Gastrin transactivates the chromogranin A gene through MEK-1/ERK- and PKC-dependent phosphorylation of Sp1 and CREB.
Our previous work revealed that gastrin regulates chromogranin A (CgA) transcription through enhanced binding of Sp1, CREB and Egr-1 to a proximal gastrin-responsive promoter element (Gas-RE). Here, we provide a detailed characterization of the signalling pathways transmitting the effect of gastrin on the CgA promoter. Gastrin treatment of gastric AGS-B cells potently stimulated MEK-1 as well as MAP kinases ERK-1/-2, JNK and p38 in a time-dependent manner. Interruption of ERK-1/-2/MEK-1 pathways abolished the transactivating effect of gastrin, whereas blockade of JNK or p38 activity was without effect. Functional promoter analysis revealed that the minimal element CgA-85/-64 was sufficient and necessary to confer MEK-1/ERK responsiveness. Analysis of proximal signalling pathways showed that activation of the MEK-1/ERK-1/2 module by gastrin does not require Ras, PI3-kinase or intracellular calcium signals, but depends on activation of kinases of the PKC family. This report demonstrates that a pathway comprising PKCs>Raf-1>MEK-1>ERK-1/-2 mediates the effect of gastrin on the CgA promoter, and strongly suggests that enhanced phosphorylation of Sp1 and CREB is crucial for CgA transactivation through the G protein-coupled CCK-B/gastrin receptor.
Cramer
Thorsten
T
Laboratory for Angiogenesis and Tumor Metastasis, Charité - Universitätsmedizin Berlin, Campus Virchow-Klinikum, Germany.
Jüttner
Stefan
S
Plath
Thomas
T
Mergler
Stefan
S
Seufferlein
Thomas
T
Wang
Timothy C
TC
Merchant
Juanita
J
Höcker
Michael
M
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D050882:CREB-Binding Protein / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D053379:Chromogranin A / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005755:Gastrins / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D043887:Receptor, Cholecystokinin B / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000378:metabolism / Q000473:pathology
D053379:Chromogranin A; D005755:Gastrins; D043887:Receptor, Cholecystokinin B; D016329:Sp1 Transcription Factor; D050882:CREB-Binding Protein; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; D002118:Calcium