How fluorescent tags tracked the movement
- Mark the membrane network
- Researchers tagged TGBp3 red and used a green marker for the interior of the endoplasmic reticulum.
- Both colors appeared in the structures near the cell’s edge, supporting an origin in the endoplasmic reticulum. [1]
- Follow other proteins
- TGBp3 redirected the related TGBp2 protein and two tested membrane proteins from other viruses.
- The team observed retargeting in this set of proteins from more than one virus. [1]
- Test a membrane anchor alone
- The team tethered fluorescent reporters to the membrane of the endoplasmic reticulum. The reporters still did not follow TGBp3 into the structures near the cell’s edge.
- The result suggested that the targeting signal involves something more specific than a membrane anchor. [1]
What does rerouting mean here?
The researchers compared where a fluorescently tagged protein appeared with and without TGBp3. A shift in the label meant the protein had changed location. The membrane-anchor experiment tested whether starting at the same internal membrane was sufficient for that shift. [1]
What can the images tell us about the route?
The two colors showed which proteins and markers ended up together. Whether the proteins touched directly or the structures remained connected to the membrane needed other tests. Follow-up work identified which parts of the same movement protein contribute to its targeting. [1][2]
Why did the researchers use mammalian cells too?
TGBp2 also changed location when researchers made mammalian cells produce the relevant viral proteins. The authors used those cells to test the targeting behavior in another setting. The experiment expressed individual proteins and did not test infection in a mammal. [1]
Original research
- Zamyatnin et al. (2002), Journal of General Virology. Dual-colour imaging of membrane protein targeting directed by poa semilatent virus movement protein TGBp3 in plant and mammalian cells. Primary dual-color imaging and artificial membrane-anchor comparison.
- Schepetilnikov et al. (2008), Journal of Virology. Intracellular targeting of a hordeiviral membrane-spanning movement protein: sequence requirements and involvement of an unconventional mechanism. Follow-up study on the sequence requirements and intracellular pathway.