ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: The feasibility of using a permeabilized preparation of human SH-SY-5Y neuroblastoma cells for studies of muscarinic acetylcholine receptor (mAChR) sequestration has been evaluated. Exposure of cells permeabilized with digitonin, streptolysin-O, or the α-toxin from Staphylococcus aureus to oxotremorine-M (Oxo-M) for 30 min resulted in a 25–30% reduction in the number of cell surface mAChRs, as monitored by the loss of N[3H]methyl- scopolamine ([3H]NMS) binding sites. The corresponding value for intact cells was 40%. For cells permeabilized with 20 μM digitonin, the Oxo-M-mediated reduction in [3H]NMS binding was time (t1/2∼ 5 min) and concentration (EC50∼ 10 μM) dependent and was agonist specific (Oxo M 〉 bethanechol = arecoline = pilocarpine). In contrast, no reduction in total mAChR number, as monitored by the binding of [3H]quinuclidinyl benzilate, occurred following Oxo-M treatment. The loss of [3H]NMS sites observed in the presence of Oxo-M was unaffected by omission of either ATP or Ca2+, both of which are required for stimulated phosphoinositide hydrolysis, but could be inhibited by the inclusion of guanosine 5′-O-(2-thiodiphosphate). mAChRs sequestered in response to Oxo-M addition were unmasked when the cells were permeabilized in the presence of higher concentrations of digitonin (80 μM). The results indicate (a) that permeabilized SH-SY-5Y cells support an agonist-induced sequestration of mAChRs, the magnitude of which is ∼ 65–70% of that observed for intact cells, (b) that when internalized, mAChRs are located in a cellular compartment to which [3H]NMS has only a limited access despite the removal of the plasma membrane barrier, and (c) that the production of phosphoinositide-derived second messengers is not a prerequisite for mAChR sequestration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1471-4159.1994.62051795.x
