title: Inward relocation of exogenous phosphatidylserine triggered by IGF-1 in non-apoptotic C2C12 cells is concentration dependent.
abstract: The plasma membrane is composed of two leaflets that are asymmetric with regard to their phospholipid composition with phosphatidylserine (PS) predominantly located within the inner leaflet whereas other phospholipids such as phosphatidylcholine (PC) are preferentially located in the outer leaflet. An intimate relationship between cellular physiology and the composition of the plasma membrane has been demonstrated, with for example apoptosis requiring PS exposure for macrophage recognition. In skeletal muscle development, differentiation also requires PS exposure in myoblasts to create cell-cell contact areas allowing the formation of multinucleate myotubes. Although it is clearly established that membrane composition/asymmetry plays an important role in cellular physiology, the role of cytokines in regulating this asymmetry is still unclear. When incubated with myoblasts, insulin-like growth factor I (IGF-1) has been shown to promote proliferation versus differentiation in a concentration dependent manner and therefore, may be a potential candidate regulating cell membrane asymmetry. We show, in non-apoptotic C2C12 cells, that relocation of an exogenous PS analogue, from the outer into the inner leaflet, is accelerated by IGF-1 in a concentration-dependent manner and that maintenance of membrane asymmetry triggered by IGF-1 is however independent of the PI3K inhibitor wortmannin.
authors.affiliation: Royal Veterinary College, Muscle & Molecular Biology Unit, Royal College Street, London, NW1 OTU, UK.
authors.forename: Cyril
authors.initials: C
authors.lastname: Rauch
authors.forename: Paul T
authors.initials: PT
authors.lastname: Loughna
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives; D000730:Androstadienes / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D051379:Mice; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D009327:4-Chloro-7-nitrobenzofurazan; D000730:Androstadienes; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D010718:Phosphatidylserines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D000077191:Wortmannin