Investigations into the Biological Roles of the E3 ligase Ariadne 2/TRIAD1

The process of ubiquitination plays an essential role in numerous cell functions, including apoptosis and the induction of immune responses. Ariadne 2 is a RING finger E3 ligase and is part of the highly conserved RBR (RING-B-Box-RING) superfamily, however, little is known of its function in mammalian systems. To further examine the physiological role, Ariadne 2 deficient mice were generated. In a mixed background, Ariadne 2 deficient (Arih2-/-) mice die prematurely after birth however lethality is not fully penetrant. Adult mice that escape lethality have lower body weight and reduced viability due to an apparent lymphoproliferative disorder. In a C57BL/6 background, Ariadne 2 deficiency leads to a fully penetrate embryonic lethality, occurring after embryonic day 16.5. Arih2-/- foetal liver have reduced cellularity and increased apoptosis, however haematopoietic cells are capable of differentiating into myeloid and granulocytic progenitors and can fully reconstitute lethally irradiated Rag1-/- recipient mice. These Rag1-/-Arih2-/- chimeras recapitulate the lymphoproliferative disorder observed in the mixed background Arih2-/- mice. Further analysis show Rag1-/-Arih2-/- chimeras display increased number of lymphocytes, granulocytes, macrophages and dendritic cells, increased serum immunoglobulin levels and pro-inflammatory cytokines, and dramatic heterogeneous cellular organ infiltration, consisting mainly of T cells. T cell homeostasis is also altered, as seen by increased activated and ‘memory-like’ T cells, elevated TH1 and TH2 cytokines, increased regulatory T cells (Treg), and increased T cell proliferation. This may be due to an observed premature maturation of Arih2-/- dendritic cells. Arih2-/- foetal liver derived dendritic cells (FLDC) express high levels of maturation markers CD80/B7.1, CD86/B7.2, CD83, CD40 and MHCII and are capable of activating T cells in the RIP-GP model of induced diabetes. This may be linked to modulation of the NFκB and ERK pathways, in particular increase in nuclear p65/RelA and phospho-p65/RelA leading to an increase in NFκB and AP-1 binding to DNA and sustained and hyperactive NFκB response in Arih2-/- dendritic cells. Overall, Ariadne 2 is shown to be a negative regulator in the activation of immune cells, in particular dendritic cells, and is a novel regulator in the maintenance of peripheral tolerance and the pathogenesis of autoimmunity.

Department dc:contributor.department

Medical Biophysics

Year dc:date.issued

2010

Author dc:creator

• Lin, Amy Erica

Advisor dc:contributor.advisor

• Mak, Tak Wah

• E3 ligase
• Ariadne 2

Language dc:language.iso

en_ca

Handle dc:identifier.uri

http://hdl.handle.net/1807/29972

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/29972