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Calpain-mediated cleavage negatively regulates the expression level of ABCG1

Natsuki Hori1, Hisamitsu Hayashi, Yuichi Sugiyama

  • 1Laboratory of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Atherosclerosis
|February 8, 2011
PubMed
Abstract

Insights

Calpain degrades ATP-binding cassette transporter ABCG1 on the cell surface, reducing cholesterol efflux. Inhibiting calpain increases ABCG1 levels and function, offering a potential strategy against atherosclerosis.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Molecular Medicine

Background:

  • ATP-binding cassette transporter ABCG1 is crucial for cholesterol efflux from macrophages.
  • ABCG1 prevents macrophage foam-cell formation, a key process in atherosclerosis.
  • Regulatory mechanisms of ABCG1, particularly its degradation, are not well understood.

Purpose of the Study:

  • To investigate the role of calpain in the degradation of ABCG1.
  • To elucidate how calpain activity affects ABCG1 expression and function.

Main Methods:

  • In vitro cleavage assays using purified μ-calpain and membrane fractions.
  • Experiments in human embryonic kidney 293 (HEK293) cells expressing ABCG1.
  • Calpain inhibition using calpeptin.
  • Biotinylation assays to assess cell surface protein levels.
  • Clathrin heavy-chain (CHC) knockdown to study protein internalization.
  • Experiments in mouse peritoneal macrophages.

Main Results:

  • Purified μ-calpain directly cleaved ABCG1.
  • Calpeptin treatment inhibited ABCG1 degradation in both HEK293 cells and macrophages.
  • Calpeptin increased ABCG1 expression and cholesterol efflux function.
  • ABCG1 accumulation was observed at the cell surface with calpeptin treatment, independent of clathrin-mediated endocytosis.

Conclusions:

  • Calpain promotes ABCG1 degradation by cleaving cell surface-resident ABCG1.
  • This degradation reduces ABCG1 expression and its cholesterol efflux capacity.
  • Inhibiting calpain-mediated ABCG1 cleavage presents a novel therapeutic approach for atherosclerosis.

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