1
|
Phadte A, Dhole C, Hegishte S, Sarathi V, Lila A, Gada JV, Memon SS, Arya S, Karlekar M, Patil V, Varthakavi PK, Shah N, Bhagwat NM, Bandgar T. Steroidogenic acute regulatory protein (STAR) deficiency: Our experience and systematic review for phenotype-genotype correlation. Clin Endocrinol (Oxf) 2024; 100:431-440. [PMID: 38368602 DOI: 10.1111/cen.15032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 01/18/2024] [Accepted: 02/04/2024] [Indexed: 02/20/2024]
Abstract
OBJECTIVE Lipoid congenital adrenal hyperplasia (LCAH) is caused by mutations in STAR. A systematic review of phenotype-genotype correlation and data on testicular histology in LCAH patients is unavailable. We aim to describe our experience and provide phenotype-genotype correlation. DESIGN, PATIENTS AND MEASUREMENTS: Retrospective review of three genetically proven LCAH patients from our centre and per-patient data analysis from a systematic review of 292 probands. The phenotypic subgroups of 46,XY were Group A (typical female genitalia), Group B (atypical genitalia) and Group C (typical male genitalia). RESULTS We report three new LCAH probands from India, all diagnosed post-infancy with preserved gonadal function and one novel variant. The systematic review reports 46,XY to 46,XX LCAH ratio of 1.1 (155:140). Patients with 46,XY LCAH in Group A were diagnosed in infancy (116/117) and had higher mineralocorticoid involvement than Group C (96.4% vs. 75%, p = 0.035), whereas Group C had preserved gonadal function. Hyperplastic adrenals are noted in ~60% of LCAH diagnosed with primary adrenal insufficiency in infancy. There was no report of gonadal germ cell cancer and rare reports of germ cell neoplasia in situ in adolescents, especially with intraabdominal gonads. Two-thirds of LCAH probands were East-Asian and 11/16 regional recurrent variants were from East Asia. There was minimal overlap between variants in Groups A (n = 55), B (n = 9) and C (n = 8). All nonsense and frameshift and most of the splice-site variants and deletion/insertions were present in Group A. CONCLUSIONS We report three new cases of LCAH from India. We propose a phenotype-derived genotypic classification of reported STAR variants in 46,XY LCAH.
Collapse
Affiliation(s)
- Aditya Phadte
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Charushila Dhole
- Department of Endocrinology, Topiwala National Medical College and BYL Nair Charitable Hospital, Mumbai, India
| | - Samiksha Hegishte
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Vijaya Sarathi
- Department of Endocrinology, Vydehi Institute of Medical Sciences and Research Centre, Bangalore, India
| | - Anurag Lila
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Jugal V Gada
- Department of Endocrinology, Topiwala National Medical College and BYL Nair Charitable Hospital, Mumbai, India
| | - Saba Samad Memon
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Sneha Arya
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Manjiri Karlekar
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Virendra Patil
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Premlata K Varthakavi
- Department of Endocrinology, Topiwala National Medical College and BYL Nair Charitable Hospital, Mumbai, India
| | - Nalini Shah
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| | - Nikhil M Bhagwat
- Department of Endocrinology, Topiwala National Medical College and BYL Nair Charitable Hospital, Mumbai, India
| | - Tushar Bandgar
- Department of Endocrinology, Seth G S Medical College and KEM Hospital, Mumbai, India
| |
Collapse
|
2
|
Role of STAR and SCP2/SCPx in the Transport of Cholesterol and Other Lipids. Int J Mol Sci 2022; 23:ijms232012115. [PMID: 36292972 PMCID: PMC9602805 DOI: 10.3390/ijms232012115] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 09/30/2022] [Accepted: 10/08/2022] [Indexed: 11/21/2022] Open
Abstract
Cholesterol is a lipid molecule essential for several key cellular processes including steroidogenesis. As such, the trafficking and distribution of cholesterol is tightly regulated by various pathways that include vesicular and non-vesicular mechanisms. One non-vesicular mechanism is the binding of cholesterol to cholesterol transport proteins, which facilitate the movement of cholesterol between cellular membranes. Classic examples of cholesterol transport proteins are the steroidogenic acute regulatory protein (STAR; STARD1), which facilitates cholesterol transport for acute steroidogenesis in mitochondria, and sterol carrier protein 2/sterol carrier protein-x (SCP2/SCPx), which are non-specific lipid transfer proteins involved in the transport and metabolism of many lipids including cholesterol between several cellular compartments. This review discusses the roles of STAR and SCP2/SCPx in cholesterol transport as model cholesterol transport proteins, as well as more recent findings that support the role of these proteins in the transport and/or metabolism of other lipids.
Collapse
|
3
|
Galano M, Li Y, Li L, Sottas C, Papadopoulos V. Role of Constitutive STAR in Leydig Cells. Int J Mol Sci 2021; 22:2021. [PMID: 33670702 PMCID: PMC7922663 DOI: 10.3390/ijms22042021] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/13/2021] [Accepted: 02/17/2021] [Indexed: 12/15/2022] Open
Abstract
Leydig cells contain significant amounts of constitutively produced steroidogenic acute regulatory protein (STAR; STARD1). Hormone-induced STAR plays an essential role in inducing the transfer of cholesterol into the mitochondria for hormone-dependent steroidogenesis. STAR acts at the outer mitochondrial membrane, where it interacts with a protein complex, which includes the translocator protein (TSPO). Mutations in STAR cause lipoid congenital adrenal hyperplasia (lipoid CAH), a disorder characterized by severe defects in adrenal and gonadal steroid production; in Leydig cells, the defects are seen mainly after the onset of hormone-dependent androgen formation. The function of constitutive STAR in Leydig cells is unknown. We generated STAR knockout (KO) MA-10 mouse tumor Leydig cells and showed that STAR KO cells failed to form progesterone in response to dibutyryl-cAMP and to TSPO drug ligands, but not to 22(R)-hydroxycholesterol, which is a membrane-permeable intermediate of the CYP11A1 reaction. Electron microscopy of STAR KO cells revealed that the number and size of lipid droplets were similar to those in wild-type (WT) MA-10 cells. However, the density of lipid droplets in STAR KO cells was drastically different than that seen in WT cells. We isolated the lipid droplets and analyzed their content by liquid chromatography-mass spectrometry. There was a significant increase in cholesteryl ester and phosphatidylcholine content in STAR KO cell lipid droplets, but the most abundant increase was in the amount of diacylglycerol (DAG); DAG 38:1 was the predominantly affected species. Lastly, we identified genes involved in DAG signaling and lipid metabolism which were differentially expressed between WT MA-10 and STAR KO cells. These results suggest that constitutive STAR in Leydig cells is involved in DAG accumulation in lipid droplets, in addition to cholesterol transport. The former event may affect cell functions mediated by DAG signaling.
Collapse
Affiliation(s)
| | | | | | | | - Vassilios Papadopoulos
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, CA 90089, USA; (M.G.); (Y.L.); (L.L.); (C.S.)
| |
Collapse
|
4
|
Parivesh A, Barseghyan H, Délot E, Vilain E. Translating genomics to the clinical diagnosis of disorders/differences of sex development. Curr Top Dev Biol 2019; 134:317-375. [PMID: 30999980 PMCID: PMC7382024 DOI: 10.1016/bs.ctdb.2019.01.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The medical and psychosocial challenges faced by patients living with Disorders/Differences of Sex Development (DSD) and their families can be alleviated by a rapid and accurate diagnostic process. Clinical diagnosis of DSD is limited by a lack of standardization of anatomical and endocrine phenotyping and genetic testing, as well as poor genotype/phenotype correlation. Historically, DSD genes have been identified through positional cloning of disease-associated variants segregating in families and validation of candidates in animal and in vitro modeling of variant pathogenicity. Owing to the complexity of conditions grouped under DSD, genome-wide scanning methods are better suited for identifying disease causing gene variant(s) and providing a clinical diagnosis. Here, we review a number of established genomic tools (karyotyping, chromosomal microarrays and exome sequencing) used in clinic for DSD diagnosis, as well as emerging genomic technologies such as whole-genome (short-read) sequencing, long-read sequencing, and optical mapping used for novel DSD gene discovery. These, together with gene expression and epigenetic studies can potentiate the clinical diagnosis of DSD diagnostic rates and enhance the outcomes for patients and families.
Collapse
Affiliation(s)
- Abhinav Parivesh
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC, United States
| | - Hayk Barseghyan
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC, United States; Department of Genomics and Precision Medicine, The George Washington University, Washington, DC, United States
| | - Emmanuèle Délot
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC, United States; Department of Genomics and Precision Medicine, The George Washington University, Washington, DC, United States.
| | - Eric Vilain
- Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC, United States; Department of Genomics and Precision Medicine, The George Washington University, Washington, DC, United States.
| |
Collapse
|
5
|
Chang JW, Yeh HS, Yong J. Alternative Polyadenylation in Human Diseases. Endocrinol Metab (Seoul) 2017; 32:413-421. [PMID: 29271615 PMCID: PMC5744726 DOI: 10.3803/enm.2017.32.4.413] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 11/23/2017] [Accepted: 11/27/2017] [Indexed: 12/02/2022] Open
Abstract
Varying length of messenger RNA (mRNA) 3'-untranslated region is generated by alternating the usage of polyadenylation sites during pre-mRNA processing. It is prevalent through all eukaryotes and has emerged as a key mechanism for controlling gene expression. Alternative polyadenylation (APA) plays an important role for cell growth, proliferation, and differentiation. In this review, we discuss the functions of APA related with various physiological conditions including cellular metabolism, mRNA processing, and protein diversity in a variety of disease models. We also discuss the molecular mechanisms underlying APA regulation, such as variations in the concentration of mRNA processing factors and RNA-binding proteins, as well as global transcriptome changes under cellular signaling pathway.
Collapse
Affiliation(s)
- Jae Woong Chang
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Twin Cities College of Biological Sciences, Minneapolis, MN, USA
| | - Hsin Sung Yeh
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Twin Cities College of Biological Sciences, Minneapolis, MN, USA
| | - Jeongsik Yong
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota Twin Cities College of Biological Sciences, Minneapolis, MN, USA.
| |
Collapse
|
6
|
Tsai YY, Rainey WE, Bollag WB. Very low-density lipoprotein (VLDL)-induced signals mediating aldosterone production. J Endocrinol 2017; 232:R115-R129. [PMID: 27913572 PMCID: PMC8310676 DOI: 10.1530/joe-16-0237] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 12/02/2016] [Indexed: 01/14/2023]
Abstract
Aldosterone, secreted by the adrenal zona glomerulosa, enhances sodium retention, thus increasing blood volume and pressure. Excessive production of aldosterone results in high blood pressure and contributes to cardiovascular and renal disease, stroke and visual loss. Hypertension is also associated with obesity, which is correlated with other serious health risks as well. Although weight gain is associated with increased blood pressure, the mechanism by which excess fat deposits increase blood pressure remains unclear. Several studies have suggested that aldosterone levels are elevated with obesity and may represent a link between obesity and hypertension. In addition to hypertension, obese patients typically have dyslipidemia, including elevated serum levels of very low-density lipoprotein (VLDL). VLDL, which functions to transport triglycerides from the liver to peripheral tissues, has been demonstrated to stimulate aldosterone production. Recent studies suggest that the signaling pathways activated by VLDL are similar to those utilized by AngII. Thus, VLDL increases cytosolic calcium levels and stimulates phospholipase D (PLD) activity to result in the induction of steroidogenic acute regulatory (StAR) protein and aldosterone synthase (CYP11B2) expression. These effects seem to be mediated by the ability of VLDL to increase the phosphorylation (activation) of their regulatory transcription factors, such as the cAMP response element-binding (CREB) protein family of transcription factors. Thus, research into the pathways by which VLDL stimulates aldosterone production may identify novel targets for the development of therapies for the treatment of hypertension, particularly those associated with obesity, and other aldosterone-modulated pathologies.
