Tài liệu Báo cáo khoa học: Role of transcription factor activator protein 1 (AP1) in epidermal

Role of transcription factor activator protein 1 (AP1) in

epidermal growth factor-mediated protection against

apoptosis induced by a DNA-damaging agent

Kenji Takeuchi, Yu-ichiro Motoda and Fumiaki Ito

Department of Biochemistry, Faculty of Pharmaceutical Sciences, Setsunan University, Osaka, Japan

Diverse chemotherapeutic drugs can kill tumor cells

by activating apoptotic pathways. The intracellular

machinery responsible for apoptosis depends on a fam￾ily of cysteine aspases (caspases), and action of the

two main apoptotic pathways, the death receptor and

mitochondria pathways, results in the activation of

caspase 8 and caspase 9, respectively. Apoptotic trig￾gers such as chemotherapeutic drugs activate the latter

pathway, which requires disruption of the mitochond￾rial membrane and release of cytochrome c from the

mitochondria. Cytochrome c functions with Apaf-1 to

activate caspase 9, thereby activating a set of down￾stream caspases [1].

Bcl-2 was originally identified in B-cell lymphomas

[2] and is now known to belong to a growing family of

apoptosis regulatory proteins, known as the Bcl-2 fam￾ily, which may be either death antagonists (e.g. Bcl-2

and Bcl-XL) or death agonists (e.g. Bax and Bad) [3].

Keywords

activator protein 1 (AP1); adriamycin; Bcl-XL;

epidermal growth factor; MAP kinase

Correspondence

K. Takeuchi, Department of Biochemistry,

Faculty of Pharmaceutical Sciences,

Setsunan University, Hirakata, Osaka

573-0101, Japan

Fax: +81 72 866 3117

Tel. +81 72 866 3118

E-mail: [email protected]

(Received 31 March 2006, revised 3 June

2006, accepted 14 June 2006)

doi:10.1111/j.1742-4658.2006.05377.x

We investigated the survival signals of epidermal growth factor (EGF) in

human gastric adenocarcinoma cell line TMK-1. Treatment of TMK-1 cells

with adriamycin (ADR) caused apoptosis and apoptosis-related reactions

such as the release of cytochrome c from mitochondria and the activation

of caspase 9. However, EGF treatment greatly reduced the ADR-induced

apoptosis as well as these reactions. We previously reported that hepato￾cyte growth factor transmitted protective signals against ADR-induced

apoptosis by causing activation of the phosphatidylinositol-3¢-OH kinase

(PtdIns3-K)⁄Akt signaling pathway in human epithelial cell line MKN74

[Takeuchi K & Ito F (2004) J Biol Chem 279, 892–900]. However, PtdIns3-

K ⁄Akt signaling did not mediate the antiapoptotic action of EGF in

TMK-1 cells. EGF increased the expression of the Bcl-XL protein, an

antiapoptotic member of the Bcl-2 family, but not that of other anti (Bcl￾2) or proapoptotic (Bad and Bax) protein members. Expression of the

c-Fos and c-Jun, components of activator protein 1 (AP1), which are

known to regulate bcl-XL gene transcription, were increased in response to

EGF. Pretreatment of the cells with PD98059, an inhibitor of MAP kinase

kinase, inhibited the EGF-induced c-Fos and c-Jun expression, AP1 DNA

binding, Bcl-XL expression, and the resistance against ADR-induced apop￾tosis, suggesting that EGF transmitted the antiapoptotic signal in such a

way that it activated AP1 via a MAP kinase signaling pathway. TMK-1

cells stably transfected with TAM67, c-Jun dominant-negative mutant, did

not display EGF-induced Bcl-XL expression or resistance against ADR￾induced apoptosis. These results indicate that AP1-mediated upregulation

of Bcl-XL expression is critical for protection of TMK-1 cells against

ADR-induced apoptosis.

Abbreviations

ADR, adriamycin; AP1, activator protein 1; EGF, epidermal growth factor; EMSA, electrophoretic mobility shift assay; HRP, horseradish

peroxidase; PMSF, phenylmethylsulfonyl fluoride; PtdIns3-K, phosphatidylinositol-3¢-OH kinase.

FEBS Journal 273 (2006) 3743–3755 ª 2006 The Authors Journal compilation ª 2006 FEBS 3743