Interaction of Golgin-84 with the COG Complex Mediates the Intra-Golgi Retrograde Transport

Abstract

The coiled-coil Golgi membrane protein golgin-84 functions as a tethering factor for coat protein I (COPI) vesicles. Protein interaction analyses have revealed that golgin-84 interacts with another tether, the conserved oligomeric Golgi (COG) complex, through its subunit Cog7. Therefore, we explored the function of golgin-84 as the tether for COPI vesicles of intra-Golgi retrograde traffic. First, glycosylic maturation of both plasma membrane (CD44) and lysosomal (lamp1) glycoproteins was distorted in golgin-84 knockdown (KD) cells. The depletion of golgin-84 caused fragmentation of the Golgi with the mislocalization of Golgi resident proteins, resulting in the accumulation of vesicles carrying intra-Golgi soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and cis-Golgi membrane protein GPP130. Similar observations were obtained by diminution of the COG complex, suggesting a strong correlation between the two tethers. Indeed, COG complex-dependent (CCD) vesicles that accumulate in Cog3 or Cog7 KD cells carried golgin-84. Surprisingly, the interaction between golgin-84 and another candidate tethering partner CASP (CDP/cut alternatively spliced product) decreased in Cog3 KD cells. These results indicate that golgin-84 on COPI vesicles interact with the COG complex before SNARE assembly, suggesting that the interaction of golgin-84 with COG plays an important role in the tethering process of intra-Golgi retrograde vesicle traffic.

Multipronged interaction of the COG complex with intracellular membranes

“…This exciting new assay urges for a confirmation of many of the individual protein-protein interactions that have been previously described for the COG complex. 16,[18][19][20]31 These results also shed new light on the steady-state membrane/ cytosol distribution of the COG complex. Previously it was published that the yeast COG complex was preferentially in a soluble pool 32 .…”

“…18 Finally, the COG complex will also interact with βCOP and coiled-coil tethers p115, GM130, Giantin, golgin84, TMF, and CASP. [18][19][20][21] This extensive range of COG interactions with trafficking regulators provides for a multipronged method of attachment of COG subunits to Golgi and vesicle membranes.…”

Mutations inCog7affect Golgi structure, meiotic cytokinesis and sperm development duringDrosophilaspermatogenesis

“…Studies in yeast and mammalian cells suggest a primary role for the COG complex in tethering retrograde vesicles that traffic within the Golgi (Bruinsma et al, 2004;Oka et al, 2004;Sohda et al, 2010;Suvorova et al, 2002;Zolov and Lupashin, 2005) and between endosomal compartments and the Golgi (Laufman et al, 2011;Smith et al, 2009;VanRheenen et al, 1999), thus contributing to the normal structure and function of the Golgi apparatus (Smith and Lupashin, 2008;Ungar et al, 2006). The dependence of other trafficking steps, such as endoplasmic reticulum (ER) export and ER-to-Golgi transport (VanRheenen et al, 1998;VanRheenen et al, 1999;Wu et al, 2004;Wuestehube et al, 1996) on Cog proteins may be secondary to a primary role in maintaining Golgi integrity and function.…”

“…Depletion of Cog3 in HeLa cells resulted in the accumulation of COG complexdependent (CCD) vesicles carrying Golgi v-SNARE proteins but no anterograde cargo molecules (Zolov and Lupashin, 2005). Consistent with a role in Golgi trafficking, COG subunits interact with intra-Golgi SNAREs, the COPI coat, small GTPases and other tethering proteins (Laufman et al, 2011;Sohda et al, 2007;Sohda et al, 2010;Suvorova et al, 2002).…”

Molecular Insights into Vesicle Tethering at the Golgi by the Conserved Oligomeric Golgi (COG) Complex and the Golgin TATA Element Modulatory Factor (TMF)

“…Given that the only protein motifs in COG are predicted coiled coils (32), a plausible molecular function for COG is to act as a protein interaction hub. Indeed, the yeast ortholog was found in a direct physical interaction with the Rab Ypt1p and the vesicle coat COPI (33), whereas mammalian COG has been found to interact with the SNAREs syntaxin5 and 6 (34,35), the SM protein Sly1 (36), several Rabs (37), and the golgins p115 and golgin-84 (38,39). Development of a general model for COG mediated tethering is hampered by the lack of knowledge about the full set of protein interactions that the complex is involved in.…”