Collapse
Affiliation(s)
- Ying-Ying Tsai
- Department of PhysiologyMedical College of Georgia at Augusta University (formerly Georgia Regents University), Augusta, Georgia, USA
| | - William E Rainey
- Departments of Molecular & Integrative Physiology and Internal MedicineUniversity of Michigan, Ann Arbor, Michigan, USA
| | - Wendy B Bollag
- Department of PhysiologyMedical College of Georgia at Augusta University (formerly Georgia Regents University), Augusta, Georgia, USA
- Charlie Norwood VA Medical CenterOne Freedom Way, Augusta, Georgia, USA
| |
Collapse
|
7
|
Miller WL. Disorders in the initial steps of steroid hormone synthesis. J Steroid Biochem Mol Biol 2017; 165:18-37. [PMID: 26960203 DOI: 10.1016/j.jsbmb.2016.03.009] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 03/01/2016] [Accepted: 03/03/2016] [Indexed: 12/29/2022]
Abstract
Steroidogenesis begins with cellular internalization of low-density lipoprotein particles and subsequent intracellular processing of cholesterol. Disorders in these steps include Adrenoleukodystrophy, Wolman Disease and its milder variant Cholesterol Ester Storage Disease, and Niemann-Pick Type C Disease, all of which may present with adrenal insufficiency. The means by which cholesterol is directed to steroidogenic mitochondria remains incompletely understood. Once cholesterol reaches the outer mitochondrial membrane, its delivery to the inner mitochondrial membrane is regulated by the steroidogenic acute regulatory protein (StAR). Severe StAR mutations cause classic congenital lipoid adrenal hyperplasia, characterized by lipid accumulation in the adrenal, adrenal insufficiency, and disordered sexual development in 46,XY individuals. The lipoid CAH phenotype, including spontaneous puberty in 46,XX females, is explained by a two-hit model. StAR mutations that retain partial function cause a milder, non-classic disease characterized by glucocorticoid deficiency, with lesser disorders of mineralocorticoid and sex steroid synthesis. Once inside the mitochondria, cholesterol is converted to pregnenolone by the cholesterol side-chain cleavage enzyme, P450scc, encoded by the CYP11A1 gene. Rare patients with mutations of P450scc are clinically and hormonally indistinguishable from those with lipoid CAH, and may also present as milder non-classic disease. Patients with P450scc defects do not have the massive adrenal hyperplasia that characterizes lipoid CAH, but adrenal imaging may occasionally fail to distinguish these, necessitating DNA sequencing.
Collapse
Affiliation(s)
- Walter L Miller
- Center for Reproductive Sciences, University of California, San Francisco, CA 94143-0556, United States.
| |
Collapse
|
8
|
Khoury K, Barbar E, Ainmelk Y, Ouellet A, Lavigne P, LeHoux JG. Thirty-Eight-Year Follow-Up of Two Sibling Lipoid Congenital Adrenal Hyperplasia Patients Due to Homozygous Steroidogenic Acute Regulatory (STARD1) Protein Mutation. Molecular Structure and Modeling of the STARD1 L275P Mutation. Front Neurosci 2016; 10:527. [PMID: 27917104 PMCID: PMC5116571 DOI: 10.3389/fnins.2016.00527] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 10/31/2016] [Indexed: 11/13/2022] Open
Abstract
Objective: Review the impact of StAR (STARD1) mutations on steroidogenesis and fertility in LCAH patients. Examine the endocrine mechanisms underlying the pathology of the disorder and the appropriate therapy for promoting fertility and pregnancies. Design: Published data in the literature and a detailed 38-year follow-up of two sibling LCAH patients. Molecular structure and modeling of the STARD1 L275P mutation. Setting: University hospital. Patients: Patient A (46,XY female phenotype) and patient B (46,XX female) with LCAH bearing the L275P mutation in STARD1. Interventions: Since early-age diagnosis, both patients underwent corticoid replacement therapy. Patient A received estrogen therapy at pubertal age. Clomiphene therapy was given to Patient B to induce ovulation. Pregnancies were protected with progesterone administration. Main Outcome Measures: Clinical and molecular assessment of adrenal and gonadal functions. Results: Both patients have classic manifestations of corticosteroid deficiency observed in LCAH. Time of onset and severity were different. Patient A developed into a female phenotype due to early and severe damage of Leydig cells. Patient B started a progressive pubertal development, menarche and regular non-ovulatory cycle. She was able to have successful pregnancies. Conclusions: Understanding the molecular structure and function of STARD1 in all steroidogenic tissues is the key for comprehending the heterogeneous clinical manifestations of LCAH, and the development of an appropriate strategy for the induction of ovulation and protecting pregnancies in this disease.
Collapse
Affiliation(s)
- Khalil Khoury
- Department of Pediatrics, Faculty of Medicine, University of Sherbrooke Sherbrooke, QC, Canada
| | - Elie Barbar
- Department of Biochemistry, Faculty of Medicine, University of Sherbrooke Sherbrooke, QC, Canada
| | - Youssef Ainmelk
- Department of Obstetrics and Gynecology, Faculty of Medicine, University of Sherbrooke Sherbrooke, QC, Canada
| | - Annie Ouellet
- Department of Obstetrics and Gynecology, Faculty of Medicine, University of Sherbrooke Sherbrooke, QC, Canada
| | - Pierre Lavigne
- Department of Biochemistry, Faculty of Medicine, University of Sherbrooke Sherbrooke, QC, Canada
| | - Jean-Guy LeHoux
- Department of Biochemistry, Faculty of Medicine, University of Sherbrooke Sherbrooke, QC, Canada
| |
Collapse
|
9
|
Manna PR, Stetson CL, Slominski AT, Pruitt K. Role of the steroidogenic acute regulatory protein in health and disease. Endocrine 2016; 51:7-21. [PMID: 26271515 PMCID: PMC4707056 DOI: 10.1007/s12020-015-0715-6] [Citation(s) in RCA: 119] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 08/03/2015] [Indexed: 01/10/2023]
Abstract
Steroid hormones are an important class of regulatory molecules that are synthesized in steroidogenic cells of the adrenal, ovary, testis, placenta, brain, and skin, and influence a spectrum of developmental and physiological processes. The steroidogenic acute regulatory protein (STAR) predominantly mediates the rate-limiting step in steroid biosynthesis, i.e., the transport of the substrate of all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane. At the inner membrane, cytochrome P450 cholesterol side chain cleavage enzyme cleaves the cholesterol side chain to form the first steroid, pregnenolone, which is converted by a series of enzymes to various steroid hormones in specific tissues. Both basic and clinical evidence have demonstrated the crucial involvement of the STAR protein in the regulation of steroid biosynthesis. Multiple levels of regulation impinge on STAR action. Recent findings demonstrate that hormone-sensitive lipase, through its action on the hydrolysis of cholesteryl esters, plays an important role in regulating STAR expression and steroidogenesis which involve the liver X receptor pathway. Activation of the latter influences macrophage cholesterol efflux that is a key process in the prevention of atherosclerotic cardiovascular disease. Appropriate regulation of steroid hormones is vital for proper functioning of many important biological activities, which are also paramount for geriatric populations to live longer and healthier. This review summarizes the current level of understanding on tissue-specific and hormone-induced regulation of STAR expression and steroidogenesis, and provides insights into a number of cholesterol and/or steroid coupled physiological and pathophysiological consequences.
Collapse
Affiliation(s)
- Pulak R Manna
- Department of Immunology and Molecular Microbiology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, 79430, USA.
| | - Cloyce L Stetson
- Department of Dermatology, Texas Tech University Health Sciences Center, Lubbock, TX, 79430, USA
| | - Andrzej T Slominski
- Department of Dermatology, VA Medical Center, University of Alabama Birmingham, Birmingham, AL, 35294, USA
| | - Kevin Pruitt
- Department of Immunology and Molecular Microbiology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, 79430, USA
| |
Collapse
|
10
|
Chiapparino A, Maeda K, Turei D, Saez-Rodriguez J, Gavin AC. The orchestra of lipid-transfer proteins at the crossroads between metabolism and signaling. Prog Lipid Res 2015; 61:30-9. [PMID: 26658141 DOI: 10.1016/j.plipres.2015.10.004] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 10/15/2015] [Indexed: 01/12/2023]
Abstract
Within the eukaryotic cell, more than 1000 species of lipids define a series of membranes essential for cell function. Tightly controlled systems of lipid transport underlie the proper spatiotemporal distribution of membrane lipids, the coordination of spatially separated lipid metabolic pathways, and lipid signaling mediated by soluble proteins that may be localized some distance away from membranes. Alongside the well-established vesicular transport of lipids, non-vesicular transport mediated by a group of proteins referred to as lipid-transfer proteins (LTPs) is emerging as a key mechanism of lipid transport in a broad range of biological processes. More than a hundred LTPs exist in humans and these can be divided into at least ten protein families. LTPs are widely distributed in tissues, organelles and membrane contact sites (MCSs), as well as in the extracellular space. They all possess a soluble and globular domain that encapsulates a lipid monomer and they specifically bind and transport a wide range of lipids. Here, we present the most recent discoveries in the functions and physiological roles of LTPs, which have expanded the playground of lipids into the aqueous spaces of cells.
Collapse
Affiliation(s)
- Antonella Chiapparino
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
| | - Kenji Maeda
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
| | - Denes Turei
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany; European Molecular Biology Laboratory (EMBL), European Bioinformatics Institute (EBI), Cambridge CB10 1SD, UK
| | - Julio Saez-Rodriguez
- European Molecular Biology Laboratory (EMBL), European Bioinformatics Institute (EBI), Cambridge CB10 1SD, UK
| | - Anne-Claude Gavin
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Meyerhofstrasse 1, D-69117 Heidelberg, Germany; European Molecular Biology Laboratory (EMBL), Molecular Medicine Partnership Unit (MMPU), Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
| |
Collapse
|
11
|
Mayr JA. Lipid metabolism in mitochondrial membranes. J Inherit Metab Dis 2015; 38:137-44. [PMID: 25082432 DOI: 10.1007/s10545-014-9748-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 07/10/2014] [Accepted: 07/15/2014] [Indexed: 12/26/2022]
Abstract
Mitochondrial membranes have a unique lipid composition necessary for proper shape and function of the organelle. Mitochondrial lipid metabolism involves biosynthesis of the phospholipids phosphatidylethanolamine, cardiolipin and phosphatidylglycerol, the latter is a precursor of the late endosomal lipid bis(monoacylglycero)phosphate. It also includes mitochondrial fatty acid synthesis necessary for the formation of the lipid cofactor lipoic acid. Furthermore the synthesis of coenzyme Q takes place in mitochondria as well as essential parts of the steroid and vitamin D metabolism. Lipid transport and remodelling, which are necessary for tailoring and maintaining specific membrane properties, are just partially unravelled. Mitochondrial lipids are involved in organelle maintenance, fission and fusion, mitophagy and cytochrome c-mediated apoptosis. Mutations in TAZ, SERAC1 and AGK affect mitochondrial phospholipid metabolism and cause Barth syndrome, MEGDEL and Sengers syndrome, respectively. In these disorders an abnormal mitochondrial energy metabolism was found, which seems to be due to disturbed protein-lipid interactions, affecting especially enzymes of the oxidative phosphorylation. Since a growing number of enzymes and transport processes are recognised as parts of the mitochondrial lipid metabolism, a further increase of lipid-related disorders can be expected.
