Polarized epithelial membrane traffic: conservation and plasticity.

Most cells are polarized and have distinct plasma membrane domains, which are the result of polarized trafficking of proteins and lipids. Great progress has been made in elucidating the highly conserved polarized targeting machinery. A pre-eminent challenge now is to understand the plasticity of polarized traffic, how it is altered by differentiation and dedifferentiation during development, as well as the adaptation of differentiated cells to meet changing physiological needs.