Protein kinase A regulates nicotinic cholinergic receptors and subunit messenger ribonucleic acids in PC 12 cells.
To delineate mechanisms regulating the expression of neuronal nicotinic cholinergic receptors (nAcChRs), we studied the cAMP-dependent second messenger system. PC 12 cells were grown in (Bu)2cAMP (0.001-1.0 mM) or vehicle for 7 days, and specific [3H] nicotine binding was measured. (Bu)2cAMP (0.1 mM) increased specific binding 2- and 4-fold at 3 and 7 days, respectively, whereas 1.0 mM enhanced binding 4-fold at both time intervals. Cells grown in 8-bromo-cAMP (1.0 mM) showed a 2-fold increase in [3H]nicotine binding at 3 days. Forskolin (10-100 microM), in combination with isobutyl-methylxanthine (1.0 mM), enhanced [3H]nicotine binding 2- to 3-fold at 7 days; forskolin or isobutyl-methylxanthine alone had no effect. Specific [3H] nicotine binding to PC 12 cell mutants (A126.1B2 and A123.7), deficient in cAMP-responsive protein kinase A types I and II, were unaffected by (Bu)2cAMP. Northern gel analysis of nAcChR subunit messenger RNAs showed that the alpha-3, alpha-5, and beta-4 subunits were significantly decreased by (Bu)2cAMP at 4 h. However, (Bu)2cAMP caused an increase in the beta-2 messenger RNA transcript at 4 h, which returned to baseline by 24 h. These studies indicate that the cAMP-protein kinase A system regulates expression of nAcChR by PC 12 cells. These studies also suggest that enhancement of [3H]nicotine binding by activated protein kinase A may not involve synthesis of new receptor subunit proteins.
Madhok
T C
TC
Department of Medicine, Hennepin County Medical Center, Minneapolis, Minnesota.
Beyer
H S
HS
Sharp
B M
BM
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D004789:Enzyme Activation; D009154:Mutation; D009538:Nicotine / Q000378:metabolism; D016716:PC12 Cells; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015854:Up-Regulation
D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D003994:Bucladesine; D009538:Nicotine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases