Activation of oral epithelial EphA2-EFGR signaling by Candida albicans virulence factors

Abstract

19The induction of antifungal proinflammatory signaling during oropharyngeal candidiasis (OPC) is 20 crucial to limit Candida albicans proliferation and induce fungal clearance. Previously, we 21 determined that the ephrin type-A receptor 2 (EphA2) functions as a β-glucan receptor that senses 22 Importance 39Host cell receptors for fungi have typically been evaluated from one of two different perspectives, 40 their role in inducing the invasion of the organism or their role in stimulating the host inflammatory 41 response. We had found previously that EGFR mediates the endocytosis of C. albicans by oral 42 epithelial cells, and that epithelial cell EphA2 mediates the production of chemokines and 43 proinflammatory cytokines in response to C. albicans. Here, we demonstrate that EGFR and 44EphA2 interact with each other, both physically and functionally. EGFR is required for sustained 45EphA2 activation and for epithelial cells to secrete proinflammatory mediators in response to both 46 C. albicans and IL-17A. Therefore, while activation of EGFR by C. albicans enhances 47 pathogenicity by inducing the endocytosis of the fungus, it also augments the host defense 48 against OPC by stimulating the host inflammatory response. 49 50

The globular C1q receptor is required for epidermal growth factor receptor signaling during Candida albicans infection

“…As a control, we used siRNA to knock down EGFR in the epithelial cells. Consistent with previous results (13,16), knockdown of EGFR modestly reduced the number of cell-associated C. albicans cells and decreased the number of endocytosed organisms by almost 50% (Fig. 2A).…”

“…Inhibition of surfaceexpressed gC1qR significantly reduced the production of all four inflammatory mediators (Fig 4C-F), although the absolute levels of IL-1β and IL-8 were somewhat different when measured by the cytometric bead array instead of the ELISA. Inhibition of EGFR with gefitinib also significantly decreased the levels of IL-1β, IL-8, and GM-CSF, but had no effect on IL-1α levels, as reported previously (15,16). The finding that inhibition of gC1qR reduced IL-1α production whereas inhibition of EGFR had no effect suggests that gC1qR is required for the production of IL-α by interacting with a receptor other than EGFR.…”

“…To verify that the selected proteins were associated with EGFR in intact oral epithelial cells and to determine their subcellular location with respect to C. albicans cells, we used a proximity ligation assay (16). This assay forms a flourescent spot where two proteins are located within 40 nm of one another (31).…”

“…Activation of EGFR is also required for C. albicans to induce sustained phosphorylation of the EphA2 receptor tyrosine kinase (11,16). We determined that inhibition of gC1qR decreased C. albicans-induced EphA2 phosphorylation (Figs.…”

“…EGFR interacts with the ephrin type-A receptor 2 (EphA2), HER2, E-cadherin, src family kinases, and the aryl hydrocarbon receptor, triggering changes in the actin cytoskeleton that lead to the endocytosis of the fungus (11,13,14). EGFR also interacts with EphA2 to stimulate epithelial cells to secrete proinflammatory mediators, including defensins, IL-1α, IL-1β, CXCL8/IL-8, and CCL20 (11,15,16). The defensins have direct candidacidal activity, while the cytokines and chemokines recruit phagocytes to the focus of infection and enhance their capacity to kill the invading fungus.…”