Antisense studies in PC12 cells suggest a role for H218, a sphingosine 1-phosphate receptor, in growth-factor-induced cell-cell interaction and neurite outgrowth.

Our previous studies of H218, a sphingosine 1-phosphate (S1P) receptor and a member of the G-protein-coupled receptor superfamily, suggest that it may participate in mammalian nervous system development. Thus, brain levels of H218 mRNA are higher during early neurogenesis than postnatally. In addition, embryonic H218 immunoreactivity is preferentially localized in young neuronal cell bodies during their early stages of differentiation and in axons during their extension. This report describes the morphological effects of reducing native H218 levels in PC12 cells. Western blot analyses demonstrated that PC12 cells stably transfected with an expression vector carrying an antisense-oriented H218 cDNA contain less H218 protein than vector-transfected control cells. When differentiated with growth factors, the antisense-H218 cells display more neurite production and form less cell-cell contacts than the control cells. Therefore, these data, along with our previous H218 expression studies and a recent, independent study of H218 overexpression, support the possibility that H218 contributes to developmental processes regulating neuronal interaction and axon growth. The data are also consistent with reports that H218 is a S1P receptor, that S1P is present in serum, like that used in our PC12 cell cultures, and that it causes PC12 cell neurite retraction. Finally, and in agreement with a S1P receptor role for H218, we find that the antisense-H218 cells display less S1P-induced neurite retraction than control cells.