No 12 /November 29, 2001
How Cells Find Their Way
Cells have to be able to communicate with each other in order
to collaborate and to react to their environment. Only then can they develop,
migrate, detect bacteria and viruses, build axons and blood vessels. These
processes are important for the development of embryos, for the functioning of
the immune system, for wound healing, the creation of the nervous system and
angiogenesis. They are triggered by extracellular chemical signals, socalled
chemoattractants. Cells are able to detect and follow these chemoattractants in
a directed way (chemotaxis). How do they do that? “All living cells can sense their environment”,
said Peter Devreotes, cell biologist and Professor at Johns Hopkins University
in Baltimore (USA) at the international conference on “Cell Migration in Development and Disease” of the Max Delbrück
Center for Molecular Medicine (MDC) Berlin-Buch on Thursday, November 29, 2001.
In recent years scientist have elucidated some of the molecules and signalling pathways involved in this process they call “directional sensing”. They use amobae to study this phenomenon, as “chemotaxis is strikingly exhibited during the life cycle the social amobae”, Peter Devreotes explained. Also white blood cells (leukocytes) are used to study directional sensing, as they seek out invaders.
In eukaryotic cells (they have a nucleus and a cell membrane), such as leukocytes and amobae, directional sensing is mediated by socalled G-protein-linked signalling pathways, according to Peter Devreotes. These pathways play a crucial role in signal transduction. When receptors get activated by signal binding, G proteins get activated by the receptor and send the signal into the cell.
Receptors are evenly distributed around the cell
Peter Devreotes and his group found out that the receptors and G-protein subunits are uniformly distributed around the cell. However, this finding is somewhat surprising, since it does not explain, how cells know, which direction the chemical signal comes from and in which direction to move.
Part of the answer is to be found in the cell`s membrane. “Chemoattractants induce the appearance of binding sites for specific proteins on the inner face of the cell`s membrane for a short period of time”, Peter Devreotes explained. It is thought that these binding sites are specific and rare phospholipids. In gradients, these lipids are persistently present on the side of the cell facing the higher concentration of chemoattractants. “Thus, the cell senses direction by spatially regulating the activity of the signal transduction pathway”.
Barbara Bachtler
Press and Public Affairs
Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch
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Phone: +49 (0) 30 94 06 - 38 96
Fax: +49 (0) 30 94 06 - 38 33
e-mail: presse@mdc-berlin.de
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