The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Vassilios Papadopoulos - One of the best experts on this subject based on the ideXlab platform.
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identification of sec23ip part of 14 3 3γ protein network as a regulator of acute Steroidogenesis in ma 10 leydig cells
Endocrinology, 2020Co-Authors: Yasaman Aghazadeh, Josip Blonder, Vassilios Papadopoulos, Sathvika Venugopal, Daniel B Martinezarguelles, Annie BoisvertAbstract:Testosterone production occurs in the Leydig cells of the testes and is essential for virilization, development, reproduction, and quality of life. Although the steroidogenic proteins involved in cholesterol conversion to testosterone (T) are well characterized, the causes of reduced T during fetal, neonatal, and adult life remain uncertain. It is well established that normal cellular function is achieved through fine-tuning of multiple rather than single protein networks. Our objective was to use mass spectrometry (MS)-based proteomics to identify which cellular pathways, other than the steroidogenic machinery, influence testosterone production in MA-10 mouse tumor Leydig cells. The 14-3-3 family of scaffolds mediate protein-protein interactions facilitating the crosstalk between protein networks. We previously showed that in MA-10 cells, 14-3-3gamma is a critical regulator of Steroidogenesis. Therefore, identifying proteins that interact with 14-3-3gamma during Steroidogenesis could provide clues into the other networks involved. Using liquid chromatography (LC)-MS, we identified 688 proteins that interact with 14-3-3gamma and thus potentially impact MA-10 cell Steroidogenesis. The identified proteins belong to multiple protein networks, including endoplasmic reticulum-Golgi cargo sorting and vesicle biogenesis, micro ribonucleic acid-induced gene silencing, inflammation, and vesicle trafficking, to name a few. We found that silencing one of the candidates, Sec23ip, a protein known to be involved in vesicle trafficking, resulted in decreased Steroidogenesis. We further showed that in Sec23ip-silenced MA-10 cells, cholesterol mobilization from the cytoplasmic membrane to mitochondria is impaired. Taken together these data suggest that Sec23ip is involved in cholesterol trafficking to supply cholesterol for acute Steroidogenesis through its interactions with 14-3-3gamma.
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translocator protein mediated pharmacology of cholesterol transport and Steroidogenesis
Molecular and Cellular Endocrinology, 2015Co-Authors: Vassilios Papadopoulos, Barry R. Zirkin, Yasaman Aghazadeh, Andrew Midzak, Enrico CampioliAbstract:Steroidogenesis begins with cholesterol transfer into mitochondria through the transduceosome, a complex composed of cytosolic proteins that include Steroidogenesis acute regulatory protein (STAR), 14-3-3 adaptor proteins, and the outer mitochondrial membrane proteins Translocator Protein (TSPO) and Voltage-Dependent Anion Channel (VDAC). TSPO is a drug- and cholesterol-binding protein found at particularly high levels in steroid synthesizing cells. Its aberrant expression has been linked to cancer, neurodegeneration, neuropsychiatric disorders and primary hypogonadism. Brain steroids serve as local regulators of neural development and excitability. Reduced levels of these steroids have been linked to depression, anxiety and neurodegeneration. Reduced serum testosterone is common among subfertile young men and aging men, and is associated with depression, metabolic syndrome and reduced sexual function. Although testosterone-replacement therapy is available, there are undesired side-effects. TSPO drug ligands have been proposed as therapeutic agents to regulate steroid levels in the brain and testis.
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mitochondria associated membrane formation in hormone stimulated leydig cell Steroidogenesis role of atad3
Endocrinology, 2015Co-Authors: Malena B Rone, Leeyah Issop, Kaustuv Basu, Vassilios PapadopoulosAbstract:Leydig cell Steroidogenesis is a multistep process that takes place in the mitochondria and endoplasmic reticulum (ER). The physical association between these 2 organelles could facilitate both Steroidogenesis substrate availability and mitochondrial product passage to steroidogenic enzymes in the ER, thus regulating the rate of steroid formation. Confocal microscopy, using antisera against organelle-specific antigens, and electron microscopy studies demonstrated that there is an increase in the number of mitochondria-ER contact sites in response to hormone treatment in MA-10 mouse tumor Leydig cells. Electron tomography and 3-dimensional reconstruction allowed for the visualization of mitochondria-associated membranes (MAMs). MAMs were isolated and found to contain the 67-kDa long isoform of the adenosine triphosphatase (ATPase) family, AAA domain-containing protein 3 (ATAD3). The 67-kDa ATAD3 is anchored in the inner mitochondrial membrane and is enriched in outer-inner mitochondrial membrane contact si...
