Exploring Liquid-Liquid Phase Separation in the organization of Golgi Matrix Proteins

The Golgi apparatus is a critical organelle in protein sorting and lipid metabolism. Characterized by its stacked, flattened cisternal structure, the Golgi exhibits distinct polarity with its cis - and trans -faces orchestrating various protein maturation and transport processes. At the heart of its structural integrity and organization are the Golgi Matrix Proteins (GMPs), predominantly comprising Golgins and GRASPs. These proteins contribute to this organelle’s unique stacked and polarized structure and ensure the precise localization of Golgi-resident enzymes, which is crucial for accurate protein processing. Despite over a century of research since its discovery, the Golgi architecture’s intricate mechanisms still need to be fully understood. Here, we demonstrate that GMPs present a significant tendency to form biocondensates through Liquid-Liquid Phase Separation (LLPS) across different Eukaryotic lineages. Moreover, we validated experimentally that members of the GRASP family also exhibit a strong tendency for LLPS. Our findings offer a new perspective on the possible roles of protein disorder and LLPS of GMPs in the Golgi organization.