The plasma membrane is both a physical barrier that borders the cell and a complex communication device that governs the cell’s interactions with its environment and other cells. Thus, endocytic membrane trafficking, which controls the surface expression of transporters, as well as signaling, adhesion, immune and nutrient receptors is highly regulated.
We study clathrin-mediated endocytosis (CME), the major and best understood endocytic pathway. In this complex, multistep process clathrin and adaptor complexes assemble onto the cytosolic surface of the plasma membrane to form clathrin-coated pits (CCPs) that concentrate integral membrane proteins, invaginate and pinch off to form clathrin-coated vesicles that carry their cargo into the cell. In addition to the major coat proteins, CME requires the large GTPase dynamin and a plethora of endocytic accessory proteins (EAPs) of poorly defined function.
We have shown that dynamin plays a dual role in CME: it functions early to regulate an endocytic checkpoint that monitors the fidelity of CCP maturation, and then self-assembles into collar-like structures at the necks of deeply invaginated CCPs to drive membrane fission. We use molecular cell biology, biochemistry, biophysics and quantitative live-cell total internal reflection fluorescence microscopy to study the factors that regulate CME and to determine the mechanism of action of the dynamin.