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Bose HS. Dry molten globule conformational state of CYP11A1 (SCC) regulates the first step of steroidogenesis in the mitochondrial matrix. iScience 2024; 27:110039. [PMID: 38868187 PMCID: PMC11167429 DOI: 10.1016/j.isci.2024.110039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 02/18/2024] [Accepted: 05/16/2024] [Indexed: 06/14/2024] Open
Abstract
Multiple metabolic events occur in mitochondria. Mitochondrial protein translocation from the cytoplasm across compartments depends on the amino acid sequence within the precursor. At the mitochondria associated-ER membrane, misfolding of a mitochondrial targeted protein prior to import ablates metabolism. CYP11A1, cytochrome P450 cholesterol side chain cleavage enzyme (SCC), is imported from the cytoplasm to mitochondrial matrix catalyzing cholesterol to pregnenolone, an essential step for metabolic processes and mammalian survival. Multiple steps regulate the availability of an actively folded SCC; however, the mechanism is unknown. We identified that a dry molten globule state of SCC exists in the matrix by capturing intermediate protein folding steps dictated by its C-terminus. The intermediate dry molten globule state in the mitochondrial matrix of living cells is stable with a limited network of interaction and is inactive. The dry molten globule is activated with hydrogen ions availability, triggering cleavage of cholesterol sidechain, and initiating steroidogenesis.
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Affiliation(s)
- Himangshu S. Bose
- Laboratory of Biochemistry, Biomedical Sciences, Mercer University School of Medicine, Savannah, GA 31404, USA
- Anderson Cancer Institute, Memorial University Medical Center, Savannah, GA 31404, USA
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Sluchanko NN, Tugaeva KV, Maksimov EG. Solution structure of human steroidogenic acute regulatory protein STARD1 studied by small-angle X-ray scattering. Biochem Biophys Res Commun 2017; 489:445-450. [DOI: 10.1016/j.bbrc.2017.05.167] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 05/28/2017] [Indexed: 12/11/2022]
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Sluchanko NN, Tugaeva KV, Faletrov YV, Levitsky DI. High-yield soluble expression, purification and characterization of human steroidogenic acute regulatory protein (StAR) fused to a cleavable Maltose-Binding Protein (MBP). Protein Expr Purif 2015; 119:27-35. [PMID: 26555181 DOI: 10.1016/j.pep.2015.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 10/21/2015] [Accepted: 11/04/2015] [Indexed: 11/24/2022]
Abstract
Steroidogenic acute regulatory protein (StAR) is responsible for the rapid delivery of cholesterol to mitochondria where the lipid serves as a source for steroid hormones biosynthesis in adrenals and gonads. Despite many successful investigations, current understanding of the mechanism of StAR action is far from being completely clear. StAR was mostly obtained using denaturation/renaturation or in minor quantities in a soluble form at decreased temperatures that, presumably, limited the possibilities for its consequent detailed exploration. In our hands, existing StAR expression constructs could be bacterially expressed almost exclusively as insoluble forms, even upon decreased expression temperatures and in specific strains of Escherichia coli, and isolated protein tended to aggregate and was difficult to handle. To maximize the yield of soluble protein, optimized StAR sequence encompassing functional domain STARD1 (residues 66-285) was fused to the C-terminus of His-tagged Maltose-Binding Protein (MBP) with the possibility to cleave off the whole tag by 3C protease. The developed protocol of expression and purification comprising of a combination of subtractive immobilized metal affinity chromatography (IMAC) and size-exclusion chromatography allowed us to obtain up to 25 mg/1 L culture of completely soluble StAR protein, which was (i) homogenous according to SDS-PAGE, (ii) gave a single symmetrical peak on a gel-filtration, (iii) showed the characteristic CD spectrum and (iv) pH-dependent ability to bind a fluorescently-labeled cholesterol analogue. We conclude that our strategy provides fully soluble and native StAR protein which in future could be efficiently used for biotechnology and drug discovery aimed at modulation of steroids production.
