Overview: membrane traffic in multicellular systems: more than just a housekeeper.

Membrane traffic is a fundamental cellular function by which molecules are transported between organelles in the post-Golgi network. Accumulating evidence supports the notion that membrane traffic is not only indispensable for normal cellular function and maintenance of cellular viability by playing housekeeping roles, but also critical for various functions characteristic of multicellular organisms. This Minireview series will focus on the latter aspects of membrane traffic. The topics discussed are: the pathophysiological impact of clathrin-associated adaptor protein (AP) complexes, the significance of membrane traffic in Alzheimer's disease, regulated exocytosis of insulin, secretory lysosomes in immune response, exosomes in physiology and pathology, viral and mammalian ubiquitin ligases modulating immune response, membrane traffic of bacterial toxins, and containment of bacterial infection by autophagy.