Arthur Molines

University of California, San Francisco

Cytoplasm Physical Properties and Their Consequences on Cellular Functions

Abstract: The cytoplasm is a crowded, viscoelastic environment whose physical properties change according to physiological or developmental states. Its complex physical properties emerge from its composition; hundreds of milligrams of proteins per milliliter, hundreds of millimolar of ions, as well as nucleic acids and carbohydrates. How the physical properties of the cytoplasm are regulated and how they impact cellular functions remain poorly understood. Here, I will highlight how we used fission yeast as a model system, and microtubule dynamics as a model for cellular reactions to tackle these questions experimentally. Through the use of various experimental schemes, nutritional perturbations, and osmotic shocks in vivo, as well as in vitro reconstitutions, we tried to further our understanding of the cytoplasm and its physical properties. Notably, we were able to show that the viscosity of the cytoplasm determines cytoskeleton dynamics (Molines et al., 2022). We then exposed the heterogeneous nature of the cytoplasmic environment using nanoparticle tracking and stochastic modeling (Garner, Molines et al., 2023). More recently, we started using nutritional perturbations such as low nitrogen conditions to decipher the relationships between metabolism, the physical properties of the cytoplasm, growth rate, and cell cycle progression. Overall, our findings highlight the complex nature of the cytoplasm and the important roles played by its physical properties in influencing cellular function.