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protein modifications regulate the role of 14 3 3γ adaptor protein in camp induced Steroidogenesis in ma 10 leydig cells
Journal of Biological Chemistry, 2014Co-Authors: Yasaman Aghazadeh, Xiaoying Ye, Josip Blonder, Vassilios PapadopoulosAbstract:Abstract The 14-3-3 protein family comprises adaptors and scaffolds that regulate intracellular signaling pathways. The 14-3-3γ isoform is a negative regulator of Steroidogenesis that is hormonally induced and transiently functions at the initiation of Steroidogenesis by delaying maximal Steroidogenesis in MA-10 mouse tumor Leydig cells. Treatment of MA-10 cells with the cAMP analog 8-Br-cAMP, which stimulates Steroidogenesis, triggers the interaction of 14-3-3γ with the steroidogenic acute regulatory protein (STAR) in the cytosol, which limits STAR activity to basal levels. Over time, this interaction ceases, allowing for a 2-fold induction in STAR activity and maximal increase in the rate of steroid formation. The 14-3-3γ-STAR pattern of interaction was found to be opposite that of the 14-3-3γ homodimerization pattern. Phosphorylation and acetylation of 14-3-3γ showed similar patterns to homodimerization and STAR binding, respectively. 14-3-3γ S58 phosphorylation and 14-3-3γ K49 acetylation were blocked using trans-activator of HIV transcription factor 1 (TAT) peptides coupled to 14-3-3γ sequences containing S58 or K49. Blocking either one of these modifications further induced 8-Br-cAMP-induced Steroidogenesis while reducing lipid storage, suggesting that the stored cholesterol is used for steroid formation. Taken together, these results indicate that S58 phosphorylation and K49 acetylation of 14-3-3γ occur in a coordinated time-dependent manner to regulate 14-3-3γ homodimerization. 14-3-3γ S58 phosphorylation is required for STAR interactions under control conditions, and 14-3-3γ K49 acetylation is important for the cAMP-dependent induction of these interactions.
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channel like functions of the 18 kda translocator protein tspo regulation of apoptosis and Steroidogenesis as part of the host defense response
Current Pharmaceutical Design, 2007Co-Authors: Leo Veenman, Vassilios Papadopoulos, Moshe GavishAbstract:Due to its channel-like properties, the peripheral-type benzodiazepine receptor (PBR) has been renamed the translocator protein (TSPO). In eukaryotes, the TSPO is primarily located in the outer mitochondrial membrane. In prokaryotes, it is found in the cell membrane. A broad spectrum of functions has been attributed to the TSPO, including various host defense responses, developmental processes, and mitochondrial functions. In the present review, we focus on the role of TSPO in immunological responses, apoptosis, and Steroidogenesis, to determine whether these functions may be governed by a common denominator including TSPO. At physiological concentrations (nM range), the TSPO specific ligands, PK 11195 and Ro5-4864, appear to be anti-apoptotic. Knockdown of TSPO by genetic manipulation, resulting a reduction by more than 50% in [3H]PK 11195 binding, was reported to show anti-apoptotic effects, suggesting a potential pro-apoptotic function of TSPO. However, a reduction of more than 70% of TSPO abundance was found to cause cell death, possibly due to impairment of other essential cell functions. The pro-apoptotic function of TSPO may involve the modulation of the channel formed by the mitochondrial voltage-dependent anion channel (VDAC) and the adenine nucleotide transporter (ANT) [i.e., the mitochondrial permeability transition pore (MPTP)]. The frequently reported pro-apoptotic effects of PK 11195 and Ro5-4864 may be due to sites with low-affinity binding for these specific TSPO ligands, and not directly related to VDAC and ANT. Also at concentrations in the nM range, PK 11195 and Ro5-4864 appear to stimulate Steroidogenesis. For this function TSPO by itself appears to suffice i.e. no involvement of VDAC and ANT. TSPO appears to operate as a translocator/channel to transfer cholesterol into mitochondria where it is converted to pregnenolone, a precursor of further Steroidogenesis. Apoptosis and steroids play important roles in various aspects of the host defense response. Thus, our review suggests that the involvement of TSPO and its ligands in such seemingly disparate biological functions as immunological responses, apoptosis, and Steroidogenesis may have a common denominator in the multidimensional role of TSPO in the host-defense response to disease and injury.
