Abstract Background Phosphorylation of the mineralocorticoid receptor (MR) at serine 843 inhibits its activity. mTOR phosphorylation of ULK1 prevents this MR phosphorylation. Purpose To study the relationship between mTOR and MR and its role in the modulation of aldosterone signaling. Methods Mouse cortical collecting duct M1 cells stably expressing the rat wild type MR or mutated MR (mu/S843A) and a Gaussia luciferase gene reporter under a hormone response promoter tyrosine aminotransferase (TAT) were incubated with mTOR activator and inhibitors in the presence and absence of aldosterone or corticosterone. Co-immunoprecipitation was performed to study protein interactions with the MR, and a phospho-serine antibody was used to demonstrate MR and ULK1 phosphorylation. Effects of mTOR knockdown in M1 cells by lentiviral transduction with CRISPR/gRNA for Raptor and Rictor were also studied. Results mTOR and the adaptor proteins of mTOR complex 1 and 2, Raptor and Rictor, respectively, co-precipitated with the MR of M1-rMR cells. Expression levels of these proteins were not changed by aldosterone. mTOR inhibitors significantly reduced ligand-induced MR reporter gene transactivation, however the mTOR activator MHY1485 had no effect. CRISPR/gRNA gene knockdown of Raptor or Rictor also inhibited MR activation stimulated by ligands, supporting a role of mTOR in maintaining the active MR. The mTOR inhibitor AZD8055 attenuated ligand-mediated MR gene transcription assessed by the reporter gene product and measurement of products of the endogenous MR target genes ACSBG1, LCN2 and Psca. AZD8055 also decreased phospho-ULK1 levels in a dose-dependent manner. We thus assumed that mTOR decreases ULK1 activity and prevents ULK1 phosphorylation of the MR at Serine (S843). Indeed, phosphorylation of the MR was increased in M1-rMR cells treated with AZD8055. However, AZD8055 still inhibited ligand-induced MR activity in cells carrying the mutated MR in which the Serine at 843 was replaced with an Alanine. These results suggest that mTOR has an additional role in MR activity unrelated to the specific phosphorylation at S843 by ULK1. This merits further investigation. Presentation: Monday, June 13, 2022 11:15 a.m. - 11:30 a.m.
Abstract Context: The involvement of urotensin II, a vasoactive peptide acting via the G protein-coupled urotensin II receptor, in arterial hypertension remains contentious. Objective: We investigated the expression of urotensin II and urotensin II receptor in adrenocortical and adrenomedullary tumors and the functional effects of urotensin II receptor activation. Design: The expression of urotensin II and urotensin II receptor was measured by real time RT-PCR in aldosterone-producing adenoma (n = 22) and pheochromocytoma (n = 10), using histologically normal adrenocortical (n = 6) and normal adrenomedullary (n = 5) tissue as control. Urotensin II peptide and urotensin II receptor protein were investigated with immunohistochemistry and immunoblotting. To identify urotensin II-related and urotensin II receptor-related pathways, a whole transcriptome analysis was used. The adrenocortical effects of urotensin II receptor activation were also assessed by urotensin II infusion with/without the urotensin II receptor antagonist palosuran in rats. Results: Urotensin II was more expressed in pheochromocytoma than in aldosterone-producing adenoma tissue; the opposite was seen for the urotensin II receptor expression. Urotensin II receptor activation in vivo in rats enhanced (by 182 ± 9%; P < 0.007) the adrenocortical expression of immunoreactive aldosterone synthase. Conclusions: Urotensin II is a putative mediator of the effects of the adrenal medulla and pheochromocytoma on the adrenocortical zona glomerulosa. This pathophysiological link might account for the reported causal relationship between pheochromocytoma and primary aldosteronism.
DNA methylation and demethylation regulate the transcription of genes. DNA methylation-associated gene expression of adrenal steroidogenic enzymes may regulate cortisol production in cortisol-producing adenoma (CPA). We aimed to determine the DNA methylation levels of all genes encoding steroidogenic enzymes involved in CPA. Additionally, the aims were to clarify the DNA methylation-associated gene expression and evaluate the difference of CPA genotype from others using DNA methylation data. Twenty-five adrenal CPA and six nonfunctioning adrenocortical adenoma (NFA) samples were analyzed. RNA sequencing and DNA methylation array were performed. The methylation levels at 118 methylation sites of the genes were investigated, and their methylation and mRNA levels were subsequently integrated. Among all the steroidogenic enzyme genes studied, CYP17A1 gene was mainly found to be hypomethylated in CPA compared to that in NFA, and the Benjamini-Hochberg procedure demonstrated that methylation levels at two sites in the CYP17A1 gene body were statistically significant. PRKACA mutant CPAs predominantly exhibited hypomethylation of CYP17A1 gene compared with the GNAS mutant CPAs. Inverse associations between CYP17A1 methylation in three regions of the gene body and its mRNA levels were observed in the NFAs and CPAs. In applying clustering analysis using CYP17A1 methylation and mRNA levels, CPAs with PRKACA mutation were differentiated from NFAs and CPAs with a GNAS mutation. We demonstrated that CPAs exhibited hypomethylation of the CYP17A1 gene body in CPA, especially in the PRKACA mutant CPAs. Methylation of CYP17A1 gene may influence its transcription levels.