Collapse
Affiliation(s)
- Johannes A Mayr
- Department of Paediatrics, Paracelsus Medical University Salzburg, Salzburg, 5020, Austria,
| |
Collapse
|
12
|
Abstract
Congenital lipoid adrenal hyperplasia (lipoid CAH) is the most fatal form of CAH, as it disrupts adrenal and gonadal steroidogenesis. Most cases of lipoid CAH are caused by recessive mutations in the gene encoding steroidogenic acute regulatory protein (StAR). Affected patients typically present with signs of severe adrenal failure in early infancy and 46,XY genetic males are phenotypic females due to disrupted testicular androgen secretion. The StAR p.Q258X mutation accounts for about 70% of affected alleles in most patients of Japanese and Korean ancestry. However, it is more prevalent (92.3%) in the Korean population. Recently, some patients have been showed that they had late and mild clinical findings. These cases and studies constitute a new entity of 'nonclassic lipoid CAH'. The cholesterol side-chain cleavage enzyme, P450scc (CYP11A1), plays an essential role converting cholesterol to pregnenolone. Although progesterone production from the fetally derived placenta is necessary to maintain a pregnancy to term, some patients with P450scc mutations have recently been reported. P450scc mutations can also cause lipoid CAH and establish a recently recognized human endocrine disorder.
Collapse
Affiliation(s)
- Chan Jong Kim
- Department of Pediatrics, Chonnam National University Hospital, Chonnam National University Medical School, Gwangju, Korea
| |
Collapse
|
13
|
Curinha A, Oliveira Braz S, Pereira-Castro I, Cruz A, Moreira A. Implications of polyadenylation in health and disease. Nucleus 2014; 5:508-19. [PMID: 25484187 DOI: 10.4161/nucl.36360] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Polyadenylation is the RNA processing step that completes the maturation of nearly all eukaryotic mRNAs. It is a two-step nuclear process that involves an endonucleolytic cleavage of the pre-mRNA at the 3'-end and the polymerization of a polyadenosine (polyA) tail, which is fundamental for mRNA stability, nuclear export and efficient translation during development. The core molecular machinery responsible for the definition of a polyA site includes several recognition, cleavage and polyadenylation factors that identify and act on a given polyA signal present in a pre-mRNA, usually an AAUAAA hexamer or similar sequence. This mechanism is tightly regulated by other cis-acting elements and trans-acting factors, and its misregulation can cause inefficient gene expression and may ultimately lead to disease. The majority of genes generate multiple mRNAs as a result of alternative polyadenylation in the 3'-untranslated region. The variable lengths of the 3' untranslated regions created by alternative polyadenylation are a recognizable target for differential regulation and clearly affect the fate of the transcript, ultimately modulating the expression of the gene. Over the past few years, several studies have highlighted the importance of polyadenylation and alternative polyadenylation in gene expression and their impact in a variety of physiological conditions, as well as in several illnesses. Abnormalities in the 3'-end processing mechanisms thus represent a common feature among many oncological, immunological, neurological and hematological disorders, but slight imbalances can lead to the natural establishment of a specific cellular state. This review addresses the key steps of polyadenylation and alternative polyadenylation in different cellular conditions and diseases focusing on the molecular effectors that ensure a faultless pre-mRNA 3' end formation.
Collapse
Key Words
- 3′ untranslated region
- 3′READS, 3′ Region Extraction and Deep Sequencing
- AD, Alzheimer disease
- APA, Alternative polyadenylation
- AREs, Au-rich elements
- BPV, bovine papilloma virus
- CAH, congenital adrenal hyperplasia
- CFIm25, Cleavage Factor Im 25 kDa
- COX-2, cyclooxygenase 2
- CPSF, Cleavage and Polyadenylation Specificity Factor
- CSTF2, cleavage stimulatory factor-64kDa
- DMKN, dermokine
- DSE, downstream sequence element
- ESC, embryonic stem cells
- FMR1, Fragil X mental retardation 1
- FOXP3, forkhead box P3
- FXPOI, fragile X-associated immature ovarian insufficiency
- FXS, Fragile X syndrome
- FXTAS, fragile X-associated tremor/ataxia syndrome
- HGRG-14, high-glucose-regulated gene
- IMP-1, Insulin-like growth factor 2 mRNA binding protein 1
- IPEX, immune dysfunction, polyendocrinopathy, enteropathy, X-linked
- LPS, lipopolysaccharide
- OPMD, oculopharyngeal muscular dystrophy
- PABPN1, poly(A) binding protein
- PAP, polyA polymerase
- PAS, polyA site
- PD, Parkinson disease
- PDXK, pyridoxal kinase
- PPIE, peptidylpropylisomerase E
- RBP, RNA-binding protein
- RNA Pol II, RNA polymerase II
- SLE, systemic lupus erythematosus
- SMA, Spinal Muscular Atrophy
- SMN, Survival Motor Neuron
- SNP, single nucleotide polymorphism
- StAR, steroigogenic acute regulatory
- TCF/LEF, T cell factor/lymphoid enhancer factor.
- TCF7L2, transcription factor 7-like 2
- TCR, T cell receptor
- TLI, tandem UTR length index
- TNF-α, tumor necrosis factor-α
- USE, upstream sequence element
- UTR, untranslated region
- WAS, Wiskott-Aldrich syndrome
- WASP, Wiskott-Aldrich syndrome protein
- aSyn, α-Synuclein
- aSynL, longest aSyn isoform
- alternative polyadenylation
- cell state
- disease
- gene expression
- miRNA, microRNA
- nuclear 1
- pA signal, polyA signal
- pA tail, polyA tail
- polyadenylation
- siRNAs, small interfering RNAs
- snRNPs, spliceosomal small nuclear ribonucleoproteins
- α-GalA, α-galactosidase A
- μ, IgM heavy-chain mRNA
Collapse
Affiliation(s)
- Ana Curinha
- a Gene Regulation Group; IBMC-Instituto de Biologia Molecular e Celular ; Universidade do Porto ; Porto , Portugal
| | | | | | | | | |
Collapse
|
14
|
Yüksel B, Kulle AE, Gürbüz F, Welzel M, Kotan D, Mengen E, Holterhus PM, Topaloğlu AK, Grötzinger J, Riepe FG. The novel mutation p.Trp147Arg of the steroidogenic acute regulatory protein causes classic lipoid congenital adrenal hyperplasia with adrenal insufficiency and 46,XY disorder of sex development. Horm Res Paediatr 2014; 80:163-9. [PMID: 23920000 DOI: 10.1159/000354086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 06/25/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The steroidogenic acute regulatory protein (StAR) is essential for steroidogenesis by mediating cholesterol transfer into mitochondria. Inactivating StAR mutations cause lipoid congenital adrenal hyperplasia. OBJECTIVE AND METHODS To identify causative mutations in a patient presenting with adrenal failure during early infancy. The objective was to study the functional and structural consequences of the novel StAR mutation p.Trp147Arg in a Turkish patient detected in compound heterozygosity with the p.Glu169Lys mutation. RESULTS Transient in vitro expression of the mutant proteins together with P450 side-chain cleavage enzyme, adrenodoxin, and adrenodoxin reductase yielded severely diminished cholesterol conversion of the p.Trp147Arg mutant. The previously described p.Glu169Lys mutant led to significantly lower cholesterol conversion than wild-type StAR protein. As derived from three-dimensional protein modeling, the residue W147 is stabilizing the C-terminal helix in a closed conformation hereby acting as gatekeeper of the ligand cavity of StAR. CONCLUSIONS The novel mutation p.Trp147Arg causes primary adrenal insufficiency and complete sex reversal in the 46,XY patient. Clinical disease, in vitro studies and three-dimensional protein modeling of the mutation p.Trp147Arg underscore the relevance of this highly conserved residue for StAR protein function.
Collapse
Affiliation(s)
- Bilgin Yüksel
- Division of Pediatric Endocrinology and Metabolism, Department of Pediatrics, Cukurova University, Balcali/Adana, Turkey
| | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Camats N, Pandey AV, Fernández-Cancio M, Fernández JM, Ortega AM, Udhane S, Andaluz P, Audí L, Flück CE. STAR splicing mutations cause the severe phenotype of lipoid congenital adrenal hyperplasia: insights from a novel splice mutation and review of reported cases. Clin Endocrinol (Oxf) 2014; 80:191-9. [PMID: 23859637 DOI: 10.1111/cen.12293] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 05/29/2013] [Accepted: 07/11/2013] [Indexed: 11/27/2022]
Abstract
OBJECTIVE The steroidogenic acute regulatory protein (StAR) transports cholesterol to the mitochondria for steroidogenesis. Loss of StAR function causes lipoid congenital adrenal hyperplasia (LCAH) which is characterized by impaired synthesis of adrenal and gonadal steroids causing adrenal insufficiency, 46,XY disorder of sex development (DSD) and failure of pubertal development. Partial loss of StAR activity may cause adrenal insufficiency only. PATIENT A newborn girl was admitted for mild dehydration, hyponatremia, hyperkalemia and hypoglycaemia and had normal external female genitalia without hyperpigmentation. Plasma cortisol, 17OH-progesterone, DHEA-S, androstendione and aldosterone were low, while ACTH and plasma renin activity were elevated, consistent with the diagnosis of primary adrenal insufficiency. Imaging showed normal adrenals, and cytogenetics revealed a 46,XX karyotype. She was treated with fluids, hydrocortisone and fludrocortisone. DESIGN, METHODS AND RESULTS Genetic studies revealed a novel homozygous STAR mutation in the 3' acceptor splice site of intron 4, c.466-1G>A (IVS4-1G>A). To test whether this mutation would affect splicing, we performed a minigene experiment with a plasmid construct containing wild-type or mutant StAR gDNA of exons-introns 4-6 in COS-1 cells. The splicing was assessed on total RNA using RT-PCR for STAR cDNAs. The mutant STAR minigene skipped exon 5 completely and changed the reading frame. Thus, it is predicted to produce an aberrant and shorter protein (p.V156GfsX19). Computational analysis revealed that this mutant protein lacks wild-type exons 5-7 which are essential for StAR-cholesterol interaction. CONCLUSIONS STAR c.466-1A skips exon 5 and causes a dramatic change in the C-terminal sequence of the protein, which is essential for StAR-cholesterol interaction. This splicing mutation is a loss-of-function mutation explaining the severe phenotype of our patient. Thus far, all reported splicing mutations of STAR cause a severe impairment of protein function and phenotype.
