Myosin V Function and Regulation in the Morphogenesis of Aspergillus Fumigatus

Abstract

Over the last decade, a growing number of fungal infections of animals and plants has risen and persisted. The lack of diversity in antifungal drugs as well as rising antifungal resistance in many pathogens has exacerbated the problem. Thus there is a critical need for basic molecular understanding of fungal morphogenesis and pathogenesis to design new ways to combat these diseases. One of the fungal infections in need of new treatments is Aspergillus fumigatus, the etiological agent of invasive aspergillosis. A. fumigatus is an obligate filamentous fungus that is commonly found in the soil and air. It generally does not cause invasive disease in immunocompetent hosts; however immunocompromised people are at risk for invasive aspergillosis. To better understand the morphogenesis and pathogenesis of this fungus, I decided to study myosins, a group of actin-based motor proteins that are involved in myriad of integral processes in other organisms.Through gene deletion, I revealed the importance of the class II myosin, MyoB, in septal formation and conidiation. The class V myosin, MyoE, was required for hyphal polarity, radial extension, septal frequency and conidiation. Importantly, MyoE was required for full virulence in a murine model of invasive aspergillosis. Given the importance of MyoE in critical processes such as hyphal growth and pathogenesis, I aimed to understand the molecular requirements of MyoE. Through iterative truncations of MyoE’s N-terminal tail domain, I revealed the importance of the tail domain in hyphal growth, polarity, and MyoE localization. I identified several phosphorylated residues on the MyoE protein, but mutational analysis did not reveal that any one residue was required for MyoE function. In the absence of the serine/threonine phosphatase, calcineurin, MyoE was phosphorylated at an additional residue. Mutational analysis of a residue in the tail domain revealed it was required for septal localization but not hyphal tip localization, growth, or septation.Because MyoE is a cargo binding protein, it likely participates in several pathways that are required for growth and septation of the fungus. To identify novel roles of class V myosins, I identified the MyoE interactome using LC-MS/MS analysis. This analysis revealed several components of the COPII pathway for ER to Golgi transport, suggesting that MyoE may play a role in this protein transport system. My future work aims to understand this role.