Cells change course with help from a laser

Scientists from the University of North Carolina at Chapel Hill have succeeded in using a beam of laser light to alter the course of moving cells.

Microscopic living structures move a little or a lot, healing wounds, developing embryos, scouting and attacking disease-causing invaders and, sometimes, spreading cancer.

Now, using a beam of laser light only a few microns in diameter, University of North Carolina at Chapel Hill scientists have succeeded for the first time in getting such light to alter the course of a moving cell.

They have accomplished that by having the laser create active proteins from what are called ‘caged’ proteins that they introduced into the cell.

‘We put caging groups on particular amino acids of the protein we were interested in inside single cells and that makes the proteins less active,’ said Dr. Kenneth A. Jacobson, professor of cell and developmental biology at the UNC School of Medicine. ‘Then we directed the laser beam into part of the cells to break the bond between the caging group and the amino acid so that the protein became active again. Afterward, depending on where we shined the light, cells turned by as much as 90 degrees.’

Their experiments might be likened to putting the breaks on one rear wheel of a car so that the car would tend to pull to one side or another, said Jacobson.

The team carried out their work on cells taken from fish scales that are somewhat comparable to human skin cells, said Dr. Partha Roy, a postdoctoral fellow.

‘The laser technique we used is novel and powerful because it allows us to actually manipulate proteins in specific places inside cells and do it instantaneously,’ said Dr. Partha Roy, a postdoctoral fellow. ‘That’s a huge advantage over conventional genetic approaches, which take a lot of time and can be compensated for by cells making other proteins that nullify the original genetic manipulation.’

Light-directed disruption studies promise to teach scientists much about cell movement and behaviour, said Roy.

‘We think this opens a lot of possibilities for learning what many signalling molecules do inside cells,’ he said. ‘If you can understand the behaviour of an internal protein, then you can make inhibitors or promoters that have implications for drug discovery.

‘In some cases, such as formation of new blood vessels in the treatment of coronary artery disease, you might want to speed up cell movement. On the other hand, you’d want to stop movement of cancer cells.’

Through a project with UNC’s Centre for Inflammatory Disorders, Jacobson’s laboratory is now applying the photo-release technique to a major puzzle — how blood cells can migrate through layers of other cells to sites of infection, said Jacobson.