All 19-carbon androgens derive from 21-carbon steroids via sequential 17 -hydroxylase and 17,20-lyase activities of cytochrome P450c17 (CYP17A1). Thecomplex chemistry of the 17,20-lyase reaction is selectively stimulated up to 10-fold bycytochrome b5 (b5). In contrast to the interactions of b5 with some other cytochromesP450, which apparently involve electron transfer from b5, our data argue that b5allosterically activates the 17,20-lyase activity of CYP17A1. We have identified aspecific region of b5 that is critical for stimulation of 17,20-lyase activity and have shownthat the magnitude of this stimulation is substrate-dependent. We now propose toelucidate the mechanism of action of b5 on 17,20-lyase activity and to compare themechanistic and structural features of the b5-CYP17A1 interaction with b5 action onother P450-mediated reactions.
In Aim 1, we will determine the steric and electronic requirements of key residueson CYP17A1 and b5 necessary to stimulate 17,20-lyase activity.
In Aim 2, we willdeduce the microscopic steps of the 17,20-lyase reaction that are enhanced by b5 usingrapid and pre-steady state kinetics experiments.
In Aim 3, we will determine if the samesurface of b5 important for stimulating 17,20-lyase activity also modulates the activitiesof other cytochromes P450 and whether the same mechanistic principles apply to theseother reactions.
In Aim 4, we will engineer soluble forms of b5 that also stimulate 17,20-lyase activity, setting the stage for future structural studies of the CYP17A1-b5 complex.We thus will systematically define the mechanism of action of b5 on CYP17A1,potentially identifying novel approaches for suppressing androgen production, bytargeting the CYP17A1-b5 interaction. Diseases that involve androgen overproduction (such as polycystic ovarysyndrome) and diseases that require androgens (such as prostate cancer) can betreated by inhibition of androgen synthesis. Currently available agents aresuboptimal. By defining how the enzyme 17-hydroxylase/17,20-lyase makesandrogens, we hope to establish new approaches to treating androgen-dependenthuman diseases. We will also determine if these principles apply to other similarenzymes that metabolize drugs. Inhibition of androgen synthesis is the current treatment of human diseases like prostatecancer and polycystic ovary syndrome. This approach is suboptimal. By defining how theenzyme responsible synthesizes these androgens, we hope to establish newapproaches to treatment. Our study will apply to other enzymes that metabolize drugs.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
7R01GM086596-03
Application #
8438169
Study Section
Special Emphasis Panel (ZRG1-DKUS-B (03))
Program Officer
Okita, Richard T
Project Start
2009-09-30
Project End
2013-08-31
Budget Start
2011-09-01
Budget End
2013-08-31
Support Year
3
Fiscal Year
2010
Total Cost
$248,087
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Turcu, Adina F; Nanba, Aya T; Auchus, Richard J (2018) The Rise, Fall, and Resurrection of 11-Oxygenated Androgens in Human Physiology and Disease. Horm Res Paediatr 89:284-291
Rege, Juilee; Turcu, Adina F; Kasa-Vubu, Josephine Z et al. (2018) 11-Ketotestosterone Is the Dominant Circulating Bioactive Androgen During Normal and Premature Adrenarche. J Clin Endocrinol Metab 103:4589-4598
Peng, Hwei-Ming; Barlow, Chase; Auchus, Richard J (2018) Catalytic modulation of human cytochromes P450 17A1 and P450 11B2 by phospholipid. J Steroid Biochem Mol Biol 181:63-72
Capper, C P; Liu, J; McIntosh, L R et al. (2018) Functional characterization of the G162R and D216H genetic variants of human CYP17A1. J Steroid Biochem Mol Biol 178:159-166
Auchus, Richard J (2017) Steroid 17-hydroxylase and 17,20-lyase deficiencies, genetic and pharmacologic. J Steroid Biochem Mol Biol 165:71-78
Alzahrani, Ali S; Alswailem, Meshael M; Murugan, Avaniyapuram Kannan et al. (2017) A high rate of novel CYP11B1 mutations in Saudi Arabia. J Steroid Biochem Mol Biol 174:217-224
Borges, Beatriz C; Garcia-Galiano, David; da Silveira Cruz-Machado, Sanseray et al. (2017) Obesity-Induced Infertility in Male Mice Is Associated With Disruption of Crisp4 Expression and Sperm Fertilization Capacity. Endocrinology 158:2930-2943
Turcu, Adina F; Mallappa, Ashwini; Elman, Meredith S et al. (2017) 11-Oxygenated Androgens Are Biomarkers of Adrenal Volume and Testicular Adrenal Rest Tumors in 21-Hydroxylase Deficiency. J Clin Endocrinol Metab 102:2701-2710
Turcu, Adina F; Auchus, Richard J (2017) Clinical significance of 11-oxygenated androgens. Curr Opin Endocrinol Diabetes Obes 24:252-259
Peng, Hwei-Ming; Auchus, Richard J (2017) Molecular Recognition in Mitochondrial Cytochromes P450 That Catalyze the Terminal Steps of Corticosteroid Biosynthesis. Biochemistry 56:2282-2293

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