Transcription Profiles Associated with Inducible Adhesion in Candida parapsilosis

Abstract

Candida parapsilosis has emerged as a frequent cause of invasive candidiasis with increasing evidence of unique biological features relative to C. albicans. As it adapts to conditions within a mammalian host, rapid changes in gene expression are necessary to facilitate colonization and persistence in this environment. Adhesion of the organism to biological surfaces is a key first step in this process and is the focus of this study. Building on previous observations showing the importance of a member of the ALS gene family in C. parapsilosis adhesion, three clinical isolates were cultured under two conditions that mimic the mammalian host and promote adhesion, incubation at 37°C in tissue culture medium 199 or in human plasma. Transcriptional profiles using RNA-seq were obtained in these adhesion-inducing conditions and compared to profiles following growth in yeast media that suppress adhesion to identify gene expression profiles associated with adhesion. Overall gene expression profiles among the three strains were similar in both adhesion-inducing conditions and distinct from adhesion-suppressing conditions. Pairwise analysis among the three growth conditions identified 133 genes that were differentially expressed at a cutoff of ±4-fold, with the most upregulated genes significantly enriched in iron acquisition and transmembrane transport, while the most downregulated genes were enriched in oxidation-reduction processes. Gene family enrichment analysis identified gene families with diverse functions that may have an important role in this important step for colonization and disease. IMPORTANCE Invasive Candida infections are frequent complications of the immunocompromised and are associated with substantive morbidity and mortality. Although C. albicans is the best-studied species, emerging infections by non-albicans Candida species have led to increased efforts to understand aspects of their pathogenesis that are unique from C. albicans. C. parapsilosis is a frequent cause of invasive infections, particularly among premature infants. Recent efforts have identified important virulence mechanisms that have features distinct from C. albicans. C. parapsilosis can exist outside a host environment and therefore requires rapid modifications when it encounters a mammalian host to prevent its clearance. An important first step in the process is adhesion to host surfaces. This work takes a global, nonbiased approach to investigate broad changes in gene expression that accompany efficient adhesion. As such, biological pathways and individual protein targets are identified that may be amenable to manipulation to reduce colonization and disease from this organism.

High Biofilm Formation of Non-Smooth Candida parapsilosis Correlates with Increased Incorporation of GPI-Modified Wall Adhesins

“…Two recent studies reported on C. parapsilosis ALS gene expression using real-time PCR [49] or RNAseq analysis [50] of strains with different adhesive capacity under adhesioninducing as well as non-inducing conditions. Both studies suggest that, despite some observed upregulation of ALS7/CPAR2_404800 in one strain under adhesion-inducing conditions [50], the regulation of ALS genes depended more on phenotypic strain variability than on growth conditions. Our data concur with this view, and indicate that this is also the case for the Hwp and Hyr adhesin families.…”

Candida parapsilosis cell wall proteins—CPAR2_404800 and CPAR2_404780—Are adhesins that bind to human epithelial and endothelial cells and extracellular matrix proteins

“…Although transcriptomic studies carried out so far suggested that the proteins encoded by the ALS genes may represent an important inducible factor in the virulence of C. parapsilosis , responsible for the adhesion of yeast to host cells and proteins (Bliss et al, 2021; Neale et al, 2018), the surface exposition of their protein products and actual involvement in interactions with host cells have only occasionally been confirmed (Karkowska‐Kuleta et al, 2017; Kozik et al, 2015). As previous reports indicated enhanced expression of genes encoding C. parapsilosis adhesins under conditions that mimic the host environment (Bliss et al, 2021), in the current studies we first verified the surface exposition of Als proteins on the fungal cell wall using LC‐MS/MS and direct tryptic hydrolysis of proteins displayed on intact fungal cells, after the growth of C. parapsilosis in DMEM or MCDB131 media, which are routinely used to cultivate cells of the epithelial cell line A431 and the endothelial cell line HMEC‐1, respectively. The data obtained confirmed the presence of both proteins—CPAR2_404800 and CPAR2_404780—on the fungal cell surface under the growth conditions used, while other proteins from this family were not identified in this study by the method applied (Supporting Information: Table ).…”

“…Therefore, initially, our objective was to investigate the direct involvement of these two fungal proteins in the binding of human epithelial and endothelial cells. Observations from gene expression studies obtained to date only indirectly indicated the involvement of Als proteins from C. parapsilosis in interactions with host cells, considering, in particular, the complexity of the adhesion process and differentiation in fungal adhesive phenotypes (Bertini et al, 2016; Bliss et al, 2021; Zoppo, Di Luca et al, 2020; Zoppo, Fiorentini, et al, 2020). Therefore, in the current study we decided to use proteins CPAR2_404800 and CPAR2_404780 after their isolation from the cell surface and chromatographic purification, and then test their ability to interact with human cells.…”

“…The majority of data concerning the functions of C. parapsilosis Als proteins was based on the analysis of changes in the corresponding genes' expression levels (Bliss et al, 2021; Moreno‐Martínez et al, 2021; Neale et al, 2018; Oh et al, 2019; Pryszcz et al, 2013; Zoppo, Di Luca, et al, 2020) and experiments with deletion mutants (Bertini et al, 2016; Zoppo, Di Luca, et al, 2020; Zoppo, Fiorentini, et al, 2020). Interestingly, it has been demonstrated by Pryszcz et al (2013) that various strains of C. parapsilosis may differ significantly in the number of copies of genes encoding proteins from the Als family.…”

“…It was also demonstrated that in the adhesive phenotype of C. parapsilosis that strongly interacts with extracellular matrix (ECM) proteins under physiological fluid shear conditions, two ALS genes— CPAR2_404800 and CPAR2_404780 —were overexpressed, indirectly confirming the role of the protein products of these genes in adhesion (Neale et al, 2018). Additionally, recent studies describing the expression of the ALS genes of C. parapsilosis demonstrated overexpression of the CPAR2_404800 gene under adhesion‐inducing conditions that mimic the mammalian host (Bliss et al, 2021). Moreover, the comparison of seven clinical isolates with a high biofilm formation capacity on polystyrene revealed increased levels of the proteins CPAR2_404800 and CPAR2_404780 in the fungal cell walls, in addition to CPAR2_404790 protein present also at the surface of reference strain CDC317 (Moreno‐Martínez et al, 2021).…”