Candida albicans Secreted Aspartyl Protease Sap6 Mediates Hypha-Specific Cell-to-Cell Aggregation
Known functions of secreted aspartyl proteinases are proteolytic degradation of host tissues and promotion of fungal adhesion. Kumar et al. (p. 2614–2626) find that infecting mice with Candida albicans overexpressing Sap6 results in significantly higher tongue infection in oropharyngeal candidiasis (OPC). Sap6-overexpressing cells form large cellular aggregates only upon germination. Addition of Sap6 to wild-type C. albicans hyphal cells also induces aggregation independent of Sap6 protease activity but is mediated by its RGD motif. Thus, a new role for C. albicans Sap6 is mediation of hypha-specific cell-to-cell aggregation that increases fungal adhesion to the epithelium and virulence in OPC.
An Autotransporter Promotes Citrobacter rodentium Virulence while Limiting Innate Recognition by the Host
Secreted serine protease autotransporters of Enterobacteriaceae (SPATEs) are believed to promote bacterial pathogenesis, but despite numerous in vitro studies, little is known about their role in vivo. Bhullar et al. (p. 2636–2650) study the role of a class 2 SPATE, Pic (protein involved in intestinal colonization), during infection by the enteric pathogen Citrobacter rodentium. While acting as a mucinase, Pic also modulates bacterial surface structures that facilitate pathogen interactions with intestinal mucus. Pic is also protective by limiting activation of the host's innate immune system. Thus, Pic plays a complex role in bacterial pathogenesis in the host intestine.
Vibrio cholerae Type 3 Secretion System Vops Function in Colonization and Translocation
In the absence of the toxin-coregulated pilus, non-O1/non-O139 serogroup Vibrio cholerae strains can use a type 3 secretion system (T3SS) to colonize host intestinal tissues. Chaand and coworkers (p. 2862–2869) use the infant mouse model to identify V. cholerae T3SS translocated proteins (Vops) important for colonization and find that several Vops are essential for infection. Additional studies reveal that a subset is required for translocation of other effectors, suggesting that some Vops function as components of the structural apparatus. The V. parahaemolyticus T3SS2 encodes homologous proteins, supporting a hypothesis for conserved T3SS-mediated mechanisms between the two species.
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