The Cell Wall: Glycoproteins, Remodeling, and Regulation

Abstract

This chapter provides an update on cell wall structure and, in particular, cell wall glycoproteins (CWPs), cell wall remodeling, and cell wall regulation. Proteins associated with glycolysis, like enolase and alcohol dehydrogenase, are well-known cytoplasmic proteins but have also been identified at the cell surface; this dual location has led them to be termed “moonlighting” proteins. Glycosylphosphatidylinositol (GPI) anchoring is encountered in every eukaryotic cell, including unicellular yeast cells, several parasites, and highly specialized mammalian cells. Analyses of the Candida albicans and C. dubliniensis genomes to identify intragenic tandem repeats found a significant enrichment of putative CWPs. Mutants of GAS genes in C. albicans, Saccharomyces cerevisiae, C. glabrata, and Aspergillus fumigatus had defects in cell wall organization and morphogenesis. Single and double disruption of the A. fumigatus Gas orthologues GEL1 and GEL2 showed that the enzymatic activity was required for morphogenesis and virulence. The poor resolution of fungal glycoproteins through sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis has prompted alternative nongel technologies to study the complement of proteins in the cell wall. Transcript profiling of C. albicans cells from in vivo models has identified a number of cell wall-associated genes whose expression is altered compared to those in in vitro-grown cells. As well as being exposed to different stimuli that are independently known to alter expression of cell wall-related genes, the invading fungus will also be under attack by the host’s enzymes and immune cells.