Light Used to Move Molecules

Light-triggered chemistry can help move individual molecules around inside living cells, sending them to exact locations at precise times.

This new tool, according to its developers at Johns Hopkins University, will allow visualization of how molecules in certain cell locations can influence cell behavior and help determine whether cells will grow, die, move or divide.
Studying how just one signaling molecule communicates in various parts of a living cell has posed a challenge for scientists investigating how different interactions influence cell behavior, such as the decision to move, change shape or divide.

“By using one magical chemical set off by light, we modified our previous technique for moving molecules around and gained much more control,” said Takanari Inoue, assistant professor of cell biology. “The advantage of using light is that it is very controllable, and by confining the light, we can manipulate communication of molecules in only a tiny region of the cell.”

Specifically, Inoue and his colleagues designed a way to initiate and spatially restrict the molecular interactions to a small portion of the cell by attaching a light-triggered chemical to a bulky molecule, the bond between which would break when researchers shone an ultraviolet beam on it. This enabled the chemical to enter the cell and force two different and specific proteins in that cell to mingle when they otherwise wouldn’t. Normally, these proteins would have nothing to do with each other without the presence of the light-triggered chemical, but researchers decided to take advantage of this mingling to explore how certain proteins in a cell behave when transported to precise locations.

Next, the researchers modified the two mingling proteins by attaching special molecules to them – one sent a protein to the edge of the cell, and another caused ripples to form on the edge of the cell – so that if ripples form on the edge of the cell, they would know that the proteins were interacting there.

The researchers put both modified proteins inside human skin cells and bathed the cells in the light-triggered chemical tool. Then they shone a tiny UV beam on approximately 10 percent of the edge of a skin cell. Ripples appeared only on the region of the cell near where the light touched, demonstrating that the tool could limit cell activity to a precise location in the cell.

The tool can be used in larger cells, Inoue said, to monitor as little as 1 percent of a specific molecule if the beam intensity is varied. That, in turn, could reveal in even more detail the secret affairs of proteins in cellular cubbyholes. The work was reported in the Dec. 13, 2010, online edition of the Journal of the American Chemical Society.

“With this technique, we can get a finer understanding of cell function on the molecular level,” Inoue said. “Our technique allows us to monitor whatever molecule we choose in whichever tiny space we choose, so that we can understand how a molecule functions in a specific part of a live cell.”

For more information, visit: www.jhu.edu