Dual actions of lanthanides on ACTH-inhibited leak K+ channels

2002 ◽  
Vol 282 (6) ◽  
pp. E1255-E1266 ◽  
Author(s):  
John J. Enyeart ◽  
Lin Xu ◽  
Judith A. Enyeart
Keyword(s):  
Binding Sites ◽  
Hormone Receptors ◽  
Peptide Hormone ◽  
Receptor Activation ◽  
Zona Fasciculata ◽  
Ionic Radii ◽  
Whole Cell Patch Clamp ◽  
Acth Receptor ◽  
Dependent Inhibition ◽  
Peptide Hormone Receptors

Bovine adrenal zona fasciculata cells express background K+ channels ( I ACchannels) whose activity is potently inhibited by ACTH. In whole cell patch clamp recordings, it was discovered that the trivalent lanthanides (Ln3+s) lanthanum and ytterbium interact with two binding sites to modulate K+ flow through these channels. Despite large differences in ionic radii, these Ln3+s inhibited I AC channels half-maximally with IC50 values near 50 μM. In addition, these Ln3+s blocked and reversed ACTH-mediated inhibition of I AC K+ channels at similar concentrations. The Ln3+s did not alter inhibition of I AC by angiotensin II or cAMP. Ln3+-induced uncoupling of ACTH receptor activation from I AC inhibition was prevented by raising the external Ca2+ concentration from 2 to 10 mM. The divalent cation Ni2+ (500 μM) also blocked ACTH-dependent inhibition of I AC through a Ca2+-sensitive mechanism. The results are consistent with a model in which Ln3+s produce opposing actions on I AC K+ currents through two separate binding sites. In addition to directly inhibiting I AC, Ln3+s (and Ni2+) bind with high affinity to a Ca2+-selective site associated with the ACTH receptor. By displacing Ca2+ from this site, Ln3+s prevent ACTH from binding and accelerate its dissociation. These results identify Ln3+s as a relatively potent group of noncompetitive ACTH receptor antagonists. Allosteric actions of trivalent and divalent metal cations on hormone binding, mediated through Ca2+-specific sites, may be common to a variety of peptide hormone receptors.

Agonist binding to peptide hormone receptors

2003 ◽  
Vol 31 (1) ◽  
pp. 35-39 ◽  
Author(s):  
M. Wheatley ◽  
S.R. Hawtin ◽  
V.J. Wesley ◽  
H.C. Howard ◽  
J. Simms ◽  
...  
Keyword(s):  
Hormone Receptors ◽  
Specific Binding ◽  
Peptide Hormone ◽  
Receptor Activation ◽  
Site Directed Mutagenesis ◽  
Receptor Interaction ◽  
Agonist Binding ◽  
Absolute Requirement ◽  
N Terminus ◽  
Peptide Hormone Receptors

A fundamental issue in molecular pharmacology is to define how agonist–receptor interaction differs from that of antagonist–receptor interaction. The V1a vasopressin receptor (V1aR) is a member of a family of related G-protein-coupled receptors (GPCRs) that are activated by vasopressin, oxytocin (OT) and related peptides. A segment of the N-terminus that was required for agonist binding, but not antagonist binding, was identified by characterizing truncated V1aR constructs. Site-directed mutagenesis revealed that a single residue (Arg46) was critical for agonist binding and receptor activation. The N-terminus of the related OT receptor (OTR) could recover agonist binding in a chimaeric OTRN–V1aR construct. Furthermore, Arg34 of the human OTR, which corresponds to Arg46 of the rat V1aR, provided agonist-specific binding epitopes in the OTR, indicating a conserved function of this locus throughout this GPCR subfamily. Mutation of Arg46 revealed that high-affinity agonist binding had an absolute requirement for arginine at this position.

scholarly journals Adrenal fasciculata cells express T-type and rapidly and slowly activating L-type Ca2+ channels that regulate cortisol secretion

2015 ◽  
Vol 308 (11) ◽  
pp. C899-C918 ◽  
Author(s):  
John J. Enyeart ◽  
Judith A. Enyeart
Keyword(s):  
Hormone Receptors ◽  
Peptide Hormone ◽  
Selective Inhibition ◽  
Northern Blotting ◽  
Cell Physiology ◽  
Zona Fasciculata ◽  
Cortisol Secretion ◽  
Ang Ii ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent