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Affiliation(s)
- Nikolai N Sluchanko
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia.
| | - Kristina V Tugaeva
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia; Department of Biochemistry, School of Biology, Moscow State University, Moscow, Russia
| | - Yaroslav V Faletrov
- Research Institute for Physical Chemical Problems, Belarusian State University, Minsk, Belarus
| | - Dmitrii I Levitsky
- A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia; A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
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Thomas JL, Bose HS. Regulation of human 3-beta-hydroxysteroid dehydrogenase type-2 (3βHSD2) by molecular chaperones and the mitochondrial environment affects steroidogenesis. J Steroid Biochem Mol Biol 2015; 151:74-84. [PMID: 25448736 DOI: 10.1016/j.jsbmb.2014.11.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 10/09/2014] [Accepted: 11/19/2014] [Indexed: 10/24/2022]
Abstract
Human 3-β-hydroxysteroid dehydrogenase/isomerase types 1 and 2 (3βHSD1 and 3βHSD2, respectively) are expressed in a tissue-specific pattern by different genes. Site-directed mutagenesis studies have confirmed the function of the catalytic amino acids (Tyr154, Lys 158, Ser124 in both isoenzymes), substrate/inhibitor isoform-specific residues (His156 and Arg195 in 3βHSD1) and cofactor binding residues (Asp36 provides NAD(+) specificity in both isoenzymes). However, detailed analysis of isoform-specific organelle localization and characterization is difficult due to the 93% amino acid identity between the two isoforms. With recent advances in the knowledge of mitochondrial architecture and localization of the various translocases, our laboratory has studied the mechanisms regulating mitochondrial 3βHSD2 localization. The mitochondrial N-terminal leader sequence of 3βHSD2 directs its entry into the mitochondria where it is localized to the intermembrane space (IMS). Unlike other mitochondrial proteins, the N-terminal signal sequence of 3βHSD2 is not cleaved upon mitochondrial import. 3βHSD2 interacts with the mitochondrial translocase, Tim50, to regulate progesterone and androstenedione formation. Our studies suggest that its activity at the IMS is facilitated in a partially unfolded "molten globule" conformation by the proton pump between the matrix and IMS. The unfolded protein is refolded by the mitochondrial chaperones. The protons at the IMS are absorbed by the lipid vesicles, to maintain the proton pump and recycle 3βHSD2. As a result, one molecule of 3βHSD2 may participate in multiple catalytic reactions. In summary, the steroidogenic cell recycles 3βHSD2 to catalyze the reactions needed to produce androstenedione, progesterone and 17α-hydroxyprogesterone on demand in coordination with the mitochondrial translocase, Tim50. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.
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Affiliation(s)
- James L Thomas
- Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, GA 31207, USA
| | - Himangshu S Bose
- Departments of Biochemistry, Biomedical Sciences, Mercer University School of Medicine, Savannah, GA 31404, USA; Memorial University Medical Center, Anderson Cancer Institute, Savannah, GA 31404, USA.
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Thomas JL, Rajapaksha M, Mack VL, DeMars GA, Majzoub JA, Bose HS. Regulation of human 3β-hydroxysteroid dehydrogenase type 2 by adrenal corticosteroids and product-feedback by androstenedione in human adrenarche. J Pharmacol Exp Ther 2014; 352:67-76. [PMID: 25355646 DOI: 10.1124/jpet.114.219550] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In human adrenarche during childhood, the secretion of dehydroepiandrosterone (DHEA) from the adrenal gland increases due to its increased synthesis and/or decreased metabolism. DHEA is synthesized by 17α-hydroxylase/17,20-lyase, and is metabolized by 3β-hydroxysteroid dehydrogenase type 2 (3βHSD2). In this study, the inhibition of purified human 3βHSD2 by the adrenal steroids, androstenedione, cortisone, and cortisol, was investigated and related to changes in secondary enzyme structure. Solubilized, purified 3βHSD2 was inhibited competitively by androstenedione with high affinity, by cortisone at lower affinity, and by cortisol only at very high, nonphysiologic levels. When purified 3βHSD2 was bound to lipid vesicles, the competitive Ki values for androstenedione and cortisone were slightly decreased, and the Ki value of cortisol was decreased 2.5-fold, although still at a nonphysiologic level. The circular dichroism spectrum that measured 3βHSD2 secondary structure was significantly altered by the binding of cortisol, but not by androstenedione and cortisone. Our import studies show that 3βHSD2 binds in the intermitochondrial space as a membrane-associated protein. Androstenedione inhibits purified 3βHSD2 at physiologic levels, but similar actions for cortisol and cortisone are not supported. In summary, our results have clarified the mechanisms for limiting the metabolism of DHEA during human adrenarche.
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Affiliation(s)
- James L Thomas
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Maheshinie Rajapaksha
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Vance L Mack
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Geneva A DeMars
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Joseph A Majzoub
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
| | - Himangshu S Bose
- Division of Basic Medical Sciences (J.L.T., V.L.M.) and Department of Ob-Gyn (J.L.T.), Mercer University School of Medicine, Macon, Georgia; Department of Biochemistry, Mercer University School of Medicine, Savannah, Georgia (M.R., G.A.D., H.S.B.); Memorial University Medical Center, Anderson Cancer Institute, Savannah, Georgia (H.S.B.); and Division of Endocrinology, Boston Children's Hospital, and Harvard Medical School, Boston, Massachusetts (J.A.M.)
