The roles of ceramide and complex sphingolipids in neuronal cell function.

The roles of sphingolipids, and particularly of the complex glycosphingolipids (GSLs), the gangliosides, have been studied for many years in neurons, glia, and cell lines derived from these tissues, due to their abundance in tissues of neuronal origin. More recently, significant attention has been paid to the simple sphingolipids, particularly ceramide, glucosylceramide (GlcCer), and sphingosine-1-phosphate (S1P), each of which appears to be involved in the regulation of specific aspects of neuronal proliferation, differentiation, survival and apoptosis. In this review, we will summarize studies performed in our laboratory over the past few years using cultured hippocampal neurons in an attempt to define the precise roles of these lipids, and to define their mechanisms of action by identifying down-stream targets with which they interact. We will also discuss work suggesting that complex GSLs, such as gangliosides GM2 and GD3, can also regulate neuronal development, although the down-stream targets with which they interact are less well defined. Our work will be reviewed in light of studies from other laboratories, with particular emphasis on the use of models of sphingolipid storage diseases to determine how these lipids affect neuronal function.