title: Sphingosine kinase activity is required for sphingosine-mediated phospholipase D activation in C2C12 myoblasts.
abstract: Sphingosine (Sph) has been implicated as a modulator of membrane signal transduction systems and as a regulatory element of cardiac and skeletal muscle physiology, but little information is presently available on its precise mechanism of action. Recent studies have shown that sphingosine 1-phosphate (S1P), generated by the action of sphingosine kinase (SphK) on Sph, also possesses biological activity, acting as an intracellular messenger, as well as an extracellular ligand for specific membrane receptors. At present, however, it is not clear whether the biological effects elicited by Sph are attributable to its conversion into S1P. In the present study, we show that Sph significantly stimulated phospholipase D (PLD) activity in mouse C2C12 myoblasts via a previously unrecognized mechanism that requires the conversion of Sph into S1P and its subsequent action as extracellular ligand. Indeed, Sph-induced activation of PLD was inhibited by N,N-dimethyl-D-erythro-sphingosine (DMS), at concentrations capable of specifically inhibiting SphK. Moreover, the crucial role of SphK-derived S1P in the activation of PLD by Sph was confirmed by the observed potentiated effect of Sph in myoblasts where SphK1 was overexpressed, and the attenuated response in cells transfected with the dominant negative form of SphK1. Notably, the measurement of S1P formation in vivo by employing labelled ATP revealed that cell-associated SphK activity in the extracellular compartment largely contributed to the transformation of Sph into S1P, with the amount of SphK released into the medium being negligible. It will be important to establish whether the mechanism of action identified in the present study is implicated in the multiple biological effects elicited by Sph in muscle cells.
authors.affiliation: Dipartimento di Scienze Biochimiche, Università degli Studi di Firenze, Viale G.B.Morgagni 50, 50134 Florence, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Meacci
authors.forename: Francesca
authors.initials: F
authors.lastname: Cencetti
authors.forename: Chiara
authors.initials: C
authors.lastname: Donati
authors.forename: Francesca
authors.initials: F
authors.lastname: Nuti
authors.forename: Laura
authors.initials: L
authors.lastname: Becciolini
authors.forename: Paola
authors.initials: P
authors.lastname: Bruni
mesh_terms: D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D008246:Lysophospholipids / Q000096:biosynthesis / Q000378:metabolism; D051379:Mice; D032448:Myoblasts, Skeletal / Q000201:enzymology*; D010739:Phospholipase D / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology; D000099157:Sphingosine Kinase
chemical_list: D008246:Lysophospholipids; D010739:Phospholipase D; D017853:Phosphotransferases (Alcohol Group Acceptor); D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate; C061800:N,N-dimethylsphingosine