Angiotensin II-dependent transcriptional activation of human steroidogenic acute regulatory protein gene by a 25-kDa cAMP-responsive element modulator protein isoform and Yin Yang 1

Cypermethrin triggers YY1-mediated testosterone biosynthesis suppression

Cypermethrin (CYP), an extensively-used broad-spectrum pyrethroid pesticide, is regarded as a potential environmental endocrine disruptor with the anti-androgenic characteristic. To explore underlying roles of non-coding RNAs and the Jak/Stat pathway in CYP-mediated testosterone biosynthesis suppression, SD rats and Leydig cells were employed in this work. Results displayed that β-CYP decreased plasma testosterone levels and led to abnormal alterations of testicular histomorphology and ultrastructures. LncRNA XIST and miR-142-5p were co-localized in the cytoplasm of Leydig cells, but the expression of XIST was inhibited by β-CYP while that of miR-142-5p was induced. Then overexpressed miR-142-5p dampened the Jak1/Stat1 pathway by directly targeting Jak1. Transcription factors NFκB and YY1 impeded by β-CYP were positively regulated by the Jak1/Stat1 pathway. Bidirectional Co-IP and ChIP assays demonstrated that NFκB interacted with and modulated YY1 by directly binding to the promoter region of YY1. ChIP, qPCR, and YY1 knockdown/overexpression assays indicated that YY1 acted as a transcriptional activator to directly modulate steroidogenic StAR and 3β-HSD in Leydig cells. Taken together, miR-142-5p sponged by lncRNA XIST directly targets the Jak1/Stat1 pathway, which regulates steroidogenic StAR and 3β-HSD via NFκB and YY1, and ultimately dampens testosterone production in Leydig cells.

Current knowledge on the acute regulation of steroidogenesis

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 rate-limiting 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.

SFMBT2 (Scm-like with four mbt domains 2) negatively regulates cell migration and invasion in prostate cancer cells

Metastatic prostate cancer is the leading cause of morbidity and mortality in men. In this study, we found that expression level of SFMBT2 is altered during prostate cancer progression and has been associated with the migration and invasion of prostate cancer cells. The expression level of SFMBT2 is high in poorly metastatic prostate cancer cells compared to highly metastatic prostate cancer cells. We also found that SFMBT2 knockdown elevates MMP-2, MMP-3, MMP-9, and MMP-26 expression, leading to increased cell migration and invasion in LNCaP and VCaP cells. SFMBT2 interacts with YY1, RNF2, N-CoR and HDAC1/3, as well as repressive histone marks such as H3K9me2, H4K20me2, and H2AK119Ub which are associated with transcriptional repression. In addition, SFMBT2 knockdown decreased KAI1 gene expression through up-regulation of N-CoR gene expression. Expression of SFMBT2 in prostate cancer was strongly associated with clinicopathological features. Patients having higher Gleason score (≥ 8) had substantially lower SFMBT2 expression than patients with lower Gleason score. Moreover, tail vein or intraprostatic injection of SFMBT2 knockdown LNCaP cells induced metastasis. Taken together, our findings suggest that regulation of SFMBT2 may provide a new therapeutic strategy to control prostate cancer metastasis as well as being a potential biomarker of metastatic prostate cancer.

Nicotine Suppressed Fetal Adrenal StAR Expression via YY1 Mediated-Histone Deacetylation Modification Mechanism

