Different expression of sphingosine 1-phosphate receptor 1 in skeletal muscle in relation to gender, age and use.

Sphingosine 1-phosphate (S1P) is a bioactive signaling lipid that regulates important cellular processes, including proliferation, survival, growth, differentiation and migration. The extracellular action of S1P is mediated by the binding to five high-affinity G proteincoupled receptors (S1P1-5) that generate multiple downstream signals. In skeletal muscle, we demonstrated that S1P1 and S1P3 receptors are localized in the plasma and T-tubule membranes, consistently with a trophic action exerted by S1P in denervated muscle (Zanin et al. Am J Physiol 294:C36–46, 2008). These receptors are also evident at the neuromuscular junction level and in the nuclear membrane. S1P1 and S1P3 are also demonstrated in quiescent satellite cells, whereas S1P2 receptor is only transitorily expressed in activated satellite cells, validating the role of S1P in muscle regeneration (Danieli-Betto et al. Am J Physiol 298:C550–8, 2010). In the present work we analyzed the expression of S1P1 receptor in different muscles and conditions. Western blot analysis shows that rat and mouse muscles express two different S1P1 protein bands, whose relative proportion depends on the muscle type (slow and fast), gender and age of animals. Moreover, denervation, regeneration and electrical stimulation differently affect both the relative expression level and membrane-to nucleus localization of the two S1P1 forms. Funded by PRIN 2008.