Dynamics of the interphase mammalian Golgi complex as revealed through drugs producing reversible Golgi disassembly.

We focus on research aimed at understanding normal Golgi complex dynamics through the use of nocodazole and other drugs which cause Golgi disassembly. In vivo nocodazole binds to tubulin, produces microtubule depolymerization, and subsequent fragmentation of the Golgi complex. These processes may be traced in living cells through the application of fluorescent green protein (GFP) conjugates. The cycling of individual Golgi proteins through the endoplasmic reticulum (ER) may be probed in vivo through the use of an organelle-specific molecular trap. One such molecular trap is protein unfolding. Golgi proteins conjugated with a domain temperature sensitive in protein folding exhibit temperature-sensitive folding properties and if misfolded during protein cycling from the Golgi become trapped in the ER. The properties of individual Golgi complex subcompartments may be characterized through antibodies to multiple subcompartment-specific proteins within the same cell line. Because of the limited availability of antibodies, normally distributed epitope tagged proteins are employed to give multiple subcompartment-specific Golgi complex markers. From experiments employing these tools, new models suggesting continuous cycling of Golgi proteins are emerging. Cycling of Golgi proteins through the ER can lead to assembly of the Golgi stack at or about ER exit sites. A major future challenge will be the characterization of the protein machineries involved in Golgi protein cycling and its regulation.