Abstract Mel 1a melatonin receptors belong to the superfamily of guanine nucleotide-binding regulatory protein (G protein)-coupled receptors. So far, interest in receptor signaling has focused mainly on modulation adenylyl cyclase pathway via pertussis toxin (PTX)-sensitive G proteins. To further investigate human receptor, we have developed an antibody directed against C terminus this receptor. This detected as a with apparent molecular mass approximately 60 kDa immunoblots after separation...

Glutamatergic neurotransmission is controlled by presynaptic metabotropic glutamate receptors (mGluRs). A subdomain in the intracellular carboxyl-terminal tail of group III mGluRs binds calmodulin and heterotrimeric guanosine triphosphate–binding protein (G protein) βγ subunits a mutually exclusive manner. Mutations interfering with binding antagonists inhibit G protein–mediated modulation ionic currents mGluR 7. Calmodulin also prevent inhibition excitatory via mGluRs. These results reveal...

G protein alpha subunits expose specific binding sites that allow for the sequential, conformation-dependent of reaction partners, e.g., beta gamma dimers, receptors, and effectors. These domains represent potential low-molecular-weight inhibitors. We tested following suramin analogues as antagonists: 8-(3-nitrobenzamido)-1,3,5-naphtalenetrisulfonic acid (NF007), 8-(3-(3-nitrobenzamido)benzamido)-1,3,5-naphtalenetrisulfonic++ + NF018),...

Many membrane proteins incur a folding problem during biosynthesis; only fraction thereof is exported from the endoplasmic reticulum (ER), because quality control stringent. This also true for G protein-coupled receptors. Here, we identify deubiquitinating enzyme Usp4 as an interaction partner of A2a adenosine receptor, Gs-coupled receptor. binds to carboxyl terminus A2A receptor and allows its accumulation deubiquinated protein. relaxes ER enhances cell surface expression functionally...

Signaling by D₂-dopamine receptors in neurons likely proceeds the presence of Ca²⁺ oscillations. We describe here biochemical basis for a cross-talk between intracellular and D₂ receptor. By activation calmodulin (CaM), directly inhibits receptor; this conclusion is based on following observations: (i) The receptor contains CaM-binding motif NH₂-terminal end third loop, domain involved activating G_i/o. A peptide fragment encompassing...

Suramin acts as a G protein inhibitor because it inhibits the rate-limiting step in activation of α subunit, i.e., exchange GDP for GTP. Here, we have searched analogues that are selective sα . Two compounds been identified: NF449 (4,4′,4",4′"-[carbonyl-bis[imino-5,1,3-benzenetriyl bis-(carbonylimino)]]tetrakis-(benzene-1,3-disulfonate) and NF503 (4,4′-[carbonylbis[imino-3,1-phenylene-(2,5-benzimidazolylene)carbonylimino]]bis-benzenesulfonate). These ( i ) suppress association rate guanosine...

Suramin analogues act as direct antagonists of heterotrimeric G proteins because they block the rate-limiting step protein activation (i.e., dissociation GDP prebound to alpha subunit). We have used human brain A1 adenosine receptor and rat striatal D2 dopamine receptor, two prototypical Gi/G(o)-coupled receptors, a model system test whether following suppress receptor-dependent proteins: 8-(3-nitrobenzamido)-1,3,5-naphthalenetrisulfonic acid (NF007),...

The purified bovine brain A,-adenosine receptor has previously been shown to discriminate among closely related G protein a-subunits.To obtain analogous information for the human receptor, cDNA coding was inserted into a plasmid placing synthesis of under control MalE promoter.Following induction by maltose, active accumulated in Escherichia coli membranes.Binding antagonist S-~3Hlcyclopentyl-l,3-dipropylxanthine E. membranes (K, -2 MI, B,, -0.2-0.4 pmoYmg) showed appropriate pharmacological...

If stably expressed in human embryonic kidney (HEK)293 cells, the Mel_1a-melatonin receptor activates G_i-dependent, pertussis toxin-sensitive signaling pathways, i.e., inhibition of adenylyl cyclase and stimulation phospholipase Cβ; latter on condition that G_q is coactivated. The antagonist luzindole blocks effects melatonin acts as an inverse agonist at Mel_1a both intact cells isolated membranes. This suggests Mel_1areceptor endowed with...

Ulcerous lesions can arise in primary skin cancers and upon infiltration of the by malignant cells originating from other organs. These fungating wounds are difficult to treat, they cause pain, itching malodor. Distressing malodor imposes a major burden on patients. The carrion odor decaying tissue is—at least part—due bacterial breakdown products cadaverine putrescine. Here, we examined binding cadaverine, histamine, putrescine, spermidine spermine preparation micronized purified...

