Format

Send to

Choose Destination
Front Cell Infect Microbiol. 2018 Jan 11;7:534. doi: 10.3389/fcimb.2017.00534. eCollection 2017.

Ehrlichia chaffeensis TRP32 Nucleomodulin Function and Localization Is Regulated by NEDD4L-Mediated Ubiquitination.

Farris TR1, Zhu B2, Wang JY3, McBride JW1,2,3,4,5,6.

Author information

1
Departments of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States.
2
Pathology, University of Texas Medical Branch, Galveston, TX, United States.
3
Cell Biology, University of Texas Medical Branch, Galveston, TX, United States.
4
Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, United States.
5
Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX, United States.
6
Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States.

Abstract

Ehrlichia chaffeensis is an obligately intracellular bacterium that reprograms the mononuclear phagocyte through diverse effector-host interactions to modulate various host cell processes. In a previous study, we reported that the E. chaffeensis nucleomodulin TRP32 regulates transcription of host genes in several biologically relevant categories, including cell differentiation and proliferation. In this study, we investigate the effect of ubiquitination on TRP32 function and localization within the host cell. TRP32 is both mono- and polyubiquitinated on multiple lysine residues during infection and when ectopically expressed. Despite lacking a canonical PPxY motif, TRP32 interacted with, and was modified by the human HECT E3 ubiquitin (Ub) ligase NEDD4L. TRP32 ubiquitination was not by K48-linked polyUb chains, nor was it degraded by the proteasome; however, TRP32 was modified by K63-linked polyUb chains detected both in the cytosol and nucleus. HECT ligase inhibitor, heclin, altered the subnuclear localization of ectopically expressed TRP32 from a diffuse nuclear pattern to a lacy, punctate pattern with TRP32 distributed around the periphery of the nucleus and nucleoli. When a TRP32 lysine null (K-null) mutant was ectopically expressed, it exhibited a similar phenotype as single lysine mutants (K63R, K93R, and K123R). However, the K-null mutant showed increased amounts of cytoplasmic TRP32 compared to single lysine mutants or heclin-treated cells ectopically expressing TRP32. These alterations in localization corresponded to changes in TRP32 transcriptional repressor function with heclin-treated and single lysine mutants unable to repress transcription of a TRP32 target genes in a luciferase assay.

KEYWORDS:

Ehrlichia; NEDD4L; effector; localization; post-translational modification; tandem repeat protein; ubiquitination

PMID:
29376035
PMCID:
PMC5768648
DOI:
10.3389/fcimb.2017.00534
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for PubMed Central
Loading ...
Support Center