Inhibition of eukaryotic translation by tetratricopeptide-repeat proteins of Orientia tsutsugamushi

Abstract

Orientia tsutsugamushi, an obligate intracellular bacterium, is the causative agent of scrub typhus. The genome of Orientia tsutsugamushi has revealed multiple ORFs encoding tetratricopeptide-repeat (TPR) proteins. The TPR protein family has been shown to be involved in a diverse spectrum of cellular functions such as cell cycle control, transcription, protein transport, and protein folding, especially in eukaryotic cells. However, little is known about the function of the TPR proteins in O. tsutsugamushi. To investigate the potential role of TPR proteins in host-pathogen interaction, two oriential TPR proteins were expressed in E. coli and applied for GSTpull down assay. DDX3, a DEAD-box containing RNA helicase, was identified as a specific eukaryotic target of the TPR proteins. Since the RNA helicase is involved in multiple RNA-modifying processes such as initiation of translation reaction, we performed in vitro translation assay in the presence of GST-TPR fusion proteins by using rabbit reticulocyte lysate system. The TPR proteins inhibited in vitro translation of a reporter luciferase in a dose dependent manner whereas the GST control proteins did not. These results suggested TPR proteins of O. tsutsugamushi might be involved in the modulation of eukaryotic translation through the interaction with DDX3 RNA helicase after secretion into host cytoplasm.

Cells within cells: Rickettsiales and the obligate intracellular bacterial lifestyle

“…Tetratricopeptide repeat proteins (TPR) contain a 34 amino acid repeat present in a tandem array of 3-16 motifs, and are also well-known domains of effector proteins 175 . TPR proteins have been found in R. felis and Orientia tsutsugamushi where they have been shown to inhibit eukaryotic translation 176 . Ehrlichia chaffeensis encodes a number of tandem repeat proteins (TRPs) that, in addition to their roles as surface proteins described above, are secreted into host cells and interact with a range of host pathways [177][178][179] .…”

Piscirickettsia salmonis Cryptic Plasmids: Source of Mobile DNA and Virulence Factors

“…pPSLF89-3 encoded VFs contain eukaryotic-domains, and have a general function description. One is a Ras family protein (PSLF89_RS35310), responsible for animal cell proliferation among other functions [50,51], and the other is a tetratricopeptide repeat (TPR) family protein (PSLF89_RS35270), which participates in protein-protein interactions and has been described to contribute in bacterial virulence [52,53].…”

An Update on Host-Pathogen Interplay and Modulation of Immune Responses during Orientia tsutsugamushi Infection

“…The tetratricopeptide repeat structural motif, present in prokaryote and eukaryote organisms, functions as a scaffold for assembling multiprotein complexes. Every TPR fold structure may participate in several protein-protein interactions and therefore impact different facets of cellular metabolism, including the functional modulation of steroid receptors, gene regulation, cell cycle control, protein folding, and protein transport (93,94). Importantly, they serve as virulence factors in several bacterial pathogens, such as Francisella tularensis, Francisella novicida, Mycobacterium tuberculosis, Shigella spp., Pseudomonas, and Yersinia (95-103).…”

“…Proteins encoded by trp genes are expressed after L929 cell infection and interact with DDX3, as revealed by pulldown assays with ECV304 cell lysates and immunoblot assays with specific antibodies. In vitro translation assays employing reticulocyte cell lysates have shown dose-dependent translation impairment of a reporter by the TRP43 and TRP46 proteins (94).…”