APICAL TARGETING IN POLARIZED EPITHELIAL-CELLS - THERES MORE AFLOAT THAN RAFTS

Most metazoan cells are 'polarized'. A crucial aspect of this polariza tion is that tile plasma membrane is divided into two or more domains with different protein and lipid compositions - for example, the apica l and basolateral domains of epithelial cells or the axonal and somato dendritic domains of neurons. This polarity is established and maintai ned by highly specific vesicular membrane transport in the biosyntheti c, endocytic and transcytotic pathways. Two important concepts, the 'S NARE' and the 'raft' hypotheses, have been developed that together pro mise at least a partial understanding of the underlying general mechan isms that ensure the necessary specificity of these pathways.