The molecular architecture of the aquaglyceroporin gating system in Saccharomyces cerevisiae

Abstract

Aquaglyceroporins have been extensively studied in multiple systems. However, the molecular architecture and hence the precise mechanisms of action remain unknow. The yeast aquaglyceroporin Fps1 plays the main role in controlling cellular turgor. It is regulated by the two Rgc proteins which activate the Fps1 channel. To date, the molecular architecture and dynamics of the Fps1-Rgc gating system is unknown. We employed dual-coloured super-resolution millisecond fluorescence microscopy with a single-molecule sensitivity, to track Fps1 and Rgc2 in real time. Unlike previously believed, our data shows that Rgc2 mainly operates as a homodimer. At the same time, Rgc1, the seemingly redundant regulatory ortholog of Rgc2, has a clear effect on the architecture, colocalisation behaviour and molecular dynamics of the Fps1 and Rgc2 together. Moreover, Rgc1 seems to promote Rgc2 stability in response to hydrogen peroxide stress. Together, our results provide novel insights into the mechanism behind aquaglyceroporins regulation. ImportanceThe components of the Fps1 aquaglyceroporin gating system is conserved in Fungi and present in both bakers yeast Saccharomyces cerevisiae as well as common pathogenic included in the WHO fungal priority pathogens list: Candida albicans, Candida glabrata, Aspergillus fumigatus, Pichia kudriavzevii. For instance, in C. glabrata, the orthologs of both Fps1 and Rgc2 are involved in key pathogenic processes related to acetate tolerance, phagocytosis by macrophages, resistance to antifungal agents and overall drug uptake and efflux. As the Fps1 gating system is not present in metazoans, it constitutes an attractive drug target for antifungal agents. Thus, understanding the architecture and the finer mechanisms of the Fps1 pore regulation is a stepping stone in development of effective antifungal treatment and targeted antifungal drugs.