Abstract

Biomolecular condensates composed of RNAs and/or proteins are formed through phase separation like processes inside cells. There is now increasing evidence that these condensates interact mechanically with other cellular components, including lipid membranes. In this talk, I will discuss several examples of such interactions, and how they can be important for biological functions. First, during seed development of the plant Arabidopsis thaliana, micrometer-sized condensates form within the vacuolar lumen and wet the tonoplast. Distinct tonoplast shapes arise in response to membrane wetting by condensates. Conditions of low membrane spontaneous curvature and moderate wettability favour droplet-induced membrane budding, whereas high membrane spontaneous curvature and strong wettability promote membrane nanotubes that sit at the condensate interface. Second, we investigate heterogeneous nucleation of condensates on lipid membranes. We find that membrane deformation can alter the nucleation pathway and significantly lower the nucleation barrier (even to zero). Third, recent observations on the mitochondria of HeLa cells show that protein condensates form in between lipid vesicles, and we hypothesise such condensates can provide non-specific capillary adhesion mechanism. Studying the morphology of capillary bridges between a condensate droplet and two vesicles, we find three distinct morphologies, which we term bridging, enclosing and zipping. We speculate the zipping morphology may allow the formation of contact sites between two opposing membranes.