Tài liệu Báo cáo khoa học: Role of ceramide kinase in peroxisome proliferatoractivated receptor

Role of ceramide kinase in peroxisome proliferator￾activated receptor beta-induced cell survival of

mouse keratinocytes

Kiyomi Tsuji1

, Susumu Mitsutake2

, Urara Yokose2

, Masako Sugiura3

, Takafumi Kohama4 and

Yasuyuki Igarashi1,2

1 Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Advanced Life Sciences, Hokkaido University, Sapporo, Japan

2 Laboratory of Biomembrane and Biofunctional Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan

3 Biological Research Laboratories II, Daiichi-Sankyo Co. Ltd., Tokyo, Japan

4 Exploratory Research Laboratories I, Daiichi-Sankyo Co. Ltd., Tokyo, Japan

Ceramide (Cer) has been implicated in various cellular

processes including proliferation, apoptosis and cell

signaling [1]. Intracellular Cer levels are strictly regu￾lated by several enzymes, including ceramide kinase

(CerK), which converts Cer to ceramide 1-phosphate

(C1P) [2]. Previous studies have suggested that CerK

and C1P are involved in many cell functions, including

membrane fusion, phagocytosis and degranulation in

mast cells, among others [3]. Recently, several studies

have established a function for CerK in cell growth

and apoptosis. For example, in Arabidopsis plants,

mutation of CerK was associated with an accumula￾tion of Cer and enhanced symptoms during pathogen

attack [4]. In addition, in mammalian cells such as

Keywords

cell survival; ceramide; ceramide

1-phosphate; CerK; PPARb

Correspondence

Y. Igarashi, Laboratory of Biomembrane and

Biofunctional Chemistry, Faculty of

Pharmaceutical Sciences and Faculty of

Advanced Life Sciences, Hokkaido

University, Nishi 6, Kita 12, Kita-ku, Sapporo

060-0812, Japan

Fax: +81 11 706 4986

Tel: +81 11 706 3970

E-mail: [email protected]

Website: http://biomem.pharm.hokudai.ac.jp/

english/index.html

(Received 5 April 2008, revised 26 May

2008, accepted 29 May 2008)

doi:10.1111/j.1742-4658.2008.06527.x

Ceramide (Cer) is known to be a lipid mediator in apoptosis and to have

an important role in cell fate, via control of intracellular Cer levels.

Recently, ceramide kinase (CerK) was identified as an enzyme that converts

Cer to ceramide 1-phosphate (C1P). We examined potential functions of

CerK in the regulation of keratinocyte survival, and the possible involve￾ment of peroxisome proliferator-activated receptor beta (PPARb). PPARb

is known to be a nuclear receptor acting as a ligand-inducible transcription

factor and has been implicated in the control of keratinocyte survival. In

the mouse keratinocyte cell line SP1, serum starvation induced cell death

and the accumulation of intracellular Cer, an apoptotic event. However,

apoptosis was inhibited by activation of PPARb. Interestingly, activation

of PPARb enhanced the mRNA expression of CerK and CerK activity.

Furthermore, the cell survival effect of PPARb was greatly diminished in

keratinocytes isolated from CerK-null mice. Chromatin immunoprecipita￾tion revealed that, in vivo, PPARb binds to the CerK gene via a sequence

located in the first intron. Electrophoretic mobility-shift assays confirmed

that PPARb associates with this sequence in vitro. These findings indicated

that CerK gene expression was directly regulated by PPARb. In conclu￾sion, our results demonstrate that PPARb-mediated upregulation of CerK

gene expression is necessary for keratinocyte survival against serum starva￾tion-induced apoptosis.

Abbreviations

ABC, ATP-binding cassette; C1P, ceramide 1-phosphate; Cer, ceramide; CerK, ceramide kinase; ChIP, chromatin immunoprecipitation;

EMSA, electrophoretic mobility shift assays; LD, L-165,041; PI, propidium iodide; PPARb, peroxisome proliferator-activated receptor beta;

PPRE, PPAR response element; RXR, retinoid X receptor; TEWL, transepidermal water loss.

FEBS Journal 275 (2008) 3815–3826 ª 2008 The Authors Journal compilation ª 2008 FEBS 3815