Collapse
Affiliation(s)
- Núria Camats
- Pediatric Endocrinology, Department of Pediatrics and Department of Clinical Research, University Children's Hospital Bern, Bern, Switzerland
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
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.
Collapse
Affiliation(s)
- Maheshinie Rajapaksha
- Department of Biochemistry, Division of Biomedical Sciences, Mercer University School of Medicine , Savannah, Georgia 31404, United States
| | | | | | | | | |
Collapse
|
17
|
Morohashi K, Baba T, Tanaka M. Steroid Hormones and the Development of Reproductive Organs. Sex Dev 2013; 7:61-79. [DOI: 10.1159/000342272] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
|
18
|
Congenital lipoid adrenal hyperplasia (a rare form of adrenal insufficiency and ambiguous genitalia) caused by a novel mutation of the steroidogenic acute regulatory protein gene. Eur J Pediatr 2012; 171:787-93. [PMID: 22083155 DOI: 10.1007/s00431-011-1620-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 10/26/2011] [Indexed: 10/15/2022]
Abstract
UNLABELLED Congenital lipoid adrenal hyperplasia (lipoid CAH) is a rare autosomal recessive disorder of adrenal and gonadal steroidogenesis. It is most frequently caused by mutations in the steroidogenic acute regulatory protein (StAR) gene. Patients with lipoid CAH typically present with adrenal crisis in early infancy, and those with a 46,XY karyotype have female genitalia. However, it has been recently recognized that the phenotype can be quite variable, in that adrenal insufficiency is detected later in life and patients may have partially masculinized or even normal male genitalia. We report a patient assigned and reared as a female with a 46,XY karyotype and with a homozygous intron 2 (c.178+1G>C) splice site mutation of the StAR gene, which is a novel mutation that causes lipoid CAH. Her clinical presentation was somewhat atypical for a patient with classic lipoid CAH, marked by mild masculinization of the genitalia, detectable adrenal steroids at baseline, and ability to tolerate the stress of a surgical procedure with anesthesia without receiving glucocorticoid treatment. CONCLUSION There is significant phenotypic variability among patients with lipoid CAH. While splice site mutations in the StAR gene lead to premature translational termination, resulting in truncated and non-functional proteins, there is phenotypic variability among patients with such mutations. Our patient appears to have the more atypical phenotype compared to reported patients with similar mutations. The molecular mechanism underlying this heterogeneity remains unclear.
Collapse
|
19
|
Estimation of carrier frequencies of six autosomal-recessive Mendelian disorders in the Korean population. J Hum Genet 2011; 57:139-44. [PMID: 22170460 DOI: 10.1038/jhg.2011.144] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although many studies have been performed to identify mutations in Korean patients with various autosomal-recessive Mendelian disorders (AR-MDs), little is known about the carrier frequencies of AR-MDs in the Korean population. Twenty common mutations from six AR-MDs, including Wilson disease (WD), non-syndromic hearing loss (NSHL), glycogen storage disease type Ia (GSD Ia), phenylketonuria (PKU), congenital hypothyroidism (CH), and congenital lipoid adrenal hyperplasia (CLAH) were selected to screen for based on previous studies. A total of 3057 Koreans were genotyped by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry followed by confirmation using the Sanger sequencing. We found 201 and 8 carriers with either one or two mutations in different genes, respectively, yielding a total carrier frequency of 1 in 15 (6.7%). Of the six AR-MDs, NSHL has the highest carrier frequency followed by WD, CH, CLAH, GSD Ia, and PKU. As carrier screening tests are becoming prevalent and the number of mutations known and tested is rising, a priori data on the carrier frequencies in different ethnic groups is mandatory to plan a population screening program and to estimate its efficiency. In light of this, the present results can be used as a basis to establish a screening policy for common AR-MRs in the Korean population.
Collapse
|
20
|
Jadhav U, Harris RM, Jameson JL. Hypogonadotropic hypogonadism in subjects with DAX1 mutations. Mol Cell Endocrinol 2011; 346:65-73. [PMID: 21672607 PMCID: PMC3185185 DOI: 10.1016/j.mce.2011.04.017] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 04/07/2011] [Indexed: 11/17/2022]
Abstract
DAX1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1; also known as NROB1, nuclear receptor subfamily 0, group B, member 1) encodes a nuclear receptor that is expressed in embryonic stem (ES) cells, steroidogenic tissues (gonads, adrenals), the ventromedial hypothalamus (VMH), and pituitary gonadotropes. Humans with DAX1 mutations develop an X-linked syndrome referred to as adrenal hypoplasia congenita (AHC). These boys typically present in infancy with adrenal failure but later fail to undergo puberty because of hypogonadotropic hypogonadism (HHG). The adrenal failure reflects a developmental abnormality in the transition of the fetal to adult zone, resulting in glucocorticoid and mineralocorticoid deficiency. The etiology of HHG involves a combined and variable deficiency of hypothalamic GnRH secretion and/or pituitary responsiveness to GnRH resulting in low LH, FSH and testosterone. Treatment with exogenous gonadotropins generally does not induce spermatogenesis. Animal models indicate that DAX1 also plays a critical role in testis development and function. As a nuclear receptor, DAX1 has been shown to function as a transcriptional repressor, particularly of pathways regulated by other nuclear receptors, such as steroidogenic factor 1 (SF1). In addition to reproductive tissues, DAX1 is also expressed at high levels in ES cells and plays a role in the maintenance of pluripotentiality. Here we review the clinical manifestations associated with DAX1 mutations as well as the evolving information about its function based on animal models and in vitro studies.
Collapse
Affiliation(s)
| | | | - J. Larry Jameson
- Corresponding author: J. Larry Jameson, MD, PhD, Vice-President for Medical Affairs and Lewis Landsberg Dean, Northwestern University Feinberg School of Medicine, Arthur J. Rubloff Building, 420 East Superior St., 12th floor, Chicago, IL 60611, , Ph: 312-503-0340; Fax: 312-503-7757
| |
Collapse
|
21
|
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: 361] [Impact Index Per Article: 27.8] [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.
Collapse
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
| |
Collapse
|
22
|
Miller WL, Auchus RJ. The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders. Endocr Rev 2011; 32:81-151. [PMID: 21051590 PMCID: PMC3365799 DOI: 10.1210/er.2010-0013] [Citation(s) in RCA: 1432] [Impact Index Per Article: 110.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/20/2010] [Indexed: 02/08/2023]
Abstract
Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.
Collapse
Affiliation(s)
- Walter L Miller
- Distinguished Professor of Pediatrics, University of California San Francisco, San Francisco, California 94143-0978, USA.
| | | |
Collapse
|
23
|
Sahakitrungruang T, Soccio RE, Lang-Muritano M, Walker JM, Achermann JC, Miller WL. Clinical, genetic, and functional characterization of four patients carrying partial loss-of-function mutations in the steroidogenic acute regulatory protein (StAR). J Clin Endocrinol Metab 2010; 95:3352-9. [PMID: 20444910 PMCID: PMC2928910 DOI: 10.1210/jc.2010-0437] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
CONTEXT Nonclassic congenital lipoid adrenal hyperplasia (lipoid CAH) is a recently recognized disorder caused by mutations in the steroidogenic acute regulatory protein (StAR) that retain partial function. Affected individuals can present with a phenotype of late onset adrenal insufficiency with only mild or minimally disordered sexual development. OBJECTIVES The aim was to delineate the clinical spectrum of StAR mutations and correlate phenotype with StAR activity. PATIENTS Four patients had nonclassic/atypical lipoid CAH. Adrenal insufficiency was manifested at birth in two patients and at 11 months and 4 yr in the other two. Three were 46,XY with underdeveloped genitalia. METHODS The StAR gene was sequenced, mutations were recreated in expression vectors, and StAR activity was measured as pregnenolone production in COS-1 cells cotransfected with the cholesterol side-chain cleavage system. StAR mutants were expressed as N-62 StAR in bacteria, and purified proteins were tested for activity with isolated steroidogenic mitochondria and for cholesterol-binding capacity. RESULTS DNA sequencing identified mutations on all alleles. Missense mutations were R188C, G221D, L260P, and F267S; we also tested R192C described by others. The respective activities of R188C, R192C, G221D, L260P, and F267S were 8.0, 39.4, 2.4, 3.1, and 6.1% of wild-type in transfected cells, and 12.8, 54.8, 6.3, 1.8, and 9.5% with isolated mitochondria. Cholesterol binding capacities of R188C, R192C, G221D, L260P, and F267S were 6.7, 55.3, 10.2, 4.6, and 20.9%. These data are correlated to the three-dimensional structure of StAR. CONCLUSIONS There is a broad clinical spectrum of StAR mutations; StAR activities in vitro correlate well with clinical phenotypes.
Collapse
Affiliation(s)
- Taninee Sahakitrungruang
- Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, 10330 Bangkok, Thailand. [corrected]
| | | | | | | | | | | |
Collapse
|
24
|
Cellular cholesterol delivery, intracellular processing and utilization for biosynthesis of steroid hormones. Nutr Metab (Lond) 2010; 7:47. [PMID: 20515451 PMCID: PMC2890697 DOI: 10.1186/1743-7075-7-47] [Citation(s) in RCA: 304] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 06/01/2010] [Indexed: 11/28/2022] Open
Abstract
Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function and various metabolic processes. They are synthesized from cholesterol mainly in the adrenal gland and gonads in response to tissue-specific tropic hormones. These steroidogenic tissues are unique in that they require cholesterol not only for membrane biogenesis, maintenance of membrane fluidity and cell signaling, but also as the starting material for the biosynthesis of steroid hormones. It is not surprising, then, that cells of steroidogenic tissues have evolved with multiple pathways to assure the constant supply of cholesterol needed to maintain optimum steroid synthesis. The cholesterol utilized for steroidogenesis is derived from a combination of sources: 1) de novo synthesis in the endoplasmic reticulum (ER); 2) the mobilization of cholesteryl esters (CEs) stored in lipid droplets through cholesteryl ester hydrolase; 3) plasma lipoprotein-derived CEs obtained by either LDL receptor-mediated endocytic and/or SR-BI-mediated selective uptake; and 4) in some cultured cell systems from plasma membrane-associated free cholesterol. Here, we focus on recent insights into the molecules and cellular processes that mediate the uptake of plasma lipoprotein-derived cholesterol, events connected with the intracellular cholesterol processing and the role of crucial proteins that mediate cholesterol transport to mitochondria for its utilization for steroid hormone production. In particular, we discuss the structure and function of SR-BI, the importance of the selective cholesterol transport pathway in providing cholesterol substrate for steroid biosynthesis and the role of two key proteins, StAR and PBR/TSO in facilitating cholesterol delivery to inner mitochondrial membrane sites, where P450scc (CYP11A) is localized and where the conversion of cholesterol to pregnenolone (the common steroid precursor) takes place.
