B. Rothhut et al., POSTTRANSLATIONAL REGULATION OF NEURONAL ACETYLCHOLINE-RECEPTORS STABLY EXPRESSED IN A MOUSE FIBROBLAST CELL-LINE, Journal of neurobiology, 29(1), 1996, pp. 115-125
Second messenger regulation of neuronal acetylcholine receptors (AChRs
) was investigated in a mouse fibroblast cell line, M10, stably transf
ected with chicken alpha 4 and beta 2 cDNAs. Both forskolin and 8-brom
o-cyclic adenosine 3',5'-monophosphate (cAMP) induced large increases
in the numbers of AChRs. The increases were due in part to increased t
ranscription and translation of the alpha 4 and beta 2 genes. Blockade
of protein synthesis with cycloheximide, however, revealed that forsk
olin also exerts a post-translational effect, increasing the number of
surface receptors by twofold. Immunoblot analysis of sucrose gradient
fractions confirmed that the cells had a large fraction of unassemble
d subunits potentially available for receptor assembly. The post-trans
lational effect of forskolin was blocked by H-89, an inhibitor of cAMP
-dependent protein kinase, and by okadaic acid, an inhibitor of phosph
atases 1 and 2A. Nicotine also acted posttranslationally to induce a t
wofold increase in the number of surface receptors, but the mechanism
differed from that utilized by forskolin, since the effects of the two
agents were additive and were differentially affected by okadaic acid
. The results suggest that protein phosphorylation-dephosphorylation m
echanisms act post-translationally to increase the number of neuronal
AChRs maintained on the cell surface. This could be achieved by increa
sing the efficiency of receptor assembly, transport, or stabilization
on the cell surface. (C) 1996 John Wiley & Sons, Inc.