TBC1D23 is a bridging factor for endosomal vesicle capture by golgins at the trans-Golgi

The specificity of membrane traffic involves tethers at destination organelles that selectively capture incoming transport vesicles to allow SNAREs on opposing membranes to then assemble and drive fusion1,2. Tethers include both protein complexes and long coiled-coil proteins, although how they contribute to specificity remains unclear3,4. The golgin coiled-coil proteins at the Golgi apparatus capture vesicles from different origins, but the vesicle-specific molecular cues that they recognise are unknown5–8. Vesicle tethering is typically a transient process and so challenging to interrogate in vivo. We have thus used a system where an ectopic golgin causes vesicles to accumulate in a tethered state. By applying proximity biotinylation to the golgin-captured vesicles we identify TBC1D23, an apparently catalytically inactive member of a family of Rab GTPase activating proteins (GAPs), as a vesicle-golgin adaptor that is required for endosome-to-Golgi traffic. The Rab-GAP domain of TBC1D23 binds to a conserved motif at the tip of golgin-245 and golgin-97 at the trans-Golgi, while the C-terminus binds to the WASH complex on endosome-derived vesicles. Thus TBC1D23 is a specificity determinant that links vesicle to target membrane during endosome-to-Golgi trafficking.