In whole cell patch-clamp recordings, we characterized the L-type Ca2+ currents in bovine adrenal zona fasciculata (AZF) cells and explored their role, along with the role of T-type channels, in ACTH- and angiotensin II (ANG II)-stimulated cortisol secretion. Two distinct dihydropyridine-sensitive L-type currents were identified, both of which were activated at relatively hyperpolarized potentials. One activated with rapid kinetics and, in conjunction with Northern blotting and PCR, was determined to be Cav1.3. The other, expressed in approximately one-half of AZF cells, activated with extremely slow voltage-dependent kinetics and combined properties not previously reported for an L-type Ca2+ channel. The T-type Ca2+ channel antagonist 3,5-dichloro- N-[1-(2,2-dimethyl-tetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2) inhibited Cav3.2 current in these cells, as well as ACTH- and ANG II-stimulated cortisol secretion, at concentrations that did not affect L-type currents. In contrast, nifedipine specifically inhibited L-type currents and cortisol secretion, but less effectively than TTA-P2. Diphenylbutylpiperidine Ca2+ antagonists, including pimozide, penfluridol, and fluspirilene, and the dihydropyridine niguldipine blocked Cav3.2 and L-type currents and inhibited ACTH-stimulated cortisol secretion with similar potency. This study shows that bovine AZF cells express three Ca2+ channels, the voltage-dependent gating and kinetics of which could orchestrate complex mechanisms linking peptide hormone receptors to cortisol secretion through action potentials or sustained depolarization. The function of the novel, slowly activating L-type channel is of particular interest in this respect. Regardless, the well-correlated selective inhibition of T- and L-type currents and ACTH- and ANG II-stimulated cortisol secretion by TTA-P2 and nifedipine establish the critical importance of these channels in AZF cell physiology.

Hormonal interactions with the proximal Na(+)-H+ exchanger

1990 ◽  
Vol 258 (3) ◽  
pp. F514-F521 ◽  
Author(s):  
F. A. Gesek ◽  
A. C. Schoolwerth
Keyword(s):  
Binding Sites ◽  
Time Course ◽  
Hormone Receptors ◽  
Control Level ◽  
Peptide Hormone ◽  
Ang Ii ◽  
Maximum Increase ◽  
Alpha Adrenergic Receptors ◽  
22Na Uptake ◽  
Exchange Activity

Various types of catecholamine and peptide hormone receptors have been localized to the renal cortex, with the majority of these binding sites located on the proximal tubule. Both subtypes of alpha-adrenergic receptors, angiotensin II (ANG II), parathyroid hormone (PTH), and dopamine (DA) DA-1 receptors have all demonstrated binding sites on this nephron segment. One- to two-thirds of Na+ transport in the proximal nephron is proposed to be mediated by a Na(+)-H+ exchanger. Each of these hormones has been shown to alter Na(+)-H+ exchange activity. The purpose of this study was to examine the interactions of these various hormones on proximal nephron Na(+)-H+ exchange at both physiological and pharmacological concentrations. Na(+)-H+ exchange activity was determined in isolated rat proximal segments by assessing the uptake of 22Na+ that was suppressible by the Na(+)-H+ exchange inhibitor, ethylisopropylamiloride (EIPA). Time course studies indicated that a 1-min preincubation with the hormones followed by a 1-min exposure to 22Na+ was necessary to achieve a steady-state EIPA-suppressible 22Na+ uptake. Selective alpha-adrenergic agonists produced a maximum stimulation of 22Na+ uptake at approximately 10(-6) M final concentration (less than or equal to 192% above the control level of uptake); ANG II produced a maximum increase at 10(-12) M (an 82% increase above the control level). In contrast, PTH and DA inhibited 22Na+ uptake most effectively at 10(-8) M and 10(-6) M, respectively. When submaximal (10(-9) M) concentrations of alpha-agonists were incubated in combination with ANG II, a synergistic effect was observed only with selective alpha 2-agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptide Hormone Receptors

1977 ◽  
Vol 39 (1) ◽  
pp. 529-557 ◽  
Author(s):  
K J Catt ◽  
M L Dufau
Keyword(s):  
Hormone Receptors ◽  
Peptide Hormone ◽  
Peptide Hormone Receptors

scholarly journals EXPRESSION OF STEROID AND PEPTIDE HORMONE RECEPTORS, METABOLIC ENZYMES AND EMT-RELATED GENES IN PROSTATE TUMORS IN RELATION TO THE PRESENCE OF THE TMPRSS2/ERG FUSION