Collapse
|
25
|
Cholesterol binding is a prerequisite for the activity of the steroidogenic acute regulatory protein (StAR). Biochem J 2008; 412:553-62. [PMID: 18341481 DOI: 10.1042/bj20071264] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Steroidogenesis depends on the delivery of cholesterol from the outer to the inner mitochondrial membrane by StAR (steroidogenic acute regulatory protein). However, the mechanism by which StAR binds to cholesterol and its importance in cholesterol transport are under debate. According to our proposed molecular model, StAR possesses a hydrophobic cavity, which can accommodate one cholesterol molecule. In the bound form, cholesterol interacts with hydrophobic side-chains located in the C-terminal alpha-helix 4, thereby favouring the folding of this helix. To verify this model experimentally, we have characterized the in vitro activity, overall structure, thermodynamic stability and cholesterol-binding affinity of StAR lacking the N-terminal 62 amino acid residues (termed N-62 StAR). This mature form is biologically active and has a well-defined tertiary structure. Addition of cholesterol to N-62 StAR led to an increase in the alpha-helical content and T degrees (melting temperature), indicating the formation of a stable complex. However, the mutation F267Q, which is located in the C-terminal helix interface lining the cholesterol-binding site, reduced the biological activity of StAR. Furthermore, the cholesterol-induced thermodynamic stability and the binding capacity of StAR were significantly diminished in the F267Q mutant. Titration of StAR with cholesterol yielded a 1:1 complex with an apparent K(D) of 3 x 10(-8). These results support our model and indicate that StAR can readily bind to cholesterol with an apparent affinity that commensurates with monomeric cholesterol solubility in water. The proper function of the C-terminal alpha-helix is essential for the binding process.
Collapse
|
26
|
Kim CJ, Lin L, Huang N, Quigley CA, AvRuskin TW, Achermann JC, Miller WL. Severe combined adrenal and gonadal deficiency caused by novel mutations in the cholesterol side chain cleavage enzyme, P450scc. J Clin Endocrinol Metab 2008; 93:696-702. [PMID: 18182448 PMCID: PMC2266942 DOI: 10.1210/jc.2007-2330] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
CONTEXT Mitochondrial cytochrome P450scc converts cholesterol to pregnenolone in all steroidogenic tissues. Although progesterone production from the fetally-derived placenta is necessary to maintain pregnancy to term, four patients with mutations in the gene encoding P450scc (CYP11A1), have been described, one in a 46,XX female and three in underandrogenized 46,XY individuals, all with primary adrenal failure. OBJECTIVE Our aim was to determine whether P450scc mutations might be found in other children and to explore genotype/phenotype correlations. METHODS AND PATIENTS We performed mutational analysis of CYP11A1 in individuals with 46,XY disorders of sex development and primary adrenal failure, followed by functional studies of P450scc activity and of P450scc RNA splicing. RESULTS Among nine 46,XY infants with adrenal failure and disordered sexual differentiation, two infants had compound heterozygous mutations in CYP11A1. One patient harbored the novel P450scc missense mutations L141W and V415E, which retained 38 and 0% activity, respectively. The other carried a CYP11A1 frameshift mutation c835delA (0% activity) and a splice site mutation [IVS3+(2-3)insT] that prevented correct splicing of P450scc mRNA. CONCLUSIONS P450scc deficiency is a recently recognized disorder that may be more frequent than originally thought. The phenotypic spectrum ranges from severe loss-of-function mutations associated with prematurity, complete underandrogenization, and severe, early-onset adrenal failure, to partial deficiencies found in children born at term with clitoromegaly and later-onset adrenal failure. In contradistinction to congenital lipoid adrenal hyperplasia caused by steroidogenic acute regulatory protein mutations, adrenal hyperplasia has not been reported in any of the six patients with P450scc deficiency.
Collapse
Affiliation(s)
- Chan Jong Kim
- Department of Pediatrics, University of California San Francisco, San Francisco, California 94143-0978, USA
| | | | | | | | | | | | | |
Collapse
|
27
|
Abstract
Stress-responsive adrenocortical function is the final physiological response to the cascade of events that occurs when the interaction between individuals and their environment takes place. Glucocorticoids are produced in response to perturbance of homeostasis and are necessary for the energy required to restore this homeostasis. Genetics contributes to the individual variation in basal and stimulated plasma glucocorticoid levels and also to adrenal gland mass that increases in response to prolonged adrenal stimulation. This review briefly describes regulation of the adrenocortical axis, summarizes the linkage studies carried out so far in humans and in model organisms, and discusses the potential candidate genes that might contribute to the variation. The significance of individual variations in the glucocorticoid stress-responsiveness, with particular attention to their potential role in the recent explosion of obesity and the prevalence of metabolic syndrome X, is commented upon.
Collapse
Affiliation(s)
- Eva E Redei
- Northwestern University Feinberg School of Medicine, The Asher Center, Department of Psychiatry and Behavioral Sciences, Chicago, IL, USA.
| |
Collapse
|
28
|
Miller WL. Steroidogenic acute regulatory protein (StAR), a novel mitochondrial cholesterol transporter. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:663-76. [PMID: 17433772 DOI: 10.1016/j.bbalip.2007.02.012] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 02/23/2007] [Accepted: 02/26/2007] [Indexed: 10/23/2022]
Abstract
Cholesterol is a vital component of cellular membranes, and is the substrate for biosynthesis of steroids, oxysterols and bile acids. The mechanisms directing the intracellular trafficking of this nearly insoluble molecule have received increased attention through the discovery of the steroidogenic acute regulatory protein (StAR) and similar proteins containing StAR-related lipid transfer (START) domains. StAR can transfer cholesterol between synthetic liposomes in vitro, an activity which appears to correspond to the trans-cytoplasmic transport of cholesterol to mitochondria. However, trans-cytoplasmic cholesterol transport in vivo appears to involve the recently-described protein StarD4, which is expressed in most cells. Steroidogenic cells must also move large amounts of cholesterol from the outer mitochondrial membrane to the first steroidogenic enzyme, which lies on the matrix side of the inner membrane; this action requires StAR. Congenital lipoid adrenal hyperplasia, a rare and severe disorder of human steroidogenesis, results from mutations in StAR, providing a StAR knockout of nature that has provided key insights into its activity. Cell biology experiments show that StAR moves large amounts of cholesterol from the outer to inner mitochondrial membrane, but acts exclusively on the outer membrane. Biophysical data show that only the carboxyl-terminal alpha-helix of StAR interacts with the outer membrane. Spectroscopic data and molecular dynamics simulations show that StAR's interactions with protonated phospholipid head groups on the outer mitochondrial membrane induce a conformational change (molten globule transition) needed for StAR's activity. StAR appears to act in concert with the peripheral benzodiazepine receptor, but the precise itinerary of a cholesterol molecule entering the mitochondrion remains unclear.
Collapse
Affiliation(s)
- Walter L Miller
- Department of Pediatrics, Box 0978, University of California, San Francisco, CA 94122-0978, USA.
| |
Collapse
|
29
|
Miller WL. StAR Search—What We Know about How the Steroidogenic Acute Regulatory Protein Mediates Mitochondrial Cholesterol Import. Mol Endocrinol 2007; 21:589-601. [PMID: 16973755 DOI: 10.1210/me.2006-0303] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cholesterol is the starting point for biosynthesis of steroids, oxysterols and bile acids, and is also an essential component of cellular membranes. The mechanisms directing the intracellular trafficking of this insoluble molecule have received attention through the discovery of the steroidogenic acute regulatory protein (StAR) and related proteins containing StAR-related lipid transfer domains. Much of our understanding of the physiology of StAR derives from studies of congenital lipoid adrenal hyperplasia, which is caused by StAR mutations. Multiple lines of evidence show that StAR moves cholesterol from the outer to inner mitochondrial membrane, but acts exclusively on the outer membrane. The precise mechanism by which StAR's action on the outer mitochondrial membrane stimulates the flow of cholesterol to the inner membrane remains unclear. When StAR interacts with protonated phospholipid head groups on the outer mitochondrial membrane, it undergoes a conformational change (molten globule transition) that opens and closes StAR's cholesterol-binding pocket; this conformational change is required for cholesterol binding, which is required for StAR activity. The action of StAR probably requires interaction with the peripheral benzodiazepine receptor.
Collapse
Affiliation(s)
- Walter L Miller
- Department of Pediatrics, Box 0978, University of California, San Francisco, San Francisco, California 94143-0978, USA.
| |
Collapse
|
30
|
Katsumata N, Horikawa R, Tanaka T. Replacement of alanine with asparagic acid at position 203 in human steroidogenic acute regulatory protein impairs the ability to enhance steroidogenesis in vitro. Endocr J 2006; 53:427-31. [PMID: 16723808 DOI: 10.1507/endocrj.k05-174] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Steroidogenic acute regulatory protein (StAR) is a 30-kDa phosphorylated protein that rapidly appears in mitochondria of steroidogenic cells following tropic stimulation, and is required in the acute regulation of steroidogenesis. It was reported that mutations in the STAR gene encoding StAR cause congenital lipoid adrenal hyperplasia (CLAH), an autosomal recessive disorder characterized by impaired synthesis of all adrenal and gonadal steroid hormones. We previously reported a D203A polymorphism in the STAR gene in Japanese patients with CLAH as well as in normal Japanese subjects. In the present study, we analyzed the ability of the A203 StAR and D203 StAR to stimulate steroidogenesis using the in vitro functional expression system. The A203 StAR caused a twelve-fold increase in pregnenolone secretion over COS-1 cells transfected with an NH2-cholesterol side-chain cleavage enzyme (P450scc)-adrenodoxin reductase-adrenodoxin-COOH fusion protein expressing plasmid (F2) and an empty vector, whereas the D203 StAR increased pregnenolone production no more than threefold. Western blot analysis detected mainly two species of StAR consisting of the 37-kDa precursor and the 30-kDa mature form. Together, these results indicate that the alanine at position 203 in human StAR is functionally important and that the D203 StAR is extremely unlikely to be a polymorphism.
Collapse
Affiliation(s)
- Noriyuki Katsumata
- Department of Endocrinology and Metabolism, National Research Institute for Child Health and Development, Tokyo, Japan
| | | | | |
Collapse
|
31
|
Epand RM. Cholesterol and the interaction of proteins with membrane domains. Prog Lipid Res 2006; 45:279-94. [PMID: 16574236 DOI: 10.1016/j.plipres.2006.02.001] [Citation(s) in RCA: 232] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 02/02/2006] [Accepted: 02/20/2006] [Indexed: 12/18/2022]
Abstract
Cholesterol is not uniformly distributed in biological membranes. One of the factors influencing the formation of cholesterol-rich domains in membranes is the unequal lateral distribution of proteins in membranes. Certain proteins are found in cholesterol-rich domains. In some of these cases, it is as a consequence of the proteins interacting directly with cholesterol. There are several structural features of a protein that result in the protein preferentially associating with cholesterol-rich domains. One of the best documented of these is certain types of lipidations. In addition, however, there are segments of a protein that can preferentially sequester cholesterol. We discuss two examples of these cholesterol-recognition elements: the cholesterol recognition/interaction amino acid consensus (CRAC) domain and the sterol-sensing domain (SSD). The requirements for a CRAC motif are quite flexible and predict that a large number of sequences could recognize cholesterol. There are, however, certain proteins that are known to interact with cholesterol-rich domains of cell membranes that have CRAC motifs, and synthetic peptides corresponding to these segments also promote the formation of cholesterol-rich domains. Modeling studies have provided a rationale for certain requirements of the CRAC motif. The SSD is a larger protein segment comprising five transmembrane domains. The amino acid sequence YIYF is found in several SSD and in certain other proteins for which there is evidence that they interact with cholesterol-rich domains. The CRAC sequences as well as YIYF are generally found adjacent to a transmembrane helical segment. These regions appear to have a strong influence of the localization of certain proteins into domains in biological membranes. In addition to the SSD, there is also a domain found in soluble proteins, the START domain, that binds lipids. Certain proteins with START domains specifically bind cholesterol and are believed to function in intracellular cholesterol transport. One of these proteins is StAR-D1, that also has a mitochondrial targeting sequence and plays an important role in delivering cholesterol to the mitochondria of steroidogenic cells.
