Membrane deformation and Clathrin
The clathrin cage, composed of hexagons and pentagons engulfing a lipid bilayer, is the earliest membranous carrier described. The polymerization of clathrin into this cage was thought to generate the force needed to deform the membrane into a bud.
After many years of research, this view has been challenged by two facts: first, in addition to the classical soccer ball structure, many other shapes have been observed ranging from flat lattices to tubules. Secondly, the binding of clathrin to the membrane is occurring through a wide family of adaptor proteins that have been shown to deform membranes and modulate clathrin polymerization.
Even though a tremendous amount of knowledge has been acquired on the clathrin coat formation, some early essential questions are still open: How is the shape of a clathrin lattice controlled? How fast can clathrin form a membrane intermediate to achieve rapid internalization? Is clathrin polymerization the driving force for membrane budding?
The final shape of a clathrin bud is intimately dependent on the exact position and number of pentagons, hexagons and other polygons in the lattice. Thus, parameters that locally drive the polymerization of clathrin into such or such polygon can influence the final shape.
- Our first goal is to characterize the different shapes that clathrin coats can form and measure how fast they can grow. This will help us in finding the critical parameters that govern the shape of clathrin-coated structures, and their polymerization rate, at scale of the lattice.
- Our second goal is to understand how these parameters can affect locally the clathrin polymerization to trigger the right positioning of polygons in order to generate the global shape.