Protein profiling of the dimorphic, pathogenic fungus, Penicillium marneffei

Julie M Chandler¹ , Erin R Treece²^,3 , Heather R Trenary²^,4 , Jessica L Brenneman^*¹ , Tressa J Flickner^*¹ , Jonathan L Frommelt^*¹ , Zaw M Oo^*¹ , Megan M Patterson^*¹ , William T Rundle^*¹ , Olga V Valle^*¹ , Thomas D Kim²^,3 , Gary R Walker¹ and Chester R Cooper Jr¹

¹Proteomics Research Group, Department of Biological Sciences, Youngstown State University, Youngstown, OH 44555-3601, USA

²Department of Chemistry, Youngstown State University, Youngstown, OH 44555-3663, USA

³Department of Chemistry, Rochester Institute of Technology, One Lomb Memorial Drive, Rochester, NY 14623-5603, USA

⁴Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221-0172, USA

author email corresponding author email* Contributed equally

Proteome Science 2008, 6:17doi:10.1186/1477-5956-6-17


Published:	4 June 2008

Abstract

Background

Penicillium marneffei is a pathogenic fungus that afflicts immunocompromised individuals having lived or traveled in Southeast Asia. This species is unique in that it is the only dimorphic member of the genus. Dimorphism results from a process, termed phase transition, which is regulated by temperature of incubation. At room temperature, the fungus grows filamentously (mould phase), but at body temperature (37°C), a uninucleate yeast form develops that reproduces by fission. Formation of the yeast phase appears to be a requisite for pathogenicity. To date, no genes have been identified in P. marneffei that strictly induce mould-to-yeast phase conversion. In an effort to help identify potential gene products associated with morphogenesis, protein profiles were generated from the yeast and mould phases of P. marneffei.

Results

Whole cell proteins from the early stages of mould and yeast development in P. marneffei were resolved by two-dimensional gel electrophoresis. Selected proteins were recovered and sequenced by capillary-liquid chromatography-nanospray tandem mass spectrometry. Putative identifications were derived by searching available databases for homologous fungal sequences. Proteins found common to both mould and yeast phases included the signal transduction proteins cyclophilin and a RACK1-like ortholog, as well as those related to general metabolism, energy production, and protection from oxygen radicals. Many of the mould-specific proteins identified possessed similar functions. By comparison, proteins exhibiting increased expression during development of the parasitic yeast phase comprised those involved in heat-shock responses, general metabolism, and cell-wall biosynthesis, as well as a small GTPase that regulates nuclear membrane transport and mitotic processes in fungi. The cognate gene encoding the latter protein, designated RanA, was subsequently cloned and characterized. The P. marneffei RanA protein sequence, which contained the signature motif of Ran-GTPases, exhibited 90% homology to homologous Aspergillus proteins.

Conclusion

This study clearly demonstrates the utility of proteomic approaches to studying dimorphism in P. marneffei. Moreover, this strategy complements and extends current genetic methodologies directed towards understanding the molecular mechanisms of phase transition. Finally, the documented increased levels of RanA expression suggest that cellular development in this fungus involves additional signaling mechanisms than have been previously described in P. marneffei.