Volume 271, Number 45,
Issue of November 8, 1996
pp. 28176-28180
©1996 by The American Society for Biochemistry and Molecular Biology, Inc.
Genomic Cloning and Protein Expression of a Novel Rat Brain
Cytochrome P-450 CYP2D18* Catalyzing Imipramine
N-Demethylation
(Received for publication, February 7, 1996, and in revised form, August 21, 1996)
Hidenori
Kawashima
,
David J.
Sequeira
,
David R.
Nelson
§
and
Henry W.
Strobel
From the
Department of Biochemistry and Molecular
Biology, The University of Texas Medical School at Houston, Houston,
Texas 77225 and the § Department of Biochemistry, University
of Tennessee at Memphis, Memphis, Tennessee 38163
We have previously reported the isolation of two
cDNA clones, designated 2d-29 and 2d-35, which have identical open
reading frames and code for a novel brain cytochrome P-450 (P-450)
belonging to the CYP2D subfamily, and noted that the
mRNA of clone 2d-35 seems to be expressed in the brain but not in
the liver (). Although the deduced amino acid sequence of these clones
differs from that of the liver CYP2D4 by only 5 amino acids
distributed in the C-terminal region, this new P-450 cDNA clone
contained a unique 5
-extension, and we posit in this report by
analysis of a genomic clone that this 5
-untranslated sequence is
derived from a gene distinct from that of CYP2D4. Thus,
this novel P-450 was named P-450 2D18 according to the recommended
nomenclature (). The expressibility of this cDNA was confirmed by
in vitro translation using a reticulocyte system, and
protein expression was performed using COS-M6 cells. Immunoblot
analysis showed a cross-reacting band of the predicted size range with
anti-P-450 2D6 antiserum, which was not seen in control cells.
Furthermore, the CYP2D18-expressed COS cell lysate showed
N-demethylation activity toward imipramine, whereas another
brain P-450 CYP4F6-expressed COS cell lysate showed
10-hydroxylation activity. This is the first report that associates an
individual P-450 isozyme in brain with a particular metabolic
alteration of the antidepressant imipramine.