1
|
Sidhu SK, Mishra S. A cholesterol-centric outlook on steroidogenesis. VITAMINS AND HORMONES 2023; 124:405-428. [PMID: 38408806 DOI: 10.1016/bs.vh.2023.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Cholesterol, an essential and versatile lipid, is the precursor substrate for the biosynthesis of steroid hormones, and a key structural and functional component of organelle membranes in eukaryotic cells. Consequently, the framework of steroidogenesis across main steroidogenic cell types is built around cholesterol, including its cellular uptake, mobilization from intracellular storage, and finally, its transport to the mitochondria where steroidogenesis begins. This setup, which is controlled by different trophic hormones in their respective target tissues, allows steroidogenic cells to meet their steroidogenic need of cholesterol effectively without impinging on the basic need for organelle membranes and their functions. However, our understanding of the basal steroidogenesis (i.e., independent of trophic hormone stimulation), which is a cell-intrinsic trait, remains poor. Particularly, the role that cholesterol itself plays in the regulation of steroidogenic factors and events in steroid hormone-producing cells remains largely unexplored. This is likely because of challenges in selectively targeting the steroidogenic intracellular cholesterol pool in studies. New evidence suggests that cholesterol plays a role in steroidogenesis. These new findings have created new opportunities to advance our understanding in this field. In this book chapter, we will provide a cholesterol-centric view on steroidogenesis and emphasize the importance of the interplay between cholesterol and the mitochondria in steroidogenic cells. Moreover, we will discuss a novel mitochondrial player, prohibitin-1, in this context. The overall goal is to provide a stimulating perspective on cholesterol as an important regulator of steroidogenesis (i.e., more than just a substrate for steroid hormones) and present the mitochondria as a potential cell-intrinsic factor in regulating steroidogenic cholesterol homeostasis.
Collapse
Affiliation(s)
- Simarjit Kaur Sidhu
- Department of Physiology & Pathophysiology, College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada
| | - Suresh Mishra
- Department of Physiology & Pathophysiology, College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada; Department of Internal Medicine, College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
| |
Collapse
|
2
|
Manna PR, Ahmed AU, Molehin D, Narasimhan M, Pruitt K, Reddy PH. Hormonal and Genetic Regulatory Events in Breast Cancer and Its Therapeutics: Importance of the Steroidogenic Acute Regulatory Protein. Biomedicines 2022; 10:biomedicines10061313. [PMID: 35740335 PMCID: PMC9220045 DOI: 10.3390/biomedicines10061313] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 02/04/2023] Open
Abstract
Estrogen promotes the development and survival of the majority of breast cancers (BCs). Aromatase is the rate-limiting enzyme in estrogen biosynthesis, and it is immensely expressed in both cancerous and non-cancerous breast tissues. Endocrine therapy based on estrogen blockade, by aromatase inhibitors, has been the mainstay of BC treatment in post-menopausal women; however, resistance to hormone therapy is the leading cause of cancer death. An improved understanding of the molecular underpinnings is the key to develop therapeutic strategies for countering the most prevalent hormone receptor positive BCs. Of note, cholesterol is the precursor of all steroid hormones that are synthesized in a variety of tissues and play crucial roles in diverse processes, ranging from organogenesis to homeostasis to carcinogenesis. The rate-limiting step in steroid biosynthesis is the transport of cholesterol from the outer to the inner mitochondrial membrane, a process that is primarily mediated by the steroidogenic acute regulatory (StAR) protein. Advances in genomic and proteomic technologies have revealed a dynamic link between histone deacetylases (HDACs) and StAR, aromatase, and estrogen regulation. We were the first to report that StAR is abundantly expressed, along with large amounts of 17β-estradiol (E2), in hormone-dependent, but not hormone-independent, BCs, in which StAR was also identified as a novel acetylated protein. Our in-silico analyses of The Cancer Genome Atlas (TCGA) datasets, for StAR and steroidogenic enzyme genes, revealed an inverse correlation between the amplification of the StAR gene and the poor survival of BC patients. Additionally, we reported that a number of HDAC inhibitors, by altering StAR acetylation patterns, repress E2 synthesis in hormone-sensitive BC cells. This review highlights the current understanding of molecular pathogenesis of BCs, especially for luminal subtypes, and their therapeutics, underlining that StAR could serve not only as a prognostic marker, but also as a therapeutic candidate, in the prevention and treatment of this life-threatening disease.
Collapse
Affiliation(s)
- Pulak R. Manna
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
- Correspondence: ; Tel.: +1-806-743-3573; Fax: +1-806-743-3143
| | - Ahsen U. Ahmed
- Comprehensive Cancer Center, University of California Davis, Sacramento, CA 95817, USA;
| | - Deborah Molehin
- Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; (D.M.); (K.P.)
| | - Madhusudhanan Narasimhan
- Neuroscience and Pharmacology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
| | - Kevin Pruitt
- Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; (D.M.); (K.P.)
| | - P. Hemachandra Reddy
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
- Neuroscience and Pharmacology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
- Neurology, Departments of School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Public Health Department of Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Department of Speech, Language and Hearing Sciences, School Health Professions, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| |
Collapse
|
3
|
Mechanism of Action of an Environmentally Relevant Organochlorine Mixture in Repressing Steroid Hormone Biosynthesis in Leydig Cells. Int J Mol Sci 2022; 23:ijms23073997. [PMID: 35409357 PMCID: PMC8999779 DOI: 10.3390/ijms23073997] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/28/2022] [Accepted: 04/01/2022] [Indexed: 02/04/2023] Open
Abstract
Within Leydig cells, steroidogenesis is induced by the pituitary luteinizing hormone (LH). The binding of LH to its receptor increases cAMP production, which then activates the expression of genes involved in testosterone biosynthesis. One of these genes codes for the steroidogenic acute regulatory (STAR) protein. STAR is part of a complex that shuttles cholesterol, the precursor of all steroid hormones, through the mitochondrial membrane where steroidogenesis is initiated. Organochlorine chemicals (OCs) are environmental persistent organic pollutants that are found at high concentrations in Arctic areas. OCs are known to affect male reproductive health by decreasing semen quality in different species, including humans. We previously showed that an environmentally relevant mixture of OCs found in Northern Quebec disrupts steroidogenesis by decreasing STAR protein levels without affecting the transcription of the gene. We hypothesized that OCs might affect STAR protein stability. To test this, MA-10 Leydig cell lines were incubated for 6 h with vehicle or the OCs mixture in the presence or absence of 8Br-cAMP with or without MG132, an inhibitor of protein degradation. We found that MG132 prevented the OC-mediated decrease in STAR protein levels following 8Br-cAMP stimulation. However, progesterone production was still decreased by the OC mixture, even in the presence of MG132. This suggested that proteins involved in steroid hormone production in addition to STAR are also affected by the OC mixture. To identify these proteins, a whole cell approach was used and total proteins from MA-10 Leydig cells exposed to the OC mixture with or without stimulation with 8Br-cAMP were analyzed by 2D SDS-PAGE and LC-MS/MS. Bioinformatics analyses revealed that several proteins involved in numerous biological processes are affected by the OC mixture, including proteins involved in mitochondrial transport, lipid metabolism, and steroidogenesis.
