Effects of S1P on myoblastic cell contraction: Possible involvement of Ca2+-independent mechanisms

Year: 2004

Authors: Nosi D., Vassalli M., Polidori L., Giannini R., Tani A., Chellini F., Paternostro F.

Autors Affiliation: Univ Florence, Dept Anat Histol & Forens Med., Firenze, Italy;
Istituto Nazionale di Ottica Applicata, Biophoton Laboratory, Firenze, Italy

Abstract: Sphingosine-1-phosphate (S1P) is a lipid mediator, which affects many essential processes such as cell proliferation, differentiation and contraction in many cell types. We have previously demonstrated that the lipid mediator elicits Ca2+ transients in a myoblastic cell line (C2C12) by interacting with its specific receptors (S1PRs). In the present study, we wanted to correlate the Ca2+ response with activation of myoblastic cell contractility. C2C12 cells were first investigated for the expression and cellular organization of cytoskeletal proteins by immunoconfocal microscopy. We found that myoblasts exhibited a quite immature cytoskeleton, with filamentous actin dispersed as a web-like structure within the cytoplasm. To evaluate intracellular Ca2+ mobilization, the cells were loaded with a fluorescent Ca2+ indicator (Fluo-3), stimulated with S1P and simultaneously observed with differential interference contrast and fluorescence optics. Exogenous S1P-induced myoblastic cell contraction was temporally unrelated to S1P-induced intracellular Ca2+ increase; cell contraction occurred within 5 – 8 s from stimulation, whereas intracellular Ca2+ increase was evident only after 15 – 25 s. To support the Ca2+ independence of myoblastic cell contraction, the cells were pretreated with a Ca2+ chelator, BAPTA/AM, prior to stimulation with S1P. In these experimental conditions, the myoblasts were still able to contract, whereas the S1P-induced Ca2+ transients were completely abolished. On the contrary, when C2C12 cells were induced to differentiate into skeletal myotubes, they responded to S1P with a rapid cell contraction concurrent with an increase in the intracellular Ca2+. These data suggest that Ca2+-independent mechanism of cell contraction may be replaced by Ca2+-dependent ones during skeletal muscle differentiation. Copyright (C) 2004 S. Karger AG, Basel.

Journal/Review: CELLS TISSUES ORGANS

Volume: 178 (3)      Pages from: 129  to: 138

KeyWords: Ca2+ transients; cell volume; contraction; myoblasts; sphingosine-1-phosphate
DOI: 10.1159/000082243

Citations: 2
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