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Conserved Oligomeric Golgi (COG) complex controls Golgi trafficking and glycosylation, but the precise COG mechanism is unknown. The auxin-inducible acute degradation system was employed to investigate initial defects resulting from COG dysfunction. We found that acute COG inactivation caused a massive accumulation of COG-dependent (CCD) vesicles that carry the bulk of Golgi enzymes and resident proteins. v-SNAREs (GS15, GS28) and v-tethers (giantin, golgin84, and TMF1) were relocalized into CCD vesicles, while t-SNAREs (STX5, YKT6), t-tethers (GM130, p115), and most of Rab proteins remained Golgi-associated. Airyscan microscopy and velocity gradient analysis revealed that different Golgi residents are segregated into different populations of CCD vesicles. Acute COG depletion significantly affected three Golgi-based vesicular coats-COPI, AP1, and GGA, suggesting that COG uniquely orchestrates tethering of multiple types of intra-Golgi CCD vesicles produced by different coat machineries. This study provided the first detailed view of primary cellular defects associated with COG dysfunction in human cells., (© 2022 The Authors. Traffic published by John Wiley & Sons Ltd.)

Vesicular tethers and SNAREs are two key protein components that govern docking and fusion of intracellular membrane carriers in eukaryotic cells. The conserved oligomeric Golgi (COG) complex has been specifically implicated in the tethering of retrograde intra-Golgi vesicles. Using yeast two-hybrid and co-immunoprecipitation approaches, we show that the COG6 subunit of the COG complex is capable of interacting with a subset of Golgi SNAREs, namely STX5, STX6, GS27 and SNAP29. Interaction with SNAREs is accomplished via the universal SNARE-binding motif of COG6. Overexpression of COG6, or its depletion from cells, disrupts the integrity of the Golgi complex. Importantly, COG6 protein lacking the SNARE-binding domain is deficient in Golgi binding, and is not capable of inducing Golgi complex fragmentation when overexpressed. These results indicate that COG6-SNARE interactions are important for both COG6 localization and Golgi integrity., (© 2012 John Wiley & Sons A/S.)