Orientia tsutsugamushi Nucleomodulin Ank13 Exploits the RaDAR Nuclear Import Pathway To Modulate Host Cell Transcription

Abstract

Nucleomodulins are recently defined effectors used by diverse intracellular bacteria to manipulate eukaryotic gene expression and convert host cells into hospitable niches. How nucleomodulins enter the nucleus, their functional domains, and the genes that they modulate are incompletely characterized. Orientia tsutsugamushi is an intracellular bacterial pathogen that causes scrub typhus, which can be fatal. O. tsutsugamushi Ank13 is the first example of a microbial protein that coopts eukaryotic RaDAR (RanGDP-ankyrin repeats) nuclear import.

The Obligate Intracellular Bacterial Pathogen Anaplasma phagocytophilum Exploits Host Cell Multivesicular Body Biogenesis for Proliferation and Dissemination

“…Western blotting of whole cell lysates was performed as previously described ( 74 ). Briefly, normalized amounts of eluates were resolved by SDS-PAGE in 4-to-20% mini-Protean gels (Bio-Rad) at 110 V for 15 min, followed by 200 V for 25 min.…”

Anaplasma phagocytophilum Ankyrin A Protein (AnkA) Enters the Nucleus Using an Importin-β-, RanGTP-Dependent Mechanism

“…Although consistent with the RaDAR mechanism, single mutations at ARs 1-4 did not reduce AnkA nuclear localization. There is controversy regarding the requirement for the two consecutive AR principle of RaDAR function; for example, Ank13 of O. tsutsugamushi uses the RaDAR mechanism, but mutation of a single AR 13 th residue is sufficient to reduce nuclear entry (Adcox et al, 2021). While replacement of hydrophobic with hydrophilic 13 th residues of the consecutive AR3/AR4 resulted in a reduction of nuclear localization, mutations that increase hydrophobicity at AR1/ AR2 and AR2/AR3 also reduce nuclear localization, a finding inconsistent with a stringent interpretation of the RaDAR mechanism.…”

“…Similar to A. phagocytophilum AnkA, Orientia tsutsugamushi ARPs Ank1 and Ank6 require importin-b, but Ank13 utilizes the RaDAR pathway (Evans et al, 2018;Adcox et al, 2021), suggesting the coexistence of both processes utilized by a single bacterium, albeit for distinct proteins, and that perhaps two consecutive ARs with 13 th position hydrophobic residues are not required for prokaryotic proteins. Interestingly, a related tickborne pathogen, Ehrlichia chaffeensis, uses an AR-rich protein, p200, to modify transcriptional activity of its host monocyte (Zhu et al, 2009).…”

Moonlighting in Rickettsiales: Expanding Virulence Landscape

“…Ank13 effector was recently identified as a bona fide nucleomodulin that interacts with the RanGDP-ankyrin repeats (RaDAR) nuclear import pathway to enter the nucleus and downregulate several host genes, including genes involved in epigenetic regulation, transcriptional control, mRNA stability, cell cycle control, and inflammatory response. Furthermore, this effector can be present in the cytoplasm modulating gene expression and reprogramming the host cell transcription by binding to SCF1 complex and transcription factors, promoting their polyubiquitination and consequent proteasomal degradation [108].…”

“…Interacts with RaDAR and downregulates multiple host genes, acting as a nucleomodulin Modulates cytoplasm gene expression Reprograms host cell transcription [108] spp.…”