Pulse-Chase in the Light Microscope

A diagram summarizing the visualization of pulse–chase of connexin 43 (Cx43) in gap junctions. Two cells are diagrammed; the boxed area of cell–cell interaction is enlarged in panels A–D. (A) Cells transfected with tetracysteine-tagged Cx43 are labeled with FlAsH-EDT₂, which stains the gap junction fluorescent green. Following a wash, to remove excess FlAsH-EDT₂, cells are treated with ReAsH-EDT₂ to label all newly synthesized Cx43 fluorescent red. (B–D) Over time, newly synthesized Cx43 (red) replaces pre-existing Cx43 (green) by accretion at the edges of the gap junction with concomitant removal of connexons from the center.