TRAF2 regulates TNF and NF-κB signalling to suppress apoptosis and skin inflammation independently of Sphingosine kinase-1
- Walter and Eliza Hall Institute of Medical Research, Australia
- Monash University, Australia
- Cornell University, United States
- SA Pathology, Australia
- University of Zurich, Switzerland
- Olivia Newton-John Cancer Research Institute, Australia
Abstract
TRAF2 is a component of TNF superfamily signalling complexes and plays an essential role in the regulation and homeostasis of immune cells. TRAF2 deficient mice die around birth, therefore its role in adult tissues is not well-explored. Furthermore, the role of the TRAF2 RING is controversial. It has been claimed that the atypical TRAF2 RING cannot function as a ubiquitin E3 ligase but counterclaimed that TRAF2 RING requires a co-factor, sphingosine-1-phosphate, that is generated by the enzyme sphingosine kinase-1, to function as an E3 ligase. Keratinocyte specific deletion of Traf2, but not Sphk1 deficiency, disrupted TNF mediated NF-κB and MAP kinase signalling and caused epidermal hyperplasia and psoriatic skin inflammation. This inflammation was driven by TNF, cell death, non-canonical NF-κB and the adaptive immune system and might therefore represent a clinically relevant model of psoriasis. TRAF2 therefore has essential tissue specific functions that do not overlap with those of Sphk1.
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Ethics
Animal experimentation: Mice were maintained at the Walter and Eliza Hall Institute (WEHI) under the approval of WEHI ethics committee and Institute guidelines. All procedures were specifcally approved under WEHI Ethics Project Number 2011.013 and 2014.015.
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© 2015, Etemadi et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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TRAF2 regulates TNF and NF-κB signalling to suppress apoptosis and skin inflammation independently of Sphingosine kinase-1
eLife 4:e10592.
https://doi.org/10.7554/eLife.10592
Further reading
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- Biochemistry and Chemical Biology
- Microbiology and Infectious Disease
Glutamine synthetases (GS) are central enzymes essential for the nitrogen metabolism across all domains of life. Consequently, they have been extensively studied for more than half a century. Based on the ATP-dependent ammonium assimilation generating glutamine, GS expression and activity are strictly regulated in all organisms. In the methanogenic archaeon Methanosarcina mazei, it has been shown that the metabolite 2-oxoglutarate (2-OG) directly induces the GS activity. Besides, modulation of the activity by interaction with small proteins (GlnK1 and sP26) has been reported. Here, we show that the strong activation of M. mazei GS (GlnA1) by 2-OG is based on the 2-OG dependent dodecamer assembly of GlnA1 by using mass photometry (MP) and single particle cryo-electron microscopy (cryo-EM) analysis of purified strep-tagged GlnA1. The dodecamer assembly from dimers occurred without any detectable intermediate oligomeric state and was not affected in the presence of GlnK1. The 2.39 Å cryo-EM structure of the dodecameric complex in the presence of 12.5 mM 2-OG demonstrated that 2-OG is binding between two monomers. Thereby, 2-OG appears to induce the dodecameric assembly in a cooperative way. Furthermore, the active site is primed by an allosteric interaction cascade caused by 2-OG-binding towards an adaption of an open active state conformation. In the presence of additional glutamine, strong feedback inhibition of GS activity was observed. Since glutamine dependent disassembly of the dodecamer was excluded by MP, feedback inhibition most likely relies on the binding of glutamine to the catalytic site. Based on our findings, we propose that under nitrogen limitation the induction of M. mazei GS into a catalytically active dodecamer is not affected by GlnK1 and crucially depends on the presence of 2-OG.
