The golgin Pplmh1 mediates reversible cisternal stacking in the Golgi of the budding yeast Pichia pastoris

The adhesive force for cisternal stacking of Golgi needs to be reversible - to be initiated and undone in a continuous cycle to keep up with the cistemal maturation. Microscopic evidence in support of such a reversible nature of stacking, in the form of TGN peeling,' has been reported in various species, suggesting a potential evolutionarily conserved mechanism. However, knowledge of such mechanism has remained sketchy. Here, we have explored this issue in the budding yeast Pichia pastoris which harbors stacked Golgi. We observed that deletion of GRIP domain golgin P. pastoris (Pp)lMH1 increases the peeling of late cistema, causing unstacking of the Golgi stack. Our results suggest that the Pplmh1 dimer mediates reversible stacking through a continuous association-dissociation cycle of its GRIP domain to the middle and late Golgi cistema under the GTP hydrolysis-based regulation of Arl3-Arl1 GTPase cascade switch. The reversible cisternal stacking function of Pplmh1 is independent of its vesicle-capturing function. Since GRIP domain proteins are conserved in plants, animals and fungi, it is plausible that this reversible mechanism of Golgi stacking is evolutionarily conserved. This article has an associated First Person interview with the first author of the paper.