Septins’ Role in Morphogenesis, Development, and Pathogenesis of the Human Fungal Pathogen Aspergillus fumigatus

Loading...
Thumbnail Image

Date

2017

Authors

Vargas-Muniz, Jose M.

Advisors

Steinbach, William J

Journal Title

Journal ISSN

Volume Title

Repository Usage Stats

176
views
341
downloads

Abstract

Aspergillus fumigatus, the main etiology of invasive aspergillosis, is a leading cause of fungal mortality in immunocompromised patients. Although the incidence of invasive aspergillosis has increased in the last two decades due to a rise in the immunocompromised patient population, there is a lack of effective treatments and basic understanding of growth and disease. Septins are conserved GTPases that are involved in a myriad of cellular processes, ranging from cytokinesis to cell morphology. Here we describe the role of septins in A. fumigatus growth, development, and pathogenesis. Through gene deletion, we revealed that all 5 septin genes are dispensable for growth under basal conditions. Nonetheless, AspA, AspB, AspC, and AspE are required for regular septation and the core septins are required for conidia production. The ΔaspB strain was hypervirulent in the Galleria mellonella model of infection, while virulence was similar to the wild-type strain in our murine model of invasive aspergillosis. Deletion of aspB also lead to an increase in susceptibility to anti-cell wall agents. AspB, which under basal conditions interacts with 334 proteins, alters its protein interaction after exposure to a clinically relevant concentration of the antifungal caspofungin. A total of 69 of the basal interactants do not interact with AspB, and 54 new interactants were identified following caspofungin exposure. Of the interactants studied, only PpoA was implicated in the response to anti-cell wall agents.

Due to the pleiotropic role of AspB, we characterized how posttranslational modifications regulate AspB function. Gene deletion analyses revealed that Cla4 and ParA are indispensable for hyphal extension. Gin4, Cla4, and ParA contributes to both septation and conidiation of A. fumigatus. Deletion of cla4 and parA lead to hyperseptation, while deletion of gin4 leads to larger apical compartments that were similar in length to the ΔaspB strain. Cla4, Gin4, and ParA contribute to proper localization of AspB. Phosphoproteomic analyses show that AspB is phosphorylated at 7 residues: 5 in the GTPase domain, and 2 at C-terminus. Deletion of gin4 and cla4 did not alter the phosphorylated residues in AspB. Deletion of parA results in 2 new phosphorylation sites identified, one in the N-terminal polybasic region (T68) and one in the coil-coiled domain (S447). Mutation of T68 to glutamic acid leads to a slight increase in interseptal distances. These results demonstrate the key role of septins in response to anti-cell wall agents, as well as how phosphorylation regulates septin function in A. fumigatus.

Description

Provenance

Citation

Citation

Vargas-Muniz, Jose M. (2017). Septins’ Role in Morphogenesis, Development, and Pathogenesis of the Human Fungal Pathogen Aspergillus fumigatus. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/14384.

Collections


Dukes student scholarship is made available to the public using a Creative Commons Attribution / Non-commercial / No derivative (CC-BY-NC-ND) license.