Deletion of Non-histidine Domains of Histidine Kinase CHK1 Diminishes the Infectivity of Candida albicans in an Oral Mucosal Model

Abstract

ObjectivesThe histidine kinase (HK) CHK1 and other protein kinases in Candida albicans are key players in the development of hyphae. This study is designed to determine the functional roles of the S_Tkc domain (protein kinase) and the GAF domain of C. albicans CHK1 in hyphal formation and mucosal invasion.MethodsThe domain mutants CHK25 (ΔS_TkcCHK1/Δchk1) and CHK26 (ΔS_TkcΔgafCHK1/Δchk1) were first constructed by the his1-URA3-his1 method and confirmed by sequencing and Southern blots. A mouse tongue infection model was used to evaluate the hyphal invasion and fungal loads in each domain mutant, full-gene deletion mutant CHK21 (chk1Δ/chk1Δ), re-constituted strain CHK23 (chk1Δ/CHK1), and wild type (WT) from day 1 to day 5. The degree of invasion and damage to the oral mucosa of mice in each strain-infected group was evaluated in vivo and compared with germ tube rate and hyphal formation in vitro.ResultWhen compared with severe mucosal damage and massive hyphal formation in WT- or CHK23-infected mouse tongues, the deletion of S_Tkc domain (CHK25) caused mild mucosal damage, and fungal invasion was eliminated as we observed in full-gene mutant CHK21. However, the deletion of S_Tkc and GAF (CHK26) partially restored the hyphal invasion and mucosal tissue damage that were exhibited in WT and CHK23. Regardless of the in vivo results, the decreased hyphal formation and germ tube in vitro were less apparent and quite similar between CHK25 and CHK26, especially at the late stage of the log phase where CHK26 was closer to WT and CHK23. However, growth defect and hyphal impairment of both domain mutants were similar to CHK21 in the early stages.ConclusionOur data suggest that both protein kinase (S_Tkc) and GAF domains in C. albicans CHK1 are required for hyphal invasiveness in mucosal tissue. The appropriate initiation of cell growth and hyphal formation at the lag phase is likely mediated by these two functional domains of CHK1 to maintain in vivo infectivity of C. albicans.

The mitochondrial complex I proteins of Candida albicans moderate phagocytosis and the production of pro‐inflammatory cytokines in murine macrophages and dendritic cells

“…Reduced phagocytosis in vitro seems not to correlate with decreased colonization of mutants in tissues, since previous studies have shown that tissue loads of mutants with PPM loss were significantly reduced in disseminated murine and oral candidiasis models 12,49,50 . At the same time, they are easily killed by immune cells in vitro 12,21 .…”

“…3.8 | Mutants with less phagocytosis are readily killed in the presence of serum Reduced phagocytosis in vitro seems not to correlate with decreased colonization of mutants in tissues, since previous studies have shown that tissue loads of mutants with PPM loss were significantly reduced in disseminated murine and oral candidiasis models. 12,49,50 At the same time, they are easily killed by immune cells in vitro. 12,21 Following standard procedures, we exposed each mutant and WT strain to pre-opsonized murine macrophages or human neutrophils from serum to calculate the extent of fungal killing.…”

Unveiling the complexity of early childhood caries: Candida albicans and Streptococcus mutans cooperative strategies in carbohydrate metabolism and virulence

“…The CHK1 gene in C. albicans is involved in various functions, including enhancing its virulence, upregulating the quorum sensing and enabling responses to stress [ 24 ]. Recent studies have highlighted the importance of CHK1 gene during oral mucosal infections, its plays a crucial role in mediating cross-kingdom interactions, which can potentially increase the cariogenic potential of these microbiomes within the oral cavity [ 23 , 25 , 26 ].…”