Abstract Disclosure: N. Iwahashi: None. H. Umakoshi: None. T. Seki: None. C. Gomez-Sanchez: None. K. Mukai: None. M. Suematsu: None. Y. Umezawa: None. M. Oya: None. T. Kosaka: None. M. Seki: None. Y. Suzuki: None. Y. Horiuchi: None. K. Nishimoto: None. Y. Ogawa: None. Context: The adrenal cortex consists of zona glomerulosa (ZG), fasciculata (ZF), and reticularis. Aldosterone-producing cell clusters (APCCs) that express aldosterone synthase (CYP11B2) strongly can be frequently found in adult adrenals and harbor somatic mutations that are also present in aldosterone-producing adenomas (APAs). Primary aldosteronism is mainly caused by APAs or idiopathic hyperaldosteronism (IHA). We presume that APCCs are causing IHA and are precursors of APAs. However, the gene expression characteristics and especially the development of APCCs are not well understood. Objective: This study aimed to analyze the transcriptome of APCCs at single-cell resolution and infer the developmental trajectory. Methods: Single-cell RNA sequencing (scRNA-seq) was performed on two adult adrenals. Results: Immunohistochemical analyses confirmed the presence of APCCs in the two adrenals. scRNA-seq data of 6770 adrenal cells were obtained and 2928 high-quality cells were selected after quality control procedures. Unsupervised clustering and marker gene expressions such as CYP11A1 and NR5A1 identified 1765 adrenocortical cells, which were further divided into six clusters (B1-6). Using the list of APCC/ZG upregulated genes from our previously reported DNA microarray study, three clusters (B1, B3, and B6, totaling 923 cells) were identified as APCC/ZG cells. By further subclustering, the APCC/ZG cells were divided into 3 clusters (C1, C2, and C3). The APCC cluster (C3, 64 cells) and ZG cluster (C1, 447 cells) were identified. Cluster C2 seemed to be ZG-to-ZF transitional cells. RNA velocity analysis, which aimed to infer the direction of differentiation, inferred a direction of development from ZG cells to APCCs. Conclusion: Our results revealed the gene expression characteristics of APCC at single-cell resolution and show that some ZG cells remodel into APCCs. Presentation: Friday, June 16, 2023
Primary aldosteronism is the most common cause of secondary hypertension, most frequently due to an aldosterone-producing adenoma or idiopathic hyperaldosteronism. Somatic mutations of the potassium channel KCNJ5 in the region of the selectivity filter have been found in a significant number of aldosterone-producing adenomas. There are also familial forms of primary aldosteronism, one of which, familial hyperaldosteronism type 3 which to date has been found in one family who presented with a severe abnormality in aldosterone and 18-oxocortisol production and hypertrophy and hyperplasia of the transitional zone of the adrenal cortex. In familial hyperaldosteronism type 3, there is a genomic mutation causing a T158A change of amino acids within the selectivity filter region of the KCNJ5 gene. We are reporting our studies demonstrating that lentiviral-mediated expression of a gene carrying the T158A mutation of the KCNJ5 in the HAC15 adrenal cortical carcinoma cell line causes a 5.3-fold increase in aldosterone secretion in unstimulated HAC15-KCNJ5 cells and that forskolin-stimulated aldosterone secretion was greater than that of angiotensin II. Expression of the mutated KCNJ5 gene decreases plasma membrane polarization, allowing sodium and calcium influx into the cells. The calcium channel antagonist nifedipine and the calmodulin inhibitor W-7 variably inhibited the effect. Overexpression of the mutated KCNJ5 channel resulted in a modest decrease in HAC15 cell proliferation. These studies demonstrate that the T158A mutation of the KCNJ5 gene produces a marked stimulation in aldosterone biosynthesis that is dependent on membrane depolarization and sodium and calcium influx into the HAC15 adrenal cortical carcinoma cells.
The 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta HSD-2) enzyme is thought to confer aldosterone specificity upon mineralocorticoid target tissues by protecting the mineralocorticoid receptor from binding by the more abundant glucocorticoids, corticosterone and cortisol. We have developed a Chinese hamster ovary cell line stably transfected with a plasmid containing the rat 11 beta HSD-2 complementary DNA. This cell line has expressed the enzyme consistently for many generations. The 11 beta HSD-2 was located primarily in the microsomes, but significant amounts also existed in the nuclei and mitochondria. The enzymatic reaction was unidirectional, oxidative, and inhibited by the product, 11-dehydrocorticosterone, with an IC50 of approximately 200 nM. The K(m) for corticosterone was 9.6 +/- 3.1 nM, and that for NAD+ was approximately 8 microM. The enzyme did not convert dexamethasone to 11-dehydrodexamethasone. Tunicamycin, an N-glycosylation inhibitor, had no effect on enzyme activity. 11 alpha-Hydroxyprogesterone (11 alpha OH-P) was an order of magnitude more potent a competitive inhibitor of the 11 beta HSD-2 than was glycyrrhetinic acid (GA) (approximate IC50 = 0.9 vs. 15 nM). 11 beta OH-P, progesterone, and GA were almost equipotent (IC50 = 10 and 6 nM, respectively), and 5 alpha-pregnandione and 5 beta-pregnandione were less potent (IC50 = 100 and 500 nM, respectively) inhibitors of the enzyme. When the inhibitory activities were examined with intact transfected cells, 11 alpha OH-P was more potent than GA (IC50 = 5 and 150 nM, respectively). 11 alpha OH-P was not metabolized by 11 beta HSD-2. We were unable to demonstrate the presence of 11 alpha OH-P in human urine. In conclusion, a cell line stably transfected with the rat 11 beta HSD-2 was created, and the enzyme kinetics, including inhibition, were characterized. 11 alpha OH-P was found to be a potent relatively specific inhibitor of the 11 beta HSD-2 enzyme. Its potential importance is that it is the most specific inhibitor of the 11 beta HSD-2 so far encountered and would aid in the study of the physiological importance of the isoenzyme.
