Crystal growth of human estrogenic 17β-hydroxysteroid dehydrogenase

New insights into the substrate inhibition of human 17β-hydroxysteroid dehydrogenase type 1

Human type 1 17β-hydroxysteroid dehydrogenase (17β-HSD1),a member of the short-chain dehydrogenase/reductase family, catalyzes the last step in the bioactivation of the most potent estrogen estradiol with high specificity and is thus involved in estrogen-dependent diseases. As an oxidoreductase, 17β-HSD1 can utilize both triphosphate and diphosphate cofactors in reaction at the molecular level, but more specific with triphosphate cofactor. The NADPH is much higher than NADP+ in living cells leading to preliminary reduction action. The enzyme also showed substrate-induced inhibition unprecedented in other members of 17β-HSDs. Our previous study elucidated the structural mechanism of substrate inhibition is due to the reversely bound estrone (E1) in the substrate-binding pocket of the enzyme resulting in a dead-end complex. However, the effect of the cofactor preference on the substrate inhibition of the enzyme is not yet clear. In the present study, we solved the ternary crystal structures of 17β-HSD1 in complex with E1 and cofactor analog NAD+ . Combined with molecular dynamics simulation using the enzyme with NADH/NADPH and different oriented E1 (normally oriented, E1N; reversely oriented, E1R), such ternary structure provides a complete picture of enzyme-substrate-cofactor interactions. The results reveal that different cofactors and substrate binding mode affect the allosteric effect between the two subunits of the enzyme. And the results from MD simulations confirmed that His²²¹ plays a key role in the formation of dead-end complex in NADPH complex, and the absence of stable interaction between His²²¹ and E1R in the NADH complex should be the main reason for its lack of substrate inhibition.

Crystal structures of human 17β-hydroxysteroid dehydrogenase type 1 complexed with estrone and NADP+ reveal the mechanism of substrate inhibition

Human 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) catalyses the last step in estrogen activation and is thus involved in estrogen-dependent diseases (EDDs). Unlike other 17β-HSD members, 17β-HSD1 undergoes a significant substrate-induced inhibition that we have previously reported. Here we solved the binary and ternary crystal structures of 17β-HSD1 in complex with estrone (E1) and cofactor analog NADP⁺ , demonstrating critical enzyme-substrate-cofactor interactions. These complexes revealed a reversely bound E1 in 17β-HSD1 that provides the basis of the substrate inhibition, never demonstrated in estradiol complexes. Structural analysis showed that His²²¹ is the key residue responsible for the reorganization and stabilization of the reversely bound E1, leading to the formation of a dead-end complex, which exists widely in NADP(H)-preferred enzymes for the regulation of their enzymatic activity. Further, a new inhibitor is proposed that may inhibit 17β-HSD1 through the formation of a dead-end complex. This finding indicates a simple mechanism of enzyme regulation in the physiological background and introduces a pioneer inhibitor of 17β-HSD1 based on the dead-end inhibition model for efficiently targeting EDDs. DATABASES: Coordinates and structure factors of 17β-HSD1-E1 and 17β-HSD1-E1-NADP⁺ have been deposited in the Protein Data Bank with accession code 6MNC and 6MNE respectively. ENZYMES: 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) EC 1.1.1.62.

Combined Biophysical Chemistry Reveals a New Covalent Inhibitor with a Low-Reactivity Alkyl Halide

17β-Hydroxysteroid dehydrogenase type 1 (17β-HSD1) plays a pivotal role in the progression of estrogen-related diseases because of its involvement in the biosynthesis of estradiol (E2), constituting a valuable therapeutic target for endocrine treatment. In the present study, we successfully cocrystallized the enzyme with the reversible inhibitor 2-methoxy-16β-( m-carbamoylbenzyl)-E2 (2-MeO-CC-156) as well as the enzyme with the irreversible inhibitor 3-(2-bromoethyl)-16β-( m-carbamoylbenzyl)-17β-hydroxy-1,3,5(10)-estratriene (PBRM). The structures of ternary complexes of 17β-HSD1-2-MeO-CC-156-NADP⁺ and 17β-HSD1-PBRM-NADP⁺ comparatively show the formation of a covalent bond between His²²¹ and the bromoethyl side chain of the inhibitor in the PBRM structure. A dynamic process including beneficial molecular interactions that favor the specific binding of a low-reactivity inhibitor and subsequent N-alkylation event through the participation of His²²¹ in the enzyme catalytic site clearly demonstrates the covalent bond formation. This finding opens the door to a new design of alkyl halide-based specific covalent inhibitors as potential therapeutic agents for different enzymes, contributing to the development of highly efficient inhibitors.

Aromatase, estrone sulfatase, and 17β-hydroxysteroid dehydrogenase: structure-function studies and inhibitor development

Aromatase, estrone sulfatase, and 17β-hydroxysteroid dehydrogenase type 1 are involved in the key steps of 17β-estradiol biosynthesis. Structure-function studies of aromatase, estrone sulfatase and 17β-hydroxysteroid dehydrogenase type 1 are important to evaluate the molecular basis of the interaction between these enzymes and their inhibitors. Selective and potent inhibitors of the three enzymes have been developed as antiproliferative agents in hormone-dependent breast carcinoma. New treatment strategies for hormone-dependent breast cancer are discussed.

Binary and ternary crystal structure analyses of a novel inhibitor with 17β-HSD type 1: a lead compound for breast cancer therapy

Oestradiol is a well-characterized sex hormone that stimulates breast cancer and other oestrogen-related diseases. 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) catalyses the last step in the synthesis of oestradiol and androstenediol in breast tumour tissue. The enzyme's high expression and activity after simultaneous blockade of oestrogen receptors and inhibition of aromatase in the tumour shows the necessity for its inhibition as a requirement for breast cancer therapy. In the present paper, we report structures of the binary and ternary complexes of 17β-HSD1 with a new inhibitor E2B {3-[3′,17′β-dihydroxyestra-1′,3′,5′(10′)-trien-16′β-methyl]benzamide}, and the enzyme inhibition by the later. The IC50 value for E2B was determined to be 42 nM in T47D cells. Multiple interactions between E2B and the enzyme include hydrogen bonds and hydrophobic interactions, as well as π–π interactions. A kinetic study demonstrated that E2B inhibits the enzyme's reduction forming oestradiol from oestrone, with a Ki of 0.9±0.15 nM. Such strong inhibition is in agreement with its extensive interaction with the enzyme, suggesting its potential as a lead compound for breast cancer therapy. In fact, this possibility is enhanced by its capacity for cell penetration similar to natural steroids. Such inhibitors that block oestrogen synthesis to suppress the sulfatase pathway producing oestradiol can be used in adjuvant therapies with oestrogen receptor blockade, opening a new orientation of breast cancer treatment.