Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report the isolation of a novel human circulating proopiomelanocortin-derived peptide, VA-beta-MSH, from hemofiltrate and its pharmacological characterization. Screening for lipolytic activity in differentiated 3T3-L1 adipocytes led to the isolation from a hemofiltrate peptide library by alternating reverse phase and cation exchange chromatography. In the course of this isolation, we also identified human beta-MSH-(1-22). We synthesized VA-beta-MSH by the N-(9-fluorenyl)-methoxycarbonyl (F-moc) solid phase method and used synthetic beta-MSH-(1-22) to confirm that both isolated peptides are lipolytically active in a dose-dependent manner in differentiated 3T3-L1 adipocytes in the nanomolar range. Using cAMP ELISA, we demonstrate that stimulation with both peptides caused a strong cAMP elevation in this cell system. Furthermore, we show that the selective inhibitors of cAMP-dependent protein kinase, 8-(4-Chlorophenylthio)adenosine-3',5'-cyclic monophosphorothioate, Rp-isomer (Rp-8-CPT-cAMPS); N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H89), significantly reduce VA-beta-MSH- and beta-MSH-(1-22)-mediated lipolysis. Although isolated after its lipolytic activity on 3T3-L1 cells, this newly identified circulating human melanocortin may serve other functions in human physiology. Moreover, the fact that these peptides have been identified after a functional assay, but have been overseen in large proteomic approaches, underscores the importance of such approaches in identifying previously undescribed circulating bioactive molecules.
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PMID:Isolation and characterization of a novel proopiomelanocortin-derived peptide from hemofiltrate of chronic renal failure patients. 1565 78

In the human adrenal cortex, the peptide hormone adrenocorticotropin (ACTH) directs cortisol and adrenal androgen biosynthesis by activating a cAMP/cAMP-dependent protein kinase (PKA) pathway. Carboxyl-terminal binding protein 1 (CtBP1) is a corepressor that regulates transcription of the CYP17 gene by periodically interacting with steroidogenic factor-1 in response to ACTH signaling. Given that CtBP1 function is regulated by NADH binding, we hypothesized that ACTH-stimulated changes in cellular pyridine nucleotide concentrations modulate the ability of CtBP1 to repress CYP17 transcription. Further, we postulated that PKA evokes changes in the phosphorylation status of CtBP1 that control the ability of the protein to bind to steroidogenic factor-1 and the coactivator GCN5 (general control nonderepressed 5) and repress CYP17 gene expression. We show that ACTH alters pyridine nucleotide redox state and identify amino acid residues in CtBP1 that are targeted by PKA and PAK6. Both ACTH/cAMP signaling and NADH/NAD+ ratio stimulate nuclear-cytoplasmic oscillation of both CtBP proteins. We provide evidence that PKA 1) induces metabolic changes in the adrenal cortex and 2) phosphorylates CtBP proteins, particularly CtBP1 at T144, resulting in CtBP protein partnering and ACTH-dependent CYP17 transcription.
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PMID:Phosphorylation of CtBP1 by cAMP-dependent protein kinase modulates induction of CYP17 by stimulating partnering of CtBP1 and 2. 1818 56

Bovine adrenal zona fasciculata (AZF) cells express bTREK-1 K(+) channels that set the resting membrane potential and function pivotally in the physiology of cortisol secretion. Inhibition of these K(+) channels by adrenocorticotropic hormone (ACTH) or cAMP is coupled to depolarization and Ca(2+) entry. The mechanism of ACTH and cAMP-mediated inhibition of bTREK-1 was explored in whole cell patch clamp recordings from AZF cells. Inhibition of bTREK-1 by ACTH and forskolin was not affected by the addition of both H-89 and PKI (6-22) amide to the pipette solution at concentrations that completely blocked activation of cAMP-dependent protein kinase (PKA) in these cells. The ACTH derivative, O-nitrophenyl, sulfenyl-adrenocorticotropin (NPS-ACTH), at concentrations that produced little or no activation of PKA, inhibited bTREK-1 by a Ca(2+)-independent mechanism. Northern blot analysis showed that bovine AZF cells robustly express mRNA for Epac2, a guanine nucleotide exchange protein activated by cAMP. The selective Epac activator, 8-pCPT-2'-O-Me-cAMP, applied intracellularly through the patch pipette, inhibited bTREK-1 (IC(50) = 0.63 microM) at concentrations that did not activate PKA. Inhibition by this agent was unaffected by PKA inhibitors, including RpcAMPS, but was eliminated in the absence of hydrolyzable ATP. Culturing AZF cells in the presence of ACTH markedly reduced the expression of Epac2 mRNA. 8-pCPT-2'-O-Me-cAMP failed to inhibit bTREK-1 current in AZF cells that had been treated with ACTH for 3-4 d while inhibition by 8-br-cAMP was not affected. 8-pCPT-2'-O-Me-cAMP failed to inhibit bTREK-1 expressed in HEK293 cells, which express little or no Epac2. These findings demonstrate that, in addition to the well-described PKA-dependent TREK-1 inhibition, ACTH, NPS-ACTH, forskolin, and 8-pCPT-2'-O-Me-cAMP also inhibit these K(+) channels by a PKA-independent signaling pathway. The convergent inhibition of bTREK-1 through parallel PKA- and Epac-dependent mechanisms may provide for failsafe membrane depolarization by ACTH.
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PMID:ACTH inhibits bTREK-1 K+ channels through multiple cAMP-dependent signaling pathways. 1866 35