Collapse
|
4
|
Nagyová E, Němcová L, Camaioni A. Cumulus Extracellular Matrix Is an Important Part of Oocyte Microenvironment in Ovarian Follicles: Its Remodeling and Proteolytic Degradation. Int J Mol Sci 2021; 23:54. [PMID: 35008478 PMCID: PMC8744823 DOI: 10.3390/ijms23010054] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/07/2021] [Accepted: 12/17/2021] [Indexed: 12/14/2022] Open
Abstract
The extracellular matrix (ECM) is an essential structure with biological activities. It has been shown that the ECM influences gene expression via cytoskeletal components and the gene expression is dependent upon cell interactions with molecules and hormones. The development of ovarian follicles is a hormone dependent process. The surge in the luteinizing hormone triggers ovulatory changes in oocyte microenvironment. In this review, we discuss how proteolytic cleavage affects formation of cumulus ECM following hormonal stimulation; in particular, how the specific proteasome inhibitor MG132 affects gonadotropin-induced cytoskeletal structure, the organization of cumulus ECM, steroidogenesis, and nuclear maturation. We found that after the inhibition of proteolytic cleavage, gonadotropin-stimulated oocyte-cumulus complexes (OCCs) were without any signs of cumulus expansion; they remained compact with preserved cytoskeletal F-actin-rich transzonal projections through the oocyte investments. Concomitantly, a significant decrease was detected in progesterone secretion and in the expression of gonadotropin-stimulated cumulus expansion-related transcripts, such as HAS2 and TNFAIP6. In agreement, the covalent binding between hyaluronan and the heavy chains of serum-derived the inter-alpha-trypsin inhibitor, essential for the organization of cumulus ECM, was missing.
Collapse
Affiliation(s)
- Eva Nagyová
- Institute of Animal Physiology and Genetics, Czech Academy of Sciences, 27721 Libechov, Czech Republic;
| | - Lucie Němcová
- Institute of Animal Physiology and Genetics, Czech Academy of Sciences, 27721 Libechov, Czech Republic;
| | - Antonella Camaioni
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Via Montpelier 1, 00133 Rome, Italy;
| |
Collapse
|
5
|
Song P, Yue Q, Fu Q, Li X, Li X, Zhou R, Chen X, Tao C. Integrated analysis of miRNA-mRNA interaction in ovaries of Turpan Black Sheep during follicular and luteal phases. Reprod Domest Anim 2020; 56:46-57. [PMID: 33098173 DOI: 10.1111/rda.13848] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 10/19/2020] [Indexed: 12/21/2022]
Abstract
To investigate the regulatory mechanism of the follicular-luteal phase transition in Turpan black sheep (Ovis aries), the genome-wide expression patterns of microRNAs (miRNAs) and genes were investigated in ovaries of six sheep (3 years and single lamb with 3 consecutive births) during follicular and luteal phases of the oestrous cycle. Bioinformatic analysis was used to screen potential miRNAs and genes related to Turpan black sheep ovarian function. RT-qPCR was used to validate the sequencing results. In total, we identified 139 known and 71 novel miRNAs in the two phases with miRNA-seq, and a total of 19 miRNAs were significantly differentially expressed, of which 7 were up-regulated and 12 were down-regulated in the follicular phase compared with luteal phase. A total of 150 genes were significantly differentially expressed, including 63 up-regulated and 87 down-regulated in the follicular phase compared with the luteal phase by RNA-seq data analysis. Those DEGs were significantly enriched in 103 GO terms and several KEGG pathways, including metabolic pathway, ovarian steroidogenesis, steroid hormone biosynthesis and oestrogen signalling pathway. In addition, we created a miRNA-mRNA regulatory network to further elucidate the mechanism of follicular-luteal transition. Finally, we identified key miRNAs and genes including miR-143, miR-99a, miR-150, miR-27a, miR-125b, STAR, STAT1, which might play crucial roles in reproductive hormone biosynthesis and follicular development. The miRNA-mRNA interactive network clearly illustrates molecular basis involving in follicular-luteal transition.
Collapse
Affiliation(s)
- Pengyan Song
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Qiaoxian Yue
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Qiang Fu
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Xiangyun Li
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Xujing Li
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Rongyan Zhou
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Xiaoyong Chen
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| | - Chenyu Tao
- College of Animal Science and Technology, Hebei Agricultural University, Baoding, China
| |
Collapse
|
6
|
Medwid S, Guan H, Yang K. Bisphenol A stimulates steroidogenic acute regulatory protein expression via an unknown mechanism in adrenal cortical cells. J Cell Biochem 2019; 120:2429-2438. [PMID: 30206973 DOI: 10.1002/jcb.27574] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 08/02/2018] [Indexed: 01/24/2023]
Abstract
Bisphenol A (BPA) is one of the most widespread endocrine disrupting chemicals in the environment. Exposure to BPA is known to be associated with disruption of steroidogenesis in reproductive tissues, but little is known about its effects on the adrenal gland. We previously showed that prenatal BPA exposure resulted in elevated plasma corticosterone levels concomitant with increased adrenal levels of steroidogenic acute regulatory protein (StAR), the rate-limiting step in steroidogenesis, in adult female mouse offspring. However, the molecular mechanisms underlying the BPA-induced StAR protein expression in the adrenal gland remain unknown. Therefore, the current study was designed to address this important question using the human cortical cell line, H295A cells, as an in vitro model system. We found that: (1) BPA increased StAR protein levels in a dose-dependent manner; (2) both estrogen receptor alpha (ERα)- and ERβ-specific agonists mimicked while the ER antagonist ICI abrogated the stimulatory effects of BPA on StAR protein levels; and (3) BPA did not alter StAR messenger RNA, 37kDa preprotein or protein half-life. Taken together, these findings demonstrate that BPA increases StAR protein levels through an unknown mechanism independent of StAR gene transcription, translation, and protein half-life. Furthermore, such effects are likely mediated by ERα and/or ERβ.
