Abstract

Ceramide kinase (CERK) produces the bioactive lipid ceramide-1-phosphate (C1P) and is a key regulator of ceramide and dihydroceramide levels.

It is likely that CERK and C1P play a role in inflammatory processes but the cells involved and the mechanisms used remain to be clarified.

In particular, the impact of CERK on T-cell biology has not been studied so far. Here, we used Cerk^-/- mice backcrossed with DO11.10/RAG1^-/- mice to probe the effect of CERK ablation on T-cell activation.

Levels of interleukin (IL)-2, IL-4, IL-5, IL-13, of tumor necrosis factor (TNF)-α, and of interferon (INF)-γ were recorded following ovalbumin challenge in vivo and using ovalbumin-treated splenocytes ex- vivo.

Absence of CERK led to a significant decrease in the production of IL-4, thus suggesting that CERK may polarize T cells towards the T_H2 cell subtype.

However, the importance of CERK to T_H2 cell biology will have to be investigated further because in a model of asthma, which is T_H2-cell driven, Cerk^-/- mice responded like wild-type animals.

Other Sections▼

• • Abstract
  • Background
  • Methods
  • Results
  • Discussion
  • Abbreviations
  • Competing interests
  • Authors' contributions
  • References

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Background

Ceramide kinase (CERK), together with sphingosine kinases (SPHK) 1 and 2, belongs to the diacyglycerol kinase family of lipid kinases. CERK is the only enzyme known to produce ceramide-1-phosphate (C1P) [1].

However, studies with CERK deficient (Cerk^-/-) mice have shown that another route for production of C1P must exist, at least in mammals [2,3].

The best described signaling properties reported for C1P include, on the one hand, a positive effect on cell proliferation and cell survival [4,5] and, on the other hand, the control of cytosolic phospholipase A2 (cPLA2) activity [6-9].

Of note, however, neither knocking down the Cerk gene [3] nor using a CERK inhibitor [10] could recapitulate these findings, which suggests compensation by other C1P pools that do not depend on CERK for their synthesis.

The physiological role of CERK and its relevance to disease is only starting to be addressed. Using a gene knockdown strategy Igarashi and coworkers have shown preliminary evidence for a role of CERK in emotional behavior [11].

Based on ex- vivo work with CERK-deficient endothelial cells together with use of the CERK inhibitor NVP-231 [10] our laboratory has recently proposed a role for CERK in the regulation of angiogenesis [12].

CERK may also be relevant to immune cell biology.

In fact, neutrophils represent one of the first cell types where CERK/C1P were described [13-15] and subsequently shown to promote phagolysosome formation [16].

More recently, the study of C1P/CERK in mast cells has suggested their function in the degranulation process [17].

Consistently, in a model of passive cutaneous anaphylaxis, Cerk^-/- animals were partially protected [3].

However, Cerk^-/- responded similarly to control littermates during a model of active cutaneous anaphylaxis [3].

In fact, work in vitro with CERK-deficient primary bone marrow derived mast cells or with the NVP-231 inhibitor failed to clarify a putative role of CERK/C1P in mast cell biology [3,10].

In an antigen-induced arthritis model, Cerk^-/- mice were not protected, thus inconsistent with the hypothesis that C1P made by CERK is key for cPLA2 activation in vivo -- parallel pharmacological inhibition of cPLA2 could indeed dampen disease development [3].

In sharp contrast, absence of CERK prevented Cerk^-/- animals from mounting an effective response against a pulmonary insult by Streptococcus pneumoniae [3]. Altogether, although CERK seems to play a role in inflammation, the overall picture remains contrasted and no consensus has emerged yet.

The study reported here was undertaken to examine T-cell specific responses in the absence of CERK. To this aim we made use of the established DO11.10 RAG1^-/- background [18-20].

In DO11.10 mice all thymocytes and peripheral T cells express the transgenic TCR receptor from a T cell hybridoma, DO11.10, that recognizes chicken ovalbumin (OVA) in the context of I-A^d class II MHC molecules.

Furthermore, in DO11.10/RAG1^-/- mice, the endogenous TCR α-chains are eliminated, and T cells can only express the transgenic receptor.

• This model has proven useful for studying T-cell specific responses.

Therefore, we backcrossed Cerk^-/- mice with DO11.10/RAG1^-/- mice to probe the effect of CERK ablation on T-cell activation.

In parallel, we also backcrossed Sphk1^-/- and Sphk2^-/- to the same background for comparison.  

Lipids Health Dis. 2010; 9: 2.

doi: 10.1186/1476-511X-9-2.  

Satoru Niwa,¹ Nicole Urtz,^1,2 Thomas Baumruker,¹ Andreas Billich,¹ and Frédéric Bornancin¹

¹Novartis Institutes for BioMedical Research, Brunnerstrasse 59, A-1235 Vienna, Austria ²Current address: German Heart Centre Munich, Lazarettstrasse 36, D-80636 München, Germany Corresponding author.

• Satoru Niwa: satoru.niwa@novartis.com ;
• Nicole Urtz: urtz@dhm.mhn.de ;
• Thomas Baumruker thomas.baumruker@novartis.com
• Andreas Billich: andreas.billich@novartis.com ;
• Frédéric Bornancin: frederic.bornancin@novartis.com

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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