Novel T3SS effector EseK in Edwardsiella piscicida is chaperoned by EscH and EscS to express virulence

Abstract

Bacterium usually utilises type III secretion systems (T3SS) to deliver effectors directly into host cells with the aids of chaperones. Hence, it is very important to identify bacterial T3SS effectors and chaperones for better understanding of host-pathogen interactions. Edwardsiella piscicida is an invasive enteric bacterium, which infects a wide range of hosts from fish to human. Given E. piscicida encodes a functional T3SS to promote infection, very few T3SS effectors and chaperones have been identified in this bacterium so far. Here, we reported that EseK is a new T3SS effector protein translocated by E. piscicida. Bioinformatic analysis indicated that escH and escS encode two putative class I T3SS chaperones. Further investigation indicated that EscH and EscS can enhance the secretion and translocation of EseK. EscH directly binds EseK through undetermined binding domains, whereas EscS binds EseK via its N-terminal α-helix. We also found that EseK has an N-terminal chaperone-binding domain, which binds EscH and EscS to form a ternary complex. Zebrafish infection experiments showed that EseK and its chaperones EscH and EscS are necessary for bacterial colonisation in zebrafish. This work identified a new T3SS effector, EseK, and its two T3SS chaperones, EscH and EscS, in E. piscicida, which enriches our knowledge of bacterial T3SS effector-chaperone interaction and contributes to our understanding of bacterial pathogenesis.

A critical role of the T3SS effector EseJ in intracellular trafficking and replication ofEdwardsiella piscicidain non-phagocytic cells

“…The finding that the T3SS plays a critical role in the inhibition of endosome maturation and E. piscicida lysosome degradation raised the question of what T3SS effectors are involved in this process. To date, several E. piscicida T3SS effectors including EseG [16], EseJ [17], EseH [18] and EseK [19] have been identified. To assess the role of individual effectors, we tested the ability of WT and isogenic E. piscicida effector mutants to replicate inside non-phagocytic host cells.…”

“…Previous studies have shown that T3SS and T6SS mechanisms are essential for the virulence of E. piscicida [15]. An increasing number of T3SS and T6SS effectors have been identified, including EseG [16], EseJ [17], EseH [18], EseK [19] and EvpP [20]. EseG was reported to localize to the ECV membrane, but its function remains undefined [21].…”

Dysregulated hemolysin liberates bacterial outer membrane vesicles for cytosolic lipopolysaccharide sensing

“…Lentiviral particles were prepared in HEK239T cells as previously described [31]. HT-29 or Caco-2 cells were prepared in approximately 30% density and infected with lentiviral particles containing 10 μg/mL polybrene for 24 h. Transfected cells were selected with puromycin (2 μg/mL).…”

Edwardsiella piscicida Type III Secretion System Effector EseK Inhibits Mitogen-Activated Protein Kinase Phosphorylation and Promotes Bacterial Colonization in Zebrafish Larvae

“…Very recently, we identified a new E. piscicida T3SS effector, EseK, which can be translocated into host cells with the aid of two chaperones, EscH and EscS. We found that EseK is required for bacterial virulence in zebrafish with unknown mechanisms (24).…”