Sphingosine 1-phosphate inhibits cell migration in C2C12 myoblasts

This study shows that sphingosine 1-phosphate (S1P) exerts an anti-migratory action in C2C12 myoblasts by reducing directional cell motility and fully abrogating the chemotactic response to insulin-like growth factor-1. The anti-migratory response to S1P required ligation to S1P(2), being attenuated in myoblasts where the receptor was down-regulated by specific antisense oligodeoxyribonucleotides or small interfering RNA (siRNA) and conversely potentiated in S1P(2)-overexpressing myoblasts. The investigation of RhoA and Rac GTPases, critically implicated in cell motility regulation, demonstrated that RhoA was rapidly activated by S1P, while Rac1 was unaffected within the first 5 min but stimulated thereafter. RhoA, but not Rac activation, was identified as a S1P(2)-dependent pathway in experiments in which receptor expression was attenuated by siRNA treatment or up-regulated by S1P(2)-encoding plasmid transfection. Finally, by expression of the dominant negative mutant of RhoA, the GTPase was found implicated in the anti-migratory action of S1P, whereas modulation of Rac1 functionality unaffected the anti-chemotactic effect of S1P, ruling out a role for this protein in the biological response. Since S1P was previously shown to inhibit myoblast proliferation and stimulate myogenesis, the here identified novel biological activity is in favour of a complex physiological role of the sphingolipid in the process of muscle repair.