Cog4 is one of the subunits of the conserved oligomeric Golgi (COG) complex, a tethering complex that is similar to GARP. The COG complex contains eight subunits (Cog1–Cog8), and its structure can be divided into two lobes: lobe A consists of Cog2, Cog3, and Cog4 and lobe B consists of Cog5, Cog6, Cog7, and Cog8, while Cog1 connects the two lobes (VanRheenen et al. 1999; Kim et al. 2001; Ram et al. 2002). The COG complex mediates vesicle traffic within the Golgi apparatus, between the Golgi and endosomes, as well as between the ER and Golgi (VanRheenen et al. 1999; Suvorova et al. 2002; Bruinsma et al. 2004; Oka et al. 2004; Zolov and Lupashin 2005). In addition, lobe A is directly involved in autophagy because it is localized to the PAS and required for the formation of the autophagosome (Yen et al. 2010).