title: UVA irradiation induces energy-independent phospholipid-flip in mammalian plasma membrane.
abstract: Translocation from the outer to the inner membrane leaflet (flip) of phospholipids after ultraviolet A (UVA) irradiation was investigated in Chinese hamster ovary cells. Fluorescent 1-palmitoyl-2-[6-[(7-nitro-2-1,3-benzox- adiazol-4-yl)amino]caproyl]-sn-glycero-3-phosphoserine (NBD-labeled phosphatidylserine [NBD-PS]) was used to assay transbilayer lipid movement. A marked increase in flip of NBD-PS was observed immediately after low-dose UVA irradiation which was not lethal and returned to the basal level after 6 h. UVA-induced flip was not attributed to the increase of permeability by UVA irradiation because cells that were negative for staining with propidium iodide also showed increased flip of NBD-PS. Furthermore, the enhancement was independent of adenosine 5'-triphosphate, demonstrating the lack of involvement of phospholipid translocase. Marked increases were also observed in flip of both NBD-phosphatidylethanolamine and NBD-phosphatidylcholine immediately after UVA irradiation, showing that the increase was independent on the head groups of phospholipids. These findings indicated that UVA changes the flip-flop of phospholipids and that the cell membrane is a molecular and cellular target of UVA.
authors.affiliation: Laboratory of Radiation Biology, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, 52-1 Yada, Shizuoka-shi 422-8526, Japan. ibuki@sea.u-shizuoka-ken.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Ibuki
authors.forename: A
authors.initials: A
authors.lastname: Suzuki
authors.forename: R
authors.initials: R
authors.lastname: Goto
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D016466:CHO Cells / Q000378:metabolism / Q000528:radiation effects; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D006224:Cricetinae; D008051:Lipid Bilayers / Q000378:metabolism / Q000528:radiation effects; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D002352:Carrier Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins; C034296:N-(7-nitro-2,1,3-benzoxadiazol-4-yl)phosphatidylserine; D010718:Phosphatidylserines; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D000255:Adenosine Triphosphate; D009327:4-Chloro-7-nitrobenzofurazan