Sphingomyelin depletion impairs anionic phospholipid inward translocation and induces cholesterol efflux.

Abstract

The phosphatidylserine (PS) floppase activity (outward translocation) of ABCA1 leads to plasma membrane remodeling that plays a role in lipid efflux to apolipoprotein A-I (apoAI) generating nascent high density lipoprotein. The Tangier disease W590S ABCA1 mutation has defective PS floppase activity and diminished cholesterol efflux activity. Here, we report that depletion of sphingomyelin by inhibitors or sphingomyelinase caused plasma membrane remodeling, leading to defective flip (inward translocation) of PS, higher PS exposure, and higher cholesterol efflux from cells by both ABCA1-dependent and ABCA1-independent mechanisms. Mechanistically, sphingomyelin was connected to PS translocation in cell-free liposome studies that showed that sphingomyelin increased the rate of spontaneous PS flipping. Depletion of sphingomyelin in stably transfected HEK293 cells expressing the Tangier disease W590S mutant ABCA1 isoform rescued the defect in PS exposure and restored cholesterol efflux to apoAI. Liposome studies showed that PS directly increased cholesterol accessibility to extraction by cyclodextrin, providing the mechanistic link between cell surface PS and cholesterol efflux. We conclude that altered plasma membrane environment conferred by depleting sphingomyelin impairs PS flip and promotes cholesterol efflux in ABCA1-dependent and -independent manners.

• Authors: Kailash Gulshan, Gregory Brubaker, Shuhui Wang, Stanley L Hazen, Jonathan D Smith
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 288 Issue 52 Pg. 37166-79 (Dec 27 2013) ISSN: 1083-351X [Electronic] United States
• PMID: 24220029 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• ABCA1 protein, human
• ABCA1 protein, mouse
• ATP Binding Cassette Transporter 1
• Enzyme Inhibitors
• Liposomes
• Phospholipids
• Sphingomyelins
• Cholesterol
• Sphingomyelin Phosphodiesterase

Topics

• ATP Binding Cassette Transporter 1 (genetics, metabolism)
• Animals
• Biological Transport, Active (drug effects, physiology)
• Cell Membrane (genetics, metabolism)
• Cell-Free System
• Cholesterol (genetics, metabolism)
• Enzyme Inhibitors (pharmacology)
• HEK293 Cells
• Humans
• Liposomes
• Mice
• Phospholipids (genetics, metabolism)
• Sphingomyelin Phosphodiesterase (antagonists & inhibitors, genetics, metabolism)
• Sphingomyelins (genetics, metabolism)
• Tangier Disease (genetics, metabolism)