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Rajapaksha M, Kaur J, Bose M, Whittal RM, Bose HS. Cholesterol-mediated conformational changes in the steroidogenic acute regulatory protein are essential for steroidogenesis. Biochemistry 2013; 52:7242-53. [PMID: 24053410 DOI: 10.1021/bi401125v] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although the mechanism by which the steroidogenic acute regulatory protein (StAR) promotes steroidogenesis has been studied extensively, it remains incompletely characterized. Because structural analysis has revealed a hydrophobic sterol-binding pocket (SBP) within StAR, this study sought to examine the regulatory role of cholesterol concentrations on protein folding and mitochondrial import. Stopped-flow analyses revealed that at low concentrations, cholesterol promotes StAR folding. With increasing cholesterol concentrations, an intermediate state is reached followed by StAR unfolding. With 5 μg/mL cholesterol, the apparent binding was 0.011 s(-1), and the unfolding time (t1/2) was 63 s. The apparent binding increased from 0.036 to 0.049 s(-1) when the cholesterol concentration was increased from 50 μg/mL to 100 μg/mL while t1/2 decreased from 19 to 14 s. These cholesterol-induced conformational changes were not mediated by chemical chaperones. Protein fingerprinting analysis of StAR in the absence and presence of cholesterol by mass spectrometry revealed that the cholesterol binding region, comprising amino acids 132-188, is protected from proteolysis. In the absence of cholesterol, a longer region of amino acids from position 62 to 188 was protected, which is suggestive of organization into smaller, tightly folded regions with cholesterol. In addition, rapid cholesterol metabolism was required for the import of StAR into the mitochondria, suggesting that the mitochondria have a limited capacity for import and processing of steroidogenic proteins, which is dependent on cholesterol storage. Thus, cholesterol regulates StAR conformation, activating it to an intermediate flexible state for mitochondrial import and its enhanced cholesterol transfer capacity.
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Affiliation(s)
- Maheshinie Rajapaksha
- Department of Biochemistry, Division of Biomedical Sciences, Mercer University School of Medicine , Savannah, Georgia 31404, United States
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Rajapaksha M, Prasad M, Thomas JL, Whittal RM, Bose HS. Chaperones rejuvenate folding and activity of 3-β hydroxysteroid dehydrogenase 2. ACS Chem Biol 2013; 8:1000-8. [PMID: 23485106 DOI: 10.1021/cb400052s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The steroidogenic enzyme 3-β hydroxysteroid dehydrogenase 2 (3βHSD2) mediates the conversion of pregnenolone to progesterone and dehydroepiandrosterone to androstenedione through both its dehydrogenase and isomerase activities, making it necessary for the protein to undergo a reversible conformational change. We hypothesized that chaperones assist 3βHSD2 in switching between the conformations to initiate, enhance, and maintain activity. In the presence of the chaperone lauryl maltoside (LM), 3βHSD2 immediately converted pregnenolone to progesterone, with a 6.4-fold increase in synthesis. Using far-UV circular dichroism (CD), we found that addition of LM increased 3βHSD2's α-helical content, which over time reverted to control levels, suggesting the formation of a stable but reversible conformation possibly due to hydrophobic interactions of the protein with LM micelles. We also found that LM increased fluorescence resonance energy transfer (FRET) about 11-fold between 3βHSD2 and fluorescing ANS molecules. This observation supports the idea that detergent(s) act as chaperones to assist 3βHSD2 in forming stable complexes, which in turn promotes proper folding. Mass spectrometric fingerprinting illustrated that LM incubation resulted in an ordered fragmentation of molecular mass from 39 to 13 kDa, as compared to limited or no proteolysis in the absence of LM. In addition, space-filling modeling demonstrated that 3βHSD2 association with detergents likely exposed the hydrophobic region, leading to its proteolysis. We conclude that detergents help 3βHSD2 to refold in order to rejuvenate, contributing to the ability of cells to rapidly produce steroids when needed.
