A Molecular Network for the Transport of the TI-VAMP/VAMP7 Vesicles from Cell Center to Periphery

SummaryThe compartmental organization of eukaryotic cells is maintained dynamically by vesicular trafficking. SNARE proteins play a crucial role in intracellular membrane fusion and need to be targeted to their proper donor or acceptor membrane. The molecular mechanisms that allow for the secretory vesicles carrying the v-SNARE TI-VAMP/VAMP7 to leave the cell center, load onto microtubules, and reach the periphery to mediate exocytosis are largely unknown. Here, we show that the TI-VAMP/VAMP7 partner Varp, a Rab21 guanine nucleotide exchange factor, interacts with GolginA4 and the kinesin 1 Kif5A. Activated Rab21-GTP in turn binds to MACF1, an actin and microtubule regulator, which is itself a partner of GolginA4. These components are required for directed movement of TI-VAMP/VAMP7 vesicles from the cell center to the cell periphery. The molecular mechanisms uncovered here suggest an integrated view of the transport of vesicles carrying a specific v-SNARE toward the cell surface.

Graphical AbstractFigure optionsDownload high-quality image (250 K)Download as PowerPoint slideHighlights
► Rab21 coordinates a molecular network moving secretory vesicles to the cell periphery
► The Rab21 GEF Varp links a Golgin and a kinesin motor to the v-SNARE TI-VAMP/VAMP7
► Rab21 further organizes these interactions at the Golgi, via the spectraplakin MACF1
► This network regulates anterograde transport of secretory vesicles on microtubules