Myosin V-Mediated Cargo Traffic toward the Trans-Golgi Network and Myosin v Implications in Snc1 Exocytosis
Retrieval of cargo proteins from the endosome towards the trans-Golgi network (TGN) is a crucial intracellular process for cellular homeostasis. Its dysfunction is associated with pathogenesis of Alzheimer and Parkinson's diseases. Myosin family proteins are cellular motors walking along actin filaments by utilizing the chemical energy from ATP hydrolysis, known to involve in pleiotropic cellular trafficking pathways. However, the question of whether myosins play a role in the trafficking of Snc1 and Vps10 has not been addressed yet. The present study assesses the potential roles of all five yeast myosins in the recycling of two membrane cargo, Snc1 and Vps10. It appears that, of the five yeast myosins, only Myo2 is required for Sync1 sorting and trafficking and that the Myo1 and 2 are important for Vsp10 retrieval from the endosome. Multiple myo2 mutants harboring a point mutation in the actin binding or the cargo binding tail domain were shown to have abnormal Vps10-GFP and GFP-Snc1 distribution phenotypes, suggesting a severe defect in their sorting and trafficking at the endosome. Furthermore, Vps10-GFP patches in all tested myo2 mutants were found to be near stationary with quantitative live cell imaging. Finally, I found that actin cables in the myo2 mutant cells were considerably disrupted, which may aggravate the trafficking of Vps10 from the endosome. Together, my results provide novel insights into the function of Myo-family proteins in the recycling traffic of Vps10 and Snc1 destined for the TGN.