2018 ◽  
Vol 40 (2) ◽  
pp. 101-108 ◽  
Author(s):  
G V Gerashchenko ◽  
L V Mevs ◽  
L I Chashchina ◽  
M V Pikul ◽  
O P Gryzodub ◽  
...  
Keyword(s):  
Gene Expression ◽  
Prostate Cancer ◽  
Expression Pattern ◽  
Hormone Receptors ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Peptide Hormone ◽  
Metabolic Enzymes ◽  
Prostate Tumors ◽  
Peptide Hormone Receptors

Aim: To analyze an expression pattern of the steroid and peptide hormone receptors, metabolic enzymes and EMT-related genes in prostate tumors in relation to the presence of the TMPRSS2/ERG fusion; and to examine a putative correlation between gene expression and clinical characteristics, to define the molecular subtypes of prostate cancer. Materials and Methods: The relative gene expression (RE) of 33 transcripts (27 genes) and the presence/absence of the TMPRSS2/ERG fusion were analyzed by a quantitative PCR. 37 prostate cancer tissues (T) paired with conventionally normal prostate tissue (CNT) and 21 samples of prostate adenomas were investigated. RE changes were calculated, using different protocols of statistics. Results: We demonstrated differences in RE of seven genes between tumors and CNT, as was calculated, using the 2−ΔCT model and the Wilcoxon matched paired test. Five genes (ESR1, KRT18, MKI67, MMP9, PCA3) showed altered expression in adenocarcinomas, in which the TMPRSS2/ERG fusion was detected. Two genes (INSR, isoform B and HOTAIR) expressed differently in tumors without fusion. Comparison of the gene expression pattern in adenomas, CNT and adenocarcinomas demonstrated that in adenocarcinomas, bearing the TMPRSS2/ ERG fusion, genes KRT18, PCA3, and SCHLAP1 expressed differently. At the same time, we detected differences in RE of AR (isoform 2), MMP9, PRLR and HOTAIR in adenocarcinomas without the TMPRSS2/ERG fusion. Two genes (ESR1 and SRD5A2) showed differences in RE in both adenocarcinoma groups. Fourteen genes, namely AR (isoforms 1 and 2), CDH1, OCLN, NKX3-1, XIAP, GCR (ins AG), INSR (isoform A), IGF1R, IGF1R tr, PRLR, PRL, VDR and SRD5A2 showed correlation between RE and tumor stage. RE of four genes (CDH2, ESR2, VDR and SRD5A2) correlated with differentiation status of tumors (Gleason score). Using the K-means clustering, we could cluster adenocarcinomas in three groups, according to gene expression profiles. A specific subtype of prostate tumors is characterized by the activated ERG signaling, due to the presence of TMPRSS2/ERG fusion, and also by high levels of the androgen receptor, prolactin, IGF, INSR and PCA3. Conclusions: We have found the specific differences in expression of the steroid and peptide hormone receptors, metabolic enzymes and EMT-related genes, depending on the presence/absence of the TMPRSS2/ERG fusion in prostate adenocarcinomas, CNT and adenomas. We showed three different gene expression profiles of prostate adenocarcinomas. One of them is characteristic for adenocarcinomas with the TMPRSS2/ERG fusion. Further experiments are needed to confirm these data in a larger cohort of patients.

scholarly journals Mechanistic insight into a peptide hormone signaling complex mediating floral organ abscission

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Julia Santiago ◽  
Benjamin Brandt ◽  
Mari Wildhagen ◽  
Ulrich Hohmann ◽  
Ludwig A Hothorn ◽  
...  
Keyword(s):  
Hormone Receptors ◽  
Peptide Hormone ◽  
Binding Pocket ◽  
Binding Mode ◽  
Floral Organ ◽  
Activation Mechanism ◽  
Signaling Complex ◽  
Floral Abscission ◽  
Peptide Hormone Receptors ◽  
Insight Into

Plants constantly renew during their life cycle and thus require to shed senescent and damaged organs. Floral abscission is controlled by the leucine-rich repeat receptor kinase (LRR-RK) HAESA and the peptide hormone IDA. It is unknown how expression of IDA in the abscission zone leads to HAESA activation. Here we show that IDA is sensed directly by the HAESA ectodomain. Crystal structures of HAESA in complex with IDA reveal a hormone binding pocket that accommodates an active dodecamer peptide. A central hydroxyproline residue anchors IDA to the receptor. The HAESA co-receptor SERK1, a positive regulator of the floral abscission pathway, allows for high-affinity sensing of the peptide hormone by binding to an Arg-His-Asn motif in IDA. This sequence pattern is conserved among diverse plant peptides, suggesting that plant peptide hormone receptors may share a common ligand binding mode and activation mechanism.

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