Tài liệu Báo cáo khoa học: Cytochrome P450 Cyp4x1 is a major P450 protein in mouse brain doc

Cytochrome P450 Cyp4x1 is a major P450 protein

in mouse brain

Mohammed Al-Anizy1

, Neill J. Horley1

, C.-W. S. Kuo1

, Lorna C. Gillett2

, Charles A. Laughton2

,

David Kendall3

, David A. Barrett2

, Terry Parker3 and David R. Bell1

1 School of Biology, University of Nottingham, UK

2 School of Pharmacy, University of Nottingham, UK

3 School of Biomedical Sciences, University of Nottingham, UK

Cytochromes P450 are a superfamily of proteins [1]

which are involved in the oxidative metabolism of both

foreign and endogenous compounds [2]. The cyto￾chrome P450 4A family is known to be highly induced

by peroxisome proliferators in mouse liver [3,4],

although there is constitutive expression of one gene

[5]. The CYP4A [6], CYP4B [7,8] and CYP4F [9,10]

proteins are known to have fatty acid hydroxylase

activity, and there is extensive speculation that the

formation of hydroxylated fatty acids by cytochrome

P450 leads to the production of physiologically active

metabolites that regulate physiological function [11–16].

Cytochrome P450 metabolism of fatty acids may also

be of fundamental importance in brain [17–19], and it

is known that neurotransmitters and fatty acids can be

actively metabolized by cytochrome P450 in brain

[18,20,21]. Although the specific content of cytochrome

P450 in brain is relatively low compared with liver

[17,22,23], this level of cytochrome P450 can be induced

by various agents [24]. A peculiar feature of brain P450

is that it is difficult to account for the total P450 con￾tent with previously characterized P450 proteins [17].

We describe the cloning of human and mouse

cDNAs for the CYP4x1 P450, a molecular model of

the protein, and tissue-specific localization of the RNA

in mouse and human. The Cyp4x1 protein was locali￾zed by immunohistochemistry and shown to be a

major P450 protein in mouse brain.

Keywords

Cytochrome P450; peroxisome proliferators;

brain; aorta

Correspondence

D.R. Bell, School of Biology, University of

Nottingham, University Park, Nottingham.

NG7 2RD, UK

Fax: +44 115 9513251

Tel: +44 115 9513210

E-mail: [email protected]

(Received 16 November 2005, revised 20

December 2005, accepted 23 December

2005)

doi:10.1111/j.1742-4658.2006.05119.x

A novel cytochrome P450, CYP4x1, was identified in EST databases on

the basis of similarity to a conserved region in the C-helix of the CYP4A

family. The human and mouse CYP4x1 cDNAs were cloned and found

to encode putative cytochrome P450 proteins. Molecular modelling of

CYP4x1 predicted an unusual substrate binding channel for the CYP4 fam￾ily. Expression of human CYP4x1 was detected in brain by EST analysis,

and in aorta by northern blotting. The mouse cDNA was used to demon￾strate that the Cyp4x RNA was expressed principally in brain, and at much

lower levels in liver; hepatic levels of the Cyp4x1 RNA were not affected

by treatment with the inducing agents phenobarbital, dioxin, dexametha￾sone or ciprofibrate, nor were the levels affected in PPARa– ⁄ – mice. A

specific antibody for Cyp4x1 was developed, and shown to detect Cyp4x1

in brain; quantitation of the Cyp4x1 protein in brain demonstrated
10 ng

of Cyp4x1 proteinÆmg)1 microsomal protein, showing that Cyp4x1 is a

major brain P450. Immunohistochemical localization of the Cyp4x1 protein

in brain showed specific staining of neurons, choroids epithelial cells and

vascular endothelial cells. These data suggest an important role for Cyp4x1

in the brain.

Abbreviations

DAB, 3,3¢-diaminobenzidine; TCDD, 2,3,7,8 tetrachlorodibenzo-p-dioxin.

936 FEBS Journal 273 (2006) 936–947 ª 2006 The Authors Journal compilation ª 2006 FEBS