(469a) Multimeric Protein Nanoparticles for Engineering Biomolecular Condensate Surfaces

Cells possess a multitude of organelles, which are compartmentalized to coordinate countless biochemical reactions. These numerous, synchronized reactions occurring in different organelles ensure the proper functioning of the cell. While organelles like lysosomes and mitochondria are bound by membranes, many others are not and are referred to as biomolecular condensates. Recent research has revealed that many of these biomolecular condensates are viscoelastic polymer solutions formed through the phase separation of proteins and nucleic acids.

The nucleolus is one such condensate that contains multiple liquid-like layers, aiding in the creation of ribosomes - the cell’s protein synthesizer. The transport of proteins and nucleic acids between nucleoli and nucleoplasm is essential to ribosome biogenesis and proteins at the surface plays a crucial role in this transport. Therefore, in this work, we focused on designing synthetic proteins that resemble amphiphilic surfactants and localize at the interface between the nucleoli and nucleoplasm. Similar to amphiphilic surfactants that consist of hydrophilic and hydrophobic components, we designed proteins with “nucleoli-philic” and “nucleoli-phobic” domains. Both proteins engineered with optogenetic dimerization domains were genetically integrated into mammalian cells using lentiviral transduction. When exposed to blue light, the nucleoli-philic and nucleoli-phobic units form a complex and enrich at the surface of nucleoli. This engineered “nucleolar surfactant” sheds light on key aspects of the biophysics of nucleolar surfaces and enables the modulation of nucleolar surface properties and functions. We envision that discovering methods to manipulate biomolecular interfaces could have therapeutic implications for diseases such as cancer and ribosomopathies, where alterations in nucleolar surface properties are frequently observed.