May 2016
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93 Reads
The host gut epithelial membrane is shielded by complex glycans to protect the cell. Gastroenteritis begins when invasive pathogens bind and degrade the glycans at the epithelial barrier to gain access of host membrane. While glycan degradation is crucial for infection, this process is poorly understood. We hypothesized that Salmonella deploys its glycosyl hydrolases (GHs) to target and degrade host glycans leading to altered infection and glycan remodeling. Salmonella was grown in defined medium containing 18 different synthetic glycans modeled after human glycans as the sole carbon source. Significantly differentially expressed (q<0.05) GHs were identified and genetically deleted to determine the specific effect on adhesion and invasion in vitro with differentiated colonic epithelial cells (Caco-2). HPLC-Chip-QTOF MS was used to determine the glycan composition and structure with specific set of enzymes used during infection. Growth analysis showed that Salmonella is able to digest and metabolize synthetic glycans. GHs recognized terminal monosaccharides and significantly (p<0.05) altered invasion in vitro. Sialic acid depletion reduced adherence of Salmonella during infection. Salmonella used its two GHs nanH and malS for internalization. Host glycans were altered during Salmonella association via the induction of Nglycan biosynthesis pathways leading to host glycan remodeling by increasing fucosylation, mannosylation, and hybrid glycan content, while decreasing sialylation. Gene expression analysis indicated that the host cell responded by regulating more than 50 genes showing that remodeled glycans are in response to Salmonella infection. Our study established the glycan structures on colonic epithelial cells, determined that Salmonella required two GHs for internalization, the host cell remodeled the glycan during infection, and host glycan landscape influences the host-microbe interaction. Microbial GHs are understudied and unrecognized virulence factors that may be new therapeutic targets. I