An electron microscopic study of TGN38/41 dynamics.

We have used electron microscopy to further characterize details of the dynamics of TGN38/41, a protein found to cycle between the trans-Golgi network and the plasma membrane. Immunogold-labeling of NRK cells under steady-state conditions shows the majority of TGN38/41 is localized to the trans-most Golgi cisternae and the trans-Golgi network. Small amounts of this molecule can be detected in early endosomes. Capture of cycling TGN38/41 molecules at the cell surface altered the steady state distribution. This was accomplished by binding TGN38/41 luminal domain antibodies to solid supports (beads), which were introduced to the culture media of cells. As increasing numbers of antigen-antibody complexes formed, the beads were internalized by the 'zippering mechanism' of phagocytosis. This provides a system that can address many questions related to the function of TGN38/41 and the trans-Golgi network itself.