Membrane traffic and fusion at post-Golgi compartments

Abstract

Complete sequencing of the Arabidopsis genome a decade ago has facilitated the functional analysis of various biological processes including membrane traffic by which many proteins are delivered to their sites of action and turnover. In particular, membrane traffic between post-Golgi compartments plays an important role in cell signaling, taking care of receptor-ligand interaction and inactivation, which requires secretion, endocytosis, and recycling or targeting to the vacuole for degradation. Here, we discuss recent studies that address the identity of post-Golgi compartments, the machinery involved in traffic and fusion or functionally characterized cargo proteins that are delivered to or pass through post-Golgi compartments. We also provide an outlook on future challenges in this area of research.

Keywords: endocytosis; endosome; exocytosis; plant; recycling; secretion; trans-Golgi network.

Figure 1

Illustrated overview of post-Golgi traffic. In the vacuolar trafficking pathway (purple-colored), there is a controversy over the precise location where VSR recycling occurs (pale purple-colored dashed line). There are different populations of RAB-F-positive endosomes, but their origin is unknown. There is no clear evidence for multiple secretory pathways to the PM (indicated by the green-colored dashed line). Cell-plate formation mainly relies on the secretory pathway (green-colored). Molecular machineries involved in protein retrieval from the cell plate (salmon-colored) and in endocytosis (red-colored) may be similar, including clathrin (gray-colored dashed line). It is not clear whether clathrin is also involved in the vacuolar trafficking pathway. Although there seem to be multiple types of REs (blue and pale blue-colored), their origin and identity are unknown. Small-sized letters indicate representative molecular markers for post-Golgi trafficking pathways. For simplicity, polar location of BOR1 is not shown. For details, see the text.