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dc.creatorWang, Jennifer Y.
dc.date.accessioned2020-07-20T15:33:54Z
dc.date.available2020-07-20T15:33:54Z
dc.date.created2020-05
dc.date.submittedMay 2020
dc.identifier.urihttps://hdl.handle.net/2152.3/11243
dc.description.abstractEhrlichia chaffeensis (E. chaffeensis) exploits evolutionarily conserved Notch and Wnt host cell signaling pathways to downregulate innate immune host defenses and promote infection. The multifunctional E. chaffeensis TRP120 effector which has HECT E3 ubiquitin ligase activity, interacts with the host nuclear tumor suppressor F-BOX and WD domain repeating-containing 7 (FBW7). FBW7 is the substrate recognition subunit of the Skp1-cullin-1-FBOX E3 ubiquitin (Ub) ligase complex (SCF) known to negatively regulate a network of oncoproteins (Notch, cyclin E, c-Jun, MCL1 and cMYC). In this study, we demonstrate that TRP120 and FBW7 colocalize strongly in the nucleus by confocal immunofluorescent microscopy and interactions between TRP120 and FBW7 FBOX and WD40 domains were demonstrated by ectopic expression and co-immunoprecipitation. Although FBW7 gene expression increased during E. chaffeensis infection, FBW7 levels significantly decreased (>70%) by 72 h post infection. Moreover, an iRNA knockdown of FBW7 coincided with increased E. chaffeensis infection and levels of Notch intracellular domain (NICD), phosphorylated c-Jun, MCL-1 and cMYC, which are negatively regulated by FBW7. An increase in FBW7 K48 ubiquitination was detected during infection by co-IP, and FBW7 degradation was inhibited in infected cells treated with the proteasomal inhibitor bortezomib. Direct TRP120 ubiquitination of native and recombinant FBW7 was demonstrated in vitro and confirmed by ectopic expression of TRP120 HECT Ub ligase catalytic site mutant. This study identifies the tumor suppressor, FBW7, as a TRP120 HECT E3 Ub ligase substrate, and demonstrates that TRP120 ligase activity promotes ehrlichial infection by degrading FBW7 to maintain stability of Notch and other oncoproteins involved in cell survival and apoptosis.
dc.format.mimetypeapplication/pdf
dc.subjectEhrlichia chaffeensis
dc.subjectintracellular pathogen
dc.subjectcell biology
dc.subjectcell signaling
dc.subjectubiquitination
dc.subjectapoptosis
dc.subjectpost-translational modifications
dc.subjectFBW7
dc.subjectTRP120
dc.subjectNotch
dc.subjectprotein degradation
dc.titleEhrlichia chaffeensis E3 Ligase TRP120 Ubiquitinates Tumor Suppressor FBW7 for Degradation to Promote Infection
dc.typeThesis
dc.date.updated2020-07-20T15:33:56Z
dc.type.materialtext
thesis.degree.nameCell Biology (Doctoral)
thesis.degree.levelDoctoral
thesis.degree.grantorThe University of Texas Medical Branch at Galveston
thesis.degree.departmentCell Biology


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