Collapse
Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, Health Sciences Centre, McMaster University, 1200 Main Street, Hamilton, Ont., Canada L8N 3Z5.
| |
Collapse
|
32
|
Papadimitriou A, Fountzoula I, Nicolaidou P, Tzortzatou G. Ovarian insufficiency in congenital lipoid adrenal hyperplasia begins in infancy. J Pediatr Endocrinol Metab 2006; 19:271-4. [PMID: 16607929 DOI: 10.1515/jpem.2006.19.3.271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The aim of the present study was to investigate ovarian function in a 46,XX female patient with congenital lipoid adrenal hyperplasia (lipoid CAH) during infancy and childhood. We measured serum gonadotropin and estradiol levels regularly from 6 months to 10.9 years of age. Serum FSH levels were clearly elevated during the first 2 years of life; they decreased gradually until the age of 5 years and they then fell into the normal range for a prepubertal female. Serum LH levels were elevated until the age of 2 years and they then fell into the normal range. Serum estradiol levels were always in the normal prepubertal range. Pelvic ultrasonography performed at the age of 9 months and at 9.8 years of age showed normal uterine and ovarian morphology for a prepubertal female. In conclusion, our data suggest that ovarian insufficiency in lipoid CAH begins in infancy.
Collapse
|
33
|
Baker BY, Yaworsky DC, Miller WL. A pH-dependent Molten Globule Transition Is Required for Activity of the Steroidogenic Acute Regulatory Protein, StAR. J Biol Chem 2005; 280:41753-60. [PMID: 16234239 DOI: 10.1074/jbc.m510241200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The steroidogenic acute regulatory protein (StAR) simulates steroid biosynthesis by increasing the flow of cholesterol from the outer mitochondrial membrane (OMM) to the inner membrane. StAR acts exclusively on the OMM, and only StAR's carboxyl-terminal alpha-helix (C-helix) interacts with membranes. Biophysical studies have shown that StAR becomes a molten globule at acidic pH, but a physiologic role for this structural transition has been controversial. Molecular modeling shows that the C-helix, which forms the floor of the sterol-binding pocket, is stabilized by hydrogen bonding to adjacent loops. Molecular dynamics simulations show that protonation of the C-helix and adjacent loops facilitates opening and closing the sterol-binding pocket. Two disulfide mutants, S100C/S261C (SS) and D106C/A268C (DA), designed to limit the mobility of the C-helix but not disrupt overall conformation, were prepared in bacteria, and their correct folding and positioning of the disulfide bonds was confirmed. The SS mutant lost half, and the DA mutant lost all cholesterol binding capacity and steroidogenic activity with isolated mitochondria in vitro, but full binding and activity was restored to each mutant by disrupting the disulfide bonds with dithiothreitol. These data strongly support the model that StAR activity requires a pH-dependent molten globule transition on the OMM.
Collapse
Affiliation(s)
- Bo Y Baker
- Department of Pediatrics and Metabolic Research Unit, University of California, San Francisco, California 94143, USA
| | | | | |
Collapse
|
34
|
Clem BF, Clark BJ. Association of the mSin3A-histone deacetylase 1/2 corepressor complex with the mouse steroidogenic acute regulatory protein gene. Mol Endocrinol 2005; 20:100-13. [PMID: 16109738 DOI: 10.1210/me.2004-0495] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Several factors have been identified in the transcriptional repression of the steroidogenic acute regulatory protein (StAR) gene promoter; yet, no associating corepressor complexes have been characterized for the mouse promoter in MA-10 mouse Leydig tumor cells. We now report that Sp3, CAGA element binding proteins, and a corepressor complex consisting of mSin3A, histone deacetylase (HDAC)1, and HDAC2 associates with a transcriptional repressor region within the mouse StAR promoter. 5'-Promoter deletion analysis localized the negative regulatory region between -180 and -150 bp upstream of the transcription start site, and mutations in both the CAGA and Sp binding elements were required to relieve the repression of basal StAR promoter activity. Protein-DNA binding analysis revealed Sp3 and specific CAGA element-binding protein(s) associated with the repressor region. Coimmunoprecipitation analysis identified the presence of the mSin3A, HDAC1, and HDAC2 corepressor complex in MA-10 cells. Furthermore, chromatin immunoprecipitation assays revealed Sp3, mSin3A, and HDAC1/2 association with the proximal region of the StAR promoter in situ. In addition, HDAC inhibition resulted in a dose-dependent activation of a mouse StAR reporter construct, whereas mutations within the repressor region diminished this effect by 44%. In sum, these data support a novel regulatory mechanism for transcriptional repression of the mouse StAR promoter by DNA binding of Sp3 and CAGA element-binding proteins, and association of the Sin3 corepressor complex exhibiting HDAC activity.
Collapse
Affiliation(s)
- Brian F Clem
- Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, Kentucky 40292, USA
| | | |
Collapse
|
35
|
Hiort O, Holterhus PM, Werner R, Marschke C, Hoppe U, Partsch CJ, Riepe FG, Achermann JC, Struve D. Homozygous disruption of P450 side-chain cleavage (CYP11A1) is associated with prematurity, complete 46,XY sex reversal, and severe adrenal failure. J Clin Endocrinol Metab 2005; 90:538-41. [PMID: 15507506 DOI: 10.1210/jc.2004-1059] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Disruption of the P450 side-chain cleavage cytochrome (P450scc) enzyme due to deleterious mutations of the CYP11A1 gene is thought to be incompatible with fetal survival because of impaired progesterone production by the fetoplacental unit. We present a 46,XY patient with a homozygous disruption of CYP11A1. The child was born prematurely with complete sex reversal and severe adrenal insufficiency. Laboratory data showed diminished or absent steroidogenesis in all pathways. Molecular genetic analysis of the CYP11A1 gene revealed a homozygous single nucleotide deletion leading to a premature termination at codon position 288. This mutation will delete highly conserved regions of the P450scc enzyme and thus is predicted to lead to a nonfunctional protein. Both healthy parents were heterozygous for this mutation. Our report demonstrates that severe disruption of P450scc can be compatible with survival in rare instances. Furthermore, defects in this enzyme are inherited in an autosomal-recessive fashion, and heterozygote carriers can be healthy and fertile. The possibility of P450scc-independent pathways of steroid synthesis in addition to the current concept of luteoplacental shift of progesterone synthesis in humans has to be questioned.
Collapse
Affiliation(s)
- Olaf Hiort
- Department of Pediatrics, Division of Pediatric Endocrinology, University Hospital Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany.
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Miller WL. Disorders of androgen synthesis--from cholesterol to dehydroepiandrosterone. Med Princ Pract 2005; 14 Suppl 1:58-68. [PMID: 16103714 DOI: 10.1159/000086185] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2004] [Accepted: 08/14/2004] [Indexed: 01/29/2023] Open
Abstract
Androgens and estrogens are primarily made from dehydroepiandrosterone (DHEA), which is made from cholesterol via four steps. First, cholesterol enters the mitochondria with the assistance of the steroidogenic acute regulatory protein (StAR). Mutations in the StAR gene cause congenital lipoid adrenal hyperplasia (lipoid CAH), a potentially lethal disease in which virtually no steroids are made. Lipoid CAH is common among Palestinian Arabs and people from eastern Arabia, and among Korean and Japanese people. Second, within the mitochondria, cholesterol is converted to pregnenolone by the cholesterol side chain cleavage enzyme, P450scc; disorder of this enzyme is very rare, probably due to embryonic lethality. Third, pregnenolone undergoes 17alpha-hydroxylation by microsomal P450c17. 17alpha-Hydroxylase deficiency, manifesting as female sexual infantilism and hypertension, is rare except in Brazil. Finally, 17-OH pregnenolone is converted to DHEA by the 17,20 lyase activity of P450c17. The ratio of the 17,20 lyase to 17alpha-hydroxylase activity of P450c17 determines the ratio of C21 to C19 steroids produced. This ratio is regulated posttranslationally by at least three factors: the abundance of the electron-donating protein P450 oxidoreductase (POR), the presence of cytochrome b5 and the serine phosphorylation of P450c17. Mutations of POR are a new, recently described disorder manifesting as the Antley-Bixler skeletal dysplasia syndrome, and a form of polycystic ovary syndrome.
Collapse
Affiliation(s)
- Walter L Miller
- Department of Pediatrics, University of California, San Francisco, California 94142-0978, USA.
| |
Collapse
|
37
|
Fleury A, Mathieu AP, Ducharme L, Hales DB, LeHoux JG. Phosphorylation and function of the hamster adrenal steroidogenic acute regulatory protein (StAR). J Steroid Biochem Mol Biol 2004; 91:259-71. [PMID: 15336703 DOI: 10.1016/j.jsbmb.2004.04.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2003] [Accepted: 04/30/2004] [Indexed: 10/26/2022]
Abstract
In order to study the effect of phosphorylation on the function of the steroidogenic acute regulatory protein (StAR), 10 putative phosphorylation sites were mutated in the hamster StAR. In pcDNA3.1-StAR transfected COS-1 cells, decreases in basal activity were found for the mutants S55A, S185A and S194A. Substitution of S185 by D or E to mimic phosphorylation resulted in decreased activity for all mutants; we concluded that S185 was not a phosphorylation site and we hypothesized that mutations on S185 created StAR conformational changes resulting in a decrease in its binding affinity for cholesterol. In contrast, the mutation S194D resulted in an increase in StAR activity. We have calculated the relative rate of pregnenolone formation (App. V(max)) in transfected COS-1 cells with wild type (WT) and mutant StAR-pcDNA3.1 under control and (Bu)(2)-cAMP stimulation. The App. V(max) values refer to the rate of cholesterol transported and metabolized by the cytochrome P450scc enzyme present in the inner mitochondrial membrane. The App. V(max) was 1.61 +/- 0.28 for control (Ctr) WT StAR and this value was significantly increased to 4.72 +/- 0.09 for (Bu)(2)-cAMP stimulated preparations. App. V(max) of 5.53 (Ctr) and 4.82 ((Bu)(2)-cAMP) found for S194D StAR preparations were similar to that of the WT StAR stimulated preparations. At equal StAR quantity, an anti-phospho-(S/T) PKA substrate antibody revealed four times more phospho-(S/T) in (Bu)(2)-cAMP than in control preparations. The intensity of phosphorylated bands was decreased for the S55A, S56A and S194A mutants and it was completely abolished for the S55A/S56A/S194A mutant. StAR activity of control and stimulated preparations were diminished by 73 and 72% for the mutant S194A compared to 77 and 83% for the mutant S55A/S56A/S194A. The remaining activity appears to be independent of phosphorylation at PKA sites and could be due to the intrinsic activity of non-phosphorylated StAR or to an artefact due to the pharmacological quantity of StAR expressed in COS-1. In conclusion we have shown that (Bu)(2)-cAMP provokes an augmentation of both the quantity and activity of StAR, and that an enhancement in StAR phosphorylation increases its activity. The increased quantity of StAR upon (Bu)(2)-cAMP stimulation could be due to an augmentation of its mRNA or protein synthesis stability, or both; this is yet to be determined.
