MEK and Cdc2 kinase are sequentially required for Golgi disassembly in MDCK cells by the mitotic Xenopus extracts

At the onset of mitosis, the Golgi apparatus, which consists of several cis ternae, disperses throughout the cell to be partitioned into daughter cells ,The molecular mechanisms of this process are now beginning to be understoo d,To investigate the biochemical requirements and kinetics of mitotic Golgi membrane dynamics in polarized cells, we have reconstituted the disassembl y of the Golgi apparatus by introducing Xenopus egg extracts into permeabil ized Mardin-Darby canine kidney (MDCK) cells. We used green fluorescence pr otein (GFP)-tagged galactosyltransferase-expressing MDCK cells to analyze t he morphological changes of the Golgi membrane in the semi-intact system. A nalyses by fluorescence and electron microscopies showed that the Golgi dis assembly can be dissected into two elementary processes morphologically. In the first process, the perinuclear Golgi stacks break into punctate struct ures, intermediates, which are comprised of mini-stacks of cisternae associ ating with apical microtubule networks. In the second process, the structur es fragment more thoroughly or substantially relocate to the ER, Our analys es further showed that cdc2 kinase and mitogen-activated protein kinase kin ase (MAPKK = MEK) are differently involved in these two processes: the firs t process is mainly regulated by MEK and the second mainly by cdc2.