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Cholesterol-dependent and -independent CD40 internalization and signaling activation in cardiovascular endothelial

Jianjun Chen1, Lu Chen, Gang Wang

  • 1Institute of Microbiology, Chinese Academy of Sciences, Beijing, China 100101.

Arteriosclerosis, Thrombosis, and Vascular Biology
|July 14, 2007
PubMed

Insights

CD40 receptor uses cholesterol-dependent or -independent pathways for trafficking and signaling in endothelial cells, depending on the agonist form. This impacts cardiovascular inflammation.

Area of Science:

  • Immunology
  • Cell Biology
  • Cardiovascular Research

Background:

  • CD40 receptor activation is crucial in immune responses and cardiovascular diseases.
  • The precise mechanisms of CD40 endocytosis and signaling by various agonists remain unclear.
  • Lipid rafts are known regulators of cell surface receptor function.

Purpose of the Study:

  • To investigate the differential regulation of CD40 trafficking and signaling by lipid rafts.
  • To determine how different forms of CD40 agonists influence CD40's interaction with lipid rafts.
  • To elucidate the role of lipid rafts in CD40-mediated proinflammatory activation of endothelial cells.

Main Methods:

  • Fluorescent microscopy and flow cytometry were employed to track CD40.
  • Cholesterol depletion using methyl-beta-cyclodextrin (MCD) and caveolin-1 knockdown were used to disrupt lipid rafts.
  • CD40L variants (soluble, antibody, and megamer) were used as agonists.
  • Analysis of CD40 translocation to specific raft fractions (Brij58-insoluble) and downstream signaling activation.

Main Results:

  • Soluble CD40L and agonistic antibody G28.5 induced CD40 internalization via a clathrin-independent, caveolae-raft pathway sensitive to cholesterol depletion.
  • A membrane-bound CD40L mimic (megamer) induced CD40 aggregation in distinct rafts, independent of conventional lipid rafts and cholesterol levels.
  • Both agonists caused CD40 translocation to Brij58-insoluble rafts, but only G28.5-induced signaling was inhibited by cholesterol depletion.

Conclusions:

  • CD40 engagement by different agonists leads to distinct lipid raft-dependent trafficking and signaling pathways.
  • Endothelial cell CD40 activation involves either a cholesterol-dependent or -independent mechanism based on agonist type.
  • These findings highlight the complex regulation of CD40 in cardiovascular inflammation.
Abstract

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