Me. Morton et al., CHARACTERIZATION OF MUSCARINIC ACETYLCHOLINE-RECEPTORS EXPRESSED BY AN ATRIAL CELL-LINE DERIVED FROM A TRANSGENIC MOUSE-TUMOR, Circulation research, 74(4), 1994, pp. 752-756
The properties of muscarinic acetylcholine receptors in the cell line
MCM1, derived from an SV40 T-antigen-induced atrial tumor in a transge
nic mouse, were determined. Binding studies using the nonselective mus
carinic antagonist [H-3]quinuclidinyl benzilate, the M1-selective anta
gonist pirenzepine, and the M2-selective antagonist AFDX-116 indicate
that the receptors have the pharmacological properties of the cardiac
(M2) receptor subtype. The receptors could be immunoprecipitated with
a monoclonal antibody specific for the cardiac receptor, thus confirmi
ng the identity of the receptors expressed in these cells. The types o
f G proteins expressed in the cells were determined by Northern blot a
nalyses: mRNA encoding the alpha subunits of G(s), G(o), and G(i-2), b
ut not G(i-1) or G(i-3), were detected, consistent with previous obser
vations of neonatal mammalian atria. The muscarinic receptors were fun
ctionally active, as demonstrated by the ability of the agonist to sti
mulate phosphoinositide turnover and to inhibit adenylyl cyclase activ
ity. The availability of a mammalian atrial cell line that continues t
o express the appropriate functionally coupled subtype of muscarinic r
eceptor may provide a useful system for the investigation of the regul
ation of expression and function of cardiac muscarinic receptors.