ORF13 in the Type III secretion system gene cluster of Edwardsiella tarda binds to the mammalian factor Cugbp2

Abstract

The Type III secretion system (TTSS) is essential for the intracellular replication of Edwardsiella tarda in phagocytes of fish and mammals, and a hypothetical gene (orf13) located in the TTSS gene cluster is required for intracellular replication and virulence of E. tarda. Here, we show that under TTSS-inducing conditions, the protein ORF13 was secreted into culture supernatant. Then, using a yeast 2-hybrid screen, we show that the mammalian factor Cugbp2, which regulates apoptosis in breast cancer cells, directly interacts with ORF13. A pull-down assay revealed that ORF13 binds to the C-terminal region of Cugbp2. Our results suggest that ORF13 may facilitate E. tarda replication in phagocytes by binding to Cugbp2.KEY WORDS: Edwardsiella tarda · Type III secretion system · ORF13 · Mammalian factor Cugbp2Resale or republication not permitted without written consent of the publisher

Secreted in a Type III Secretion System-Dependent Manner, EsaH and EscE Are the Cochaperones of the T3SS Needle Protein EsaG of Edwardsiella piscicida

“…Unexpectedly, our previous study revealed that EscE can be secreted and translocated in a T3SS-dependent manner, and it regulates the secretion of the T3SS proteins according to its own steady-state protein level inside E. piscicida ( 28 ). Accordingly, it was verified that EscE (Orf13) is secreted and directly interacts with mammalian factor Cugbp2 upon its translocation ( 29 ).…”

“…EscE is required to stabilize EsaH, and it can be secreted through the T3SS ( 28 , 29 ). But will EsaH also be secreted upon secretion of EscE?…”

“…EscE is translocated into host cells in a T3SS-dependent manner ( 28 , 29 ), but can EsaH also be translocated? CyaA fusions have been used in many bacteria, including Edwardsiella , Yersinia , and Xanthomonas , to successfully monitor the translocation of bacterial T3SS effectors ( 28 , 32 – 35 ).…”

“…The EscE of E. piscicida can be translocated into host cells, where it interacts directly with mammalian factor Cugbp2 ( 28 , 29 ). Although secreted, EsaH failed to be translocated.…”