Regulation of protein clustering and spread by organelle geometry and dynamics

Synopsis

Among their many features, living cells maintain spatial organization and send internal signals to sustain their health and functional capacity. Both spread and concentration of proteins are key to spatial organization and intracellular signaling. This talk will focus on the physical principles that control the clustering of proteins on the endoplasmic reticulum and spread of proteins within dynamic mitochondrial networks. I will examine the dynamics of IRE1 protein clusters on the tubes of the endoplasmic reticulum (ER), an organelle composed of a cell-spanning network sheets and tubes. With a lattice gas model, we find that narrow ER tubes facilitate IRE1 cluster wrapping around the tubes, allowing clusters to grow more rapidly, evaporate more slowly, and remain stable at lower protein concentrations. Mitochondria, popularly known as powerhouses of the cell, form dynamic tubular networks. Using two quantitative models of mitochondrial dynamics, we show that the formation of three-way junctions, which enable branching of mitochondrial tubes, is crucial for efficient spread through the network. Overall, organelle geometry and dynamics are important factors in protein clustering and transport in cell biology.