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Journal of neurochemistry

Intracellular distribution of functional M(1) -muscarinic acetylcholine receptors in N1E-115 neuroblastoma cells.


PMID 21740440

Abstract

Signaling by muscarinic agonists is thought to result from the activation of cell surface acetylcholine receptors (mAChRs) that transmit extracellular signals to intracellular systems. In N1E-115 neuroblastoma cells, we detected both plasma membrane and intracellular M(1) -mAChRs using both biochemical and pharmacological methods. In intact cells, both plasma membrane and intracellular M(1) -mAChRs were detected by the hydrophobic ligand probe, 1-quinuclidinyl-[phenyl-4-(3) H]-benzilate ([(3) H]-QNB) whereas the hydrophilic probe, 1-[N-methyl-(3) H] scopolamine ([(3) H]-NMS), detected only cell surface receptors. These probes detected comparable numbers of receptors in isolated membrane preparations. Immunohistochemical studies with M(1) -mAChR antibody also detected both cell-surface and intracellular M(1) -mAChRs. Carbachol-stimulated phosphatidylinositol hydrolysis and Ca(2+) mobilization were completely inhibited by a cell-impermeable M(1) antagonist, muscarinic toxin -7 and the G(q/11) inhibitor YM-254890. However, carbachol-stimulated extracellular-regulated kinase 1/2 activation was unaffected by muscarinic toxin-7, but was blocked by the cell-permeable antagonist, pirenzepine. extracellular regulated kinase 1/2 phosphorylation was resistant to blockade of G(q/11) (YM-254890) and protein kinase C (bisindolylmaleimide I). Our data suggest that the geographically distinct M(1) -mAChRs (cell surface versus intracellular) can signal via unique signaling pathways that are differentially sensitive to cell-impermeable versus cell-permeable antagonists. Our data are of potential physiological relevance to signaling that affects both cognitive and neurodegenerative processes.

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