The Function Of GRASP55and GRASP65in Mediating Golgi Membrane Stacking

In mammalian cells, the Golgi apparatus show stacked architecture, and there are two proteins involved in this process, GRASP55and GRASP65. GRASP proteins are composed of an N-terminal GRASP domain and a C-terminal tail. GRASP domain contains two tandem PDZ domains, which are required to tether the Golgi membranes. However, the mechanism of how GRASP proteins mediate the Golgi stacking is unknown. According to the GRASP proteins’ structures information, we speculate several sites that are functional on the PDZ2-PDZ2and PDZ1-CT interface, and we have tested these mutations in cells. Our results are consistent with the in vitro assay, suggesting a novel model of membrane tethering by GRASP proteins and provide insights into the mechanism of Golgi stacking.