The goal of this project is to study the role and mechanisms by which host sphingolipids are involved in controlling the infection caused by the pathogenic fungus Cryptococcus neoformans (Cn). A rapidly emerging area of research is the study of the role of sphingolipids in the regulation of infectious diseases (Reviewed in1). Although some sphingolipids have been linked to antibacterial activity of phagocytic cells,2,3 very little is known about the role of host sphingolipids against fungal infections. One of the host sphingolipid-metabolizing enzymes shown to regulate immune responses is sphingomyelin synthase (SMS), encoded by the SMS1 and SMS2 genes.4-6 SMS transfers a choline phosphate moiety from phosphatidylcholine (PC) to ceramide, therefore producing sphingomyelin (SM) and diacylglycerol (DAG).7-9 Very interestingly, the lipids regulated by SMS have been implicated in the activation of pro-inflammatory responses, suggesting that the regulation of SMS activity in immune cells may assume a critical role in controlling infections. In our preliminary and published studies10,11 we found that: 1) inhibition of SMS activity profoundly impairs the ability of phagocytic cells to kil Cn cells by affecting extracellular killing in absence of phagocytosis; 2) SMS regulates production of DAG at the Golgi; 3) DAG produced at the Golgi by SMS regulates protein secretion via activation of protein kinase D (PKD); 4) inhibition of SMS or PKD blocks extracellular killing of Cn and peptide secretion (such as defensins) by neutrophils; and 5) neutropenia significantly exacerbates Cn infection. Based on these observations, we hypothesize that SMS activity plays a key role in controlling the extracellular killing of neutrophils through the regulation of a DAG-PKD-mediated secretion pathway (Figure 1). Thus, we propose the following aims: 1) To establish the role of SMS against Cn; and 2) To determine the mechanism by which SMS regulates Cn killing. The studies proposed in this applications are significant and novel at different levels: i) they will establish novel animal models for the study of fungal infection that are more clinically relevant to the human infection than current models; ii) they will define the role of phagocytes in the host response to fungal infections; and iii) they will identify novel regulators of the phagocytes' response against the infection which can be engineered to boost the host immune system.
Fungal infections have dramatically increased during the last decade afflicting both immunodeficient and immunocompetent individuals including military personnel. This proposal focuses on a better understanding of host resistance and susceptibility with important implications for the developing of new therapeutic strategies.
|Raj, Shriya; Nazemidashtarjandi, Saeed; Kim, Jihyun et al. (2017) Changes in glucosylceramide structure affect virulence and membrane biophysical properties of Cryptococcus neoformans. Biochim Biophys Acta 1859:2224-2233|
|Singh, Ashutosh; MacKenzie, Andrew; Girnun, Geoffrey et al. (2017) Analysis of sphingolipids, sterols, and phospholipids in human pathogenic Cryptococcus strains. J Lipid Res 58:2017-2036|
|Singh, Ashutosh; Del Poeta, Maurizio (2016) Sphingolipidomics: An Important Mechanistic Tool for Studying Fungal Pathogens. Front Microbiol 7:501|
|Mor, Visesato; Farnoud, Amir M; Singh, Ashutosh et al. (2016) Glucosylceramide Administration as a Vaccination Strategy in Mouse Models of Cryptococcosis. PLoS One 11:e0153853|
|Bryan, Arielle M; Del Poeta, Maurizio (2016) Secretory aspartyl proteinases induce neutrophil chemotaxis in vivo. Virulence 7:737-9|
|Rella, Antonella; Farnoud, Amir M; Del Poeta, Maurizio (2016) Plasma membrane lipids and their role in fungal virulence. Prog Lipid Res 61:63-72|
|Joffe, Luna S; Nimrichter, Leonardo; Rodrigues, Marcio L et al. (2016) Potential Roles of Fungal Extracellular Vesicles during Infection. mSphere 1:|
|Rollin-Pinheiro, Rodrigo; Singh, Ashutosh; Barreto-Bergter, Eliana et al. (2016) Sphingolipids as targets for treatment of fungal infections. Future Med Chem 8:1469-84|
|Fernandes, C M; de Castro, P A; Singh, A et al. (2016) Functional characterization of the Aspergillus nidulans glucosylceramide pathway reveals that LCB ?8-desaturation and C9-methylation are relevant to filamentous growth, lipid raft localization and Psd1 defensin activity. Mol Microbiol 102:488-505|
|Nimrichter, Leonardo; de Souza, Marcio M; Del Poeta, Maurizio et al. (2016) Extracellular Vesicle-Associated Transitory Cell Wall Components and Their Impact on the Interaction of Fungi with Host Cells. Front Microbiol 7:1034|
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