Bovine adrenal zona fasciculata (AZF) cells express bTREK-1 K+ channels whose inhibition by cAMP is coupled to membrane depolarization and cortisol secretion through complex signaling mechanisms. cAMP analogs with substitutions in the 6 position of the adenine ring selectively activate cAMP-dependent protein kinase (PKA) but not exchange proteins activated by cAMP (Epacs). In whole-cell patch-clamp recordings from AZF cells, we found that 6-benzoyl-cAMP (6-Bnz-cAMP) and 6-monobutyryl-cAMP potently inhibit bTREK-1 K+ channels, even under conditions in which PKA activity was abolished. Specifically, when applied through the patch electrode, 6-Bnz-cAMP inhibited bTREK-1 with an IC(50) of less than 0.2 microM. Inhibition of bTREK-1 by 6-Bnz-cAMP was not diminished by PKA antagonists, including N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline (H-89), adenosine 3'-5'cyclic monophosphothiate, Rp-isomer, protein kinase inhibitor (PKI) (6-22) amide, and myristoylated PKI (14-22), applied alone or in combination, externally and intracellularly through the patch pipette. Under similar conditions, these same antagonists completely blocked PKA activation by 6-Bnz-cAMP. Inhibition of bTREK-1 by 6-Bnz-cAMP was voltage-independent and eliminated in the absence of ATP in the pipette solution. 6-Bnz-cAMP also produced delayed increases in cortisol synthesis and the expression of CYP11a1 mRNA that were only partially blocked by PKA antagonists. These results indicate that 6-Bnz-cAMP and other 6-substituted cAMP analogs can inhibit bTREK-1 K+ channels and stimulate delayed increases in cortisol synthesis by AZF cells through a PKA- and Epac-independent mechanism. They also suggest that adrenocorticotropin and cAMP function in these cells through a third cAMP-dependent protein. Finally, although 6-modified cAMP analogs exhibit high selectivity in activating PKA over Epac, they also may interact with other unidentified proteins expressed by eukaryotic cells.
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PMID:N6-substituted cAMP analogs inhibit bTREK-1 K+ channels and stimulate cortisol secretion by a protein kinase A-independent mechanism. 1973 21

The functions of the phosphodiesterase 8B (PDE8) family of phosphodiesterases have been largely unexplored because of the unavailability of selective pharmacological inhibitors. Here, we report a novel function of PDE8B as a major regulator of adrenal steroidogenesis using a genetically ablated PDE8B mouse model as well as cell lines treated with either a new PDE8-selective inhibitor or a short hairpin RNA (shRNA) construct against PDE8B. We demonstrate that PDE8B is highly enriched in mouse adrenal fasciculata cells, and show that PDE8B knockout mice have elevated urinary corticosterone as a result of adrenal hypersensitivity toward adrenocorticotropin. Likewise, ablation of PDE8B mRNA transcripts by an shRNA construct potentiates steroidogenesis in the commonly used Y-1 adrenal cell line. We also observed that the PDE8-selective inhibitor (PF-04957325) potentiates adrenocorticotropin stimulation of steroidogenesis by increasing cAMP-dependent protein kinase activity in both primary isolated adrenocortical cells and Y-1 cells. It is noteworthy that PDE8s have their greatest control under low adrenocorticotropin-stimulated conditions, whereas other higher K(m) PDE(s) modulate steroidogenesis more effectively when cells are fully stimulated. Finally, both genetic ablation of PDE8B and long-term pharmacological inhibition of PDE8s cause increased expression of steroidogenic enzymes. We conclude that PDE8B is a major regulator of one or more pools of cAMP that promote steroidogenesis via both short- and long-term mechanisms. These findings further suggest PDE8B as a potential therapeutic target for the treatment of several different adrenal diseases.
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PMID:The high-affinity cAMP-specific phosphodiesterase 8B controls steroidogenesis in the mouse adrenal gland. 2118 69

We have shown that hypoxia reduces plasma insulin, which correlates with corticotropin-releasing hormone (CRH) receptor 1 (CRHR1) in rats, but the mechanism remains unclear. Here, we report that hypobaric hypoxia at an altitude of 5,000 m for 8 h enhances rat plasma CRH, corticosterone, and glucose levels, whereas the plasma insulin and pancreatic ATP/ADP ratio is reduced. In islets cultured under normoxia, CRH stimulated insulin release in a glucose- and CRH-level-dependent manner by activating CRHR1 and thus the cAMP-dependent protein kinase pathway and calcium influx through L-type channels. In islets cultured under hypoxia, however, the insulinotropic effect of CRH was inactivated due to reduced ATP and cAMP and coincident loss of intracellular calcium oscillations. Serum and glucocorticoid-inducible kinase 1 (SGK1) also played an inhibitory role. In human volunteers rapidly ascended to 3,860 m, plasma CRH and glucose levels increased without a detectable change in plasma insulin. By contrast, volunteers with acute mountain sickness (AMS) exhibited a marked decrease in HOMA insulin sensitivity (HOMA-IS) and enhanced plasma CRH. In conclusion, hypoxia may attenuate the CRH-insulinotropic effect by reducing cellular ATP/ADP ratio, cAMP and calcium influx, and upregulated SGK1. Hypoxia may not affect HOMA-IS in healthy volunteers but reduces it in AMS volunteers.
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PMID:Inactivation of corticotropin-releasing hormone-induced insulinotropic role by high-altitude hypoxia. 2527 97


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