Entry at the trans-face of the Golgi

Abstract

The trans-Golgi network (TGN) receives a select set of proteins from the endocytic pathway-about 5% of total plasma membrane glycoproteins (Duncan and Kornfeld 1988). Proteins that are delivered include mannose 6-phosphate receptors (MPRs), TGN46, sortilin, and various toxins that hitchhike a ride backward through the secretory pathway to intoxicate cells after they exit into the cytoplasm from the endoplasmic reticulum (ER). This article will review work on the molecular players that drive protein transport from the endocytic pathway to the TGN. Distinct requirements have revealed multiple routes for retrograde transport; in addition, the existence of multiple, potential coat proteins and/or cargo adaptors imply that multiple vesicular transfers are likely involved. Several comprehensive reviews have appeared recently and should be sought for additional details (Bonifacino and Rojas 2006; Johannes and Popoff 2008).

Figure 1.

Multiple routes of protein transport from the endocytic pathway to the trans-Golgi network. For details, see text.

Figure 2.

Three dimensional electron microscopic tomography reveals a complex architecture for the TGN. The three trans-most cisternae are shown in dark blue, gold, and red. The clathrin coated, trans-most cisternae is solid, unlike the fenestrated, penultimate trans-cisternae. Adapted from Mogelsvang et al. (2004) and reprinted with permission from John Wiley & Sons © 2004.

Figure 3.

Depletion of the putative vesicle tethering factor, RhoBTB3 causes the Golgi to appear altered. Shown is the localization of GCC185 in control or RhoBTB3 depleted cells. For details, see Espinosa et al. (2009).