The ability of cells to move and change shape is significant in many biological processes. White blood corpuscles gather at “hotspots” like infections and inflammations. Stem cells in the embryo move off in different directions to make the organs of the body. One unwanted movement is the movement of tumour cells, which lead to cancer metastasis.
Cells have a clear leading and trailing edge and move by a broad, thin membrane protrusion shooting out in front while the rest of the cell follows it. Small, finger-like filopodia (the green parts of the human renal cell pictured at left) can also project out from the protrusion, probably a type of cellular antenna that senses the chemical environment – bacterial secretions, for example.
But what governs this ability to move? Water, say the Linköping research team, who set out their hypothesis in the scientific journal PLOS One.
For a cell to be able to initiate a movement there needs to be a complex interaction between the outer cell membrane and the cytoskeleton on the inside. One of the most important components is the protein actin, which has the ability to create dynamic fibres that can grow at one end and recede at the other. The current thinking is that, in this way, the membrane can push out and create the protrusions. But experiments and modelling have led the LiU researchers to another picture of the mechanism.
“We looked at how cells create the membrane protrusions they need in order to be able to move. We showed that the water flow out of and into the cells through water channels, or aquaporins, in the cell membrane is important,” says Thommie Karlsson, researcher in medical microbiology and principal author of the article.