Golgi apparatus and TGN during endocytosis

Abstract

Wheat germ agglutinin labelled with horseradish peroxidase (WGA) was used for analyses of endosomal compartments and Golgi apparatus in HepG(2) hepatoma cells during early and late periods of endocytosis. WGA was rapidly transferred into the Golgi region. Transport of internalised WGA into the Golgi apparatus could be classified in three stages. A short stage I, characterised by predominance of vesicular endosomes, was followed by stage II showing new formations of extended endocytic trans Golgi networks (TGNs); the endocytic TGNs comprised reticular and globular parts, showed intimate associations with segments of the endoplasmic reticulum and budding of multiple coated vesicles. Parts of the endocytic TGNs associated with trans Golgi cisternae and became integrated into Golgi stacks. During stage III, concomitantly with integration into the stacks, the endocytic TGNs decreased in size and stacked Golgi cisternae became prominent endocytic compartments. Our results show that endocytosis of WGA is connected with extensive membrane dynamics at the trans Golgi side: an endocytic TGN is newly formed, increases in size and is consumed again. The findings suggest that incorporation of TGN elements into Golgi stacks provides a mechanism for uptake of internalised WGA into the Golgi apparatus.

Death receptor ligation triggers membrane scrambling between Golgi and mitochondria

“…External HPA rapidly accumulated underneath the plasmamembrane, without inducing significant cytotoxic effects (Figure 3b). Contrary to the internalization of another agglutinin, 23 endocytosed HPA hardly labelled the peri-Golgi region of untreated cells (Figure 3). However, FasL treatment greatly increased the intracellular diffusion of internalized HPA, which progressively intermixed with secretory organelles near the cell periphery, as indicated by the increased merging with both GM130-and ERGIC53-labelled membranes (Figure 3b).…”

Fas Death Receptor Enhances Endocytic Membrane Traffic Converging into the Golgi Region

“…We additionally found that Fas stimulation with either its cognate ligand or the agonist antibody CH-11 equally enhanced a wave of endocytosis that was caspase independent, because genetic ablation of caspase-8 or inhibition with the pan-caspase reagent z-VAD did not modify Fas-enhanced internalization of dextrans (Matarrese et al, 2008) and HPA (Degli Esposti, 2008). HPA has been used here as the reference membrane marker because it can access multiple pathways of membrane traffic, similarly to other lectins such as WGA (Vetterlein et al, 2002;Cresawn et al, 2007;Degli Esposti, 2008).…”

Architecture of the Mammalian Golgi

“…Other types of membranebounded carriers also travel in both anterograde and retrograde directions between the TGN and distinct endosomal intermediates (see Pfeffer 2011). Hence, the membrane complexity of the TGN is determined by both biosynthetic traffic coming from the Golgi stack and incoming traffic from the endocytic system (Farquhar and Palade 1981;Kornfeld and Mellman 1989;Vetterlein et al 2002). The cargo and destinations of TGN derived COPI-coated vesicles have not been especially studied, but they likely represent a retrograde pathway Martinez-Menarguez et al 2001).…”