Collapse
Affiliation(s)
- Samantha Medwid
- Departments of Obstetrics & Gynaecology and Physiology & Pharmacology, Children's Health Research Institute & Lawson Health Research Institute, Western University, London, Ontario, Canada
| | - Haiyan Guan
- Departments of Obstetrics & Gynaecology and Physiology & Pharmacology, Children's Health Research Institute & Lawson Health Research Institute, Western University, London, Ontario, Canada
| | - Kaiping Yang
- Departments of Obstetrics & Gynaecology and Physiology & Pharmacology, Children's Health Research Institute & Lawson Health Research Institute, Western University, London, Ontario, Canada
| |
Collapse
|
7
|
The Biological Role of Hyaluronan-Rich Oocyte-Cumulus Extracellular Matrix in Female Reproduction. Int J Mol Sci 2018; 19:ijms19010283. [PMID: 29346283 PMCID: PMC5796229 DOI: 10.3390/ijms19010283] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 01/16/2018] [Accepted: 01/16/2018] [Indexed: 12/16/2022] Open
Abstract
Fertilization of the mammalian oocyte requires interactions between spermatozoa and expanded cumulus extracellular matrix (ECM) that surrounds the oocyte. This review focuses on key molecules that play an important role in the formation of the cumulus ECM, generated by the oocyte-cumulus complex. In particular, the specific inhibitors (AG1478, lapatinib, indomethacin and MG132) and progesterone receptor antagonist (RU486) exerting their effects through the remodeling of the ECM of the cumulus cells surrounding the oocyte have been described. After gonadotropin stimulus, cumulus cells expand and form hyaluronan (HA)-rich cumulus ECM. In pigs, the proper structure of the cumulus ECM depends on the interaction between HA and serum-derived proteins of the inter-alpha-trypsin inhibitor (IαI) protein family. We have demonstrated the synthesis of HA by cumulus cells, and the presence of the IαI, tumor necrosis factor-alpha-induced protein 6 and pentraxin 3 in expanding oocyte-cumulus complexes (OCC). We have evaluated the covalent linkage of heavy chains of IαI proteins to HA, as the principal component of the expanded HA-rich cumulus ECM, in porcine OCC cultured in medium with specific inhibitors: AG1478 and lapatinib (both inhibitors of epidermal growth factor receptor tyrosine kinase activity); MG132 (a specific proteasomal inhibitor), indomethacin (cyclooxygenase inhibitor); and progesterone receptor antagonist (RU486). We have found that both RU486 and indomethacin does not disrupt the formation of the covalent linkage between the heavy chains of IαI to HA in the expanded OCC. In contrast, the inhibitors AG1478 and lapatinib prevent gonadotropin-induced cumulus expansion. Finally, the formation of oocyte-cumulus ECM relying on the covalent transfer of heavy chains of IαI molecules to HA has been inhibited in the presence of MG132.
Collapse
|
8
|
Liang JJ, Rasmusson AM. Overview of the Molecular Steps in Steroidogenesis of the GABAergic Neurosteroids Allopregnanolone and Pregnanolone. CHRONIC STRESS (THOUSAND OAKS, CALIF.) 2018; 2:2470547018818555. [PMID: 32440589 PMCID: PMC7219929 DOI: 10.1177/2470547018818555] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/19/2018] [Indexed: 12/23/2022]
Abstract
Allopregnanolone and pregnanolone-neurosteroids synthesized from progesterone in the brain, adrenal gland, ovary and testis-have been implicated in a range of neuropsychiatric conditions including seizure disorders, post-traumatic stress disorder, major depression, post-partum depression, pre-menstrual dysphoric disorder, chronic pain, Parkinson's disease, Alzheimer's disease, neurotrauma, and stroke. Allopregnanolone and pregnanolone equipotently facilitate the effects of gamma-amino-butyric acid (GABA) at GABAA receptors, and when sulfated, antagonize N-methyl-D-aspartate receptors. They play myriad roles in neurophysiological homeostasis and adaptation to stress while exerting anxiolytic, antidepressant, anti-nociceptive, anticonvulsant, anti-inflammatory, sleep promoting, memory stabilizing, neuroprotective, pro-myelinating, and neurogenic effects. Given that these neurosteroids are synthesized de novo on demand, this review details the molecular steps involved in the biochemical conversion of cholesterol to allopregnanolone and pregnanolone within steroidogenic cells. Although much is known about the early steps in neurosteroidogenesis, less is known about transcriptional, translational, and post-translational processes in allopregnanolone- and pregnanolone-specific synthesis. Further research to elucidate these mechanisms as well as to optimize the timing and dose of interventions aimed at altering the synthesis or levels of these neurosteroids is much needed. This should include the development of novel therapeutics for the many neuropsychiatric conditions to which dysregulation of these neurosteroids contributes.
Collapse
Affiliation(s)
| | - Ann M. Rasmusson
- Boston
University School of Medicine, Boston, MA,
USA
- National Center for PTSD, Women’s Health
Science Division, Department of Veterans Affairs, Boston, MA, USA
- VA Boston Healthcare System, Boston, MA,
USA
| |
Collapse
|
9
|
The role of Lon-mediated proteolysis in the dynamics of mitochondrial nucleic acid-protein complexes. Sci Rep 2017; 7:631. [PMID: 28377575 PMCID: PMC5428876 DOI: 10.1038/s41598-017-00632-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 03/07/2017] [Indexed: 11/15/2022] Open
Abstract
Mitochondrial nucleoids consist of several different groups of proteins, many of which are involved in essential cellular processes such as the replication, repair and transcription of the mitochondrial genome. The eukaryotic, ATP-dependent protease Lon is found within the central nucleoid region, though little is presently known about its role there. Aside from its association with mitochondrial nucleoids, human Lon also specifically interacts with RNA. Recently, Lon was shown to regulate TFAM, the most abundant mtDNA structural factor in human mitochondria. To determine whether Lon also regulates other mitochondrial nucleoid- or ribosome-associated proteins, we examined the in vitro digestion profiles of the Saccharomyces cerevisiae TFAM functional homologue Abf2, the yeast mtDNA maintenance protein Mgm101, and two human mitochondrial proteins, Twinkle helicase and the large ribosomal subunit protein MrpL32. Degradation of Mgm101 was also verified in vivo in yeast mitochondria. These experiments revealed that all four proteins are actively degraded by Lon, but that three of them are protected from it when bound to a nucleic acid; the Twinkle helicase is not. Such a regulatory mechanism might facilitate dynamic changes to the mitochondrial nucleoid, which are crucial for conducting mitochondrial functions and maintaining mitochondrial homeostasis.
