The School of Molecular and Cellular Biology at the University of Illinois at Urbana-Champaign

Fungal cell walls are dynamic three-dimensional complexes of polysaccharides and glycoproteins that confer cell integrity and dictate cell shape, yet which also permit cell expansion and cell division. Because the wall is essential for cell viability and because surface glycoproteins are adhesins and virulence determinants in fungal pathogens, inhibition of cell wall biogenesis should be an excellent strategy for combating the life-threatening fungal infections that afflict immunocompromised patients. We are using biochemistry, molecular genetics, and bioinformatics to study fungal cell wall biogenesis and identify new drug targets.

We have focused on the biosynthesis of glycosylphosphatidylinositols (GPIs), a class of glycolipid that is assembled by enzymes in the membrane of the rough endoplasmic reticulum (ER). GPIs are transferred to selected glycoproteins that are then transported to the plasma membrane, where they remain anchored to the outer face of the plasma membrane via their GPI or become cross-linked to the cell wall. We isolated the first GPI synthesis mutants in the model organism Saccharomyces cerevisiae, and have shown that GPI anchoring is essential for viability and normal cell wall construction in bakers yeast as well as the human pathogenic fungus Candida albicans.

We also study biosynthesis of the polysaccharide chitin, a structural component of fungal cell walls and the exoskeleton of insects and crustacea. The enzymes that polymerize chitin, a polymer of beta-1,4-linked N-acetylglucosamine, use a sugar nucleotide substrate available only in the cytoplasm and extrude their product into the cell wall on the extracellular side of the plasma membrane. Chitin (and related cellulose) synthases have multiple transmembrane domains, and these may form a pore involved in product translocation. Our interests are in the mechanism and regulation of chitin synthases, using yeast chitin synthase as a model.

Representative Publications

Orlean, P. Architecture and Biosynthesis of the Yeast Cell Wall. In: YeastBook. Cell Signaling & Development (P. Pryciak and J. Thorner, Eds.) Genetics, under revision.

Scarcelli, J.J., Colussi, P.A., Fabre, A.-L., Keller, M., Boles, E., Orlean, P., and Taron, C.H. (2012) Uptake of radiolabeled GlcNAc into Saccharomyces cerevisiae via native hexose transporters and its in vivo incorporation into GPI precursors in cells expressing heterologous GlcNAc kinase. FEMS Yeast Research DOI: 10.1111/j.1567-1364.2011.00778.

Orlean, P. (2009) Phosphoethanolamine addition to glycosylphosphatidylinositols. In: The Enzymes,, Vol. XXVI, Glycosylphosphatidylinositol (GPI) Anchoring of Proteins. Edited by A.K. Menon, T. Kinoshita, P. Orlean, and F. Tamanoi. Academic Press.

Orlean, P. and Menon, A.K. (2007) GPI anchoring of protein in yeast and mammalian cells or: how we learned to stop worrying and love glycophospholipids. Journal of Lipid Research 48: 993-1011.

Wiedman, J.M., Fabre, A.-L., Taron, B.W., Taron, C.H., and Orlean, P. (2007) In vivo characterization of the GPI assembly defect in yeast mcd4-174 mutants and bypass of the Mcd4p-dependent step in mcd4 null mutants. FEMS Yeast Research 7: 78-83.

Grimme, S.J., Colussi, P.A., Taron, C.H., and Orlean, P. (2004) Deficiencies in the essential Smp3 mannosyltransferase block glycosylphosphatidylinositol assembly and lead to defects in growth and cell wall biogenesis in Candida albicans. Microbiology 150: 3115-3128. [Abstract]

Complete Publications List