Receptor for the lysosphingolipid sphingosine 1-phosphate (S1P). S1P is a bioactive lysophospholipid that elicits diverse physiological effect on most types of cells and tissues. Is coupled to both the G(i/0)alpha and G(12) subclass of heteromeric G-proteins (By similarity). May play a regulatory role in the transformation of radial glial cells into astrocytes and may affect proliferative activity of these cells. Widely expressed in the brain, most prominently in the corpus callosum, which is predominantly white matter. Detected in spleen, peripheral blood leukocytes, placenta, lung, aorta and fetal spleen. Low-level signal detected in many tissue extracts. Overexpressed in leukemic large granular lymphocytes. Isoform 1 is predominantly expressed in peripheral tissues. Isoform 2 is expressed in brain, spleen and peripheral blood leukocytes. At 24 weeks of gestation, fragments of radial glial fibers are positive within the cortical plate and subplate of allocortical areas. These positive fragments often appear enlarged as varicosities and some of them terminate at blood vessels. Between 28 and 30 weeks of gestation, all iso- and allocortical areas contain immunolabeled radial glial fibers revealing curvature next to sulci. After 32 weeks of gestation, radial glial fibers gradually disappear; instead positive transitional stages between radial glia and astrocytes were found. Belongs to the G-protein coupled receptor 1 family.