Collapse
|
10
|
Paz C, Cornejo Maciel F, Gorostizaga A, Castillo AF, Mori Sequeiros García MM, Maloberti PM, Orlando UD, Mele PG, Poderoso C, Podesta EJ. Role of Protein Phosphorylation and Tyrosine Phosphatases in the Adrenal Regulation of Steroid Synthesis and Mitochondrial Function. Front Endocrinol (Lausanne) 2016; 7:60. [PMID: 27375556 PMCID: PMC4899475 DOI: 10.3389/fendo.2016.00060] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 05/25/2016] [Indexed: 12/17/2022] Open
Abstract
In adrenocortical cells, adrenocorticotropin (ACTH) promotes the activation of several protein kinases. The action of these kinases is linked to steroid production, mainly through steroidogenic acute regulatory protein (StAR), whose expression and activity are dependent on protein phosphorylation events at genomic and non-genomic levels. Hormone-dependent mitochondrial dynamics and cell proliferation are functions also associated with protein kinases. On the other hand, protein tyrosine dephosphorylation is an additional component of the ACTH signaling pathway, which involves the "classical" protein tyrosine phosphatases (PTPs), such as Src homology domain (SH) 2-containing PTP (SHP2c), and members of the MAP kinase phosphatase (MKP) family, such as MKP-1. PTPs are rapidly activated by posttranslational mechanisms and participate in hormone-stimulated steroid production. In this process, the SHP2 tyrosine phosphatase plays a crucial role in a mechanism that includes an acyl-CoA synthetase-4 (Acsl4), arachidonic acid (AA) release and StAR induction. In contrast, MKPs in steroidogenic cells have a role in the turn-off of the hormonal signal in ERK-dependent processes such as steroid synthesis and, perhaps, cell proliferation. This review analyzes the participation of these tyrosine phosphates in the ACTH signaling pathway and the action of kinases and phosphatases in the regulation of mitochondrial dynamics and steroid production. In addition, the participation of kinases and phosphatases in the signal cascade triggered by different stimuli in other steroidogenic tissues is also compared to adrenocortical cell/ACTH and discussed.
Collapse
Affiliation(s)
- Cristina Paz
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Fabiana Cornejo Maciel
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Alejandra Gorostizaga
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Ana F. Castillo
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - M. Mercedes Mori Sequeiros García
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Paula M. Maloberti
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Ulises D. Orlando
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Pablo G. Mele
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Cecilia Poderoso
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
| | - Ernesto J. Podesta
- Departamento de Bioquímica Humana, Facultad de Medicina, Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Buenos Aires (UBA-CONICET), Ciudad Autónoma de Buenos Aires, Argentina
- *Correspondence: Ernesto J. Podesta, ,
| |
Collapse
|
11
|
Bahat A, Perlberg S, Melamed-Book N, Isaac S, Eden A, Lauria I, Langer T, Orly J. Transcriptional activation of LON Gene by a new form of mitochondrial stress: A role for the nuclear respiratory factor 2 in StAR overload response (SOR). Mol Cell Endocrinol 2015; 408:62-72. [PMID: 25724481 DOI: 10.1016/j.mce.2015.02.022] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Revised: 02/19/2015] [Accepted: 02/19/2015] [Indexed: 01/19/2023]
Abstract
High output of steroid hormone synthesis in steroidogenic cells of the adrenal cortex and the gonads requires the expression of the steroidogenic acute regulatory protein (StAR) that facilitates cholesterol mobilization to the mitochondrial inner membrane where the CYP11A1/P450scc enzyme complex converts the sterol to the first steroid. Earlier studies have shown that StAR is active while pausing on the cytosolic face of the outer mitochondrial membrane while subsequent import of the protein into the matrix terminates the cholesterol mobilization activity. Consequently, during repeated activity cycles, high level of post-active StAR accumulates in the mitochondrial matrix. To prevent functional damage due to such protein overload effect, StAR is degraded by a sequence of three to four ATP-dependent proteases of the mitochondria protein quality control system, including LON and the m-AAA membranous proteases AFG3L2 and SPG7/paraplegin. Furthermore, StAR expression in both peri-ovulatory ovarian cells, or under ectopic expression in cell line models, results in up to 3-fold enrichment of the mitochondrial proteases and their transcripts. We named this novel form of mitochondrial stress as StAR overload response (SOR). To better understand the SOR mechanism at the transcriptional level we analyzed first the unexplored properties of the proximal promoter of the LON gene. Our findings suggest that the human nuclear respiratory factor 2 (NRF-2), also known as GA binding protein (GABP), is responsible for 88% of the proximal promoter activity, including the observed increase of transcription in the presence of StAR. Further studies are expected to reveal if common transcriptional determinants coordinate the SOR induced transcription of all the genes encoding the SOR proteases.
Collapse
Affiliation(s)
- Assaf Bahat
- Department of Biological Chemistry at the Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Shira Perlberg
- Department of Biological Chemistry at the Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Naomi Melamed-Book
- Bio-Imaging Unit at the Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Sara Isaac
- Department of Cell & Developmental Biology at the Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Amir Eden
- Department of Cell & Developmental Biology at the Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Ines Lauria
- CECAD Research Center, Institute for Genetics, University of Cologne, 50931 Cologne, Germany
| | - Thomas Langer
- CECAD Research Center, Institute for Genetics, University of Cologne, 50931 Cologne, Germany
| | - Joseph Orly
- Department of Biological Chemistry at the Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| |
Collapse
|
12
|
Castillo AF, Orlando U, Helfenberger KE, Poderoso C, Podesta EJ. The role of mitochondrial fusion and StAR phosphorylation in the regulation of StAR activity and steroidogenesis. Mol Cell Endocrinol 2015; 408:73-9. [PMID: 25540920 DOI: 10.1016/j.mce.2014.12.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 12/12/2014] [Accepted: 12/13/2014] [Indexed: 12/16/2022]
Abstract
The steroidogenic acute regulatory (StAR) protein regulates the rate-limiting step in steroidogenesis, i.e. the delivery of cholesterol from the outer (OMM) to the inner (IMM) mitochondrial membrane. StAR is a 37-kDa protein with an N-terminal mitochondrial targeting sequence that is cleaved off during mitochondrial import to yield 30-kDa intramitochondrial StAR. StAR acts exclusively on the OMM and its activity is proportional to how long it remains on the OMM. However, the precise fashion and the molecular mechanism in which StAR remains on the OMM have not been elucidated yet. In this work we will discuss the role of mitochondrial fusion and StAR phosphorylation by the extracellular signal-regulated kinases 1/2 (ERK1/2) as part of the mechanism that regulates StAR retention on the OMM and activity.
