Differential regulation of neuronal nicotinic ACh receptor subunit genes in cultured neonatal rat sympathetic neurons: specific induction of alpha 7 by membrane depolarization through a Ca2+/calmodulin-dependent kinase pathway.
We have examined the regulation of neuronal nicotinic ACh receptor (nAChR) genes and ACh-evoked currents by neonatal rat sympathetic neurons developing in culture. These neurons contain 5 nAChR transcripts: alpha 3, alpha 5, alpha 7, beta 2, and beta 4. When developing in culture, the neurons express 4 of these transcripts, alpha 3, alpha 5, beta 2, and beta 4, at levels similar to those in neurons developing in vivo: alpha 3 mRNA levels increase two- to threefold over the first week, whereas the levels for alpha 5, beta 2, and beta 4 remain essentially constant. In contrast, alpha 7 mRNA levels drop by 60-75% within the first 48 hr and remain low. We show that during the first week, the ACh-evoked current densities on these cultured neurons increase twofold and correlate well with the increase in alpha 3 mRNA levels. Depolarizing the neurons with 40 mM KCl for 1-2 d upregulates the alpha 7 gene; this specific change in alpha 7 mRNA level correlates with an increase in alpha-bungarotoxin (alpha-BTX) binding on the surface of the neurons. Depolarization has little effect on the expression of the other four transcripts, or on the magnitude or kinetics of the ACh-evoked currents. Furthermore, activators or inhibitors of protein kinase A (PKA), protein kinase C (PKC), or tyrosine kinase do not affect nAChR transcript levels in these cultured neurons. The effect of membrane depolarization on alpha 7 expression is a result of Ca2+ influx through L-type Ca2+ channels, and we show that alpha 7 is upregulated through a Ca2+/calmodulin-dependent protein kinase (CaM kinase) pathway. The identification of CaM kinase as a link between activity and neurotransmitter receptor expression may indicate a novel mechanism that underlies some forms of synaptic plasticity.
De Koninck
P
P
Department of Physiology, McGill University, Montréal, Québec, Canada.
Cooper
E
E
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives*; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002038:Bungarotoxins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D002794:Choline / Q000494:pharmacology; D004594:Electrophysiology; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D007546:Isoquinolines / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D011494:Protein Kinases / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000235:genetics*; D014158:Transcription, Genetic
D002038:Bungarotoxins; D015220:Calcium Channels; D007546:Isoquinolines; D010879:Piperazines; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002794:Choline; D000109:Acetylcholine; D002118:Calcium