Quantitative analysis of endocytosis and cytokinesis

From Q-bio

We use a combination of biophysical methods, quantitative fluorescence microscopy of live cells and mathematical modeling to understand how fission yeast assemble actin filaments into complicated structures used for endocytosis and cytokinesis. Endocytosis depends on nucleation of actin filaments by Arp2/3 complex at sites of clathrin-mediated endocytosis. Over about 10 seconds, tens to hundreds of copies of more than a dozen different regulatory proteins guide the assembly of about 200 short actin filaments, which subsequently disassemble rapidly as the vesicle moves away from the plasma membrane. Cytokinesis depends on nucleation of actin filaments by formin proteins located in 65 nodes around the equator of the cell. Myosin motors in nearby nodes transiently capture and pull on these filaments to assemble the nodes into a contractile ring. Some time later the contractile ring constricts to pinch the cell in two. In both cases, stochastic mechanisms work reliably to assemble highly reproducible structures.