Fig. 7. Model of the organization of the early secretory pathway and sorting of anterograde and retrograde traffic in the ERGIC. The cycling protein GFP-ERGIC-53 (green) and anterograde cargo, such as VSV-G-GFP or ssDsRed (red), leave the ER at ER-exit sites (ERES) of the transitional elements of the rough ER (TE) and are transported to the ER-Golgi intermediate compartment (ERGIC) by a microtubule-independent process. The ERGIC is a collection of stationary tubulovesicular clusters exhibiting short range, non-directional, but microtubule-dependent movement. The clusters can split or fuse with one another (dashed arrow). Sorting in the ERGIC leads to anterograde carriers (AC), mediating transport of ssDsRed to the cis-Golgi and to retrograde carriers (RC) mediating transport of GFP-ERGIC-53 back to the ER. Both pathways are dependent on intact microtubules. Individual ERGIC-clusters are connected by fast-moving carriers (FC) that carry both markers and are transported along microtubules. MT, microtubules.