All 19-carbon androgens derive from 21-carbon steroids via sequential 17?-hydroxylase and 17,20-lyase activities of cytochrome P450c17 (CYP17A1). The complex chemistry of the 17,20-lyase reaction is selectively stimulated up to 10-fold by cytochrome b5 (b5) in vitro. In contrast to the interactions of b5 with some other cytochromes P450, which apparently involve electron transfer from b5, our data argue that b5 allosterically activates the 17,20-lyase activity of CYP17A1. We have identified a specific region of b5 that is critical for stimulation of 17,20-lyase activity and have shown that the magnitude of this stimulation is substrate-dependent. We now propose to elucidate the importance of this action of b5 on 17,20-lyase activity and androgen synthesis in vivo and to compare the mechanistic and structural features of the b5-CYP17A1 interaction with b5 action on other P450-mediated reactions, in preparation for a detailed interrogation of the mechanism of b5 action on CYP17A1. To first prove that b5 is essential for androgen biosynthesis, we will generate and characterize mice lacking b5 in the testis for Aim 1. We will characterize the fertility, hormone production, and testicular histology of these mice. The enzymatic activity of the testes will be studied in detail.
In Aim 2, we will determine if residues on b5 that are required for stimulating 17,20-lyase activity are also essential for modulating the activities of other cytochromes P450 and begin to determine whether the same microscopic steps are involved for all P450 enzymes. We thus will define the importance of b5 action on CYP17A1 in mammalian physiology, and we will begin to ascertain if the mechanism of action is similar to b5 action on other cytochromes P450. This knowledge will provide a novel approach for suppressing androgen production, by targeting the CYP17A1-b5 interaction.

Public Health Relevance

Inhibition of androgen synthesis is the current treatment of human diseases like prostate cancer and polycystic ovary syndrome. This approach is suboptimal. By defining how the enzyme responsible synthesizes these androgens, we hope to establish new approaches 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 #
5R01GM086596-02
Application #
7939798
Study Section
Special Emphasis Panel (ZRG1-DKUS-B (03))
Program Officer
Okita, Richard T
Project Start
2009-09-30
Project End
2011-07-31
Budget Start
2010-09-01
Budget End
2011-07-31
Support Year
2
Fiscal Year
2010
Total Cost
$93,980
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
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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