1. Fungal-Specific Mechanisms of Ras-Mediated Morphogenetic Signaling in Aspergillus fumigatus
Jarrod Fortwendel, PhD
Assistant Professor
Dept. of Microbiology and Immunology
University of South Alabama

2. The Ras GTPase: A Binary Switch
Conserved GTPase protein that controls growth and differentiation
Binary switch:
Active (GTP) and inactive (GDP)
Controlled by interaction with:
GTPase activating protein (GAP)
Guanine exchange factor (GEF)
Ras is found mutated in up to 30% of all human cancers
Ras pathways are focus of anti-cancer therapies

3. A. fumigatus Ras homologs
A. fumigatus encodes 2 Ras proteins:
RasA:
Major Ras protein in fungi
RasB :
Fungal specific Ras homolog
Minor role in growth and asexual development
RasA homologs are critical to morphogenesis and virulence in all fungi

4. Spatiotemporal Ras Regulation is Required for Morphogenesis
Fortwendel J R et al. Eukaryotic Cell 2008;7:
In Aspergilli, there are two major Ras proteins with this structure…RasA is the more important of the two…

5. Spatiotemporal Ras Regulation is Required for Morphogenesis
GDP
RasA
RasA
GTP
Deregulation
To test this hypothesis, I mutated the cysteines…
Fortwendel J R et al. Eukaryotic Cell 2011;10:

6. Ras Protein Maturation – Post-translational Lipidation
Plasma Membrane
RasA
--CC--C
RasA
--CC--CAAX
FTase
RasA
--CC--C
PATs
ER/Golgi Membrane

7. Ras Protein Maturation – Post-translational Lipidation
Plasma Membrane
RasA
--CC--C
RasA
--CC--CAAX
FTase
RasA
--CC--C
Farnesyltransferase Inhibitors
Palmitoyltransferase Inhibitors
PATs
ER/Golgi Membrane

8. Spatiotemporal Ras Regulation is Required for Morphogenesis
RasA
--CC--CAAX
Fortwendel J R et al. Eukaryotic Cell 2012;11:

9. Spatiotemporal Ras Regulation is Required for Morphogenesis
RasA
--CC--CAAX
Farnesyltransferase deletion WT
Δram1
Ram1-C’

10. Spatiotemporal Ras Regulation is Required for Virulence
Fortwendel J R et al. Eukaryotic Cell 2012;11:
ΔrasA and palmitoylation-deficient mutants exhibit reduced virulence

11. Summary of RasA Functions
Conserved aspects required for Ras pathway function
Regulation of localization and activity controls processes that support filamentous growth
Fortwendel J R et al. Eukaryotic Cell 2011;10:

12. Future Questions/Directions
Do fungal-specific Ras domains contribute to Ras-mediated growth and virulence?
Are there fungal-specific attributes of Ras network signaling that contribute to hyphal morphogenesis?
RasA

13. Acknowledgements University of South Alabama Past labs:
Rachel Lovingood, M.S.
Tiffany Norton
Haidee Custodio, M.D.
Past labs:
Bill Steinbach, M.D. (Duke)
-Praveen Juvvadi, Ph.D.
Judy Rhodes, Ph.D. (Cincinnati)
FTI studies – Lorena Beese and Mike Hast
Ras protein structure – Matt O’Meara and
Funding - NIH/NIAID
K22 - K22AI089766
R01 - R01AI106925