Na,K-ATPase transport from endoplasmic reticulum to Golgi requires the Golgi spectrin-ankyrin G119 skeleton in Madin Darby canine kidney cells

Actin microfilaments are essential for the cytological positioning and morphology of the Golgi complex

The organization and function of the Golgi complex was studied in normal rat kidney cells following disruption of the actin cytoskeleton induced by cytochalasin D. In cells treated with these reagents, the reticular and perinuclear Golgi morphology acquired a cluster shape restricted to the centrosome region. Golgi complex alteration affected all Golgi subcompartments as revealed by double fluorescence staining with antibodies to the cis/middle Mannosidase II and the trans-Golgi network TGN38 proteins or vital staining with the lipid derivate C6-NBD-ceramide. The ultrastructural and stereological analysis showed that the Golgi cisternae remained attached in a stacked conformation, but they were swollen and contained electron-dense intra-cisternal bodies. The Golgi complex cluster remained linked to microtubules since it was fragmented and dispersed after treatment with nocodazole. Moreover, the reassembly of Golgi fragments after the disruption of the microtubuli with nocodazole does not utilize the actin microfilaments. The actin microfilament requirement for the disassembly and reassembly of the Golgi complex and for the ER-Golgi vesicular transport were also studied. The results show that actin microfilaments are not needed for either the retrograde fusion of the Golgi complex with the endoplasmic reticulum promoted by brefeldin A or the anterograde reassembly after the removal of the drug, or the ER-Golgi transport of VSV-G glycoprotein. However, actin microfilaments are directly involved in the subcellular localization and the morphology of the Golgi complex.

Cytoskeletal proteins and Golgi dynamics

Association of the Golgi complex with cytoskeletal elements, in particular microtubules, is required for maintenance of the Golgi's characteristic spatial location within cells and for efficient delivery of proteins and lipids to diverse cellular sites. Recent work has suggested the mechanisms underlying this association involve components, such as ankyrin and spectrin, that facilitate Golgi membrane association with motor proteins, including cytoplasmic dynein, kinesin and myosin. Understanding how these associations are regulated and what roles they play in Golgi trafficking and dynamics is fundamental for insight into the spatial and functional integration of secretory membrane traffic.