title: Sphingosine 1-phosphate induces cytoskeletal reorganization in C2C12 myoblasts: physiological relevance for stress fibres in the modulation of ion current through stretch-activated channels.
abstract: Sphingosine 1-phosphate (S1P) is a bioactive lipid that is abundantly present in the serum and mediates multiple biological responses. With the aim of extending our knowledge on the role played by S1P in the regulation of cytoskeletal reorganization, native as well as C2C12 myoblasts stably transfected with green fluorescent protein (GFP)-tagged alpha- and beta-actin constructs were stimulated with S1P (1 microM) and observed under confocal and multiphoton microscopes. The addition of S1P induced the appearance of actin stress fibres and focal adhesions through Rho- and phospholipase D (PLD)-mediated pathways. The cytoskeletal response was dependent on the extracellular action of S1P through its specific surface receptors, since the intracellular delivery of the sphingolipid by microinjection was unable to modify the actin cytoskeletal assembly. Interestingly, it was revealed by whole-cell patch-clamp that S1P-induced stress fibre formation was associated with increased ion currents and conductance through stretch-activated channels (SACs), thereby suggesting a possible regulatory role for organized actin in channel sensitivity. Experiments aimed at stretching the plasma membrane of C2C12 cells, using the cantilever of an atomic force microscope, indicated that there was a Ca2+ influx through putative SACs. In conclusion, the present data suggest novel mechanisms of S1P signalling involving actin cytoskeletal reorganization and Ca2+ elevation through SACs that might influence myoblastic functions.
authors.affiliation: Department of Anatomy, Histology and Forensic Medicine, Interuniversitary Institute of Miology (IIM), 85 50134 Florence, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Formigli
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Meacci
authors.forename: Chiasa
authors.initials: C
authors.lastname: Sassoli
authors.forename: Flaminia
authors.initials: F
authors.lastname: Chellini
authors.forename: Rosalba
authors.initials: R
authors.lastname: Giannini
authors.forename: Franco
authors.initials: F
authors.lastname: Quercioli
authors.forename: Bruno
authors.initials: B
authors.lastname: Tiribilli
authors.forename: Roberta
authors.initials: R
authors.lastname: Squecco
authors.forename: Paola
authors.initials: P
authors.lastname: Bruni
authors.forename: Fabio
authors.initials: F
authors.lastname: Francini
authors.forename: Sandra
authors.initials: S
authors.lastname: Zecchi-Orlandini
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004594:Electrophysiology; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D017136:Ion Transport; D007477:Ions; D008246:Lysophospholipids / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D032446:Myoblasts / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010739:Phospholipase D / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000502:physiology; D022502:Stress Fibers / Q000378:metabolism; D014162:Transfection; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D007477:Ions; D008246:Lysophospholipids; D049452:Green Fluorescent Proteins; C060506:sphingosine 1-phosphate; D010739:Phospholipase D; D020741:rho GTP-Binding Proteins; D013110:Sphingosine; D002118:Calcium