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Affiliation(s)
| | | | - James L. Thomas
- Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, Georgia
31207, United States
| | - Randy M. Whittal
- Department
of Chemistry, University of Alberta, Edmonton,
Alberta, Canada T6G
2G2
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Marriott KSC, Prasad M, Thapliyal V, Bose HS. σ-1 receptor at the mitochondrial-associated endoplasmic reticulum membrane is responsible for mitochondrial metabolic regulation. J Pharmacol Exp Ther 2012; 343:578-86. [PMID: 22923735 PMCID: PMC3500540 DOI: 10.1124/jpet.112.198168] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 08/23/2012] [Indexed: 01/30/2023] Open
Abstract
The mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) is a small section of the outer mitochondrial membrane tethered to the ER by lipid and protein filaments. One such MAM protein is the σ-1 receptor, which contributes to multiple signaling pathways. We found that short interfering RNA-mediated knockdown of σ-1 reduced pregnenolone synthesis by 95% without affecting expression of the inner mitochondrial membrane resident enzyme, 3-β-hydroxysteroid dehydrogenase 2. To explore the underlying mechanism of this effect, we generated a series of σ-receptor ligands: 5,6-dimethoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide (KSCM-1), 3-methyl-N-phenyl-N-(3-(piperidin-1-yl)propyl)benzofuran-2-carboxamide (KSCM-5), and 6-methoxy-3-methyl-N-phenyl-N-(3-(piperidin-1-yl) propyl)benzofuran-2-carboxamide (KSCM-11) specifically bound to σ-1 in the nanomolar range, whereas KSCM-5 and KSCM-11 also bound to σ-2. Treatment of cells with the KSCM ligands led to decreased cell viability, with KSCM-5 having the most potent effect followed by KSCM-11. KSCM-1 increased σ-1 expression by 4-fold and progesterone synthesis, whereas the other compounds decreased progesterone synthesis. These differences probably are caused by ligand molecular structure. For example, KSCM-1 has two methoxy substituents at C-5 and C-6 of the benzofuran ring, whereas KSCM-11 has one at C-6. KSCM ligands or σ-1 knockdown did not alter the expression of ER resident enzymes that synthesize steroids. However, coimmunoprecipitation of the σ-1 receptor pulled down voltage-dependent anion channel 2 (VDAC2), whose expression was enhanced by KSCM-1. VDAC2 plays a key role in cholesterol transport into the mitochondria, suggesting that the σ-1 receptor at the MAM coordinates with steroidogenic acute regulatory protein for cholesterol trafficking into the mitochondria for metabolic regulation.
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Affiliation(s)
- Karla-Sue C Marriott
- Department of Natural Sciences, College of Science and Technology, Savannah State University, Savannah, GA, USA
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Miller WL, Bose HS. Early steps in steroidogenesis: intracellular cholesterol trafficking. J Lipid Res 2011; 52:2111-2135. [PMID: 21976778 DOI: 10.1194/jlr.r016675] [Citation(s) in RCA: 368] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Steroid hormones are made from cholesterol, primarily derived from lipoproteins that enter cells via receptor-mediated endocytosis. In endo-lysosomes, cholesterol is released from cholesterol esters by lysosomal acid lipase (LAL; disordered in Wolman disease) and exported via Niemann-Pick type C (NPC) proteins (disordered in NPC disease). These diseases are characterized by accumulated cholesterol and cholesterol esters in most cell types. Mechanisms for trans-cytoplasmic cholesterol transport, membrane insertion, and retrieval from membranes are less clear. Cholesterol esters and "free" cholesterol are enzymatically interconverted in lipid droplets. Cholesterol transport to the cholesterol-poor outer mitochondrial membrane (OMM) appears to involve cholesterol transport proteins. Cytochrome P450scc (CYP11A1) then initiates steroidogenesis by converting cholesterol to pregnenolone on the inner mitochondrial membrane (IMM). Acute steroidogenic responses are regulated by cholesterol delivery from OMM to IMM, triggered by the steroidogenic acute regulatory protein (StAR). Chronic steroidogenic capacity is determined by CYP11A1 gene transcription. StAR mutations cause congenital lipoid adrenal hyperplasia, with absent steroidogenesis, potentially lethal salt loss, and 46,XY sex reversal. StAR mutations initially destroy most, but not all steroidogenesis; low levels of StAR-independent steroidogenesis are lost later due to cellular damage, explaining the clinical findings. Rare P450scc mutations cause a similar syndrome. This review addresses these early steps in steroid biosynthesis.
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Affiliation(s)
- Walter L Miller
- Department of Pediatrics, School of Medicine, University of California, San Francisco, CA 94143; UCSF Benioff Children's Hospital, San Francisco, CA 94143.
| | - Himangshu S Bose
- Department of Biochemistry, Mercer University School of Medicine, Savannah, GA 31404; and; Memorial University Medical Center, Savannah, GA 31404
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