Yasaman Aghazadeh - One of the best experts on this subject based on the ideXlab platform.
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identification of sec23ip part of 14 3 3γ protein network as a regulator of acute Steroidogenesis in ma 10 leydig cells
Endocrinology, 2020Co-Authors: Yasaman Aghazadeh, Josip Blonder, Vassilios Papadopoulos, Sathvika Venugopal, Daniel B Martinezarguelles, Annie BoisvertAbstract:Testosterone production occurs in the Leydig cells of the testes and is essential for virilization, development, reproduction, and quality of life. Although the steroidogenic proteins involved in cholesterol conversion to testosterone (T) are well characterized, the causes of reduced T during fetal, neonatal, and adult life remain uncertain. It is well established that normal cellular function is achieved through fine-tuning of multiple rather than single protein networks. Our objective was to use mass spectrometry (MS)-based proteomics to identify which cellular pathways, other than the steroidogenic machinery, influence testosterone production in MA-10 mouse tumor Leydig cells. The 14-3-3 family of scaffolds mediate protein-protein interactions facilitating the crosstalk between protein networks. We previously showed that in MA-10 cells, 14-3-3gamma is a critical regulator of Steroidogenesis. Therefore, identifying proteins that interact with 14-3-3gamma during Steroidogenesis could provide clues into the other networks involved. Using liquid chromatography (LC)-MS, we identified 688 proteins that interact with 14-3-3gamma and thus potentially impact MA-10 cell Steroidogenesis. The identified proteins belong to multiple protein networks, including endoplasmic reticulum-Golgi cargo sorting and vesicle biogenesis, micro ribonucleic acid-induced gene silencing, inflammation, and vesicle trafficking, to name a few. We found that silencing one of the candidates, Sec23ip, a protein known to be involved in vesicle trafficking, resulted in decreased Steroidogenesis. We further showed that in Sec23ip-silenced MA-10 cells, cholesterol mobilization from the cytoplasmic membrane to mitochondria is impaired. Taken together these data suggest that Sec23ip is involved in cholesterol trafficking to supply cholesterol for acute Steroidogenesis through its interactions with 14-3-3gamma.
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translocator protein mediated pharmacology of cholesterol transport and Steroidogenesis
Molecular and Cellular Endocrinology, 2015Co-Authors: Vassilios Papadopoulos, Barry R. Zirkin, Yasaman Aghazadeh, Andrew Midzak, Enrico CampioliAbstract:Steroidogenesis begins with cholesterol transfer into mitochondria through the transduceosome, a complex composed of cytosolic proteins that include Steroidogenesis acute regulatory protein (STAR), 14-3-3 adaptor proteins, and the outer mitochondrial membrane proteins Translocator Protein (TSPO) and Voltage-Dependent Anion Channel (VDAC). TSPO is a drug- and cholesterol-binding protein found at particularly high levels in steroid synthesizing cells. Its aberrant expression has been linked to cancer, neurodegeneration, neuropsychiatric disorders and primary hypogonadism. Brain steroids serve as local regulators of neural development and excitability. Reduced levels of these steroids have been linked to depression, anxiety and neurodegeneration. Reduced serum testosterone is common among subfertile young men and aging men, and is associated with depression, metabolic syndrome and reduced sexual function. Although testosterone-replacement therapy is available, there are undesired side-effects. TSPO drug ligands have been proposed as therapeutic agents to regulate steroid levels in the brain and testis.