Steroidogenic acute regulatory (StAR) protein plays a pivotal role in steroidogenesis. Previously, we have demonstrated that prenatal nicotine exposure suppressed fetal adrenal steroidogenesis via steroidogenic factor 1 deacetylation. This study further explored the potential role of the transcriptional repressor Yin Yang 1 (YY1) in nicotine-mediated StAR inhibition. Nicotine was subcutaneously administered (1.0 mg/kg) to pregnant rats twice per day and NCI-H295A cells were treated with nicotine. StAR and YY1 expression were analyzed by real-time PCR, immunohistochemistry, and Western blotting. Histone modifications and the interactions between the YY1 and StAR promoter were assessed using chromatin immunoprecipitation (ChIP). Prenatal nicotine exposure increased YY1 expression and suppressed StAR expression. ChIP assay showed that there was a decreasing trend for histone acetylation at the StAR promoter in fetal adrenal glands, whereas H3 acetyl-K14 at the YY1 promoter presented an increasing trend following nicotine exposure. Furthermore, in nicotine-treated NCI-H295A cells, nicotine enhanced YY1 expression and inhibited StAR expression. ChIP assay showed that histone acetylation decreased at the StAR promoter in NCI-H295A cells and that the interaction between the YY1 and StAR promoter increased. These data indicated that YY1-medicated histone deacetylation modification in StAR promoters might play an important role in the inhibitory effect of nicotine on StAR expression.

Protein-DNA Interactions at the Opossum Npt2a Promoter are Dependent upon NHERF-1

BACKGROUND/AIMS

Phosphate homeostasis is controlled by the renal reabsorption of Pi by the type IIa sodium phosphate cotransporter, Npt2a, which is localized in the proximal tubule brush border membrane. Regulation of Npt2a expression is a key control point to maintain phosphate homeostasis with most studies focused on regulating protein levels in the brush border membrane. Molecular mechanisms that control Npt2a mRNA, however, remain to be defined. We have reported that Npt2a mRNA and protein levels correlate directly with the expression of the Na+/H+ exchanger regulatory factor 1 (NHERF-1) using opossum kidney (OK) cells and the NHERF-1-deficient OK-H cells. The goal of this study was to determine whether NHERF-1 contributes to transcriptional and/or post-transcriptional mechanisms controlling Npt2a mRNA levels.

METHODS

Npt2a mRNA half-life was compared between OK and NHERF-1 deficient OK-H cell lines. oNpt2a promoter-reporter gene assays and electrophoretic mobility shift assays (EMSA) were used identify a NHERF-1 responsive region within the oNpt2a proximal promoter.

RESULTS

Npt2a mRNA half-life is the same in OK and OK-H cells. The NHERF-1 responsive region lies within the proximal promoter in a region that contains a highly conserved CAATT box and G-rich element. Specific protein-DNA complex formation with the CAATT element is altered by the absence of NHERF-1 (OK v OK-H EMSA) although NHERF-1 does not directly contribute to complex formation.

CONCLUSION

NHERF-1 helps maintain steady-state Npt2a mRNA levels in OK cells through indirect mechanisms that help promote protein-DNA interactions at the Npt2a proximal promoter.

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)

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.

Effect of swimming on the production of aldosterone in rats

It has been demonstrated that exercise is one of the stresses known to increase the aldosterone secretion. Both potassium and angiotensin II (Ang II) levels are shown to be correlated with aldosterone production during exercise, but the mechanism is still unclear. In an in vivo study, male rats were catheterized via right jugular vein (RJV), and divided into four groups namely water immersion, swimming, lactate infusion (13 mg/kg/min) and pyruvate infusion (13 mg/kg/min) groups. Each group was treated for 10 min. Blood samples were collected at 0, 10, 15, 30, 60 and 120 min from RJV after administration. In an in vitro study, rat zona glomerulosa (ZG) cells were challenged by lactate (1–10 mM) in the presence or absence of Ang II (10⁻⁸ M) for 60 min. The levels of aldosterone in plasma and medium were measured by radioimmunoassay. Cell lysates were analyzed by immunoblotting assay. After exercise and lactate infusion, plasma levels of aldosterone and lactate were significantly higher than those in the control group. Swimming for 10 min significantly increased the plasma Ang II levels in male rats. Administration of lactate plus Ang II significantly increased aldosterone production and enhanced protein expression of steroidogenic acute regulatory protein (StAR) in ZG cells. These results demonstrated that acute exercise led to the increase of both aldosterone and Ang II secretion, which is associated with lactate action on ZG cells and might be dependent on the activity of renin-angiotensin system.

