Partitioning of ribonucleoprotein complexes from the cellular actin cortex
Isaac Angert1,2,3, Siddarth Reddy Karuka1, Louis M. Mansky2,3,4, Joachim D. Mueller1,2,5
1- School of Physics and Astronomy, University of Minnesota, Minneapolis. 2- Institute of Molecular Virology, University of Minnesota, Minneapolis. 3- Division of Basic Sciences, School of Dentistry, University of Minnesota, Minneapolis. 4- Masonic Cancer Center, University of Minnesota, Minneapolis. 5- Department of Biomedical Engineering, University of Minnesota, Minneapolis
The cell cortex plays a crucial role in cell mechanics, signaling, and development. However, little is known about the influence of the cortical meshwork on the spatial distribution of cytoplasmic biomolecules. Here, we describe a new fluorescence microscopy method to infer the intracellular distribution of labeled biomolecules with sub-resolution accuracy. Unexpectedly, we find that RNA-binding proteins are partially excluded from the cytoplasmic volume adjacent to the plasma membrane that corresponds to the actin cortex. Complementary diffusion measurements of RNA-protein complexes suggest that a rudimentary model based on excluded volume interactions can explain this partitioning effect. Our results suggest the actin cortex meshwork may play a role in regulating the biomolecular content of the volume immediately adjacent to the plasma membrane.