Our pursuit for effective antifungal agents targeting fungal cell wall components: where are we?

Abstract

Invasive mycotic infections present unacceptably high mortality rates in humans. These infections are initiated by the fungal cell wall, which mediates host-fungi interactions. The cell wall is associated with the physiology of fungi and is involved in essential processes in the entire cell functionality. Components of the fungal cell wall are synthesised and modified in the cell wall space by the activities of cell wall proteins through a range of signalling pathways that have been described uniquely in many fungi, therefore making them suitable drug targets. The echinocandin class of cell-wall-active drugs blocks cell wall β-1,3-glucan biosynthesis through inhibiting the catalytic subunit of the synthetic protein complex. Resistance to echinocandins can occur through the acquisition of single nucleotide polymorphisms and/or through activation of cell wall signalling pathways resulting in an altered cell wall proteome and elevated chitin content in the cell wall. Countering the cell wall remodelling process will enhance the effectiveness of β-1,3-glucan-active antifungal agents. Cell surface proteins are also important antifungal targets that can be used to develop rapid and robust diagnostics and more effective therapeutics. The cell wall remains a crucial target in fungi that needs to be harnessed to combat mycotic infections.