Abstract 2215 Cryptococcus neoformans capsule glucuronoxylomannan stimulates brain endothelial barrier disruption via RhoA signaling

The pathogenic yeast Cryptococcus neoformans is the most common cause of fungal meningitis, especially in immunocompromised patients. C. neoformans can bypass the blood-brain barrier and colonize neuronal tissue through multiple mechanisms, including transcytosis, phagocytosis and via phagocyties in a "Trojan Horse" mechanism. Virulence of this pathogen is related to its polysaccharide capsule component glucuronoxylomannan (GXM), which can accumulate in tissues of infected individuals. We hypothesized that GXM is an important signaling molecule for C. neoformans brain invasion by controlling the fidelity of endothelial cell-cell contacts. Stimulation of human endothelial in culture with GXM initiates separation of endothelial monolayers. The breakdown of endothelial monolayers is caused by the internalization of the adherens junction protein VE-cadherin and the tight junction proteins claudin and occludin. We have discovered that GXM controls these junction proteins. In addition, endothelial barrier disfunction is accompanied by actin stress-fiber formation. Our findings demonstrate that GXM treatment activates the monomeric GTPase RhoA, which signals through RhoA-activated Kinase (ROCK) to control cellular junction proteins and the actin cytoskeleton. Importantly, inhibition of RhoA blocks endothelial barrier instability in the presence of GXM, and improves post-infection survival in vivo. These results suggest that the RhoA signaling pathway is a promising target for the development of new therapeutics for prevention and treatment of C. neoformans fungal meningitis. NIH: R01AI145559.