Differential regulation of the high affinity choline transporter and the cholinergic locus by cAMP signaling pathways.
Synthesis, storage and release of acetylcholine (ACh) require the expression of several specialized enzymes, including choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT) and the high-affinity choline transporter (CHT). Extracellular factors that regulate CHT expression and their signaling pathways remain poorly characterized. Using the NSC-19 cholinergic cell line, derived from embryonic spinal cord, we compared the effects of the second messenger cAMP on the expression of CHT and the cholinergic locus containing the ChAT and VAChT genes. Treatment of NSC-19 cells with dbcAMP and forskolin, thus increasing intracellular cAMP levels, significantly reduced CHT mRNA expression, while it upregulated ChAT/VAChT mRNA levels and ChAT activity. The cAMP-induced CHT downregulation was independent of PKA activity, as shown in treatments with the PKA inhibitor H-89. The alternative Epac-Rap pathway, when stimulated by a specific Epac activator, led to significant downregulation of CHT and ChAT, and, to a lesser extent, VAChT. In contrast, the PKA activator 6-BNZ-cAMP stimulated the expression of all three genes, but with varying concentration-dependence profiles. Our results indicate that elevations of intraneuronal cAMP concentration have differential effects on the cholinergic phenotype, depending on the involvement of different downstream effectors. Interestingly, although CHT is expressed predominantly in cholinergic cells, its regulation appears to be distinct from that of the cholinergic locus.
Brock
Martina
M
Department of Pathology and Laboratory Medicine, Boston University School of Medicine, 715 Albany Street, Room L-808C, Boston, MA 02118, USA.
Nickel
Ann-Christin
AC
Madziar
Beata
B
Blusztajn
Jan Krzysztof
JK
Berse
Brygida
B
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D045744:Cell Line, Tumor; D002795:Choline O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002799:Cholinergic Fibers / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000187:drug effects / Q000378:metabolism; D006825:Hybridomas; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D050494:Vesicular Acetylcholine Transport Proteins / Q000235:genetics
C488255:CHT1 protein, mouse; C482601:Epac protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; C493460:Slc18a3 protein, mouse; D050494:Vesicular Acetylcholine Transport Proteins; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP; D002795:Choline O-Acetyltransferase; D017868:Cyclic AMP-Dependent Protein Kinases; D000109:Acetylcholine