To front-load evolution is an attempt to design future states through the present. To accomplish this, future evolutionary events would be fundamentally dependent on the originally designed state that has in some way propagated across deep time. While one might be tempted to believe that millions of years of evolutionary noise would drown out the design signal from the past, research in evolutionary biology indicates otherwise.

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Paxillin is a protein with multiple domains that hangs out at focal adhesions with various other proteins, including integrins. Focal adhesions are essentially points on the cell membrane where the actin cytoskeleton inside the cell is connected up to the extra-cellular matrix in multi-cellular organisms. Thus, the focal adhesions turn out to be useful nodes for signal transduction, where extra-cellular messages can quickly be converted into intra-cellular messages via activity at these adhesions. Paxillin functions as a multi-purpose adaptor protein that is involved in conveying signals and altering the cell’s cytoskeleton.

Recently, researchers at UC San Diego published videos of paxillin migrating from the cell periphery toward the nucleus along the cytoskeletal tracks. The interesting and educational video can be downloaded and viewed here:

One more thing. Paxillin, which is clearly very useful in metazoan life, is also found in unicellular organisms. In fact, according to one study of amoba, the paxillin-related signaling pathway is “similar to the one used in mammalian cells.” (Flores-Robles D, Rosales C, Rosales-Encina JL, Talamas-Rohana P. 2003. Entamoeba histolytica: a beta 1 integrin-like fibronectin receptor assembles a signaling complex similar to those of mammalian cells. Exp Parasitol. 103:8-15.