Collapse
Affiliation(s)
- Ana F Castillo
- Biomedical Research Institute, INBIOMED, Department of Biochemistry, School of Medicine University of Buenos Aires, Ciudad Autónoma de Buenos Aires (CABA), C1121ABG, Argentina
| | - Ulises Orlando
- Biomedical Research Institute, INBIOMED, Department of Biochemistry, School of Medicine University of Buenos Aires, Ciudad Autónoma de Buenos Aires (CABA), C1121ABG, Argentina
| | - Katia E Helfenberger
- Biomedical Research Institute, INBIOMED, Department of Biochemistry, School of Medicine University of Buenos Aires, Ciudad Autónoma de Buenos Aires (CABA), C1121ABG, Argentina
| | - Cecilia Poderoso
- Biomedical Research Institute, INBIOMED, Department of Biochemistry, School of Medicine University of Buenos Aires, Ciudad Autónoma de Buenos Aires (CABA), C1121ABG, Argentina
| | - Ernesto J Podesta
- Biomedical Research Institute, INBIOMED, Department of Biochemistry, School of Medicine University of Buenos Aires, Ciudad Autónoma de Buenos Aires (CABA), C1121ABG, Argentina.
| |
Collapse
|
13
|
Duarte A, Castillo AF, Podestá EJ, Poderoso C. Mitochondrial fusion and ERK activity regulate steroidogenic acute regulatory protein localization in mitochondria. PLoS One 2014; 9:e100387. [PMID: 24945345 PMCID: PMC4063759 DOI: 10.1371/journal.pone.0100387] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 05/27/2014] [Indexed: 11/21/2022] Open
Abstract
The rate-limiting step in the biosynthesis of steroid hormones, known as the transfer of cholesterol from the outer to the inner mitochondrial membrane, is facilitated by StAR, the Steroidogenic Acute Regulatory protein. We have described that mitochondrial ERK1/2 phosphorylates StAR and that mitochondrial fusion, through the up-regulation of a fusion protein Mitofusin 2, is essential during steroidogenesis. Here, we demonstrate that mitochondrial StAR together with mitochondrial active ERK and PKA are necessary for maximal steroid production. Phosphorylation of StAR by ERK is required for the maintenance of this protein in mitochondria, observed by means of over-expression of a StAR variant lacking the ERK phosphorylation residue. Mitochondrial fusion regulates StAR levels in mitochondria after hormone stimulation. In this study, Mitofusin 2 knockdown and mitochondrial fusion inhibition in MA-10 Leydig cells diminished StAR mRNA levels and concomitantly mitochondrial StAR protein. Together our results unveil the requirement of mitochondrial fusion in the regulation of the localization and mRNA abundance of StAR. We here establish the relevance of mitochondrial phosphorylation events in the correct localization of this key protein to exert its action in specialized cells. These discoveries highlight the importance of mitochondrial fusion and ERK phosphorylation in cholesterol transport by means of directing StAR to the outer mitochondrial membrane to achieve a large number of steroid molecules per unit of StAR.
Collapse
Affiliation(s)
- Alejandra Duarte
- Institute of Biomedical Investigations (INBIOMED, UBA-CONICET), Department of Biochemistry, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Ana Fernanda Castillo
- Institute of Biomedical Investigations (INBIOMED, UBA-CONICET), Department of Biochemistry, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Ernesto J. Podestá
- Institute of Biomedical Investigations (INBIOMED, UBA-CONICET), Department of Biochemistry, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
| | - Cecilia Poderoso
- Institute of Biomedical Investigations (INBIOMED, UBA-CONICET), Department of Biochemistry, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
- * E-mail:
| |
Collapse
|
14
|
Issop L, Rone MB, Papadopoulos V. Organelle plasticity and interactions in cholesterol transport and steroid biosynthesis. Mol Cell Endocrinol 2013; 371:34-46. [PMID: 23246788 DOI: 10.1016/j.mce.2012.12.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/04/2012] [Accepted: 12/04/2012] [Indexed: 12/20/2022]
Abstract
Steroid biosynthesis is a multi-step process controlled by pituitary hormones, which, via cAMP-dependent signaling pathways, drive tissue-specific steroid formation. Steroidogenesis begins with the transport of the substrate, cholesterol, from intracellular stores into the inner mitochondrial membrane, where the steroidogenic enzyme CYP11A1 converts cholesterol to pregnenolone. This process is accelerated by hormones and involves a number of proteins and protein-protein interactions. Indeed, cholesterol, stored in lipid droplets and membranes, is transferred through a hormone-induced complex of proteins derived from the cytosol, mitochondria, and other organelles termed the transduceosome to the outer mitochondrial membrane. From there, cholesterol reaches CYP11A1 through outer/inner membrane contact sites. Thus, cholesterol transfer is likely achieved through a hormone-dependent reorganization of organelles and protein distribution and interactions. The findings reviewed herein suggest the presence of a hormone-dependent organelle communication network mediated by protein-protein interactions and inter-organelle trafficking, resulting in the efficient and timely delivery of cholesterol into mitochondria for steroid synthesis.
Collapse
Affiliation(s)
- Leeyah Issop
- Research Institute of the McGill University Health Centre, Department of Medicine, McGill University, Montreal, Quebec, Canada H3G 1A4
| | | | | |
Collapse
|
15
|
Przystal JM, Umukoro E, Stoneham CA, Yata T, O'Neill K, Syed N, Hajitou A. Proteasome inhibition in cancer is associated with enhanced tumor targeting by the adeno-associated virus/phage. Mol Oncol 2013; 7:55-66. [PMID: 22951279 PMCID: PMC3553581 DOI: 10.1016/j.molonc.2012.08.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 07/31/2012] [Accepted: 08/01/2012] [Indexed: 12/18/2022] Open
Abstract
Bacteriophage (phage), which are viruses that infect bacteria only, have shown promise as vehicles for targeted cancer gene therapy, albeit with poor efficiency. Recently, we generated an improved version of phage vectors by incorporating cis genetic elements of adeno-associated virus (AAV). This novel AAV/phage hybrid (AAVP) efficiently delivered systemically administered therapeutic genes to various tumor targets by displaying an integrin tumor-targeting ligand on the phage capsid. However, inherent limitations in bacteriophage mean that these AAVP vectors still need to be improved. One of the limitations of AAVP in mammalian cells may be its susceptibility to proteasomal degradation. The proteasome is upregulated in cancer and it is known that it constitutes a barrier to gene delivery by certain eukaryotic viruses. We report here that inhibition of proteasome improved targeted reporter gene delivery by AAVP in cancer cells in vitro and in tumors in vivo after intravenous vector administration to tumor-bearing mice. We also show enhanced targeted tumor cell killing by AAVP upon proteasome inhibition. The AAVP particles persisted significantly in cancer cells in vitro and in tumors in vivo after systemic administration, and accumulated polyubiquitinated coat proteins. Our results suggest that the proteasome is indeed a barrier to tumor targeting by AAVP and indicate that a combination of proteasome-inhibiting drugs and AAVP should be considered for clinical anticancer therapy.
