Update on Brefeldin A Brefeldin A: Deciphering an Enigmatic Inhibitor of Secretion

The fungal macrocyclic lactone brefeldin A (BFA) has proved to be of great value as an inhibitor of protein trafficking in the endomembrane system of mammalian cells (Sciaky et al., 1997). BFA has also often been used as an inhibitor of secretion and vacuolar protein transport in plant cells, but just exactly how BFA achieves these effects has been a matter of debate for some time (e.g. Satiat-Jeunemaitre et al., 1996; Staehelin and Driouich, 1997). The apparently broad spectrum of BFA responses, combined with a lack of understanding of the primary target of BFA, has made it difficult to develop a coherent explanation of BFA effects, which in turn has led to a series of misconceptions that riddle the plant literature. In the last few years, there has been a tremendous increase in our understanding of the molecular targets and primary effects of BFA in mammalian and yeast systems (see below). On the plant side, several papers have recently been published that, by applying new tools and technologies, have shed fresh light onto the BFA problem (Baluska et al., 2002; Brandizzi et al., 2002; Emans et al., 2002; Ritzenthaler et al., 2002; Saint-Jore et al., 2002). In this Update, we wish to evaluate these new findings and explore whether we are any closer to solving the dilemma of “what BFA really does.”