One of the first things you likely learned in your high school biology class was about cyclins, and their elegant and important discovery about 30 years ago. Cyclins are well-studied proteins that (you guessed it) cycle throughout the cell cycle and guide progress from one stage to the next. Today’s image is from a paper showing novel roles for a cyclin, and serves as a great reminder that no matter how much we may know about something, there are always new and exciting things to discover.
A cell must coordinate more than a handful of processes in order for cell division to occur correctly, and a group of proteins called cyclins helps to guide this process. Cyclin levels cycle throughout the cell cycle and activate kinases called Cdks, and together the cyclin-Cdk complexes trigger specific events. A recent paper discusses new results showing how a cyclin (Cyclin A2) regulates cytoskeletal organization and cell migration, independently of its binding to Cdk. According to Arsic and colleagues, depletion of Cyclin A2 causes a change in the distribution of actin filaments and an increase in cell migration. Cyclin A2 interacts with and activates RhoA, an actin regulator, which in turn negatively regulates migration. In addition, metastatic cancer cells show less Cyclin A2 expression than non-spreading tumor cells. In the images above, the distribution of actin (red) and focal adhesions (structures that link the cell to the underlying matrix, green) changes when Cyclin A2 is depleted (bottom row), when compared to control cells (top row).
Arsic, N., Bendris, N., Peter, M., Begon-Pescia, C., Rebouissou, C., Gadea, G., Bouquier, N., Bibeau, F., Lemmers, B., & Blanchard, J. (2012). A novel function for Cyclin A2: Control of cell invasion via RhoA signaling originally published in The Journal of Cell Biology, 196 (1), 147-162 DOI: 10.1083/jcb.201102085