Collapse
Affiliation(s)
- Justyna M. Przystal
- Division of Brain Sciences, Hammersmith Hospital Campus, Department of Medicine, Imperial College London, Burlington Danes Building, 160 Du Cane Road, London W12 0NN, United Kingdom
| | - Eloho Umukoro
- Division of Brain Sciences, Hammersmith Hospital Campus, Department of Medicine, Imperial College London, Burlington Danes Building, 160 Du Cane Road, London W12 0NN, United Kingdom
| | - Charlotte A. Stoneham
- Division of Brain Sciences, Hammersmith Hospital Campus, Department of Medicine, Imperial College London, Burlington Danes Building, 160 Du Cane Road, London W12 0NN, United Kingdom
| | - Teerapong Yata
- Division of Brain Sciences, Hammersmith Hospital Campus, Department of Medicine, Imperial College London, Burlington Danes Building, 160 Du Cane Road, London W12 0NN, United Kingdom
| | - Kevin O'Neill
- Division of Brain Sciences, Charing Cross Campus, Department of Medicine, Imperial College London, London, United Kingdom
| | - Nelofer Syed
- Division of Brain Sciences, Charing Cross Campus, Department of Medicine, Imperial College London, London, United Kingdom
| | - Amin Hajitou
- Division of Brain Sciences, Hammersmith Hospital Campus, Department of Medicine, Imperial College London, Burlington Danes Building, 160 Du Cane Road, London W12 0NN, United Kingdom
| |
Collapse
|
16
|
Bahat A, Perlberg S, Melamed-Book N, Lauria I, Langer T, Orly J. StAR enhances transcription of genes encoding the mitochondrial proteases involved in its own degradation. Mol Endocrinol 2013; 28:208-24. [PMID: 24422629 DOI: 10.1210/me.2013-1275] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Steroidogenic acute regulatory protein (StAR) is essential for steroid hormone synthesis in the adrenal cortex and the gonads. StAR activity facilitates the supply of cholesterol substrate into the inner mitochondrial membranes where conversion of the sterol to a steroid is catalyzed. Mitochondrial import terminates the cholesterol mobilization activity of StAR and leads to mounting accumulation of StAR in the mitochondrial matrix. Our studies suggest that to prevent mitochondrial impairment, StAR proteolysis is executed by at least 2 mitochondrial proteases, ie, the matrix LON protease and the inner membrane complexes of the metalloproteases AFG3L2 and AFG3L2:SPG7/paraplegin. Gonadotropin administration to prepubertal rats stimulated ovarian follicular development associated with increased expression of the mitochondrial protein quality control system. In addition, enrichment of LON and AFG3L2 is evident in StAR-expressing ovarian cells examined by confocal microscopy. Furthermore, reporter studies of the protease promoters examined in the heterologous cell model suggest that StAR expression stimulates up to a 3.5-fold increase in the protease gene transcription. Such effects are StAR-specific, are independent of StAR activity, and failed to occur upon expression of StAR mutants that do not enter the matrix. Taken together, the results of this study suggest the presence of a novel regulatory loop, whereby acute accumulation of an apparent nuisance protein in the matrix provokes a mitochondria to nucleus signaling that, in turn, activates selected transcription of genes encoding the enrichment of mitochondrial proteases relevant for enhanced clearance of StAR.
Collapse
Affiliation(s)
- Assaf Bahat
- Department of Biological Chemistry (A.B., S.P., J.O.) and Bio-Imaging Unit (N.M.-B.), The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; and Institute for Genetics (I.L., T.L.), Center for Molecular Medicine, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, 50931 Cologne, Germany
| | | | | | | | | | | |
Collapse
|
17
|
Scharwey M, Tatsuta T, Langer T. Mitochondrial lipid transport at a glance. J Cell Sci 2013; 126:5317-23. [DOI: 10.1242/jcs.134130] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Lipids are the building blocks of cellular membranes and are synthesized at distinct parts of the cell. A precise control of lipid synthesis and distribution is crucial for cell function and survival. The endoplasmic reticulum (ER) is the major lipid-synthesizing organelle. However, a subset of lipids is synthesized within mitochondria, and this aspect has become a focus of recent lipid research. Mitochondria form a dynamic membrane network that is reshaped by fusion and fission events. Their functionality therefore depends on a continuous lipid supply from the ER and the distribution of lipids between both mitochondrial membranes. The mechanisms of mitochondrial lipid trafficking are only now emerging and appear to involve membrane contact sites and lipid transfer proteins. In this Cell Science at a Glance article, we will discuss recent discoveries in the field of mitochondrial lipid trafficking that build on long-standing observations and shed new light on the shuttling of membrane lipids between mitochondria and other organelles.
Collapse
|
18
|
Anand R, Langer T, Baker MJ. Proteolytic control of mitochondrial function and morphogenesis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:195-204. [PMID: 22749882 DOI: 10.1016/j.bbamcr.2012.06.025] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 06/08/2012] [Accepted: 06/15/2012] [Indexed: 12/18/2022]
Abstract
Mitochondrial proteostasis depends on a hierarchical system of tightly controlled quality surveillance mechanisms. Proteases within mitochondria take center stage in this network. They eliminate misfolded and damaged proteins and ensure the biogenesis and morphogenesis of mitochondria by processing or degrading short-lived regulatory proteins. Mitochondrial gene expression, the mitochondrial phospholipid metabolism and the fusion of mitochondrial membranes are under proteolytic control. Furthermore, in response to stress and mitochondrial dysfunction, proteolysis inhibits fusion and facilitates mitophagy and apoptosis. Defining these versatile activities of mitochondrial proteases will be pivotal for understanding the pathogenesis of various neurodegenerative disorders associated with defective mitochondria-associated proteolysis. This article is part of a Special Issue entitled: Mitochondrial dynamics and physiology.
