Differential redistribution of protein kinase C in human aldosteronoma cells and adjacent adrenal cells stimulated with ACTH and angiotensin II

Ishizuka, Tatsuo; Miura, Kiyoshi; Nagao, Seiji; Nozawa, Yoshinori

doi:10.1016/s0006-291x(88)80543-6

Cited by 22 publications

(9 citation statements)

References 20 publications

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“…Aldosterone-and glucocorticoid-producing adrenocortical adenomas are responsive to ACTH in vivo and in vitro, suggesting the expression of functional ACTH receptors (46,47). In accord with this notion, we found high ACTH-receptor mRNA expression using Northern blotting and in situ hybridization in cortisol-producing and aldosterone-producing adenomas, whereas nonfunctional adenomas and carcinomas had low or absent ACTH-receptor mRNA levels (31) (Fig.…”

Section: Acth-receptor Mrna Expression In Tumor Tissuesupporting

confidence: 65%

ACTH-receptor expression, regulation and role in adrenocortial tumor formation

Beuschlein

Faßnacht

Klink

et al. 2001

European Journal of Endocrinology

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The regulation of the ACTH-receptor gene is unique in that it is up-regulated by its own ligand, ACTH. Ligand-induced up-regulation of ACTH-receptor expression may be an important adaptive process directed towards optimizing adrenal responsiveness to ACTH in the context of physiological stress and the maintenance of metabolic homeostasis in which the adrenals play a pivotal role. Whereas enhancement by ligand-induced up-regulation permits a more efficient and rapid glucocorticoid response, negative feedback regulation of glucocorticoids in the hypothalamus and pituitary inhibits ACTH secretion and allows a balanced adrenal response to stress. Since the cloning of the promoter region of the ACTH receptor, considerable progress in the understanding of the regulatory processes has been made. The effects of ACTH on ACTH-receptor expression is dependent on cAMP, probably mediated through AP-1.The profound effect of three SF-1-binding sites in the ACTH-receptor promoter was demonstrated by deletion experiments. Conversely, ACTH-receptor expression can be suppressed by adrenal-specific transcription factors,like DAX-1.Despite an extensive search, no activating ACTH-receptor mutations have been found in adrenal tumors,excluding the ACTH receptor as a relevant oncogene in adrenal tumorigenesis. However, the ACTH receptor may act as a differentiation factor as suggested by LOH in adrenal carcinomas with an undifferentiated tumor type.In benign adrenal tumors, a strong correlation between ACTH-receptor expression and expression of P450 steroidogenic enzymes is evident. This close regulative relationship is lost in adrenal carcinoma, probably as a result of tumor dedifferentiation. Down-regulation of ACTH-receptor expression in normal and neoplastic tissue can be achieved by adrenostatic compounds such as aminoglutethimide and metyrapone.

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Section: Acth-receptor Mrna Expression In Tumor Tissuesupporting

confidence: 65%

ACTH-receptor expression, regulation and role in adrenocortial tumor formation

Beuschlein

Faßnacht

Klink

et al. 2001

European Journal of Endocrinology

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“…HEK293 cells have been extensively used to study AE because they do not express measurable levels of endogenous AE. 30 Because Ang II activates PKC, 35 we examined the effect on anion exchange activity of the PKC activator, PMA. To optimize experiments with PMA, a dose-response curve of the phorbol 12-myristate 13-acetate esters (PMA) effect on anion exchange for AE3fl, was prepared (Figure 2A).…”

Section: Identification Of the Pkc-sensitive Ae Isoformmentioning

confidence: 99%

Molecular Basis for Angiotensin II-Induced Increase of Chloride/Bicarbonate Exchange in the Myocardium

