Prof. Di Wu
Institute of Translational Medicine, Zhejiang University School of Medicine, China
Title: Neddylation-Cullin-RING-ligases in T lymphocytes regulation
Abstract:
Neddylation-mediated activation of
Cullin-RING E3 Ligases (CRLs) are necessary for the degradation of specific
immune regulatory proteins. However, little is known about how these processes govern
the function of regulatory T (Treg) cells. Here we show that mice with Treg
cell-specific deletion of Rbx1, a dual E3 for both neddylation and
ubiquitylation by CRLs, develop an early-onset fatal inflammatory disorder,
characterized by disrupted Treg cell homeostasis and suppressive functions.
Specifically, Rbx1 is essential for the maintenance of an effector Treg cell
subpopulation, and regulates several inflammatory pathways. Similar but less
severe phenotypes are observed in mice having Ube2m, a neddylation E2
conjugation enzyme, deleted in their Treg cells. Interestingly, Treg-specific
deletion of Rbx2/Sag or Ube2f, components of a similar but distinct
neddylation-CRL complex, yields no obvious phenotype. Thus, our work
demonstrates that the Ube2m-Rbx1 axis is specifically required for intrinsic
regulatory processes in Treg cells; and that Rbx1 might also play
Ube2m-independent roles in maintaining the fitness of Treg cells, suggesting a
layer of complexity in neddylation-dependent activation of CRLs.
Since depletion of neddylation E2-E3 pair
Ube2f-Sag in regulatory T (Treg) cells had no obvious phenotype, the
same depletion of either Ube2m or Rbx1 caused inflammation disorders with
different severity. Whether these E2s or E3s compensate each other in
functional regulations of Treg cells is, however, previously
unknown. We generated Foxp3Cre;Ube2mfl/fl;Ube2ffl/fl or Foxp3Cre;Rbx1fl/fl;Sagfl/fl double-null mice by simultaneous deletion of both neddylation E2s or E3s in Treg cells, respectively. Remarkably, Ube2m&Ube2f double-null mice
developed much severe autoimmune phenotypes than did Ube2m-null mice,
indicating that Ube2m markedly compensates Ube2f in Treg cells. The minor worsened autoimmune phenotypes seen at the very early stage in Rbx1&Sag double-null than Rbx1-null mice is likely due to
already severe phenotypes of the later, indicating a minor compensation of Rbx1 for Sag. The RNA profiling-based analyses revealed that up- and
down-regulations of few signaling pathways in Treg cells are associated
with the severity of autoimmune phenotypes. Finally, severer inflammation
phenotypes seen in mice with double E3-null than with double E2-null Treg cells indicate a neddylation-independent mechanism of 2 E3s, also known to
serve as the RING component of CRLs in regulation of Treg cell
fitness.
T lymphocytes consist of αβ and γδ T cells, which mature and
differentiate from the same progenitor cells in the thymus. The role of
neddylation-CRL system in thymus development and fate determination of αβ/γδ T cells remains elusive. We generated
conditional knockout mouse models with thymus individual deletion of Ube2m or
Ube2f, 2 neddylation E2-conjugating enzymes, and Rbx1 or Sag, 2 dual
neddylation and ubiquitylation E3 ligases. We found that only Rbx1, but not
Ube2m/Ube2f, nor Sag, plays an essential role in thymus development and fate
determination of αβ/γδ T cells.
Specifically, Rbx1 loss causes shrinkage of the thymus, delayed T cell
development, increased γδ T cells in the thymus,
increased the ratio of immature Gzma + γδ T cells, and
decreased the ratio of the proliferative subpopulation. Some of these
phenotypes were moderately rescued by simultaneous Bim deletion.
Mechanistically, Rbx1 loss alters the Akt, NF-κB, and
metabolic pathways in progenitor γδ T cells/DN3a cells.
Finally, Rbx1 loss altered the γδ T1/T17 cell
population in the thymus, suggesting that Rbx1 controls the fate of γδ T cells.
Biography:
2017-present Research Assistant Professor
Institute of Translational Medicine, Zhejiang University School of Medicine, China
● 2014-2017 Postdoctoral fellow
Institute of Hematology, Peking Union Medical College, China
● 2010-2013 Doctor of philosophy
College of Life Sciences, Nankai University, China
● 2007-2010 Master
College of Life Sciences, Nankai University, China
● 2003-2007 Bachelor
College of Life Sciences, Nankai University, China