Collapse
Affiliation(s)
- Alain Fleury
- Department of Biochemistry, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4
| | | | | | | | | |
Collapse
|
38
|
Abstract
OBJECTIVE Adrenal crisis from salt-losing congenital adrenal hyperplasia (CAH) typically occurs in the first 2 weeks of life. We evaluated 3 infants with adrenal crisis who presented at 6 to 8 months of age with near-miss sudden infant death syndrome (SIDS). SUBJECTS Three 46,XY phenotypic female infants presented near death at 6 to 8 months of age with adrenal crisis and unmeasurable steroid hormones consistent with congenital lipoid adrenal hyperplasia (lipoid CAH). METHODS We sequenced genes potentially causing this phenotype: steroidogenic acute regulatory protein (StAR), the cholesterol side-chain cleavage enzyme, adrenodoxin reductase, adrenodoxin, and steroidogenic factor 1 (SF1). Site-directed mutagenesis and functional assays were performed for the missense mutation. RESULTS Hormonal values showed complete absence of adrenal and gonadal steroids. Patient 1 was a compound heterozygote for missense mutation R140P and an mRNA splice donor site mutation in the StAR gene. The R140P mutation was wholly inactive in vitro. Patient 2 was homozygous for a 7 base pair StAR deletion causing a frameshift. No mutations were found in Patient 3, suggesting a novel disease. CONCLUSIONS Although genetic disorders of steroidogenesis typically present in the first month of life, some defects, especially those in StAR, can present in mid-infancy, when adrenal hyperplasias are rarely considered. Adrenal insufficiency is a subtle disorder that may cause cardiovascular collapse, causing unexplained infant death that resembles SIDS.
Collapse
Affiliation(s)
- Heidi L Gassner
- Department of Pediatrics, University of California, San Francisco, California 94143-0978, USA
| | | | | | | |
Collapse
|
39
|
LeHoux JG, Fleury A, Ducharme L, Hales DB. Phosphorylation of the hamster adrenal steroidogenic acute regulatory protein as analyzed by two-dimensional polyacrylamide gel electrophoreses. Mol Cell Endocrinol 2004; 215:127-34. [PMID: 15026185 DOI: 10.1016/j.mce.2003.11.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Post-translational modifications such as phosphorylation and specific proteolysis affect the steroidogenic acute regulatory protein (StAR) activity. We have found that in pcDNA3.1-StAR-transfected COS-1 cells, StAR was phosphorylated on S55, S56 and S194 (Fleury et al., unpublished). In this study, we are comparing the two-dimensional gel electrophoresis (2D-PAGE) characteristics of the WT StAR with those of the S194A and S55A/S56A/S194A-StAR mutants under control and (Bu)(2)-cAMP stimulation, using an anti-StAR antibody and an anti-phospho-(Ser/Thr) PKA substrate antibody. The 2D-PAGE migration pattern of the WT StAR analyzed by immunoblotting with the anti-StAR antibody revealed many StAR species with different pI and different molecular weights. In the (Bu)(2)-cAMP-WT preparations, except for three, all these StAR species were also recognized by the anti-phospho-(Ser/Thr) PKA substrate antibody; in contrast, less phosphorylated species were found in the non-stimulated WT preparations. The two-dimensional (2D) patterns of StAR revealed by the anti-StAR and the anti-phospho-(Ser/Thr) PKA substrate antibodies were modified for the S194A mutant and further modified for the S55A/S56A/S194A mutant. Whereas many species could still be detected by the anti-StAR antibody in the triple mutant S55A/S55A/S194A, none of these could be revealed by the anti-phospho-(Ser/Thr) PKA substrate antibody. Finally we found that, in addition to phosphorylation, the formation of different StAR species was also due to the hydrolysis of the molecule at its N-terminal and to a lesser degree at its C-terminal.
Collapse
Affiliation(s)
- Jean-Guy LeHoux
- Department of Biochemistry, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Que., Canada J1H 5N4.
| | | | | | | |
Collapse
|
40
|
Abstract
CYP11A1 encodes the P450scc enzyme that catalyzes the first and rate-limiting step of steroid biosynthesis. It is expressed in the adrenals and gonads under the control of pituitary peptide hormones. Transcription factor SF-1, which binds to the CYP11A1 promoter, plays an important role in the tissue-specific and hormonally regulated expression. Transgenic mouse experiments linking the CYP11A1 promoter to a reporter gene demonstrate the importance of the SF-1-binding site in directing balanced CYP11A1 gene expression. In addition, targeted mutagenesis of Cyp11a1 also reveals the importance of this gene in steroid secretion, gene regulation, and development of genitalia. Zebrafish cyp11a1 is expressed in the gonads and interrenal glands in the adults, similar to mammals. In addition, it is expressed in yolk syncytial layer during early embryogenesis. These two animal models complement each other for the understanding of gene regulatory pathways in human diseases related to steroid imbalance.
Collapse
Affiliation(s)
- Meng-Chun Hu
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan
| | | | | | | |
Collapse
|
41
|
González AA, Reyes ML, Carvajal CA, Tobar JA, Mosso LM, Baquedano P, Solar A, Venegas A, Fardella CE. Congenital lipoid adrenal hyperplasia caused by a novel splicing mutation in the gene for the steroidogenic acute regulatory protein. J Clin Endocrinol Metab 2004; 89:946-51. [PMID: 14764819 DOI: 10.1210/jc.2003-030345] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Steroidogenic acute regulatory protein (StAR) plays a crucial role in the transport of cholesterol from the cytoplasm to the inner mitochondrial membrane, facilitating its conversion to pregnenolone by cytochrome P450scc. Its essential role in steroidogenesis was demonstrated after observing that StAR gene mutations gave rise to a potentially lethal disease named congenital lipoid adrenal hyperplasia, in which virtually no steroids are produced. We report here a 2-month-old female patient, karyotype 46XY, who presented with growth failure, convulsions, dehydration, hypoglycemia, hyponatremia, hypotension, and severe hyperpigmentation suggestive of adrenal insufficiency. Serum cortisol, 17OH-progesterone, dehydroepiandrosterone sulfate, testosterone, 17OH-pregnenolone, and aldosterone levels were undetectable in the presence of high ACTH and plasma renin activity levels. Immunohistochemical analysis of testis tissues revealed the absence of StAR protein. Molecular analysis of StAR gene demonstrated a homozygous G to T mutation within the splice donor site of exon 1 (IVS1 + 1G>T). Her parents and one brother were heterozygous for this mutation. In vitro analysis of the mutation was performed in COS cells transfected with minigenes coding regions spanning exon-intron 1 to 3 carrying the mutant and the wild-type sequences. RT-PCR analyses of the mutant gene showed an abnormal mRNA transcript of 2430 bp (normal size 433 bp). Sequence analysis of the mutant mRNA demonstrated the retention of intron 1. Immunolocalization of the StAR minigene product detected the peptide in the mitochondria of COS cells transfected with the wild-type minigene but not in those transfected with the mutant minigene. We conclude that this mutation gives rise to a truncated StAR protein, which lacks an important N-terminal region and the entire lipid transfer domain.
Collapse
Affiliation(s)
- Alexis A González
- Department of Endocrinology, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago
| | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Webb KE, Martin JF, Cotton J, Erusalimsky JD, Humphries SE. The 4830C>A polymorphism within intron 5 affects the pattern of alternative splicing occurring within exon 6 of the thrombopoietin gene. Exp Hematol 2003; 31:488-94. [PMID: 12829024 DOI: 10.1016/s0301-472x(03)00065-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE A common variant in intron 5 of the thrombopoietin (TPO) gene (4830C>A) has been associated with risk of myocardial infarction (MI). To explore the molecular mechanism of this association, the ability of the intron to act as a transcription enhancer and to influence mRNA splicing was tested. METHOD AND RESULTS In HepG2 cells the presence of intron 5 upstream of the TPO promoter decreased promoter activity to between 60% and 30%. This effect was orientation dependent; in the reverse orientation, intron 5 caused a twofold greater decrease in promoter activity compared to the forward orientation. However, the effects were similar with either the C or the 4830A allele. An in vitro exon trapping system was used to study the effect of the polymorphism on splicing events in exon 6. The full-length (TPO-1) and three previously reported splice variants (TPO-2, TPO-3, and TPO-5) were identified. The 4830A allele resulted in a small but statistically significant increase in production of the TPO-3 splice variant relative to the full-length transcript (10.6%+/-0.6%) compared to the 4830C allele (8.3%+/-0.6%) (p=0.02). Generation of TPO-5 was also slightly increased, but this did not reach significance. CONCLUSION The identification of a potential "silencer" sequence in intron 5 of the TPO gene demonstrates the complexity of control of expression of the gene. Although the precise role of the different splice variants is not known, the finding that the 4830C>A sequence change alters their relative amounts, suggests a possible molecular mechanism whereby TPO genotype may influence the risk of MI.
Collapse
Affiliation(s)
- Karen E Webb
- Centres for Cardiovascular Genetics, British Heart Foundation Laboratories, Royal Free and University College Medical School, Rayne Building, 5 University Street, London WC1E 6JF, England
| | | | | | | | | |
Collapse
|
43
|
Fujieda K, Okuhara K, Abe S, Tajima T, Mukai T, Nakae J. Molecular pathogenesis of lipoid adrenal hyperplasia and adrenal hypoplasia congenita. J Steroid Biochem Mol Biol 2003; 85:483-9. [PMID: 12943739 DOI: 10.1016/s0960-0760(03)00232-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Congenital lipoid adrenal hyperplasia (lipoid CAH) is the most severe form of CAH in which the synthesis of all gonadal and adrenal cortical steroids is markedly impaired. Lipoid CAH may be caused by the defect in either the steroidogenic acute regulatory (StAR) protein or the P450scc. More than 34 different mutations in StAR gene have been identified. Clinically, most of the patients manifest adrenal insufficiency from 1 day to 2 months of age, but some patient show delayed onset of adrenal insufficiency. Affected 46, XY subjects do not show pubertal development, whereas affected 46, XX subjects undergo spontaneous feminization, breast development and cyclical vaginal bleeding at the usual age of puberty. X-linked adrenal hypoplasia congenital (AHC) is a rare congenital adrenal disorder characterized by severe adrenal insufficiency and hypogonadotropic hypogonadism. More than 80 different several intragenic mutations of DAX-1 have been identified. The failure of pubertal development may be caused by either abnormal hypothalamic or pituitary regulation of gonadotropin secretion. In addition, although the testicular steroidogenesis is largely intact, the functional maturity of Sertoli cells and also spermatogenesis are impaired. The type of mutation does not predict clinical phenotype. Thus, unified mechanism how DAX-1 gene defect gives rise to adrenal insufficiency, hypothalamic/pituitary hypogonadism and impaired spermatogenesis remains established.