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protein modifications regulate the role of 14 3 3γ adaptor protein in camp induced Steroidogenesis in ma 10 leydig cells
Journal of Biological Chemistry, 2014Co-Authors: Yasaman Aghazadeh, Xiaoying Ye, Josip Blonder, Vassilios PapadopoulosAbstract:Abstract The 14-3-3 protein family comprises adaptors and scaffolds that regulate intracellular signaling pathways. The 14-3-3γ isoform is a negative regulator of Steroidogenesis that is hormonally induced and transiently functions at the initiation of Steroidogenesis by delaying maximal Steroidogenesis in MA-10 mouse tumor Leydig cells. Treatment of MA-10 cells with the cAMP analog 8-Br-cAMP, which stimulates Steroidogenesis, triggers the interaction of 14-3-3γ with the steroidogenic acute regulatory protein (STAR) in the cytosol, which limits STAR activity to basal levels. Over time, this interaction ceases, allowing for a 2-fold induction in STAR activity and maximal increase in the rate of steroid formation. The 14-3-3γ-STAR pattern of interaction was found to be opposite that of the 14-3-3γ homodimerization pattern. Phosphorylation and acetylation of 14-3-3γ showed similar patterns to homodimerization and STAR binding, respectively. 14-3-3γ S58 phosphorylation and 14-3-3γ K49 acetylation were blocked using trans-activator of HIV transcription factor 1 (TAT) peptides coupled to 14-3-3γ sequences containing S58 or K49. Blocking either one of these modifications further induced 8-Br-cAMP-induced Steroidogenesis while reducing lipid storage, suggesting that the stored cholesterol is used for steroid formation. Taken together, these results indicate that S58 phosphorylation and K49 acetylation of 14-3-3γ occur in a coordinated time-dependent manner to regulate 14-3-3γ homodimerization. 14-3-3γ S58 phosphorylation is required for STAR interactions under control conditions, and 14-3-3γ K49 acetylation is important for the cAMP-dependent induction of these interactions.
Andrew Midzak - One of the best experts on this subject based on the ideXlab platform.
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translocator protein mediated pharmacology of cholesterol transport and Steroidogenesis
Molecular and Cellular Endocrinology, 2015Co-Authors: Vassilios Papadopoulos, Barry R. Zirkin, Yasaman Aghazadeh, Andrew Midzak, Enrico CampioliAbstract:Steroidogenesis begins with cholesterol transfer into mitochondria through the transduceosome, a complex composed of cytosolic proteins that include Steroidogenesis acute regulatory protein (STAR), 14-3-3 adaptor proteins, and the outer mitochondrial membrane proteins Translocator Protein (TSPO) and Voltage-Dependent Anion Channel (VDAC). TSPO is a drug- and cholesterol-binding protein found at particularly high levels in steroid synthesizing cells. Its aberrant expression has been linked to cancer, neurodegeneration, neuropsychiatric disorders and primary hypogonadism. Brain steroids serve as local regulators of neural development and excitability. Reduced levels of these steroids have been linked to depression, anxiety and neurodegeneration. Reduced serum testosterone is common among subfertile young men and aging men, and is associated with depression, metabolic syndrome and reduced sexual function. Although testosterone-replacement therapy is available, there are undesired side-effects. TSPO drug ligands have been proposed as therapeutic agents to regulate steroid levels in the brain and testis.
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Effect of myxothiazol on Leydig cell Steroidogenesis: inhibition of luteinizing hormone-mediated testosterone synthesis but stimulation of basal Steroidogenesis.
