Functional characterization of the Aspergillus nidulans glucosylceramide pathway reveals that LCB Δ8‐desaturation and C9‐methylation are relevant to filamentous growth,lipid raft localization and Psd1 defensin activity |
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| Authors: | C M Fernandes P A de Castro A Singh F L Fonseca M D Pereira T V M Vila G C Atella S Rozental M Savoldi M Del Poeta G H Goldman E Kurtenbach |
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| Institution: | 1. Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil;2. Faculdade de Ciências Farmacêuticas de Ribeir?o Preto, Universidade de S?o Paulo, Ribeir?o Preto, Brazil;3. Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA;4. Centro de Desenvolvimento Tecnológico em Saúde, Funda??o Oswaldo Cruz, Rio de Janeiro, Brazil;5. Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil;6. Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil |
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| Abstract: | C8‐desaturated and C9‐methylated glucosylceramide (GlcCer) is a fungal‐specific sphingolipid that plays an important role in the growth and virulence of many species. In this work, we investigated the contribution of Aspergillus nidulans sphingolipid Δ8‐desaturase (SdeA), sphingolipid C9‐methyltransferases (SmtA/SmtB) and glucosylceramide synthase (GcsA) to fungal phenotypes, sensitivity to Psd1 defensin and Galleria mellonella virulence. We showed that ΔsdeA accumulated C8‐saturated and unmethylated GlcCer, while gcsA deletion impaired GlcCer synthesis. Although increased levels of unmethylated GlcCer were observed in smtA and smtB mutants, ΔsmtA and wild‐type cells showed a similar 9,Me‐GlcCer content, reduced by 50% in the smtB disruptant. The compromised 9,Me‐GlcCer production in the ΔsmtB strain was not accompanied by reduced filamentation or defects in cell polarity. When combined with the smtA deletion, smtB repression significantly increased unmethylated GlcCer levels and compromised filamentous growth. Furthermore, sdeA and gcsA mutants displayed growth defects and raft mislocalization, which were accompanied by reduced neutral lipids levels and attenuated G. mellonella virulence in the ΔgcsA strain. Finally, ΔsdeA and ΔgcsA showed increased resistance to Psd1, suggesting that GlcCer synthesis and fungal sphingoid base structure specificities are relevant not only to differentiation but also to proper recognition by this antifungal defensin. |
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