Structural basis for human sterol isomerase in cholesterol biosynthesis and multidrug recognition

Abstract

3-β-hydroxysteroid-Δ 8 , Δ 7 -isomerase, known as Emopamil-Binding Protein (EBP), is an endoplasmic reticulum membrane protein involved in cholesterol biosynthesis, autophagy, oligodendrocyte formation. The mutation on EBP can cause Conradi-Hunermann syndrome, an inborn error. Interestingly, EBP binds an abundance of structurally diverse pharmacologically active compounds, causing drug resistance. Here, we report two crystal structures of human EBP, one in complex with the anti-breast cancer drug tamoxifen and the other in complex with the cholesterol biosynthesis inhibitor U18666A. EBP adopts an unreported fold involving five transmembrane-helices (TMs) that creates a membrane cavity presenting a pharmacological binding site that accommodates multiple different ligands. The compounds exploit their positively-charged amine group to mimic the carbocationic sterol intermediate. Mutagenesis studies on specific residues abolish the isomerase activity and decrease the multidrug binding capacity. This work reveals the catalytic mechanism of EBP-mediated isomerization in cholesterol biosynthesis and how this protein may act as a multi-drug binder.

Integrating metabolic reprogramming and metabolic imaging to predict breast cancer therapeutic responses

“…PET/CT combines metabolic imaging from PET with anatomical structure imaging from CT, whereas PET/MRI combines the advantages of PET in metabolic imaging with MRI in functional and structural imaging of soft tissue. 18 F-FDG is the commonly used probe to detect glucose uptake for breast cancer imaging. Other probes include 18 F-FMISO (hypoxia condition detection) [73,74], 18 F-flortanidazole (hypoxia and radiotherapy-associated changes detection) [77], 18 F-4F-Gln (glutamine uptake detection) [55], 18 F-fluciclovine (leucine metabolism detection) [6], (2S,4S)4-18 F-FPArg (arginine metabolism detection) [87], 18 F-FASu (detecting levels of cystine/glutamate antiporter subunit xCT) [58,59], 18 F-FLT (thymidine metabolism) [60,61], 89 Zr-transferrin (interrogating MYC signaling pathway) [79], and so on.…”

“…18 F-FDG is the commonly used probe to detect glucose uptake for breast cancer imaging. Other probes include 18 F-FMISO (hypoxia condition detection) [73,74], 18 F-flortanidazole (hypoxia and radiotherapy-associated changes detection) [77], 18 F-4F-Gln (glutamine uptake detection) [55], 18 F-fluciclovine (leucine metabolism detection) [6], (2S,4S)4-18 F-FPArg (arginine metabolism detection) [87], 18 F-FASu (detecting levels of cystine/glutamate antiporter subunit xCT) [58,59], 18 F-FLT (thymidine metabolism) [60,61], 89 Zr-transferrin (interrogating MYC signaling pathway) [79], and so on. For breast cancer imaging, positron emission mammography (PEM) is being developed, which achieves a prone position to improve the spatial resolution and reclassify suspicious calcifications [88].…”

A proteome-wide map of 20(S)-hydroxycholesterol interactors in cell membranes

“…83,84 Despite their evolutionary relationship, Tmem97 lacks an acidic residue homologous to E122 in Ebp (human numbering), which is required for enzyme catalysis. 85 To determine a binding site for 20(S)-OHC within Tmem97, we used the recently solved cryo-EM structure of human Ebp (hEbp, PDB 6OHT) 86 as a template to predict the structure of mouse Tmem97 (82% pairwise identity with human Tmem97) using the Robetta server. 87 We embedded the resulting model within a POPC membrane and performed all-atom molecular dynamics simulations to equilibrate the membrane-bound Tmem97 structure.…”

Crystal structures of the σ2receptor template large-library docking for selective chemotypes activein vivo

“…A more sensitive hidden Markov model search with HHpred 32 identified EBP as a distant homolog, consistent with both proteins being members of the EXPERA family 7 . We used the structure of EBP 33 to build a homology model of the σ 2 receptor and performed a molecular replacement search that generated a marginally interpretable electron density map. Manual placement of an additional copy of the σ 2 receptor followed by iterative manual building and reciprocal space refinement led to high-quality final structure (Supplementary Information Table 1).…”