This dense network of colorful threads is made up of actin proteins. Each molecule was drawn as a single pixel; together they form thread-like structures. However, the distribution of the molecules is not uniform. The protein molecules form an arch that has a higher density of actin. It is part of a mechanism by which proteins are transported within a cell.
The protein actin is found in all cells with a nucleus. It forms thread-like cell structures called filaments that stabilize the external cell shape, are involved in transport within the cell and play a central role in cell movement. For the latter, the cell builds up actin filaments at the front and simultaneously breaks them down at the back. For this it is necessary that the proteins are transported through the cell. Until now, it was assumed that soluble proteins drift around randomly and only get where they are needed by chance. Researchers of the Oregon Health & Science University now show: Proteins are specifically brought to the right place in the cell. The results were published in the specialist journal nature communications.
To study the movement of proteins within a cell, the researchers marked part of the fluorescent actin in the back of the cell with a laser, so that these proteins became dark. After a few seconds, this no longer fluorescent actin was visible at the front of the cell. It was also observed that the proteins moved forward almost fifty times faster than backwards – an indication that transport is an active process.
Using various imaging techniques, the researchers were able to find that cells in a specific area actively generate directed currents. This area is delimited by a wall made of actin and myosin, another protein. This is the colored bow that can be seen in the picture. When the cell bends the barrier at certain points, the course of the flow changes so that proteins are transported to certain locations on the front of the cell.
This barrier could be made visible using a super-resolution microscopy method. The resolution of the image is 10,000 times that of a human hair.