scholarly journals Role of KCNAB2 expression in modulating hormone secretion in somatotroph pituitary adenoma

2020 ◽  
pp. 1-7
Author(s):  
Charles Ashton ◽  
Suhn K. Rhie ◽  
John D. Carmichael ◽  
Gabriel Zada
Keyword(s):  
Pituitary Adenoma ◽  
Potassium Channel ◽  
Cell Line ◽  
Quantitative Polymerase Chain Reaction ◽  
Hormone Secretion ◽  
Gh3 Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Human Pituitary ◽  
Voltage Gated ◽  
Gh Secretion

OBJECTIVEPrior profiling of the human pituitary adenoma (PA) DNA methylome showed the potassium channel subunit–encoding gene KCNAB2 to be highly differentially methylated between nonfunctional PAs (NFPAs) and growth hormone (GH)–secreting PAs, with greater KCNAB2 methylation detected in secretory PAs. KCNAB2 encodes an aldo-keto reductase that, among other things, negatively regulates members of the voltage-gated potassium channel (Kv) family. In this study, the authors aimed to determine whether modulation of Kcnab2 expression would alter GH secretion in the GH3 mammosomatotroph rat cell line. In addition, they examined whether dosing GH3 cells with the antiarrhythmic drug quinidine, a known inhibitor of Kv and voltage-gated sodium channels, would affect hormonal secretion.METHODSPreviously generated RNA-seq data were reanalyzed to compare KCNAB2 expression levels in human NFPAs and GH-secreting PAs. Kcnab2 was overexpressed in GH3 cells using plasmid transfection and knocked down using shRNA, with confirmation by quantitative polymerase chain reaction (qPCR). GH concentrations in cell culture supernatants collected 24 hours after cell seeding were measured using enzyme-linked immunosorbent assay (ELISA). Separately, quinidine was administered to GH3 cells at graduated doses. GH and prolactin concentrations in supernatants collected 48 hours after quinidine treatment were measured by fluorometric immunoassay.RESULTSModulation of expression at the transcript level in GH3 cells resulted in proportionate changes in the expression of GH mRNA and secretion of GH peptide, as confirmed by qPCR and ELISA. Specifically, partial knockdown of Kcnab2 was associated with fewer GH RNA transcripts and less GH secretion compared with controls, while augmentation of Kcnab2 expression was associated with more GH transcripts and secretion than the controls. Administration of quinidine (≥ 50 µM) reduced both GH and prolactin secretion in a dose-dependent fashion (p ≤ 0.05).CONCLUSIONSGH secretion in a somatotroph cell line is partially dependent on KCNAB2 gene expression and may be mitigated in vitro by quinidine. These results collectively suggest a potential new target and pharmacological candidate to be considered in the development of clinical therapeutics for acromegaly.

scholarly journals Characterization of SNARE Proteins in Human Pituitary Adenomas: Targeted Secretion Inhibitors as a New Strategy for the Treatment of Acromegaly?

2013 ◽  
Vol 98 (12) ◽  
pp. E1918-E1926 ◽  
Author(s):  
Edwin A. Garcia ◽  
Giampaolo Trivellin ◽  
Elena D. Aflorei ◽  
Michael Powell ◽  
Joana Grieve ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Pituitary Adenoma ◽  
Pituitary Adenomas ◽  
Hormone Secretion ◽  
Snare Proteins ◽  
University Hospitals ◽  
Human Pituitary ◽  
Human Pituitary Adenoma ◽  
Gh Secretion ◽  
Ghrh Receptor

Context: Targeted secretion inhibitors (TSIs), a new class of recombinant biotherapeutic proteins engineered from botulinum toxin, represent a novel approach for treating diseases with excess secretion. They inhibit hormone secretion from targeted cell types through cleavage of SNARE (soluble N-ethylmaleimide-sensitive factor-activating protein receptor) proteins. qGHRH-LHN/D is a TSI targeting pituitary somatotroph through binding to the GHRH-receptor and cleavage of the vesicle-associated membrane protein (VAMP) family of SNARE proteins. Objective: Our objective was to study SNARE protein expression in pituitary adenomas and to inhibit GH secretion from somatotropinomas using qGHRH-LHN/D. Design: We analyzed human pituitary adenoma analysis for SNARE expression and response to qGHRH-LHN/D treatment. Setting: The study was conducted in University Hospitals. Patients: We used pituitary adenoma samples from 25 acromegaly and 47 nonfunctioning pituitary adenoma patients. Outcome: Vesicle-SNARE (VAMP1–3), target-SNARE (syntaxin1, SNAP-23, and SNAP-25), and GHRH-receptor detection with RT-qPCR, immunocytochemistry, and immunoblotting. Assessment of TSI catalytic activity on VAMPs and release of GH from adenoma cells. Results: SNARE proteins were variably expressed in pituitary samples. In vitro evidence using recombinant GFP-VAMP2&3 or pituitary adenoma lysates suggested sufficient catalytic activity of qGHRH-LHN/D to degrade VAMPs, but was unable to inhibit GH secretion in somatotropinoma cell cultures. Conclusions: SNARE proteins are present in human pituitary somatotroph adenomas that can be targeted by TSIs to inhibit GH secretion. qGHRH-LHN/D was unable to inhibit GH secretion from human somatotroph adenoma cells. Further studies are required to understand how the SNARE proteins drive GH secretion in human somatotrophs to allow the development of novel TSIs with a potential therapeutic benefit.

scholarly journals Stimulation by Urocortin of Growth Hormone (GH) Secretion in GH-Producing Human Pituitary Adenoma Cells.

