Regulation of Golgi structure through heterotrimeric G proteins.

We have previously shown that ilimaquinone (IQ), a marine sponge metabolite, causes complete vesiculation of the Golgi stacks. By reconstituting the IQ-mediated vesiculation of the Golgi apparatus in permeabilized cells, we now demonstrate that this process does not require ARF and coatomers, which are necessary for the formation of Golgi-derived COPI vesicles. We find that IQ-mediated Golgi vesiculation is inhibited by G alpha(s)-GDP and G alpha(i3)-GDP. Interestingly, adding betagamma subunits in the absence of IQ is sufficient to vesiculate Golgi stacks. Our findings reveal that IQ-mediated Golgi vesiculation occurs through activation of heterotrimeric G proteins and that it is the free betagamma, and not the activated alpha subunit, that triggers Golgi vesiculation.