Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscarinic receptor density increased by approximately 36% after differentiation induced by retinoic acid (Bmax, control = 126 +/- 13 fmol/mg protein; Bmax, retinoic acid-treated = 170 +/- 17 fmol/mg protein; P < 0.05), corresponding to a 170% increase in receptor content per cell. The affinity of [3H]NMS for the receptors was somewhat lower in the retinoic acid-treated cells (Kd, control = 0.14 +/- 0.04 nM; Kd, retinoic acid-treated = 0.25 +/- 0.04 nM; P < 0.05). Reverse transcriptase/polymerase chain reaction analysis using subtype-specific primers revealed that undifferentiated Sk-N-SH cells transcribed mRNA for all 5 receptor subtypes; this pattern was not affected by retinoic acid treatment. [3H]NMS displacement curves with subtype selective receptor ligands (pirenzepine, m1; AFDX-116, m2; 4-DAMP, m3) indicated the predominant expression of m3 and m1 receptor subtypes, and differentiation did not affect the pharmacological profile of the expressed receptor populations. The present results indicate that differentiation induces selective changes in the expression and activity of muscarinic receptors in a neuronal cell line.
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PMID:Retinoic acid-induced differentiation of a human neuroblastoma cell line alters muscarinic receptor expression. 848 52

Muscarinic receptor subtypes in the bovine corneal epithelial cells (BCE) were characterized on the basis of their: 1) ligand binding properties, 2) linkage to Ca2+ and cAMP cell signaling pathways, and 3) gene transcripts. Receptor subtypes, m1 and m2, are indicated by competition experiments using subtype-selective muscarinic receptor ligands. [3H]N-methylscopolamine ([3H]-MS) binding was displaced with IC50s of: 1) 1 microM for the m1 antagonist, pirenzipine; 2) 51 microM for the competitive m2 antagonist, AFDX-116; 3) 100 microM for the competitive m3 antagonist, 4-DAMP. In fural2 loaded BCE, carbachol (0.001 - 100 microM) increased intracellular Ca2+ concentration ([Ca2+]i), and these responses were significantly suppressed if they were preincubated with either atropine (1 microM) or 1 microM pirenzipine. In the absence of extracellular Ca2+, these carbachol-induced increases in [Ca2+]i were depressed. A considerable fall occurred with the presence of extracellular Ca2+ and 1 microM verapamil, an L-type Ca2+ channel blocker. These responses suggest that carbachol increases Ca2+ influx through an L-type Ca2+ channel in the plasma membrane, in addition to mobilizing Ca2+ from an intracellular store. BCE also possessed muscarinic receptors which were negatively linked to cAMP production insofar as: 1) preincubation with 10 microM carbachol significantly suppressed the increases in cAMP accumulation induced by isoproterenol (1 - 25 microM); 2) this blunting effect of carbachol on cAMP production was eliminated when the BCE were preincubated with either 1 microM AFDX-116, or 100 ng/ml pertussis toxin. The results of probing for muscarinic receptor gene expression are partially consistent with the ligand binding and functional assays. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the presence of m2 but not m1, m3 or m4 gene transcripts. In summary, we obtained pharmacological and functional evidence for m1 and m2 receptors in BCE. However, only the m2 gene transcript could be detected.
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PMID:Characterization of the muscarinic receptor subtypes in the bovine corneal epithelial cells. 887 32

In the present work we have investigated which muscarinic (M) receptor subtype is responsible for the steroidogenic effect of muscarinic agonists in bovine zona fasciculata-reticularis (ZFR) cells in culture. Radioligand binding studies using the muscarinic antagonist [(3)H]quinuclidinyl benzilate ([(3)H]QNB) demonstrated binding sites of high affinity (K(d)=0.45 nM) and low capacity ( approximately 8000 sites/cell). Pharmacological characterisation of muscarinic receptors was assessed by evaluating the effects of the M(3)>M(1)>>M(2) antagonist 4-DAMP (4-diphenylacetyl-N-methylpiperidine) and the M(1)=M(4)> M(3)>>M(2) antagonist pirenzepine on the binding of [(3)H]QNB and carbachol-induced cortisol production. For both parameters, the potency of 4-DAMP was about two orders of magnitude higher than that of pirenzepine. Reverse transcriptase (RT)-PCR analysis of bovine ZFR mRNAs using specific primers for M(2), M(3) and M(4) receptors revealed the expression of only M(3) mRNA. Moreover, carbachol significantly stimulated inositol phosphate accumulation, but had no inhibitory effect on basal or ACTH-induced cAMP production. Indeed, carbachol potentiated ACTH-induced cAMP production and this effect was, in part, mediated through protein kinase C. Lastly, neomycin, an inhibitor of phosphoinositide turnover, significantly attenuated carbachol-evoked cortisol production. Thus, pharmacological, biochemical and mRNA studies indicate that the M(3) receptor subtype is responsible for the biological effects of muscarinic agonists in bovine ZFR cells.
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PMID:Characterisation of the muscarinic receptor subtype M3 in the bovine zona fasciculata-reticularis cells by receptor binding, mRNA and functional studies. 1055 83