Release of cholesterol-rich particles from the macrophage plasma membrane during movement of filopodia and lamellipodia

Abstract
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Abstract

Cultured mouse peritoneal macrophages release large numbers of ~30-nm cholesterol-rich particles. Here, we show that those particles represent fragments of the plasma membrane that are pulled away and left behind during the projection and retraction of filopodia and lamellipodia. Consistent with this finding, the particles are enriched in proteins found in focal adhesions, which attach macrophages to the substrate. The release of particles is abolished by blocking cell movement (either by depolymerizing actin with latrunculin A or by inhibiting myosin II with blebbistatin). Confocal microscopy and NanoSIMS imaging studies revealed that the plasma membrane–derived particles are enriched in 'accessible cholesterol' (a mobile pool of cholesterol detectable with the modified cytolysin ALO-D4) but not in sphingolipid-sequestered cholesterol (a pool detectable with ostreolysin A (OlyA)]. The discovery that macrophages release cholesterol-rich particles during cellular locomotion is likely relevant to cholesterol efflux and could contribute to extracellular cholesterol deposition in atherosclerotic plaques.

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All data generated or analysed during this study are included in the manuscript and supporting files.

Article and author information

Author details

Xuchen Hu

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0002-0944-624X
Thomas A Weston

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Cuiwen He

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Rachel S Jung

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Patrick J Heizer

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Brian D Young

Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Yiping Tu

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Peter Tontonoz

Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, United States

Competing interests
Peter Tontonoz, Reviewing editor, eLife.

"This ORCID iD identifies the author of this article:" 0000-0003-1259-0477
James A Wohlschlegel

Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, United States

Competing interests
No competing interests declared.
Haibo Jiang

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

For correspondence
haibo.jiang@uwa.edu.au

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0002-2384-4826
Stephen G Young

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

For correspondence
sgyoung@mednet.ucla.edu

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0001-7270-3176
Loren G Fong

Department of Medicine, University of California, Los Angeles, Los Angeles, United States

For correspondence
lfong@mednet.ucla.edu

Competing interests
No competing interests declared.

"This ORCID iD identifies the author of this article:" 0000-0002-4465-5290

Funding

National Heart, Lung, and Blood Institute (HL090553)

Stephen G Young

National Heart, Lung, and Blood Institute (HL087228)

Stephen G Young

National Heart, Lung, and Blood Institute (HL125335))

Stephen G Young

Fondation Leducq (12CVD04).)

Stephen G Young

Ruth L Kirschstein National Research Service Award (T32HL69766))

Xuchen Hu

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: Animal housing and experimental protocols were approved by UCLA's Animal Research Committee (ARC; 2004-125-51). The animals were housed in an AAALAC (Association for Assessment andAccreditation of Laboratory Animal Care International)-approved facility and cared for accordingto guidelines established by UCLA's Animal Research Committee.

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.