title: Phosphatidylethanolamine Is a Key Regulator of Membrane Fluidity in Eukaryotic Cells.
abstract: Adequate membrane fluidity is required for a variety of key cellular processes and in particular for proper function of membrane proteins. In most eukaryotic cells, membrane fluidity is known to be regulated by fatty acid desaturation and cholesterol, although some cells, such as insect cells, are almost devoid of sterol synthesis. We show here that insect and mammalian cells present similar microviscosity at their respective physiological temperature. To investigate how both sterols and phospholipids control fluidity homeostasis, we quantified the lipidic composition of insect SF9 and mammalian HEK 293T cells under normal or sterol-modified condition. As expected, insect cells show minimal sterols compared with mammalian cells. A major difference is also observed in phospholipid content as the ratio of phosphatidylethanolamine (PE) to phosphatidylcholine (PC) is inverted (4 times higher in SF9 cells). In vitro studies in liposomes confirm that both cholesterol and PE can increase rigidity of the bilayer, suggesting that both can be used by cells to maintain membrane fluidity. We then show that exogenously increasing the cholesterol amount in SF9 membranes leads to a significant decrease in PE:PC ratio whereas decreasing cholesterol in HEK 293T cells using statin treatment leads to an increase in the PE:PC ratio. In all cases, the membrane fluidity is maintained, indicating that both cell types combine regulation by sterols and phospholipids to control proper membrane fluidity.
authors.affiliation: From the Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, CP 206/02, Bd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Rosie
authors.initials: R
authors.lastname: Dawaliby
authors.affiliation: From the Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, CP 206/02, Bd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Cataldo
authors.initials: C
authors.lastname: Trubbia
authors.affiliation: Laboratory of Pharmaceutical Chemistry and Analytical Platform of the Faculty of Pharmacy, Faculty of Pharmacy, Université Libre de Bruxelles, 1050 Brussels, Belgium.
authors.forename: Cédric
authors.initials: C
authors.lastname: Delporte
authors.affiliation: Laboratory of Pharmaceutical Chemistry and Analytical Platform of the Faculty of Pharmacy, Faculty of Pharmacy, Université Libre de Bruxelles, 1050 Brussels, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Noyon
authors.affiliation: From the Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, CP 206/02, Bd du Triomphe, 1050 Brussels, Belgium.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Ruysschaert
authors.affiliation: Laboratory of Pharmaceutical Chemistry and Analytical Platform of the Faculty of Pharmacy, Faculty of Pharmacy, Université Libre de Bruxelles, 1050 Brussels, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Van Antwerpen
authors.affiliation: From the Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université Libre de Bruxelles, CP 206/02, Bd du Triomphe, 1050 Brussels, Belgium, Cedric.Govaerts@ulb.ac.be.
authors.forename: Cédric
authors.initials: C
authors.lastname: Govaerts
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002784:Cholesterol / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D005454:Fluorescence Polarization; D057809:HEK293 Cells; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008560:Membrane Fluidity; D008954:Models, Biological; D010316:Particle Size; D010713:Phosphatidylcholines / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D061987:Sf9 Cells; D013045:Species Specificity; D018411:Spodoptera; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine
keywords: cholesterol; homeostasis; membrane bilayer; membrane lipid; phosphatidylethanolamine