABCG1 degradation. PKC activation could thus be a therapeutic target to suppress the development of atherosclerosis.

Keywords: ABC protein; atherosclerosis; cholesterol; high-density lipoprotein (HDL); transporter.