Endocrinology, 2007Co-Authors: Andrew Midzak, Barry R. Zirkin, Haolin ChenAbstract:Studies of MA-10 Leydig cells have shown that intact mitochondria with active respiration are essential for LH-induced Leydig cell Steroidogenesis. To further elucidate the role played by mitochondria in Steroidogenesis, we examined the effects of the perturbation of the mitochondrial electron transport chain with myxothiazol (MYX) on testosterone production by primary cultures of Brown Norway rat Leydig cells. Analysis of the steroidogenic pathway revealed that cAMP production and the activities of each of 3β-hydroxysteroid dehydrogenase, 17α-hydroxylase/C17–20 lyase, and 17β-hydroxysteroid dehydrogenase were inhibited by MYX and that LH-stimulated testosterone production was suppressed. In contrast to the inhibition of LH-stimulated testosterone production by MYX, the incubation of Leydig cells with MYX in the absence of LH stimulated testosterone production. Although testosterone production was increased, steroidogenic acute regulatory protein was decreased in response to MYX, not increased as could be...
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Effect of Myxothiazol on Leydig Cell Steroidogenesis: Inhibition of LH-Mediated Testosterone Synthesis But Stimulation of Basal Steroidogenesis*
2007Co-Authors: Andrew Midzak, Haolin Chen, Barry R. Zirkin, Hopkins BloombergAbstract:ABSTRACT Studies of MA-10 Leydig cells have shown that intact mitochondria with active respiration are essential for LH-induced Leydig cell Steroidogenesis. To further elucidate the role played by mitochondria in Steroidogenesis, we examined the effects of the perturbation of the mitochondrial electron transport chain with myxothiazol (MYX) on testosterone production by primary cultures of Brown Norway rat Leydig cells. Analysis of the steroidogenic pathway revealed that cAMP production and the activities of each of 3β-HSD, P450c17 and 17β-HSD were inhibited by MYX, and that LH-stimulated testosterone production was suppressed. In contrast to the inhibition of LH-stimulated testosterone production by MYX, the incubation of Leydig cells with MYX in the absence of LH stimulated testosterone production. Although testosterone production was increased, StAR protein was decreased in response to MYX, not increased as could be expected. Additional electron transport chain inhibitors had stimulatory effects on testosterone production that were similar to those of MYX, strongly suggesting that the effect of MYX on basal testosterone production is related to its effect on the mitochondrial electron transport chain. Finally, incubation of the cells with a combination of MYX and the calcium chelator BAPTA-AM suppressed MYX-mediated increased basal Steroidogenesis but had no effect on hydroxycholesterol-mediated Steroidogenesis. Taken together, these results indicate that inhibition of the mitochondrial electron transport chain can block LH-stimulated testosterone production through suppression of a number of steps of the steroidogenic pathway, but also stimulates basal testosterone production through a calcium-mediated mechanism.
Douglas M Stocco - One of the best experts on this subject based on the ideXlab platform.
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Current knowledge on the acute regulation of Steroidogenesis
Biology of Reproduction, 2018Co-Authors: Vimal Selvaraj, Douglas M Stocco, Barbara J. ClarkAbstract:How rapid induction of steroid hormone biosynthesis occurs in response to trophic hormone stimulation of steroidogenic cells has been a subject of intensive investigation for approximately six decades. A key observation made very early was that acute regulation of steroid biosynthesis required swift and timely synthesis of a new protein whose role appeared to be involved in the delivery of the substrate for all steroid hormones, cholesterol, from the outer to the inner mitochondrial membrane where the process of Steroidogenesis begins. It was quickly learned that this transfer of cholesterol to the inner mitochondrial membrane was the regulated and ratelimiting step in Steroidogenesis. Following this observation, the quest for this putative regulator protein(s) began in earnest in the late 1950s. This review provides a history of this quest, the candidate proteins that arose over the years and facts surrounding their rise or decline. Only two have persisted—translocator protein (TSPO) and the steroidogenic acute regulatory protein (StAR). We present a detailed summary of the work that has been published for each of these two proteins, the specific data that has appeared in support of their role in cholesterol transport and Steroidogenesis, and the ensuing observations that have arisen in recent years that have refuted the role of TSPO in this process. We believe that the only viable candidate that has been shown to be indispensable is the StAR protein. Lastly, we provide our view on what may be the most important questions concerning the acute regulation of Steroidogenesis that need to be asked in future.Summary SentenceThe acute regulation of Steroidogenesis in the adrenal and gonads is controlled by cholesterol transfer into the mitochondria and this review covers two decades of research that has demonstrated StAR is indispensable for this process.
