Animal and human cells are not rigid objects. They actively move around, they reproduce and divide. Inside the body their motile behaviour allows them to find predetermined destinations or to envelope particles like dead cells or disease-causing pathogens and eventually ingest them.
In order to move and change their shape, they form tiny protrusions, so-called lamellipodia and filopodia. These are flat and wide or, in the latter case, of finger-like shape and extend from the cell periphery. Both lamellipodia and filopodia are produced by the polymerisation of actin into filaments.
The cytoskeleton gives support and structure to individual cells, and its controlled reorganisation triggers cell motility. Actin embodies the most dynamic part of the cytoskeleton and is indispensable for cell movement. Actin generates thin threads, known as microfilaments, which grow and shrink in response to cellular signals. In lamellipodia, actin is arranged in a criss cross fashion, whereas it is bundled in parallel in filopodia.
In lamellipodia, the generation of actin filaments is controlled by a protein assembly called Arp2/3-complex, which acts downstram of activatory signals that make the cell move. The formation of filopodia is less well understood and may involve formin-proteins for the polymerisation of actin. The exact steps a given signal path consists of and the way individual signals converge to induce motile behaviour, is being investigated by the group "Signalling and Motility"
