INTRACELLULAR LIPID HETEROGENEITY CAUSED BY TOPOLOGY OF SYNTHESIS ANDSPECIFICITY IN TRANSPORT - EXAMPLE - SPHINGOLIPIDS

The differences in lipid composition between intracellular membranes c annot be adequately explained by local synthesis and degradation, Espe cially in the case of sphingolipids, which are synthesized in the Golg i complex but enriched on the cell surface and in endocytotic organell es, there is evidence for a cellular machinery that preferentially shu ttles these lipids in vesicles to the cell surface, The machinery appe ars to involve the formation of domains of sphingolipid and cholestero l in the lumenal leaflet of Golgi membranes. Several pieces of evidenc e suggest that the selective anterograde transport of plasma membrane proteins may be mechanistically related to the sphingolipid domains.