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crucial role reported for tspo in viability and Steroidogenesis is a misconception commentary conditional steroidogenic cell targeted deletion of tspo unveils a crucial role in viability and hormone dependent steroid formation
Frontiers in Endocrinology, 2016Co-Authors: Vimal Selvaraj, Lan N Tu, Douglas M StoccoAbstract:Recent reports on Leydig cell-specific Tspo conditional knockout TspocΔ/Δ mice (1), viable global Tspo knockout (Tspo−/−) mice from two independent laboratories (2, 3), and clones of CRISPR/Cas9-mediated Tspo-deleted MA-10 Leydig cells (MA-10TspoΔ/Δ) (4) established that TSPO is not essential for steroid hormone biosynthesis or viability [reviewed in Ref. (5, 6)]. These reports refuted 25 years of dogma that described TSPO as a mitochondrial cholesterol transport protein, indispensable for Steroidogenesis. In response, the research group involved in most of the early studies linking TSPO and Steroidogenesis investigated Leydig cell-specific and adrenocortical cell-specific TspocΔ/Δ mice (7) and presented results that seem to repudiate the recent findings and revive the old model. In this commentary, we would like to point out that interpretations made in the manuscript by Fan et al. (7) are seriously flawed.
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pk11195 effect on Steroidogenesis is not mediated through the translocator protein tspo
Endocrinology, 2015Co-Authors: Lan N Tu, Amy H Zhao, Douglas M Stocco, Vimal SelvarajAbstract:Translocator protein (TSPO) is a mitochondrial outer membrane protein of unknown function with high physiological expression in steroidogenic cells. Using TSPO gene–deleted mice, we recently demonstrated that TSPO function is not essential for Steroidogenesis. The first link between TSPO and Steroidogenesis was established in studies showing modest increases in progesterone production by adrenocortical and Leydig tumor cell lines after treatment with PK11195. To reconcile discrepancies between physiological and pharmacological interpretations of TSPO function, we generated TSPO-knockout MA-10 mouse Leydig tumor cells (MA-10:TspoΔ/Δ) and examined their steroidogenic potential after exposure to either dibutyryl-cAMP or PK11195. Progesterone production in MA-10:TspoΔ/Δ after dibutyryl-cAMP was not different from control MA-10:Tspo+/+ cells, confirming that TSPO function is not essential for Steroidogenesis. Interestingly, when treated with increasing concentrations of PK11195, both control MA-10:Tspo+/+ cell...
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The Role of StAR in Leydig Cell Steroidogenesis
Contemporary Endocrinology, 2007Co-Authors: Douglas M StoccoAbstract:The steroidogenic acute regulatory (StAR) protein mediates the rate-limiting step in Steroidogenesis, the transfer of cholesterol from the outer mitochondrial membrane to the inner mitochondrial membrane, where it is cleaved to form pregnenlone. Its indispensable role in Steroidogenesis was demonstrated by showing that mutations in the StAR gene in humans cause the lipoid form of congenital adrenal hyperplasia, a potentially lethal disease resulting from an inability to synthesize steroids. Also, StAR-null mice have a phenotype that is identical to that seen in human mutations. The mechanism whereby StAR mediates the transfer of cholesterol to the inner mitochondrial membrane remains a mystery. This review will attempt to summarize what is currently known about the mechanism of action of StAR and argue that an understanding of the role played by StAR and other proteins in intramitochondrial cholesterol transfer constitutes the biggest challenge in understanding the acute regulation of Steroidogenesis.
