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. Issue 3 (25th August 2016)

• Record Type: Journal Article
• Authors: Fernandes, C. M.; de Castro, P. A.; Singh, A.; Fonseca, F. L.; Pereira, M. D.; Vila, T. V. M.; Atella, G. C.; Rozental, S.; Savoldi, M.; Del Poeta, M.; Goldman, G. H.; Kurtenbach, E.
• Is Part Of: Molecular microbiology. Volume 102:Issue 3(2016)
• Page Start: 488
• Page End: 505
• Publication Date: 2016-08-25
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.13474
• Languages: English
• ISSNs: 0950-382X

Abstract

Summary: 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 Ps d1 defensin and Galleria mellonella virulence. We showed that Δ sdeA 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, Δ smtA 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 Δ smtB 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 Δ gcsA strain. Finally, Δ sdeA and Δ gcsA showed increased resistance to Ps d1, 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. Abstract : Δ4, Δ8‐9, Me‐glucosylceramide (GlcCer) is a fungal specific sphingolipid, contributing to growth and virulence. Aspergillus nidulans strains lacking genes involved in GlcCer synthesis ( sdeA – sphingolipid Δ8‐desaturase, smtA and smtB – sphingolipid C9‐methyltransferase and gcsA – glucosylceramide synthase) were constructed and characterized. The accumulation of Δ4‐GlcCer, Δ8‐Cer and Δ4, Δ8‐9, Me‐Cer intermediates in Δ sdeA, Δ smtA niiA::smtB and Δ gcsA mutants compromised growth, suggesting that fungal GlcCer structure specificities and synthesis are relevant for A. nidulans differentiation.