PT  - JOURNAL ARTICLE
AU  - Oliver Beutel
AU  - Riccardo Maraspini
AU  - Karina Pombo-Garcia
AU  - Cécilie Martin-Lemaitre
AU  - Alf Honigmann
TI  - Phase separation of zonula occludens proteins drives formation of tight junctions
AID  - 10.1101/589580
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 589580
4099  - http://biorxiv.org/content/early/2019/03/26/589580.short
4100  - http://biorxiv.org/content/early/2019/03/26/589580.full
AB  - Tight junctions are cell adhesion complexes that seal tissues and are involved in cell polarity and signalling. Supra-molecular assembly and positioning of tight junctions as continuous networks of adhesion strands is dependent on the two membrane associated scaffolding proteins ZO1 and ZO2. To understand how ZO proteins organize junction assembly, we performed quantitative cell biology and in vitro reconstitution experiments. We discovered that ZO proteins self-organize membrane attached compartments via phase separation. We identified the multivalent interactions of the conserved PDZ-SH3-GuK supra-domain as the driver of phase separation. These interactions are regulated by phosphorylation and intra-molecular binding. Formation of condensed ZO protein compartments is sufficient to specifically enrich and localize tight junction proteins including adhesion receptors, cytoskeletal adapters and transcription factors. Our results suggest that an active phase transition of ZO proteins into a condensed membrane bound compartment drives claudin polymerization and coalescence of a continuous tight junction belt.