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roundup inhibits Steroidogenesis by disrupting steroidogenic acute regulatory star protein expression
Environmental Health Perspectives, 2000Co-Authors: Lance P Walsh, Chad Mccormick, Clyde F Martin, Douglas M StoccoAbstract:Recent reports demonstrate that many currently used pesticides have the capacity to disrupt reproductive function in animals. Although this reproductive dysfunction is typically characterized by alterations in serum steroid hormone levels, disruptions in spermatogenesis, and loss of fertility, the mechanisms involved in pesticide-induced infertility remain unclear. Because testicular Leydig cells play a crucial role in male reproductive function by producing testosterone, we used the mouse MA-10 Leydig tumor cell line to study the molecular events involved in pesticide-induced alterations in steroid hormone biosynthesis. We previously showed that the organochlorine insecticide lindane and the organophosphate insecticide Dimethoate directly inhibit Steroidogenesis in Leydig cells by disrupting expression of the steroidogenic acute regulatory (StAR) protein. StAR protein mediates the rate-limiting and acutely regulated step in Steroidogenesis, the transfer of cholesterol from the outer to the inner mitochondrial membrane where the cytochrome P450 side chain cleavage (P450scc) enzyme initiates the synthesis of all steroid hormones. In the present study, we screened eight currently used pesticide formulations for their ability to inhibit Steroidogenesis, concentrating on their effects on StAR expression in MA-10 cells. In addition, we determined the effects of these compounds on the levels and activities of the P450scc enzyme (which converts cholesterol to pregnenolone) and the 3beta-hydroxysteroid dehydrogenase (3beta-HSD) enzyme (which converts pregnenolone to progesterone). Of the pesticides screened, only the pesticide Roundup inhibited dibutyryl [(Bu)(2)]cAMP-stimulated progesterone production in MA-10 cells without causing cellular toxicity. Roundup inhibited Steroidogenesis by disrupting StAR protein expression, further demonstrating the susceptibility of StAR to environmental pollutants.
Walter L Miller - One of the best experts on this subject based on the ideXlab platform.
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Steroidogenesis unanswered questions
Trends in Endocrinology and Metabolism, 2017Co-Authors: Walter L MillerAbstract:Until the mid-1980s studies of Steroidogenesis largely depended on identifying steroid structures and measuring steroid concentrations in body fluids. The molecular biology revolution radically revolutionized studies of Steroidogenesis with the cloning of known steroidogenic enzymes, by identifying novel factors, and delineating the genetic basis of known and newly discovered diseases. Unfortunately, this dramatic success has led many young research-oriented endocrinologists to regard Steroidogenesis as a ‘solved area'. However, many important and exciting questions remain, especially concerning the mechanisms of cholesterol delivery to the steroidogenic machinery, the biochemistry of androgen synthesis, the regulation and biological role of adrenarche, fetal adrenal development and involution, the roles of steroids made in ‘extraglandular' cells, and the search for genetic disorders. This review outlines some of these questions, but this list is necessarily incomplete.
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Regulation of Steroidogenesis
Cellular Endocrinology in Health and Disease, 2014Co-Authors: Andrew A. Bremer, Walter L MillerAbstract:Steroidogenesis involves the conversion of cholesterol to glucocorticoids, mineralocorticoids, and sex steroids, which regulate development and physiology. Steroidogenesis is often discussed in a gland-specific fashion, but is better understood as a single process that is repeated in each gland with cell type-specific variations. Thus, the regulation of Steroidogenesis occurs by regulating the transcription and post-translational modification of the steroidogenic enzymes and co-factors, in a tissue-specific fashion. Most steroidogenic enzymes are either hydroxysteroid dehydrogenases or cytochrome P450 enzymes; the activities of these enzymes are modulated by post-translational modifications and co-factors, especially electron-donating redox partners. The first and rate-limiting steroidogenic step is catalyzed by P450scc in all steroidogenic tissues, determining steroidogenic capacity; the qualitative regulation of Steroidogenesis determining the class of steroid produced is principally mediated by P450c17. Understanding Steroidogenesis permits understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiologic homeostasis, and is essential for rational steroid therapies.
