Plasma membrane-compartmentalized activity of Aspergillus fumigatus RasA is required for polarized growth and virulence

Ref ID: 18358

Author:

Jarrod R.
Fortwendel, Praveen R. Juvvadi, Luise E. Rogg, and William J. Steinbach Duke

Author address:

University Medical Center, Durham, NC USA

Full conference title:

Asperfest 8

Abstract:

Ras homologs are multifunctional proteins that are localized to specific sub-cellular membranes via post-translational addition of farnesyl and palmitoyl
lipid moieties. Farnesylation of Ras directs the nascent Ras protein to the endomembrane system, whereas plamitoylation drives localization to the plasma
membrane. This “œcompartmentalization” of activity allows for specificity in signal transduction. We have previously shown that deletion of A. fumigatus
rasA causes slowed growth, malformed hyphae, and reduced cell wall integrity. However, the membrane distribution and the role of sub-cellular
compartmentalization of RasA activity in these important cellular processes are unknown. To examine the distribution of RasA, a GFP-RasA fusion was
expressed in the delta-rasA mutant background. GFP-RasA localized primarily to the plasma membrane of actively growing hyphae and septa. Expression
of GFP-RasA in the delta- rasA background resulted in recovery of the wild type phenotype, indicating the fusion was functional. Inhibition of protein
palmitoylation using 2-bromopalmitate caused hyphal deformation and reduced growth, as well as mislocalization of the GFP-RasA protein to internal
structures. To further explore the role of palmitoylation, mutations in two conserved cysteine residues, which function as palmitoylation sites, were
introduced to completely block RasA palmitoylation. The palmitoylation-deficient RasA mutant (RasA-P) displayed a decreased growth rate and hyphal
abnormalities similar to the delta-rasA strain, as well as complete mislocalization of GFP-RasA from the plasma membrane. The delta- rasA and RasA-P
mutants displayed similarly altered glucan and chitin staining, while TEM analysis revealed similar cell wall structural differences in both strains.
Virulence was decreased for both mutants in a mouse model of invasive aspergillosis. Taken together, our data reveal the importance of plasma membranelocalized RasA activity in polarized morphogenesis and virulence of A. fumigatus.

Abstract Number: 36)

Conference Year: 2011

Link to conference website: NULL

New link: NULL

Conference abstracts, posters & presentations

Showing 10 posts of 17325 posts found.

  • Title

    Author

    Year

    Number

    Poster