1997 ◽  
Vol 44 (4) ◽  
pp. 627-629 ◽  
Author(s):  
YOSHIO MURAKAMI ◽  
TOSHIAKI MORI ◽  
KUNIO KOSHIMURA ◽  
MASAMICHI KUROSAKI ◽  
TOMOKATSU HORI ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Pituitary Adenoma ◽  
Human Pituitary ◽  
Human Pituitary Adenoma ◽  
Gh Secretion

A human pituitary adenoma cell line proliferates and maintains some differentiated functions following expression of SV40 large T-antigen

1998 ◽  
Vol 9 (2) ◽  
pp. 169-184 ◽  
Author(s):  
Long Jin ◽  
Elzbieta Kulig ◽  
Xiang Qian ◽  
Bernd W. Scheithauer ◽  
Norman L. Eberhardt ◽  
...  
Keyword(s):  
Pituitary Adenoma ◽  
Cell Line ◽  
T Antigen ◽  
Large T Antigen ◽  
Sv40 Large T Antigen ◽  
Human Pituitary ◽  
Human Pituitary Adenoma ◽  
Adenoma Cell

scholarly journals Pandinus imperator scorpion venom blocks voltage-gated potassium channels in GH3 cells.

1988 ◽  
Vol 91 (6) ◽  
pp. 817-833 ◽  
Author(s):  
P A Pappone ◽  
M T Lucero
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Potassium Current ◽  
Potassium Currents ◽  
Scorpion Venom ◽  
Gh3 Cells ◽  
Pituitary Cells ◽  
Crude Venom ◽  
Voltage Gated ◽  
Voltage Dependent

We examined the effects of Pandinus imperator scorpion venom on voltage-gated potassium channels in cultured clonal rat anterior pituitary cells (GH3 cells) using the gigohm-seal voltage-clamp method in the whole-cell configuration. We found that Pandinus venom blocks the voltage-gated potassium channels of GH3 cells in a voltage-dependent and dose-dependent manner. Crude venom in concentrations of 50-500 micrograms/ml produced 50-70% block of potassium currents measured at -20 mV, compared with 25-60% block measured at +50 mV. The venom both decreased the peak potassium current and shifted the voltage dependence of potassium current activation to more positive potentials. Pandinus venom affected potassium channel kinetics by slowing channel opening, speeding deactivation slightly, and increasing inactivation rates. Potassium currents in cells exposed to Pandinus venom did not recover control amplitudes or kinetics even after 20-40 min of washing with venom-free solution. The concentration dependence of crude venom block indicates that the toxins it contains are effective in the nanomolar range of concentrations. The effects of Pandinus venom were mimicked by zinc at concentrations less than or equal to 0.2 mM. Block of potassium current by zinc was voltage dependent and resembled Pandinus venom block, except that block by zinc was rapidly reversible. Since zinc is found in crude Pandinus venom, it could be important in the interaction of the venom with the potassium channel. We conclude that Pandinus venom contains toxins that bind tightly to voltage-dependent potassium channels in GH3 cells. Because of its high affinity for voltage-gated potassium channels and its irreversibility, Pandinus venom may be useful in the isolation, mapping, and characterization of voltage-gated potassium channels.

Neuropeptide Y directly inhibits growth hormone secretion by human pituitary somatotropic tumours

1987 ◽  
Vol 115 (1) ◽  
pp. 149-154 ◽  
Author(s):  
Eric F. Adams ◽  
Maria S. Venetikou ◽  
Christine A. Woods ◽  
S. Lacoumenta ◽  
J. M. Burrin
Keyword(s):  
Growth Hormone ◽  
Neuropeptide Y ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Inhibitory Effect ◽  
Pituitary Cells ◽  
Maximal Effect ◽  
Human Pituitary ◽  
Amino Acid Peptide ◽  
Gh Secretion

Abstract. Neuropeptide Y (NPY) is a 36 amino acid peptide, widely distributed throughout the brain and is found in hypothalamic neurones. This latter finding suggests that NPY may possess a hypophysiotropic function. A number of studies have demonstrated effects of NPY on LH and GH secretion by rat pituitary cells. We report here the results of experiments investigating the effects of NPY on GH secretion by tumorous human somatotropic pituitary cells in culture. NPY (0.25–25 nmol/l) inhibited GH secretion by 20–53%, the maximal effect depending upon the tumour studied. The potency of NPY was less than that of somatostatin (SRIH). The stimulatory effects of growth hormone releasing factor (GHRH) and theophylline were reduced by NPY, but NPY did not modify the inhibitory effect of SRIH on GH secretion. It is concluded that NPY may be involved in the control of GH secretion, at least by tumorous human pituitary somatotropes.