UTP stimulates transmitter release and inhibits M-type K(+) channels in rat superior cervical ganglion neurons via G protein-coupled P2Y receptors. To investigate the underlying signaling mechanisms, we treated with either pertussis or cholera toxin; neither treatment altered inhibition of by 10 microM UTP. However, toxin reduced UTP-evoked [(3)H]noradrenaline 66%. UTP, UDP, ATP, ADP caused accumulation inositol trisphosphate a toxin-insensitive manner. Pharmacological trisphosphate-induced...

Agonist binding to the A2 adenosine receptor (A2AR) and its regulation by guanine nucleotides was studied using newly developed radioligand 125I-2-[4-(2-[2-[(4-aminophenyl)methylcarbonylamino] ethylaminnocarbonyl]ethyl)phenyl]ethylamino-5'-N- ethylcarboxamidoadenosine (125I-PAPA-APEC) photoaffinity analog 125I-azido-PAPA-APEC. A single protein of Mr 45,000, displaying appropriate A2AR pharmacology, is labeled in membranes from bovine striatum, PC12 cells, frog erythrocytes. In DDT1 MF2 cells...

Blockage of <i>β</i>₁-adrenergic receptors is one the most effective treatments in cardiovascular medicine. Esmolol was introduced some three decades ago as a short-acting <i>β</i>₁-selective antagonist. Landiolol more recent addition. Here we compared two compounds for their selectivity over <i>β</i>₂-adrenergic receptors, partial agonistic activity, signaling bias, and pharmacochaperoning action by using human embryonic kidney (HEK)293 cell lines, which...

Hypoparathyroidism is a common sequela of thyroid surgery; in this study, we aimed at exploring the pathogenesis behind it. The following premises suggest that wound fluid might be causative agent. (i) Parathyroid hormone secretion under feedback control by calcium-sensing receptor, which responds to diverse array activating ligands. (ii) Postoperative hypoparathyroidism arises from secretory deficiency parathyroid glands. Even patients later unaffected hypoparathyroidism, levels drop within...

Reconstitution experiments with purified components reproduce the basic characteristics of receptor/G protein coupling, i.e., GTP-sensitive high affinity agonist binding and receptor-promoted GTP binding. However, interaction agonists A1 adenosine receptor in rat bovine but not human brain membranes deviates from ternary complex model since agonist/receptor/G cannot be dissociated by concentrations (> or = 100 microM) hydrolysis-resistant analogue gamma S. The reason for this phenomenon...

The carboxyl terminus (C-tail) of G protein-coupled receptors is divergent in length and structure may represent an individualized cytoplasmic domain. By progressively truncating the A1 adenosine receptor, a Gi/o-coupled receptor with short stretches, we identify two inherent functions C-tail, namely role export from endoplasmic reticulum (ER) protein coupling. Deletion last 22 26 amino acids (of 36) reduced completely abolished surface expression respectively. severely truncated were...

Ca²⁺/calmodulin (Ca²⁺/CaM) and the βγ subunits of heterotrimeric G-proteins (Gβγ) have recently been shown to interact in a mutually exclusive fashion with intracellular C terminus presynaptic metabotropic glutamate receptor 7 (mGluR 7). Here, we further characterized core CaM Gβγ binding sequences. In contrast previous report, find that motif localized N-terminal region cytoplasmic tail domain mGluR is conserved related group III mGluRs 4A 8 allows these receptors also...

(–)Isoprenaline was continuously administered to rats at a rate of 0.4 mg/kg/h for 7 days via subcutaneously (s.c.) implanted osmotic minipumps. This treatment induced cardiac hypertrophy and marked decrease in basal as well catecholamine-stimulated adenylate cyclase activity ventricular plasma membrane fraction. The total number (β-adrenoceptors downregulated by one-half the amount receptor sites obtained control group. However, isoprenaline-treated group, constituted significantly smaller...

Exchanging each of the conserved aromatic residues NPxxY(x)_5,6F sequence (at boundary helices 7 and 8) generated variants A₁ adenosine receptor that were retained within cell. The mutations disconnected a link between α-helix cytosolic helix 8, likely destabilizing structure proximal carboxyl terminus. mutant receptors rescued by incubation cells with pharmacochaperone, membrane-permeable ligand homosterically binds to receptor; pharmacochaperoning restored density...