Role of the Inducible Adhesin CpAls7 in Binding of Candida parapsilosis to the Extracellular Matrix under Fluid Shear

Abstract

The yeast, , is an increasingly common cause of systemic fungal infections among the immune compromised, including premature infants. Adhesion to host surfaces is an important step in pathogenesis, but this process has not been extensively studied in this organism. A microfluidics assay was developed to test the ability of to adhere to immobilized host extracellular matrix proteins under physiologic fluid shear conditions. Growth in mammalian tissue culture media at 37°C for 3-6 hours led to induction of an adhesive phenotype at shear forces of 1-5 dynes/cm in some isolates of Glutamic acid, proline and calcium appeared to be the minimally necessary requirements for increased adhesion in these assays. To determine whether genes homologous to the gene family of were important for the adhesive phenotype, expression of 5 homologous genes were quantified using qPCR under conditions leading to increased adhesion. () and showed increased expression compared to control yeast. The extent of adhesion was variable among different isolates, and linear regression identified expression of but not to have a strong positive correlation with adhesion. A homozygous deletion strain was deficient in adhesion, whereas expression of in resulted in increased adhesion. Together, these data provide strong evidence that CpAls7 aids in the adherence of to extracellular matrix under shear forces and support its previously reported role in virulence.

Agglutinin-Like Sequence (ALS) Genes in the Candida parapsilosis Species Complex: Blurring the Boundaries Between Gene Families That Encode Cell-Wall Proteins

“…Als proteins are adhesins, yet function promiscuously, so looking toward shared function as the means for assigning names is also not an effective method. Some authors have referred to ALS genes using the label assigned in the annotation of the representative genome assembly (Bertini et al, 2016; Neale et al, 2018; Zoppo et al, 2018). This appealing approach provides a unique name for each gene and, like a street address, communicates physical location information.…”

“…Bertini et al (2016) showed that deletion of CpALS4800 resulted in a C. parapsilosis strain with reduced adhesion to human buccal epithelial cells. Neale et al (2018) documented a role for CpAls4800 in adhesion of C. parapsilosis to extracellular matrix proteins in a microfluidics assay using physiological fluid shear conditions. Zoppo et al (2018) deleted CoALS4210 and showed decreased adhesion to human buccal epithelial cells for the resulting C. orthopsilosis mutant strain.…”

“…One potential factor that is noted in the Candida literature is water quality, which despite modern purification systems, may vary widely and influence biological function of fungal cells (Nickerson et al, 2012). Neale et al (2018) measured expression of the five C. parapsilosis ALS genes using a SYBR Green-based method. Differential expression of CpALS4800 and CpALS4780 was noted when cells were transferred from saturated YPD cultures to tissue culture medium for 3 h. Like the TaqMan data presented here, expression of CpALS4790 was highest in the saturated YPD culture, with CpALS4780 next-most abundant and others at a lower level.…”

Candida parapsilosis: from Genes to the Bedside

“…The C. parapsilosis ortholog of CaALS7 is a key determinant for adhesion to host epithelial cells, as gene disruption led to a decreased ability to adhere to human buccal epithelial cells and also resulted in decreased virulence in vivo (129). CpALS7 is also necessary for C. parapsilosis to adhere to host ECM proteins under shear force (159). Additionally, C. parapsilosis cells require the presence of calcium, glutamic acid, and proline for adherence under shear flow conditions.…”

Candida parapsilosis Colony Morphotype Forecasts Biofilm Formation of Clinical Isolates

“…This feature is highly variable among individual clinical isolates [ 13 ]. In C. parapsilosis , the formation of biofilms is associated with the ability to form pseudohyphae [ 14 , 15 , 16 ] as well as the concomitant change in expression levels of cell wall-localized adhesins such as Als1-7 [ 17 , 18 , 19 ] or Rbt1 [ 20 ]. Importantly, susceptibility to commonly used azole-based antifungal agents in fungal biofilms on medical devices may be strongly reduced [ 21 , 22 ].…”