Golgi Renaissance: the pivotal role of the largest Golgi protein giantin
Golgi undergoes disorganization in response to the drugs or alcohol, but it is able to restore compact structure under recovery. This self-organization mechanism remains mostly elusive, as does the role of giantin, the largest Golgi matrix dimeric protein. Here, we found that in cells treated with Brefeldin A (BFA) or ethanol (EtOH), Golgi disassembly is associated with giantin de-dimerization, which was restored to the dimer form after BFA or EtOH washout. Cells lacking giantin are disabled for the restoration of the classical ribbon Golgi, and they demonstrate altered trafficking of proteins to the cell surface. The fusion of the nascent Golgi membranes is mediated by the cross-membrane interaction of Rab6a GTPase and giantin. Giantin is involved in the formation of long intercisternal connections, which in giantin-depleted cells was replaced by the short bridges that formed via oligomerization of GRASP65. This phenomenon occurs in advanced prostate cancer cells, in which a fragmented Golgi phenotype is maintained by the dimerization of GRASP65. Thus, we provide a model of Golgi Renaissance, which is impaired in aggressive prostate cancer.