Golgi-derived CLASP-dependent microtubules control Golgi organization and polarized trafficking in motile cells

Abstract

Microtubules are indispensable for Golgi complex assembly and maintenance that is an integral part of cytoplasm organization in interphase mammalian cells. Here, we show that two discrete microtubule subsets drive two distinct, yet simultaneous, stages of Golgi assembly. In addition to the radial centrosomal microtubule array, which positions the Golgi in the cell center, we identify a role for microtubules that form at the Golgi membranes in a manner dependent on microtubule regulators CLASPs. These Golgi-derived microtubules draw Golgi mini-stacks together in tangential fashion and are critical for establishing continuity and proper morphology of the Golgi complex. We propose that specialized functions of these two microtubule arrays arise from their specific geometries. Further, we demonstrate that directional post-Golgi trafficking and cell migration depend on Golgi-associated CLASPs suggesting that correct organization of the Golgi complex by microtubules is essential for cell polarization and motility.

MTCL1 crosslinks and stabilizes non-centrosomal microtubules on the Golgi membrane

“…Together with data from live imaging analyses 7 , these results have indicated that the formation of the Golgi ribbon proceeds in two distinct steps, in which the Golgi-derived MTs first draw the Golgi ministacks together in a tangential manner, whereas the centrosomal MTs subsequently drag the laterally clustered Golgi stacks towards the centrosome 7 . Interestingly, these studies have also demonstrated that loss of the Golgi ribbon resulted in unpolarized vesicle transport from the Golgi apparatus, and thereby impaired regulated lamellipodia development required for maintenance of directed cell migration 7,12 . Taken together, these studies have provided not only new insight into the importance of MTs in organelle architecture, but also evidence for the physiological significance of this vertebrate-specific Golgi architecture.…”

“…However, the underlying mechanism for maintaining this specific Golgi arrangement as well as its physiological significance had been unclear until the above-mentioned studies. They have demonstrated that specific disruption of the Golgi-derived MTs by knockdown of CLASPs or AKAP450/CG-NAP converted the Golgi ribbon into a cluster of Golgi stacks gathering around the centrosome 7,9 . Together with data from live imaging analyses 7 , these results have indicated that the formation of the Golgi ribbon proceeds in two distinct steps, in which the Golgi-derived MTs first draw the Golgi ministacks together in a tangential manner, whereas the centrosomal MTs subsequently drag the laterally clustered Golgi stacks towards the centrosome 7 .…”

“…They have demonstrated that specific disruption of the Golgi-derived MTs by knockdown of CLASPs or AKAP450/CG-NAP converted the Golgi ribbon into a cluster of Golgi stacks gathering around the centrosome 7,9 . Together with data from live imaging analyses 7 , these results have indicated that the formation of the Golgi ribbon proceeds in two distinct steps, in which the Golgi-derived MTs first draw the Golgi ministacks together in a tangential manner, whereas the centrosomal MTs subsequently drag the laterally clustered Golgi stacks towards the centrosome 7 . Interestingly, these studies have also demonstrated that loss of the Golgi ribbon resulted in unpolarized vesicle transport from the Golgi apparatus, and thereby impaired regulated lamellipodia development required for maintenance of directed cell migration 7,12 .…”

“…Recent studies have demonstrated that these perinuclear acetylated MTs correspond to the Golgi-derived MTs, which play essential roles in the lateral connection of the Golgi stacks and inhibit their complete clustering around the centrosome 7,9 . Consistent with these reports, MTCL1 knockdown also significantly affected the Golgi apparatus morphology (Fig.…”

“…1c, these results indicate that MTCL1 affects the Golgi ribbon formation not only by promoting the perinuclear accumulation of stable MTs, but also by mediating the linkage between the Golgi membrane and MTs. ARTICLE It has been shown that disruption of the Golgi-ribbon structures induced by CLASPs or AKAP450/CG-NAP knockdown resulted in unpolarized cell migration because of defects in polarized vesicle trafficking towards the leading edge 7,12 . We also observed similar phenotypes in MTCL1-knockdown cells (Fig.…”