Melanin-concentrating hormone stimulates human growth hormone secretion: a novel effect of MCH on the hypothalamic-pituitary axis

2006 ◽  
Vol 290 (5) ◽  
pp. E982-E988 ◽  
Author(s):  
Gabriella Segal-Lieberman ◽  
Hadara Rubinfeld ◽  
Moran Glick ◽  
Noga Kronfeld-Schor ◽  
Ilan Shimon
Keyword(s):  
Growth Hormone ◽  
Energy Homeostasis ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Pituitary Hormones ◽  
Thyroid Stimulating Hormone ◽  
Pituitary Cells ◽  
Human Pituitary ◽  
Gh Secretion ◽  
Melanin Concentrating Hormone

Melanin-concentrating hormone (MCH), a 19-amino acid orexigenic (appetite-stimulating) hypothalamic peptide, is an important regulator of energy homeostasis. It is cleaved from its precursor prepro-MCH (ppMCH) along with several other neuropeptides whose roles are not fully defined. Because pituitary hormones such as growth hormone (GH), ACTH, and thyroid-stimulating hormone affect body weight and composition, appetite, insulin sensitivity, and lipoprotein metabolism, we investigated whether MCH exerts direct effects on the human pituitary to regulate energy balance using dispersed human fetal pituitaries (21–22 wk gestation) and cultured GH-secreting adenomas. We found that MCH receptor-1 (MCH-R1), but not MCH receptor-2, is expressed in both normal (fetal and adult) human pituitary tissues and in GH cell adenomas. MCH (10 nM) stimulated GH release from human fetal pituitary cultures by up to 62% during a 4-h incubation ( P < 0.05). Interestingly, neuropeptide EI (10 nM), which is also cleaved from ppMCH, increased human GH secretion by up to 124% in fetal pituitaries. A milder, albeit significant, induction of GH secretion by MCH (20%) was seen in cultured GH-secreting pituitary adenomas. A comparable stimulation of GH secretion was seen when cultured mouse pituitary cells were treated with MCH. Treatment of cultured GH adenoma cells with MCH (100 nM) induced extracellular signal-regulated kinases 1 and 2 phosphorylation, suggesting activation of MCH-R1. In aggregate, these data suggest that MCH may regulate pituitary GH secretion and imply a potential cross-talk mechanism between appetite-regulating neuropeptides and pituitary hormones.

Induction of GH, PRL, and TSHβ mRNA by transfection of Pit-1 in a human pituitary adenoma-derived cell line

2005 ◽  
Vol 322 (2) ◽  
pp. 269-277 ◽  
Author(s):  
Shunsuke Miyai ◽  
Shinichi Yoshimura ◽  
Yasumasa Iwasaki ◽  
Susumu Takekoshi ◽  
Ricardo V. Lloyd ◽  
...  
Keyword(s):  
Pituitary Adenoma ◽  
Cell Line ◽  
Human Pituitary ◽  
Human Pituitary Adenoma

Somatostatin decreases voltage-gated Ca2+ currents in GH3 cells through activation of somatostatin receptor 2

2007 ◽  
Vol 292 (6) ◽  
pp. E1863-E1870 ◽  
Author(s):  
Seung-Kwon Yang ◽  
Helena C. Parkington ◽  
Jacques Epelbaum ◽  
Damien J. Keating ◽  
Chen Chen
Keyword(s):  
Somatostatin Receptor ◽  
Gh3 Cells ◽  
Channel Blockers ◽  
Current Response ◽  
Voltage Gated ◽  
Gh Secretion ◽  
Intracellular Ca ◽  
Sstr Subtype ◽  
Current Reduction ◽  
Perforated Patch Clamp

The secretion of growth hormone (GH) is inhibited by hypothalamic somatostatin (SRIF) in somatotropes through five subtypes of the somatostatin receptor (SSTR1–SSTR5). We aimed to characterize the subtype(s) of SSTRs involved in the Ca2+ current reduction in GH3 somatotrope cells using specific SSTR subtype agonists. We used nystatin-perforated patch clamp to record voltage-gated Ca2+ currents, using a holding potential of −80 mV in the presence of K+ and Na+ channel blockers. We first established the presence of T-, L-, N-, and P/Q-type Ca2+ currents in GH3 cells using a variety of channel blockers (Ni+, nifedipine, ω-conotoxin GVIA, and ω-agatoxin IVA). SRIF (200 nM) reduced L- and N-type but not T- or P/Q-type currents in GH3 cells. A range of concentrations of each specific SSTR agonist was tested on Ca2+ currents to find the maximal effective concentration. Activation of SSTR2 with 10−7 and 10−8 M L-797,976 decreased the voltage-gated Ca2+ current and abolished any further decrease by SRIF. SSTR1, SSTR3, SSTR4, and SSTR5 agonists at 10−7 M did not modify the voltage-gated Ca2+ current and did not affect the Ca2+ current response to SRIF. These results indicate that SSTR2 is involved mainly in regulating voltage-gated Ca2+ currents by SRIF, which contributes to the decrease in intracellular Ca2+ concentration and GH secretion by SRIF.

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