Irina Pikuleva, Ph.D.
Institute of Pathology
2085 Adelbert Road, room 303A
Cleveland, OH 44106
Cholesterol is essential for life in mammals. However, if chronically in excess,
it becomes a risk factor for cardiovascular and Alzheimer’s diseases and possibly
age-related macular degeneration. The focus of this laboratory is on the four cytochrome
P450 enzymes 7A1, 27A1, 46A1, and 11A1 that are necessary for cholesterol elimination
from different organs.
The four major cytochrome P450 enzymes that initiate cholesterol degradation in different
We are trying to understand how cholesterol-metabolizing P450s function at the molecular
level, what roles they play in the development of different diseases, and whether
these enzymes could serve as targets for cholesterol lowering medications. Currently,
there are two major projects in the laboratory. The first project is based on our
previous structural and biochemical studies showing that the enzyme active site
is conformationally flexible and can accommodate ligands other than sterols. The
goal of this project is to identify marketed drugs that can either inhibit or stimulate
the CYP46A1-mediated cholesterol hydroxylation in vivo. We use in-silico and in
vitro screening of drug libraries, X-ray crystallography, and tests on animals.
Solvent accessible area of the active site of substrate-free (orange) and cholesterol-3-sulfate-bound
(blue) CYP46A1. The wheat colored structure is substrate-free and the cyan-colored
structure is cholesterol-3-sulfate-bound.
The second project is based on studies by others showing that P450s 27A1, 11A1,
and 46A1 are expressed in the retina. We know that in extraocular tissues, deficiency
of cholesterol-metabolizing P450s is manifested clinically by cerebrotendinous xanthomatosis
with premature atherosclerosis (P450 27A1), congenital lipoid adrenal hyperplasia
(P450 11A1), and likely impairment of memory and learning and Alzheimer’s disease
(as indicated phenotypically in P450 46A1 knockout mice and human studies of P450
46A1 polymorphisms). We hypothesize that in the retina P450s 27A1, 11A1, and 46A1
are important as well. The goal of this project is to delineate the roles of P450s
27A1, 11A1 and 46A1 in the retina. We are assessing whether the unique retinal environment
affects catalytic properties of cholesterol-metabolizing CYPs, evaluating vision
function in P450 knock out mice, and characterizing human retinal samples for the
P450 expression and lipid content.
- Mast N, Liao W-L, Pikuleva IA, Turko IV. Combined use of mass spectrometry
and heterologous expression for identification of membrane-interacting peptides
in cytochrome P450 46A1 and NADPH-cytochrome P450 oxidoreductase. Arch Bioch Biophys
- Mast N, White MA, Bjorkhem I, Johnson EF, Stout CD, Pikuleva, IA. Crystal
structures of substrate-bound and substrate-free cytochrome P450 46A1, the principal
cholesterol hydroxylase in the brain. Proc. Natl. Aca. Sci. USA 2008;105:9546-9551.
- White MA, Mast N, Bjorkhem I, Johnson EF, Stout CD, Pikuleva IA. Use of complementary
cation and anion heavy-atom salt derivatives to solve the structure of cytochrome
P450 46A1. Acta Cryst. D 2008;D64:487-495.
- Pikuleva IA. Cholesterol-metabolizing cytochromes P450: implications for
cholesterol lowering. Expert Opin Drug Metab Toxicol. 2008;11:1403-1414.
- Pikuleva IA, Mast N, Liao W-L, Turko IV. Studies of membrane topology
of mitochondrial cholesterol hydroxylases CYPs 27A1 and 11A1. Lipids 2008;43:1127-1132.
- Mast N, Murtazina D, Liu H, Graham S, Bjorkhem I, Halpert J, Peterson J, Pikuleva
IA. Distinct binding of cholesterol and 5-cholestan-3,7,12-triol to cytochrome
P450 27A1: evidence from modeling and site-directed mutagenesis studies. Biochemistry
- Mast N, Graham S.E, Andersson U, Bjorkhem I, Hill C, Peterson J, Pikuleva IA.
Cholesterol binding to cytochrome P450 7A1, a key enzyme in bile acid biosynthesis.