Regulation of protein trafficking: posttranslational mechanisms and the unexplored transcriptional control

Endomembrane protein trafficking assures protein location through the endocytic and secretory routes. Trafficking pathways are diverse, depending on the proteins being trafficked, the final destination as well as their itinerary. Trafficking pathways are operated by machineries composed of a set of coordinately acting factors that transport proteins between compartments. Different machineries participate in each protein trafficking pathway, providing specificity and accuracy. Changes in the activity and abundance of trafficking proteins regulate protein flux. The preponderance of one pathway over another regulates protein location and relocation. Cellular requirements change during different processes and in response to stimuli; modulation of trafficking mechanisms must relocate proteins or alternatively increase/decrease the targeting rate of certain proteins. Conventionally, protein trafficking modulation has been explained as posttranslational modification of components of the relevant trafficking machinery. However, trafficking components are also transcriptionally regulated and several reports support that this regulation can modulate protein trafficking as well. This transcriptional modulation has an impact on plant physiology, and is a critical and fundamental mechanism. This scenario suggests a determinant mechanism that must be considered in the endomembrane protein trafficking research field.