Ceramide as a second messenger: sticky solutions to sticky problems

Much discussion has recently centred around the biochemical mechanisms by w hich ceramide is produced ifn signalling pathways. Since ceramide is virtua lly insoluble in aqueous solutions, the biological effects of ceramide shou ld be considered in the context of its generation within the membrane lipid bilayer. To this end, we now summarize recent data describing some biophysical prope rties of ceramide that are of relevance for understanding the mode of ceram ide action as a second messenger, and, as a consequence, how the site(s) of ceramide generation might impact upon its role signalling.