Neuronal alpha-bungarotoxin receptors differ structurally from other nicotinic acetylcholine receptors.
We have characterized the alpha-bungarotoxin receptors (BgtRs) found on the cell surface of undifferentiated pheochromocytoma (PC12) cells. The PC12 cells express a homogeneous population of alpha7-containing receptors that bind alpha-Bgt with high affinity (Kd = 94 pM). The BgtRs mediate most of the response elicited by nicotine, because the BgtR-specific antagonists methyllycaconitine and alpha-Bgt block approximately 90% of the whole-cell current. The binding of nicotinic agonists to cell-surface BgtRs was highly cooperative with four different agonists showing Hill coefficients in the range of 2.3-2.4. A similar agonist binding cooperativity was observed for BgtR homomers formed from chimeric alpha7/5HT3 subunits expressed in tsA 201 cells. Two classes of agonist binding sites, in the ratio of 4:1 for PC12 cell BgtRs and 3:1 for alpha7/5HT3 BgtRs, were revealed by bromoacetylcholine alkylation of the reduced sites on both PC12 BgtRs and alpha7/5HT3 BgtRs. We conclude from this data that PC12 BgtRs and alpha7/5HT3 homomers contain at least three distinguishable agonist binding sites and thus are different from other nicotinic receptors.
Rangwala
F
F
Department of Pharmacological and Physiological Sciences, University of Chicago, Chicago, IL 60637, USA.
Drisdel
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RC
Rakhilin
S
S
Ko
E
E
Atluri
P
P
Harkins
A B
AB
Fox
A P
AP
Salman
S S
SS
Green
W N
WN
D000109:Acetylcholine / Q000031:analogs & derivatives / Q000378:metabolism; D000157:Aconitine / Q000031:analogs & derivatives / Q000494:pharmacology; D000478:Alkylation; D000818:Animals; D001665:Binding Sites; D002038:Bungarotoxins / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D018678:Cholinergic Agents / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000737:chemistry; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D009538:Nicotine / Q000494:pharmacology; D016716:PC12 Cells / Q000737:chemistry; D018408:Patch-Clamp Techniques; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry*; D011985:Receptors, Serotonin / Q000737:chemistry / Q000235:genetics; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000378:metabolism; D013329:Structure-Activity Relationship; D013388:Succinimides / Q000494:pharmacology; D064569:alpha7 Nicotinic Acetylcholine Receptor
D002038:Bungarotoxins; D018678:Cholinergic Agents; C579165:Chrna7 protein, rat; D003432:Cross-Linking Reagents; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011978:Receptors, Nicotinic; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins; D013388:Succinimides; D064569:alpha7 Nicotinic Acetylcholine Receptor; C054634:methyllycaconitine; D009538:Nicotine; C035759:3,3'-dithiobis(sulfosuccinimidyl propionate); D000109:Acetylcholine; D000157:Aconitine