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early steps in Steroidogenesis intracellular cholesterol trafficking thematic review series genetics of human lipid diseases
Journal of Lipid Research, 2011Co-Authors: Walter L Miller, Himangshu S BoseAbstract:Steroid hormones are made from cholesterol, primarily derived from lipoproteins that enter cells via receptor-mediated endocytosis. In endo-lysosomes, cholesterol is released from cholesterol esters by lysosomal acid lipase (LAL; disordered in Wolman disease) and exported via Niemann-Pick type C (NPC) proteins (disordered in NPC disease). These diseases are characterized by accumulated cholesterol and cholesterol esters in most cell types. Mechanisms for trans-cytoplasmic cholesterol transport, membrane insertion, and retrieval from membranes are less clear. Cholesterol esters and “free” cholesterol are enzymatically interconverted in lipid droplets. Cholesterol transport to the cholesterol-poor outer mitochondrial membrane (OMM) appears to involve cholesterol transport proteins. Cytochrome P450scc (CYP11A1) then initiates Steroidogenesis by converting cholesterol to pregnenolone on the inner mitochondrial membrane (IMM). Acute steroidogenic responses are regulated by cholesterol delivery from OMM to IMM, triggered by the steroidogenic acute regulatory protein (StAR). Chronic steroidogenic capacity is determined by CYP11A1 gene transcription. StAR mutations cause congenital lipoid adrenal hyperplasia, with absent Steroidogenesis, potentially lethal salt loss, and 46,XY sex reversal. StAR mutations initially destroy most, but not all Steroidogenesis; low levels of StAR-independent Steroidogenesis are lost later due to cellular damage, explaining the clinical findings. Rare P450scc mutations cause a similar syndrome. This review addresses these early steps in steroid biosynthesis.
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the molecular biology biochemistry and physiology of human Steroidogenesis and its disorders
Endocrine Reviews, 2011Co-Authors: Walter L Miller, Richard J. AuchusAbstract: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.
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Mitochondrial specificity of the early steps in Steroidogenesis
The Journal of Steroid Biochemistry and Molecular Biology, 1995Co-Authors: Walter L MillerAbstract:Abstract Studies in human beings, animals, and cell systems show that the rate-limiting step in Steroidogenesis is the conversion of cholesterol to pregnenolone. In the adrenals and gonads, this step is subject to both acute and chronic regulation. Chronic regulation is primarily, but not exclusively at the level of gene transcription, leading to the production of more steroidogenic machinery and thus increasing the cellular capacity for Steroidogenesis. Chronic regulation can be inhibited by inhibiting protein synthesis with cycloheximide, but this response varies among various cell types and species. Although the P 450scc enzyme system that converts cholesterol to pregnenolone is inherently very slow, the principal site of acute regulation is at the delivery of free cholesterol to mitochondria, rather than at the delivery of reducing equivalents to P 450scc. Even when the V max of the P 450scc system is increased 6-fold by genetic engineering, delivery of cholesterol to the enzyme remains rate-limiting. Targeting of a genetically engineered fusion of the P 450scc system to either mitochondria or to the endoplasmic reticulum of non-steroidogenic cells demonstrates that the mitochondrial environment is absolutely required for the conversion of cholesterol to pregnenolone, and that this absolute requirement is not based on either the nature of the available electron donors for P 450scc or the availability of substrate. Various factors have been proposed as the essential mediator for the transport of cholesterol into mitochondria to initiate Steroidogenesis. A recently identified protein termed Steroidogenic Acute Regulatory protein (StAR) has the necessary properties of enhancing Steroidogenesis, rapid cAMP inducibility and rapid cycloheximide sensitivity that characterize the long-sought acute regulator of Steroidogenesis. StAR is expressed in steroidogenic tissues exhibiting an acute response but not in steroidogenic tissues (placenta, brain) that do not exhibit this response. Mutations in StAR are now shown to cause Congential Lipoid Adrenal Hyperplasia, the last unsolved form of CAH. The actions of StAR can be circumvented by the use of hydroxycholesterols that can freely diffuse into mitochondria, proving that StAR functions as an acute regulator of cholesterol access to mitochondria.