Álvarez

Fujinaga

Casey

2001

Circulation Research

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Abstract-Plasma membrane anion exchangers (AEs) regulate myocardial intracellular pH (pH i ) by Na ϩ -independent Cl Ϫ /HCO 3 Ϫ exchange. Angiotensin II (Ang II) activates protein kinase C (PKC) and increases anion exchange activity in the myocardium. Elevated anion exchange activity has been proposed to contribute to the development of cardiac hypertrophy. Our Northern blots showed that adult rat heart expresses AE1, AE2, AE3fl, and AE3c. Activity of each AE isoform was individually measured by following changes of pH i , associated with bicarbonate transport, in transfected HEK293 cells. Exposure to the PKC activator, PMA (150 nmol/L), increased the transport activity of only the AE3fl isoform by 50Ϯ11% (PϽ0.05, nϭ6), consistent with the increase observed in intact myocardium. Cotransfection of HEK293 cells with AE3fl and AT1 a -Ang II receptors conferred sensitivity of anion transport to Ang II (500 nmol/L), increasing the transport activity by 39Ϯ3% (PϽ0.05, nϭ4). PKC inhibition by chelerythrine (10 mol/L) blocked the PMA effect. To identify the PKC-responsive site, 7 consensus PKC phosphorylation sites of AE3fl were individually mutated to alanine. Mutation of serine 67 of AE3 prevented the PMA-induced increase of anion transport activity. Inhibition of MEK1/2 by PD98059 (50 mol/L) did not affect the response of AE3fl to Ang II, indicating that PKC directly phosphorylates AE3fl. We conclude that following Ang II stimulation of cells, PKC⑀ phosphorylates serine 67 of the AE3 cytoplasmic domain, inducing the Ang II-induced increase in anion transport observed in the hypertrophic myocardium. Key Words: hypertrophy Ⅲ anion exchange Ⅲ pH regulation Ⅲ angiotensin II Ⅲ protein kinase C I ntracellular pH (pH i ) regulates excitation-contraction coupling in cardiac cells through ionic conductances, 1 metabolic pathways, 2 Ca 2ϩ homeostasis, 3 contractility, 4 and electrical conduction. 5 Four well-characterized membrane ion transporters regulate cardiomyocyte pH i . Acid loads activate Na ϩ /H ϩ exchange (NHE) and Na ϩ /HCO 3 Ϫ symport (NBC), 6,7 whereas after an alkaline load, Na ϩ -independent Cl Ϫ /HCO 3 Ϫ exchangers (AEs) 8 and a second dual acid-loading mechanism 9 are activated. Anion exchange proteins, which facilitate the reversible electroneutral exchange of Cl Ϫ for HCO 3 Ϫ across the plasma membrane, regulate pH i , intracellular chloride concentration, bicarbonate metabolism and cell volume. The AE family comprises 3 members: AE1, AE2, and AE3. 10 Heart and retina coexpress 2 different isoforms of AE3, AE3 full length (AE3fl, the most abundant AE protein expressed in the brain) and AE3 cardiac (AE3c), which result from alternative promoter usage. 11,12 Rat AE3fl is 1227 amino acids long and AE3c contains 1034 amino acids. The C-terminal 957 amino acids of both polypeptides are identical, but the AE3c protein contains a unique N-terminal sequence of 73 amino acids, which replaces the unique first 270 amino acids of the AE3fl form. 11 A truncated form of AE1 was recently characterized in rat ventricular my...

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“…In addition, synthesis of dihydroepiandrosterone, androstenedione, and cortisol was stimulated by TPA, but ACTH-stimulated steroid synthesis was attenuated by TPA, with this attributable to a reduction in PKC [3]. We also reported previously that ACTH, TPA and AngII stimulated aldosterone secretion concomitant with translocation of PKC from cytosol to membrane in human aldosterone producing adenoma, and that in the adjacent fasciculata/reticularis cells of these aldosteronomas, TPA weakly stimulated redistribution of PKC and cortisol secretion [16]. Recently, crosstalk between phosphoinositides, cAMP, and Redistribution of PKCa (a) and f3 (b) from cytosol to membrane stimulated by 100 nM ACTH or 1 µM TPA in cortisol producing adenoma cells from 5 patients with Cushing's syndrome.…”

Section: Acthmentioning

confidence: 78%

“…Resected adenoma and adjacent adrenal tissue were immersed in ice-cold Krebs-Ringer phosphate (KRP) buffer equilibrated with 95% 02 and 5% CO2 and then cut into small pieces. The pieces were treated with 5 mg/ml collagenase and 0.01% soybean trypsin inhibitor at 37 °C for 20 min in KRP buffer and passed through silk mesh, then washed three times with glucose-free KRP buffer containing 1 % BSA as described previously [16,17]. Isolated cells were resuspended (4-8 x 106/ ml) in glucose-free KRP buffer, and divided into plastic tubes, in order to estimate the time course Immunoblot analysis of PKC: Other cells were washed with ice-cold homogenizing buffer (20 mM Tris/HCI, pH 7.5, 2 mM EGTA, 0.25 M sucrose, 20 mM 2-mercaptoethanol, 0.1 mM PMSF, 20 ug/ml leupeptin) and homogenized.…”

mentioning

confidence: 99%