Phospholipase D activity underlies very-low-density lipoprotein (VLDL)-induced aldosterone production in adrenal glomerulosa cells

Aldosterone is the mineralocorticoid responsible for sodium retention, thus increased blood volume and pressure. Excessive production of aldosterone results in high blood pressure as well as renal disease, stroke, and visual loss via both direct effects and effects on blood pressure. Weight gain is often associated with increased blood pressure, but it remains unclear how obesity increases blood pressure. Obese patients typically have higher lipoprotein levels; moreover, some studies have suggested that aldosterone levels are also elevated and represent a link between obesity and hypertension. Very-low-density lipoprotein (VLDL) functions to transport triglycerides from the liver to peripheral tissues. Although previous studies have demonstrated that VLDL can stimulate aldosterone production, the mechanisms underlying this effect are largely unclear. Here we show for the first time that phospholipase D (PLD) is involved in VLDL-induced aldosterone production in both a human adrenocortical cell line (HAC15) and primary cultures of bovine zona glomerulosa cells. Our data also reveal that PLD mediates steroidogenic acute regulatory (StAR) protein and aldosterone synthase (CYP11B2) expression via increasing the phosphorylation (activation) of their regulatory transcription factors. Finally, by using selective PLD inhibitors, our studies suggest that both PLD1 and PLD2 isoforms play an important role in VLDL-induced aldosterone production.

Angiotensin II-induced protein kinase D activates the ATF/CREB family of transcription factors and promotes StAR mRNA expression

Aldosterone synthesis is initiated upon the transport of cholesterol from the outer to the inner mitochondrial membrane, where the cholesterol is hydrolyzed to pregnenolone. This process is the rate-limiting step in acute aldosterone production and is mediated by the steroidogenic acute regulatory (StAR) protein. We have previously shown that angiotensin II (AngII) activation of the serine/threonine protein kinase D (PKD) promotes acute aldosterone production in bovine adrenal glomerulosa cells, but the mechanism remains unclear. Thus, the purpose of this study was to determine the downstream signaling effectors of AngII-stimulated PKD activity. Our results demonstrate that overexpression of the constitutively active serine-to-glutamate PKD mutant enhances, whereas the dominant-negative serine-to-alanine PKD mutant inhibits, AngII-induced StAR mRNA expression relative to the vector control. PKD has been shown to phosphorylate members of the activating transcription factor (ATF)/cAMP response element binding protein (CREB) family of leucine zipper transcription factors, which have been shown previously to bind the StAR proximal promoter and induce StAR mRNA expression. In primary glomerulosa cells, AngII induces ATF-2 and CREB phosphorylation in a time-dependent manner. Furthermore, overexpression of the constitutively active PKD mutant enhances the AngII-elicited phosphorylation of ATF-2 and CREB, and the dominant-negative mutant inhibits this response. Furthermore, the constitutively active PKD mutant increases the binding of phosphorylated CREB to the StAR promoter. Thus, these data provide insight into the previously reported role of PKD in AngII-induced acute aldosterone production, providing a mechanism by which PKD may be mediating steroidogenesis in primary bovine adrenal glomerulosa cells.

Regulation of adrenocortical steroid hormone production by RhoA-diaphanous 1 signaling and the cytoskeleton

The production of glucocorticoids and aldosterone in the adrenal cortex is regulated at multiple levels. Biosynthesis of these hormones is initiated when cholesterol, the substrate, enters the inner mitochondrial membrane for conversion to pregnenolone. Unlike most metabolic pathways, the biosynthesis of adrenocortical steroid hormones is unique because some of the enzymes are localized in mitochondria and others in the endoplasmic reticulum (ER). Although much is known about the factors that control the transcription and activities of the proteins that are required for steroid hormone production, the parameters that govern the exchange of substrates between the ER and mitochondria are less well understood. This short review summarizes studies that have begun to provide insight into the role of the cytoskeleton, mitochondrial transport, and the physical interaction of the ER and mitochondria in the production of adrenocortical steroid hormones.