Phase Separation of Membrane Scaffolding Proteins as a Mechanism to Control Formation of Tight Junctions
In this project we aim to understand how tight junctions (TJ) assemble into a continuous sub-apical belt in epithelial cells. Based on cell biological and in vitro data we hypothesize that the main scaffolding proteins of TJs, zonula occludens proteins (ZO), form a condensed compartment via phase separation on the membrane to enriched TJ adhesion receptors and cytoskeletal adapter proteins. Furthermore this compartment may ‘catalyze’ the polymerization of TJ strands, thereby driving the formation of a junctional belt. To test this hypothesis we will combine cell biology, in vitro biochemistry and theoretical modelling. We think this project will provide new insights how assembly of complex mesoscale structures such as adhesion junction can be controlled in space and time via a combination of phase separation coupled to active processes such as polymerisation and phosphorylation.
Current State of Research
We have collected convincing data indicating that the initiation of tight junction indeed requires phase separation of ZO proteins. Experimentally, we are now in the process of investigating the structural aspects of the supra-molecular organization of the TJ scaffold. One important question we want to understand is how the phase transition of ZO proteins is controlled: membrane binding, phosphorylation, mechanical forces.
This project is an interdisciplinary collaboration between the Honigmann lab (MPI-CBG) and the Weber group (MPI-PKS).
The Honigmann lab combines cell biology, biochemistry and super-resolution microscopy to understand the self-assembly mechanisms of cell membrane structures in epithelial tissues.
The Weber group is a theory group interested in how phase-separation far away from equilibrium can mediate changes of physicochemical properties in living systems.