We have used electron microscopy to further characterize details of th
e dynamics of TGN38/41, a protein found to cycle between the trans-Gol
gi network and the plasma membrane. Immunogold-labeling of NRK cells u
nder steady-state conditions shows the majority of TGN38/41 is localiz
ed to the trans-most Golgi cisternae and the trans-Golgi network. Smal
l 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 mechan
ism' of phagocytosis. This provides a system that can address many que
stions related to the function of TGN38/41 and the trans-Golgi network
itself.