Collapse
Affiliation(s)
- Kenji Fujieda
- Department of Pediatrics, Asahikawa Medical College, 2-1-1-1 Midorigaoka, Higashi, Asahikawa 078-8510, Japan.
| | | | | | | | | | | |
Collapse
|
44
|
Bose HS, Lingappa VR, Miller WL. The steroidogenic acute regulatory protein, StAR, works only at the outer mitochondrial membrane. Endocr Res 2002; 28:295-308. [PMID: 12530629 DOI: 10.1081/erc-120016800] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The steroidogenic acute regulatory protein (StAR) facilitates the movement of cholesterol into mitochondria to initiate steroidogenesis, but its site of action on the mitochondria has been uncertain. One model states that StAR has a fairly rigid structure and functions in the intramembranous space (IMS) where it transports cholesterol from the outer mitochondrial membrane (OMM) to the inner mitochondrial membrane (IMM); another model states that StAR works solely on or in the OMM and undergoes a partially open molten globule conformation while picking up and discharging cholesterol. We designed, built and tested a series of StAR fusion proteins designed to immobilize StAR on the OMM, the IMS, or the matrix side of the IMM. Only the constructs at the OMM were active, either in vivo or in vitro. As these data indicated that StAR acts at or in the OMM we hypothesized that StAR' s activity would be proportional to the amount of time it spends on the OMM. To test this hypothesis, we built a series of StAR proteins with altered mitochondrial leaders designed to speed or slow StAR's mitochondrial entry. Cell transfections showed that the constructs that slowed entry had more activity and those designed to speed entry had less activity. Analysis of import kinetics in vitro confirmed that these constructs accelerated import inversely proportional to their activity. These data show that StAR works only on the OMM, providing an unusual example of a protein that exerts its biological activity in a cellular location it occupies only transiently, rather than in the location (the matrix) to which it is targeted.
Collapse
Affiliation(s)
- Himangshu S Bose
- Department of Pediatrics, University of California, San Francisco, CA 94143-0978, USA.
| | | | | |
Collapse
|
45
|
Stocco DM. Clinical disorders associated with abnormal cholesterol transport: mutations in the steroidogenic acute regulatory protein. Mol Cell Endocrinol 2002; 191:19-25. [PMID: 12044915 DOI: 10.1016/s0303-7207(02)00048-5] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The transport of cholesterol to the inner mitochondrial membrane of steroidogenic cells constitutes the rate-limiting step in trophic hormone regulated steroid biosynthesis and requires de novo protein synthesis. Several years ago a candidate regulator protein was purified and its cDNA cloned from MA-10 mouse Leydig tumor cells. Expression of this protein resulted in an increase in steroidogenesis in unstimulated cells and it was named the Steroidogenic Acute Regulatory protein or StAR. Mutations in the StAR gene were found to be the cause of the potentially lethal disease in humans known as congenital lipoid adrenal hyperplasia (lipoid CAH), a condition characterized by an almost complete inability of the newborn to synthesize steroids. The defect in steroid synthesis in lipoid CAH is caused by the failure of affected individuals to transport cholesterol to the inner mitochondria membrane, thus proving the essential role of StAR in cholesterol transport. StAR null mice display a phenotype that is essentially identical to the human condition. In summary, both naturally occurring disorders in humans and genetic manipulation in mice have demonstrated that the StAR protein is an absolute requirement in the rate-limiting step in steroidogenesis, the transfer of cholesterol into the mitochondria.
Collapse
Affiliation(s)
- Douglas M Stocco
- Texas Technological University Health Sciences Center, 3601 4th Street, Department of Cell Biology and Biochemistry, Lubbock, TX 79430, USA.
| |
Collapse
|
46
|
Stigliano A, Caiola S, Siniscalchi E, Papini E, Crescenzi A, Monti S, Arnaldi G, Mantero F, Sciarra F, Toscano V. Mutational analysis of StAR gene in adrenal tumors. Int J Cancer 2002; 97:357-60. [PMID: 11774288 DOI: 10.1002/ijc.1604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Adrenal adenomas and carcinomas are mostly monoclonal, suggesting that a genetic alteration in a progenitor cell may contribute to their development. However, the molecular pathogenesis of these tumors still remains unclear. It has been already excluded that activating mutations of the ACTH receptor or of G protein stimulator alpha sub-units, affecting cAMP pathway, is involved in the tumorigenesis. Therefore, this work has been focused on post-transductional (ACTH) signal alterations and in particular on the mutational analysis of the Steroid Acute Regulatory protein (StAR) gene to verify whether somatic mutations or genomic polymorphisms of this gene may be correlated with adrenal tumorigenesis. Tissue DNA was extracted from 40 functional and non-functional adrenocortical tumors that were removed from patients aged between 17 and 72 years (mean 43 +/- 4). Blood DNA was obtained from 24 patients (aged between 26 and 70 years) affected by adrenal tumors and from 100 healthy subjects without radiological and clinical evidence of adrenal masses, aged between 25-35 years (90 Caucasians and 10 Africans). The DNA was used as the template for the amplification of the StAR gene using the polymerase chain reaction. The amplified DNA of each exon of the StAR gene was purified and sequenced in automatic sequenciator. With the exception of exon 5 showing in codon 203 an homozygous missense mutation, the sequence of the other exons of the StAR gene resulted normal in all tumors studied. The same homozygous mutation (Asp203Ala) was observed in the sequence of exon 5 performed on genomic DNA of the 24 affected patients and in the control subjects. The homozygosity of the mutation observed in all patients (either in tissue or blood samples) and in control subjects, independently of their ethnic origin, led us to suggest that the Asp203Ala cannot be considered as mutation or as polymorphism, but that it must be considered as a mistake in the sequence entered in the Genbank, which needs to be modified accordingly. These data, and those up to now reported in the literature, allow us to suggest that mutations of the gene coding for the protein involved in the initial step of the steroidogenesis could not be considered as a possible cause for the development of adrenal tumors.
Collapse
Affiliation(s)
- Antonio Stigliano
- II Endocrinologia, Dipartimento di Fisiopatologia Medica, Università La Sapienza, Rome, Italy
| | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Christenson LK, Strauss JF. Steroidogenic acute regulatory protein: an update on its regulation and mechanism of action. Arch Med Res 2001; 32:576-86. [PMID: 11750733 DOI: 10.1016/s0188-4409(01)00338-1] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Steroidogenic acute regulatory (StAR) protein controls the rate-limiting step in steroidogenesis: the transport of cholesterol from the outer to the inner mitochondrial membrane. Early studies indicated that rate of transcription of the StAR gene is a primary determinant of steroidogenesis. The transcription factors that govern basal and cAMP-dependent StAR expression are reviewed, as are new findings regarding chromatin modifications associated with activation of the StAR promoter. Molecular genetic studies of congenital lipoid adrenal hyperplasia, a rare disease caused by mutations in the StAR gene, and structure-function studies defined two major domains within the StAR protein, the N-terminal mitochondrial targeting sequence and the C-terminal StAR-related lipid transfer (START) domain, which promotes the translocation of cholesterol between the two mitochondrial membranes. Several models of StAR's mechanism of action have been proposed based on a combination of structure/function studies or on the crystal structure of a related START domain. The models-intermembrane shuttle hypothesis, and cholesterol desorption hypothesis-are discussed with respect to the known biochemical and biophysical events associated with steroidogenesis and the structure of StAR.
Collapse
Affiliation(s)
- L K Christenson
- Center for Research on Reproduction and Women's Health, University of Pennsylvania Medical Center, Philadelphia, PA, USA.
| | | |
Collapse
|
48
|
Achermann JC, Meeks JJ, Jeffs B, Das U, Clayton PE, Brook CG, Jameson JL. Molecular and structural analysis of two novel StAR mutations in patients with lipoid congenital adrenal hyperplasia. Mol Genet Metab 2001; 73:354-7. [PMID: 11509019 DOI: 10.1006/mgme.2001.3202] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in the gene encoding steroidogenic acute regulatory protein (StAR) cause lipoid congenital adrenal hyperplasia. We report a novel homozygous splice site mutation (IVS1 + 2T --> G) in STAR in two sisters (46XY, 46XX) who presented with primary adrenal insufficiency at birth and a novel homozygous R182H missense mutation in the putative lipid transfer domain of StAR in a phenotypic female (46XY) with adrenal failure and a parotid tumor. These cases highlight the importance of StAR-dependent steroidogenesis during fetal development and early infancy and of the critical functional role of R182 in cholesterol transport.
Collapse
Affiliation(s)
- J C Achermann
- Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, 250 East Superior Street, Chicago, IL 60611, USA
| | | | | | | | | | | | | |
Collapse
|
49
|
Tajima T, Fujieda K, Kouda N, Nakae J, Miller WL. Heterozygous mutation in the cholesterol side chain cleavage enzyme (p450scc) gene in a patient with 46,XY sex reversal and adrenal insufficiency. J Clin Endocrinol Metab 2001; 86:3820-5. [PMID: 11502818 DOI: 10.1210/jcem.86.8.7748] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Cytochrome P450scc, the mitochondrial cholesterol side chain cleavage enzyme, is the only enzyme that catalyzes the conversion of cholesterol to pregnenolone and, thus, is required for the biosynthesis of all steroid hormones. Congenital lipoid adrenal hyperplasia is a severe disorder of steroidogenesis in which cholesterol accumulates within steroidogenic cells and the synthesis of all adrenal and gonadal steroids is impaired, hormonally suggesting a disorder in P450scc. However, congenital lipoid adrenal hyperplasia is caused by mutations in the steroidogenic acute regulatory protein StAR; it has been thought that P450scc mutations are incompatible with human term gestation, because P450scc is needed for placental biosynthesis of progesterone, which is required to maintain pregnancy. In studying patients with congenital lipoid adrenal hyperplasia, we identified an individual with normal StAR and SF-1 genes and a heterozygous mutation in P450scc. The mutation was found in multiple cell types, but neither parent carried the mutation, suggesting it arose de novo during meiosis, before fertilization. The patient was atypical for congenital lipoid adrenal hyperplasia, having survived for 4 yr without hormonal replacement before experiencing life-threatening adrenal insufficiency. The P450scc mutation, an in-frame insertion of Gly and Asp between Asp271 and Val272, was inserted into a catalytically active fusion protein of the P450scc system (H2N-P450scc-Adrenodoxin Reductase-Adrenodoxin-COOH), completely inactivating enzymatic activity. Cotransfection of wild-type and mutant vectors showed that the mutation did not exert a dominant negative effect. Because P450scc is normally a slow and inefficient enzyme, we propose that P450scc haploinsufficiency results in subnormal responses to ACTH, so that recurrent ACTH stimulation leads to a slow accumulation of adrenal cholesterol, eventually causing cellular damage. Thus, although homozygous absence of P450scc should be incompatible with term gestation, haploinsufficiency of P450scc causes a late-onset form of congenital lipoid adrenal hyperplasia that can be explained by the same two-hit model that has been validated for congenital lipoid adrenal hyperplasia caused by StAR deficiency.
Collapse
Affiliation(s)
- T Tajima
- Department of Pediatrics, Hokkaido University School of Medicine N15, 060-8638 Sapporo, Japan
| | | | | | | | | |
Collapse
|
50
|
Affiliation(s)
- F Martínez
- Department of Biochemistry, Faculty of Medicine, UNAM, Mexico
| | | |
Collapse
|