Figure 1.

Schematic demonstrating the role of inhibitory G-protein (G_i) and β-arrestin in regulating sphingosine 1-phosphate receptor 1 (S1P₁) signaling in mammalian cells. β-Arrestin (Arr) associates with S1P₁ and recruits c-Src to the receptor in response to S1P ligation of the receptor. G-protein βγ subunits are essential for subsequent activation of c-Src, Raf, MEK (mitogen activated protein kinase kinase) and ERK-1/2 (extracellular signal regulated kinase-1/2). S1P₁ is internalised in endosomes via a β-arrestin-dependent mechanism and extracellular signal regulated kinase-1/2 (ERK-1/2) is recruited to the complex.