Role of Protein Glycosylation in Candida parapsilosis Cell Wall Integrity and Host Interaction

Abstract

Candida parapsilosis is an important, emerging opportunistic fungal pathogen. Highly mannosylated fungal cell wall proteins are initial contact points with host immune systems. In Candida albicans, Och1 is a Golgi α1,6-mannosyltransferase that plays a key role in the elaboration of the N-linked mannan outer chain. Here, we disrupted C. parapsilosis OCH1 to gain insights into the contribution of N-linked mannosylation to cell fitness and to interactions with immune cells. Loss of Och1 in C. parapsilosis resulted in cellular aggregation, failure of morphogenesis, enhanced susceptibility to cell wall perturbing agents and defects in wall composition. We removed the cell wall O-linked mannans by β-elimination, and assessed the relevance of mannans during interaction with human monocytes. Results indicated that O-linked mannans are important for IL-1β stimulation in a dectin-1 and TLR4-dependent pathway; whereas both, N- and O-linked mannans are equally important ligands for TNFα and IL-6 stimulation, but neither is involved in IL-10 production. Furthermore, mice infected with C. parapsilosis och1Δ null mutant cells had significantly lower fungal burdens compared to wild-type (WT)-challenged counterparts. Therefore, our data are the first to demonstrate that C. parapsilosis N- and O-linked mannans have different roles in host interactions than those reported for C. albicans.

Disruption of Protein Mannosylation Affects Candida guilliermondii Cell Wall, Immune Sensing, and Virulence

“…Therefore, to demonstrate the lack of effect of the KU70 mutation on the studied phenotypes, we included in the analyses the ATCC 6260 reference strain (WT) as an additional control. The cell wall of control strains was similar in carbohydrate and protein contents, as well as in wall porosity to the polycation DEAE-dextran, an indirect reporter of mannan arrangement (Cheng et al, 2011; Pérez-García et al, 2016). The pmr1 Δ null mutant displayed significant changes in wall composition, with a 5.8-fold and 1.8-fold increment in chitin and glucan levels, respectively (Table 1).…”

“…In addition, the mutant was found to spontaneously form pseudohyphae and cell aggregates when cultured in liquid media (Figure 2D). The cell aggregates were dispersed upon addition of 2 units/mL chitinase (Bates et al, 2006; Pérez-García et al, 2016), suggesting defects in cell separation associated to alterations of the cell wall (data not shown). The growth rate of the C. guilliermondii pmr1 Δ null mutant was significantly reduced, with doubling times of 3.64 ± 0.35 h, when compared with the control strains: 2.64 ± 0.17 h, and 2.85 ± 0.21 h for the parental (KU141) and re-integrant ( pmr1 Δ + PMR1 ) strains, respectively ( P < 0.05).…”

“…cell wall integrity, virulence, and sensing by innate immune cells has been mainly assessed using mutant cells lacking specific enzymes with key roles in the assembly of either N - or O -linked mannans (Bates et al, 2005, 2006, 2013; Munro et al, 2005; Prill et al, 2005; Mora-Montes et al, 2007, 2010; Hall et al, 2013; West et al, 2013; Pérez-García et al, 2016). Pmr1 is a Golgi-resident P-type ATPase ion pump that provides the cofactor Mn 2+ to mannosyltransferases involved in both N -linked and O -linked glycosylation (Bates et al, 2005).…”

“…Furthermore, functional differences arising from β-elimination by trimming of O -linked mannans or removal of N -linked mannans upon treatment with endoglycosidase H (endo H) have also added to our understanding of the physiological role of mannans in the biology of Candida spp. (Hamada et al, 1981; Hazen and Glee, 1994; Mormeneo et al, 1994; Goins and Cutler, 2000; Spreghini et al, 2003; Pérez-García et al, 2016). …”

Leishmania-Derived Trimannose Modulates the Inflammatory Response To Significantly Reduce Leishmania major-Induced Lesions

“…Antigen glycosylation has become increasingly recognized as a critical component of immune modulation by pathogens (6)(7)(8)(9). However, the glycan portion of the glycoconjugate was mainly considered a modulatory component with little to no antigenic properties independent of the lipid or protein that it was conjugated to.…”