ABIN2 Function Is Required To Suppress DSS-Induced Colitis by a Tpl2-Independent Mechanism

Sambit K Nanda1, Tsunehisa Nagamori1, Mark Windheim1

  • 1Medical Research Council Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee DD1 5EH, United Kingdom.

Insights

The A20-binding inhibitor of NF-κB 2 (ABIN2) mutant mice show intestinal inflammation, suggesting ABIN2

Area of Science:

  • Immunology
  • Molecular Biology
  • Inflammation Research

Background:

  • A20-binding inhibitor of NF-κB 2 (ABIN2) interacts with Met1-linked ubiquitin chains and is part of the tumor progression locus 2 (Tpl2) kinase complex.
  • The role of ABIN2's ubiquitin-binding function in Tpl2 complex stability and activation is not fully understood.
  • ABIN2's contribution to inflammatory responses, particularly in the context of colitis, requires further investigation.

Purpose of the Study:

  • To investigate the role of ABIN2's ubiquitin-binding activity in Tpl2 kinase complex function.
  • To determine the in vivo function of ABIN2 in intestinal inflammation and dextran sodium sulfate (DSS)-induced colitis.
  • To elucidate the mechanism by which ABIN2 influences inflammatory mediator production in intestinal myofibroblasts (IMFs).

Main Methods:

  • Generation of a knock-in mouse model expressing a ubiquitin-binding-defective ABIN2 mutant (ABIN2[D310N]).
  • Assessment of Tpl2 expression and activation in macrophages and fibroblasts from ABIN2[D310N] mice.
  • Induction of colitis using dextran sodium sulfate (DSS) in ABIN2[D310N] mice and analysis of inflammatory cell populations.
  • Measurement of cyclooxygenase 2 (COX2) and prostaglandin E2 (PGE2) production in response to IL-1β stimulation in mouse embryonic fibroblasts and IMFs.

Main Results:

  • ABIN2[D310N] mutation did not affect Tpl2 expression or activation, indicating ubiquitin binding is dispensable for Tpl2 stability and function.
  • ABIN2[D310N] mice exhibited spontaneous intestinal inflammation and heightened sensitivity to DSS-induced colitis, mediated by radiation-resistant cells.
  • IL-1β-induced COX2 expression and PGE2 secretion were significantly reduced in fibroblasts and IMFs from ABIN2[D310N] mice.
  • The observed reduction in COX2 and PGE2 production in ABIN2[D310N] mice mimics Tpl2 knockout phenotypes but occurs independently of Tpl2 kinase activity.

Conclusions:

  • ABIN2's interaction with ubiquitin chains is not essential for Tpl2 kinase complex stability or activation.
  • ABIN2 plays a critical role in regulating intestinal inflammation and colitis susceptibility, independent of Tpl2 kinase activity.
  • The loss of ABIN2 impairs COX2 and PGE2 production in IMFs via a Tpl2-independent pathway, contributing to colitis severity.

Related Concept Videos

Mechanical Protein Functions01:58

Mechanical Protein Functions

Proteins perform many mechanical functions in a cell. These proteins can be classified into two general categories- proteins that generate mechanical forces and proteins that are subjected to mechanical forces. Proteins providing mechanical support to the structure of the cell, such as keratin, are subjected to mechanical force, whereas proteins involved in cell movement and transport of molecules across cell membranes, such as an ion pump, are examples of generating mechanical force. 
5.6K
Mechanical Protein Function01:58

Mechanical Protein Function

2.5K
Introduction to Test of Independence01:21

Introduction to Test of Independence

In statistics, the term independence means that one can directly obtain the probability of any event involving both variables by multiplying their individual probabilities. Tests of independence are chi-square tests involving the use of a contingency table of observed (data) values.
The test statistic for a test of independence is similar to that of a goodness-of-fit test:
3.0K
Hypothesis Test for Test of Independence01:16

Hypothesis Test for Test of Independence

The test of independence is a chi-square-based test used to determine whether two variables or factors are independent or dependent. This hypothesis test is used to examine the independence of the variables. One can construct two qualitative survey questions or experiments based on the variables in a contingency table. The goal is to see if the two variables are unrelated (independent) or related (dependent). The null and alternative hypotheses for this test are:
H0: The two variables (factors)...
8.2K
Mechanisms of Retrovirus-induced Cancers01:51

Mechanisms of Retrovirus-induced Cancers

Retroviruses are RNA viruses that have been shown to cause cancers in diverse species, including chickens, mice, cats, and monkeys. The RNA genomes of these viruses are first reverse-transcribed into single and then double-stranded DNA (dsDNA) copies. This dsDNA called proviral DNA then integrates into the host genome. Subsequently, the host cell transcribes the proviral DNA in concert with the chromosomal DNA. This leads to the production of viral RNA and proteins that assemble at the host...
7.0K
Law of Independent Assortment02:03

Law of Independent Assortment

While Mendel’s Law of Segregation states that the two alleles for one gene are separated into different gametes, a different question of how different genes are inherited remains. For example, is the gene for tall plants inherited with the gene for green peas? Mendel asked this question by experimenting with a dihybrid cross; a cross in which both parents are homozygous for two distinct traits resulting in an F1 generation that are heterozygous for both traits.
62.7K