Nonlamellar-Phase-Promoting Colipids Enhance Segregation of Palmitoyl Ceramide in Fluid Bilayers

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Möuts A, Yamamoto T, Nyholm TKM, Murata M, Slotte JP
Publisher: Cell Press
Publication year: 2019
Journal: Biophysical Journal
Journal acronym: Biophys J
Volume number: 116
Issue number: 8
Start page: 1507
End page: 1515
ISSN: 1542-0086


Abstract

Ceramide is an important intermediate in sphingolipid homeostasis. We examined how colipids, with negative intrinsic curvature and which may induce curvature stress in the bilayers, affected the segregation of palmitoyl ceramide (PCer). Such colipids include 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and tetra-linoleoyl cardiolipin (CL). In 1,2-dioleoyl-sn-glycero-3-phosphocholine
(DOPC) bilayers, PCer formed ordered, gel-like domains at
concentrations above 10 mol% at 23°C, as evidenced by the change in the
average lifetime of the trans-parinaric acid emission. When
POPE or DOPE were included in the DOPC bilayer (at 20:80 or 40:60 POPE
or DOPE to DOPC, by mol), the lateral segregation of PCer was
facilitated in a concentration-dependent manner, and less PCer was
required for the formation of the ordered ceramide-rich domains.
Inclusion of CL in the DOPE bilayer (at 10:90 or 20:80 CL to PC, by mol)
also caused a similar facilitation of the lateral segregation of PCer.
The PCer-rich domains formed in the presence of POPE, DOPE, or CL in
DOPC bilayers were slightly more thermostable (by 2–10°C) when compared
to PCer-rich domains in DOPC-only bilayers. Nonlamellar phases were not
present in bilayers in which the effects of POPE or DOPE on PCer
segregation were the largest, as verified by 31P NMR. When palmitoyl sphingomyelin was added to the different bilayer compositions at 5 mol%, relative to the phospholipids,
PCer segregated into gel domains at lower concentrations (2–3 mol%
PCer), and the effect of POPE on PCer segregation was eliminated. We
suggest that the effects of POPE, DOPE, and CL on PCer segregation was
in part influenced by their effects on membrane curvature
stress and in part because of unfavorable interactions with PCer due to
their unsaturated acyl chains. These lipids are abundant in mitochondrial membranes and are likely to affect functional properties of saturated ceramides in them.


Last updated on 2020-02-04 at 07:58