Arginylation and Cell Migration

In my last post, I forgot to link to these great movies of migrating fibroblasts (available as online supplements to the arginylation paper), that illustrate how beta-actin arginylation can alter cellular behavior.

So the assay is simple, grow fibroblasts until they fill up the coverslip as a single layer of cells (or monolayer). At this stage the cells will stop dividing (by a process known as "contact inhibition of cell growth"). Then the researcher can scratch the monolayer thus removing a strip of cells. The surviving cells present at the wound edge will at once migrate into the wound.

Watch as normal cells perform this task. Note that the cells send out nice flat protrusions (or lamelopodia) into the wound and that the very edge of the protrusion "ruffles". This protrusion and ruffle is caused by a polymerizing actin meshwork.

Now here is a video of Ate1-/- cells migrating into a wound. See how they lack nice lamelopodia. Clearly actin dynamics is altered in these cells.

Video #3. On the top is an Ate1 defficient cell, that lacks arginylated beta-actin, on the bottom is an Ate1 -/- cell that expresses a version of beta-actin that has an extra arginine at it's N-terminal. As the video clearly shows, expression of the altered beta-actin restores most of the Ate1 -/- cell's protrusive activity.

In video #4 you can clearly identify the Ate1 -/- cell expressing the modified beta-actin (see arrow in figure) in a monolayer of regular Ate1 -/- cells.

Now this brings up an interesting question. Why modify actin post-translationally? Apparently not every aspect of cellular behavior is rescued by expressing this altered form of beta-actin. It will be interesting to see how this story develops.