Differential regulation of chromogranin B and synapsin I gene promoter activity by cAMP and cAMP-dependent protein kinase.
cAMP has neutrotrophic effects in the nervous system. We have investigated whether there is a correlation between cAMP-induced neurite outgrowth and induction of chromogranin B and synapsin I gene expression. These genes encode marker proteins of distinct populations of vesicles in neurons, neuroendocrine and endocrine cells, and in addition, they contain a cAMP response element (CRE) in their upstream regions, making it likely that cAMP-induced neuronal differentiation might be accompanied by increased transcription of these genes. We increased intracellular cAMP levels in neuronal and neuroendocrine cells and analyzed the levels of chromogranin B and synapsin I mRNA. Our data revealed that, while chromogranin B mRNA was in fact induced following cAMP stimulation, synapsin I mRNA was not affected. To analyze the cis-acting sequences, we constructed hybrid genes containing the upstream region of the mouse chromogranin B gene fused to a reporter gene. Similar plasmids containing the synapsin I or the glucagon promoter were constructed. Transfections of neuronal and endocrine cells, together with deletion mutagenesis, revealed that the CRE of the chromogranin B gene mediated the effect of cAMP upon transcription. This effect was mimicked by overexpression of the catalytic subunit of the cAMP-dependent protein kinase. In addition, overexpression of the negative-acting CRE-binding protein CREB-2 revealed that the chromogranin B CRE functions as a bifunctional genetic regulatory element in that it mediates basal as well as cAMP-stimulated transcription. Synapsin I gene expression, however, was not induced by either elevated intracellular cAMP concentration or by overexpression of protein kinase A, although a similar pattern of proteins, including CREB, bound to the synapsin I and chromogranin B CRE in vitro. Thus while the CRE element in the chromogranin B gene promoter is responsive to cAMP, the same element, when present in the synapsin I promoter, does not confer cAMP inducibility.
Jüngling
S
S
Institute for Genetics, University of Cologne, Germany.
Cibelli
G
G
Czardybon
M
M
Gerdes
H H
HH
Thiel
G
G
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D003994:Bucladesine / Q000494:pharmacology; D002461:Cell Line, Transformed; D053378:Chromogranin B; D002864:Chromogranins / Q000235:genetics*; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000502:physiology; D004742:Enhancer Elements, Genetic; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects*; D051379:Mice; D008969:Molecular Sequence Data; D016716:PC12 Cells; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins; D016704:Synapsins / Q000235:genetics*; D014158:Transcription, Genetic
D053378:Chromogranin B; D002864:Chromogranins; D017362:Cyclic AMP Response Element-Binding Protein; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D016704:Synapsins; C506137:chromogranin B, mouse; C506140:chromogranin B, rat; D003994:Bucladesine; D000242:Cyclic AMP; D011494:Protein Kinases; D015056:1-Methyl-3-isobutylxanthine