Acetylcholine and acetyl-CoA metabolism in differentiating SN56 septal cell line

The rate of acetylcholine (ACh) synthesis was found to depend on the activi ty of choline acetyltransferase (ChAT) and on the concentrations of the two substrates of this enzyme, choline and acetyl-CoA, In SN56 cells treated f or 3 days with 1 mM dbcAMP activities of ChAT and acetylcholinesterase (ACh E) were elevated. It was accompanied by an increased activity of ATP-citrat e lyase (ACL)-an enzyme responsible for provision of part of acetyl-CoA for ACh synthesis in cholinergic neurons, In contrast lactate dehydrogenase (L DH) and pyruvate dehydrogenase (PDH) activities were reduced by dbcAMP. Tre atment with 0.001 mM all-trans retinoic acid (RA) elevated ChAT and LDH act ivities but reduced the activities of AChE and ACL, The combined treatment with db-cAMP and tRA increased ChAT activity in supraadditive fashion. The effects of these two compounds on the other enzymes were not additive. Neit her compound altered the activities of carnitine acetyl-transferase, acetyl -CoA synthase, or acetyl-CoA hydrolase, On the other hand, they decreased a cetyl-CoA content and rate of ACh release. Overall, the results indicate th at tRA upregulates only ChAT expression, whereas dbcAMP upregulates several features of cholinergic neurons including ChAT, AChE, and ACL. Low levels of acetyl-CoA in differentiated cells may result in a low rate of ACh relea se and resynthesis during their depolarization. (C) 1999 Wiley-Liss, Inc.