Expression of ganglia-type nicotinic acetylcholine receptors and nicotinic ligand binding sites by cells of the IMR-32 human neuroblastoma clonal line.
Studies were conducted to ascertain whether cells of the IMR-32 human neuroblastoma clone express ligand binding sites and functional responsiveness attributable to ganglia-type nicotinic acetylcholine receptors (nAChR) and/or neuronal/nicotinic alpha-bungarotoxin binding sites. Some comparative studies were conducted using cells of other clonal lines, including BC3H-1 mouse muscle line cells that are known to express muscle-type nAChR. Two classes of specific binding sites for 3H-labeled acetylcholine ([3H]ACh) and a single class of high-affinity, specific 125I-labeled alpha-bungarotoxin binding sites are expressed on membrane fractions prepared from IMR-32 cells. Radioligand binding to these sites on IMR-32 cells is relatively insensitive to blockade by the muscle-type nAChR-selective inhibitors, succinyldicholine and decamethonium, indicating that they are distinct from muscle-type nAChR. [3H]ACh binding to its sites on IMR-32 cell membranes is insensitive to blockade by alpha-bungarotoxin, indicating that IMR-32 cell [3H]ACh and 125I-labeled alpha-bungarotoxin binding sites also can be distinguished. Functional nAChR ion channels of the ganglia-type are expressed by IMR-32 cells, as assessed by the abilities of nicotinic agonists to stimulate 86Rb+ efflux, the relatively higher sensitivity of those responses to blockade by mecamylamine than by d-tubocurarine, and the inability of alpha-bungarotoxin to antagonize nAChR function. These results are consistent with expression by IMR-32 cells of functional ganglia-type nAChR that correlate with high affinity [3H]ACh binding sites as well as expression of a distinct class of neuronal/nicotinic alpha-bungarotoxin binding sites that have a ganglia-type pharmacology.
Lukas
R J
RJ
Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona.
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D002038:Bungarotoxins / Q000378:metabolism; D002460:Cell Line; D005724:Ganglia / Q000378:metabolism*; D006801:Humans; D007477:Ions; D008024:Ligands; D051379:Mice; D009132:Muscles / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism*; D011978:Receptors, Nicotinic / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
D002038:Bungarotoxins; D007477:Ions; D008024:Ligands; D011978:Receptors, Nicotinic; D000109:Acetylcholine