Collapse
|
19
|
Nagyova E, Scsukova S, Nemcova L, Mlynarcikova A, Yi YJ, Sutovsky M, Sutovsky P. Inhibition of proteasomal proteolysis affects expression of extracellular matrix components and steroidogenesis in porcine oocyte-cumulus complexes. Domest Anim Endocrinol 2012; 42:50-62. [PMID: 22032857 DOI: 10.1016/j.domaniend.2011.09.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 09/07/2011] [Accepted: 09/10/2011] [Indexed: 12/25/2022]
Abstract
Porcine oocyte-cumulus complexes (OCCs) form an expanded cumulus extracellular matrix (ECM) in response to gonadotropins during meiotic maturation. Essential components of ECM are hyaluronan (HA), tumor necrosis factor α-induced protein 6 (TNFAIP6) and heavy chains (HC) of interalpha-trypsin inhibitor. To form expanded cumulus ECM, intermediate complexes (TNFAIP6-HC) must bind to HA to allow HC transfer onto HA. Protein turnover by the ubiquitin-proteasome pathway is poorly characterized in this process. It is known that the specific proteasomal inhibitor MG132 prevents cumulus expansion and formation of ECM. To determine whether inhibition of proteasomal proteolysis with MG132 affects cumulus cell steroidogenesis and expression of the cumulus expansion-related components (hyaluronan synthase type 2, HAS2, TNFAIP6) we cultured porcine OCCs and granulosa cells (GCs) in a medium supplemented with FSH/LH. Methods performed included real-time reverse transcription PCR, immunofluorescence and RIAs. The expression of TNFAIP6 and HAS2 transcripts increased significantly after the stimulation of OCCs and GCs with FSH/LH. In contrast, treatment with MG132 reduced the expression of TNFAIP6 and HAS2. Hyaluronan was detected with biotinylated HA-binding proteins within FSH/LH-stimulated expanded OCCs but not in those treated with MG132. Progesterone production, although increased almost three times after OCCs stimulation with FSH/LH, was significantly suppressed by MG132. The FSH/LH-stimulated a 40-fold increase in progesterone secretion by GCs was inhibited in the presence of MG132. In conclusion, MG132 affects progesterone secretion and expression of cumulus expansion-related components by cumulus and GCs, suggesting the requirement of ubiquitin-proteasome pathway-regulated protein turnover for formation of ECM during cumulus expansion in the preovulatory period in the pig.
Collapse
Affiliation(s)
- E Nagyova
- Academy of Sciences of the Czech Republic, Institute of Animal Physiology and Genetics, 27721 Libechov, Czech Republic.
| | | | | | | | | | | | | |
Collapse
|
20
|
Crystal structure of Lon protease: molecular architecture of gated entry to a sequestered degradation chamber. EMBO J 2010; 29:3520-30. [PMID: 20834233 DOI: 10.1038/emboj.2010.226] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 08/19/2010] [Indexed: 11/08/2022] Open
Abstract
Lon proteases are distributed in all kingdoms of life and are required for survival of cells under stress. Lon is a tandem fusion of an AAA+ molecular chaperone and a protease with a serine-lysine catalytic dyad. We report the 2.0-Å resolution crystal structure of Thermococcus onnurineus NA1 Lon (TonLon). The structure is a three-tiered hexagonal cylinder with a large sequestered chamber accessible through an axial channel. Conserved loops extending from the AAA+ domain combine with an insertion domain containing the membrane anchor to form an apical domain that serves as a gate governing substrate access to an internal unfolding and degradation chamber. Alternating AAA+ domains are in tight- and weak-binding nucleotide states with different domain orientations and intersubunit contacts, reflecting intramolecular dynamics during ATP-driven protein unfolding and translocation. The bowl-shaped proteolytic chamber is contiguous with the chaperone chamber allowing internalized proteins direct access to the proteolytic sites without further gating restrictions.
Collapse
|
21
|
A mitochondrial kinase complex is essential to mediate an ERK1/2-dependent phosphorylation of a key regulatory protein in steroid biosynthesis. PLoS One 2008; 3:e1443. [PMID: 18197253 PMCID: PMC2175533 DOI: 10.1371/journal.pone.0001443] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2007] [Accepted: 12/13/2007] [Indexed: 12/03/2022] Open
Abstract
ERK1/2 is known to be involved in hormone-stimulated steroid synthesis, but its exact roles and the underlying mechanisms remain elusive. Both ERK1/2 phosphorylation and steroidogenesis may be triggered by cAMP/cAMP-dependent protein kinase (PKA)-dependent and-independent mechanisms; however, ERK1/2 activation by cAMP results in a maximal steroidogenic rate, whereas canonical activation by epidermal growth factor (EGF) does not. We demonstrate herein by Western blot analysis and confocal studies that temporal mitochondrial ERK1/2 activation is obligatory for PKA-mediated steroidogenesis in the Leydig-transformed MA-10 cell line. PKA activity leads to the phosphorylation of a constitutive mitochondrial MEK1/2 pool with a lower effect in cytosolic MEKs, while EGF allows predominant cytosolic MEK activation and nuclear pERK1/2 localization. These results would explain why PKA favors a more durable ERK1/2 activation in mitochondria than does EGF. By means of ex vivo experiments, we showed that mitochondrial maximal steroidogenesis occurred as a result of the mutual action of steroidogenic acute regulatory (StAR) protein –a key regulatory component in steroid biosynthesis-, active ERK1/2 and PKA. Our results indicate that there is an interaction between mitochondrial StAR and ERK1/2, involving a D domain with sequential basic-hydrophobic motifs similar to ERK substrates. As a result of this binding and only in the presence of cholesterol, ERK1/2 phosphorylates StAR at Ser232. Directed mutagenesis of Ser232 to a non-phosphorylable amino acid such as Ala (StAR S232A) inhibited in vitro StAR phosphorylation by active ERK1/2. Transient transfection of MA-10 cells with StAR S232A markedly reduced the yield of progesterone production. In summary, here we show that StAR is a novel substrate of ERK1/2, and that mitochondrial ERK1/2 is part of a multimeric protein kinase complex that regulates cholesterol transport. The role of MAPKs in mitochondrial function is underlined.
Collapse
|
22
|
Dyson MT, Jones JK, Kowalewski MP, Manna PR, Alonso M, Gottesman ME, Stocco DM. Mitochondrial A-kinase anchoring protein 121 binds type II protein kinase A and enhances steroidogenic acute regulatory protein-mediated steroidogenesis in MA-10 mouse leydig tumor cells. Biol Reprod 2007; 78:267-77. [PMID: 17989356 DOI: 10.1095/biolreprod.107.064238] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The expression of the steroidogenic acute regulatory protein (STAR) is regulated by PKA in response to trophic hormone stimulation through the second messenger cAMP. However, in steroidogenic cells, the concentrations of hormone necessary to maximally induce cAMP synthesis and PKA activity are often significantly higher than is necessary to achieve maximum steroidogenesis. One general mechanism believed to make PKA signaling more effective is the use of A-kinase anchoring proteins (AKAPs) to recruit PKA to discrete subcellular compartments, which coordinates and focuses PKA action with respect to its substrates. The characterization of AKAP121 has suggested that it enhances the posttranscriptional regulation of STAR by recruiting both Star mRNA and PKA to the mitochondria, thereby permitting more effective translation and phosphorylation of STAR. Testing this hypothesis revealed that cAMP-induced STAR expression and steroidogenesis closely followed AKAP121 abundance when this AKAP was silenced or overexpressed in MA-10 cells but that these changes were effected posttranscriptionally. Moreover, silencing AKAP121 expression in these cells specifically altered the localization of type II PKA regulatory subunit alpha (PKAR2A) at the mitochondria but did not affect its relative expression within the cell. Affinity purification experiments showed that PKAR2A preferentially associated with AKAP121, and cAMP analogs that activate type II PKA induced STAR phosphorylation more efficiently than analogs stimulating type I PKA. This suggests that AKAP121 and PKAR2A serve to enhance steroidogenesis by directing the synthesis and activation of STAR at the mitochondria in response to cAMP.
Collapse
Affiliation(s)
- Matthew T Dyson
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
| | | | | | | | | | | | | |
Collapse
|
23
|
Karri S, Dertien JS, Stocco DM, Syapin PJ. Steroidogenic acute regulatory protein expression and pregnenolone synthesis in rat astrocyte cultures. J Neuroendocrinol 2007; 19:860-9. [PMID: 17927664 DOI: 10.1111/j.1365-2826.2007.01600.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Neurosteroids are steroids synthesised by brain cells. The molecular mechanism of neurosteroidogenesis from cholesterol has not yet been revealed. We studied the potential role of the steroidogenic acute regulatory (StAR) protein in neurosterodogenesis by using rat brain astrocytes. The novelty of the study is that regulation of StAR is described in primary cultures from embryonic mesencephalon and cerebellum regions of the brain. Dibutyryl cyclic AMP (dbcAMP) treatment increased StAR protein expression in astrocyte cultures. This was observed in immunoblots of mitochondrial fractions and by immunocytochemistry. Dual-labelling showed that the cyclic AMP-induced increase in StAR immunofluorescence was localised to mitochondria. In addition, mitochondrial cytochrome P450-side chain cleavage enzyme was demonstrated with a specific antibody, indicating the potential for pregnenolone production in these cells. Radioimmunoassay on ether-extracted conditioned media of control and dbcAMP treated cells demonstrated pregnenolone production by mesencephalic and cerebellar astrocyte cultures. Furthermore, 24-h pregnenolone levels, in the presence of inhibitors of further pregnenolone metabolism, were significantly increased by dbcAMP exposure. A murine StAR promoter-luciferase fusion plasmid was activated by dbcAMP in transiently transfected mesencephalic and cerebellar astrocytes. These novel results indicate that cyclic AMP signalling can regulate StAR expression and pregnenolone production in brain astrocytes, and provide additional insight into the role of StAR in neurosteroidogenesis.
Collapse
Affiliation(s)
- S Karri
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430-0001, USA.
| | | | | | | |
Collapse
|
24
|
Duarte A, Castillo AF, Castilla R, Maloberti P, Paz C, Podestá EJ, Cornejo Maciel F. An arachidonic acid generation/export system involved in the regulation of cholesterol transport in mitochondria of steroidogenic cells. FEBS Lett 2007; 581:4023-8. [PMID: 17673208 DOI: 10.1016/j.febslet.2007.07.040] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Accepted: 07/18/2007] [Indexed: 02/02/2023]
Abstract
Recent studies demonstrated the importance of the mitochondrial ATP in the regulation of a novel long-chain fatty acid generation/export system in mitochondria of diabetic rat heart. In steroidogenic systems, mitochondrial ATP and intramitochondrial arachidonic acid (AA) generation are important for steroidogenesis. Here, we report that mitochondrial ATP is necessary for the generation and export of AA, steroid production and steroidogenic acute regulatory protein induction supported by cyclic 3'-5'-adenosine monophosphate in steroidogenic cells. These results demonstrate that ATP depletion affects AA export and provide new evidence of the existence of the fatty acid generation and export system involved in mitochondrial cholesterol transport.
Collapse
Affiliation(s)
- Alejandra Duarte
- Department of Biochemistry, School of Medicine, University of Buenos Aires, Paraguay 2155 5th, (C1121ABG) Buenos Aires, Argentina
| | | | | | | | | | | | | |
Collapse
|
25
|
Granot Z, Kobiler O, Melamed-Book N, Eimerl S, Bahat A, Lu B, Braun S, Maurizi MR, Suzuki CK, Oppenheim AB, Orly J. Turnover of mitochondrial steroidogenic acute regulatory (StAR) protein by Lon protease: the unexpected effect of proteasome inhibitors. Mol Endocrinol 2007; 21:2164-77. [PMID: 17579211 DOI: 10.1210/me.2005-0458] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Steroidogenic acute regulatory protein (StAR) is a vital mitochondrial protein promoting transfer of cholesterol into steroid making mitochondria in specialized cells of the adrenal cortex and gonads. Our previous work has demonstrated that StAR is rapidly degraded upon import into the mitochondrial matrix. To identify the protease(s) responsible for this rapid turnover, murine StAR was expressed in wild-type Escherichia coli or in mutant strains lacking one of the four ATP-dependent proteolytic systems, three of which are conserved in mammalian mitochondria-ClpP, FtsH, and Lon. StAR was rapidly degraded in wild-type bacteria and stabilized only in lon (-)mutants; in such cells, StAR turnover was fully restored upon coexpression of human mitochondrial Lon. In mammalian cells, the rate of StAR turnover was proportional to the cell content of Lon protease after expression of a Lon-targeted small interfering RNA, or overexpression of the protein. In vitro assays using purified proteins showed that Lon-mediated degradation of StAR was ATP-dependent and blocked by the proteasome inhibitors MG132 (IC(50) = 20 microm) and clasto-lactacystin beta-lactone (cLbetaL, IC(50) = 3 microm); by contrast, epoxomicin, representing a different class of proteasome inhibitors, had no effect. Such inhibition is consistent with results in cultured rat ovarian granulosa cells demonstrating that degradation of StAR in the mitochondrial matrix is blocked by MG132 and cLbetaL but not by epoxomicin. Both inhibitors also blocked Lon-mediated cleavage of the model substrate fluorescein isothiocyanate-casein. Taken together, our former studies and the present results suggest that Lon is the primary ATP-dependent protease responsible for StAR turnover in mitochondria of steroidogenic cells.
Collapse
Affiliation(s)
- Zvi Granot
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|