1,25-Dihydroxyvitamin D(3) stimulates activator protein-1-dependent Caco-2 cell differentiation.
1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is a potential chemopreventive agent for human colon cancer. We have reported that 1,25(OH)(2)D(3) specifically activated protein kinase C-alpha (PKC-alpha) and also caused a reduction in proliferation while increasing apoptosis and differentiation in CaCo-2 cells, a cell line derived from a human colon cancer. The mechanisms by which this secosteroid influences these important cellular processes, however, remain unclear. The transcription factor, activator protein-1 (AP-1), regulates many genes involved in these processes. Therefore, we asked whether 1,25(OH)(2)D(3) activated AP-1 in CaCo-2 cells and, if so, by what mechanisms? 1,25(OH)(2)D(3) caused a time-dependent increase in AP-1 DNA binding activity and significantly enhanced the protein and mRNA abundance of c-Jun, a component of AP-1. 1, 25(OH)(2)D(3) also induced a rapid and transient activation of ERK2 (where ERK is extracellular signal-regulated kinase) and a more persistent activation of JNK1 (where JNK Jun N-terminal kinase). Transfection experiments revealed that 1,25(OH)(2)D(3) also increased AP-1 gene-transactivating activity. This AP-1 activation was completely blocked by PD 098059, a specific mitogen-activated protein kinase/ERK kinase inhibitor, as well as by a dominant negative JNK or a dominant negative Jun, indicating that the AP-1 activation induced by 1,25(OH)(2)D(3) was mediated by ERK and JNK. Using a specific inhibitor of the Ca(2+)-dependent PKC isoforms, Gö6976, and CaCo-2 cells stably transfected with antisense PKC-alpha cDNA, demonstrated that PKC-alpha mediated the AP-1 activation induced by this secosteroid. Inhibition of JNK activation or c-Jun protein expression significantly reduced 1, 25(OH)(2)D(3)-induced alkaline phosphatase activity, a marker of CaCo-2 cell differentiation, in secosteroid-treated cells. Taken together, the present study demonstrated that 1,25(OH)(2)D(3) stimulated AP-1 activation in CaCo-2 cells by a PKC-alpha- and JNK-dependent mechanism leading to increases in cellular differentiation.
Chen
A
A
Gastroenterology Section, Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA.
Davis
B H
BH
Bissonnette
M
M
Scaglione-Sewell
B
B
Brasitus
T A
TA
D018938:Caco-2 Cells; D002117:Calcitriol / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D003474:Curcumin / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014162:Transfection
D016755:Proto-Oncogene Proteins c-jun; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D015500:Chloramphenicol O-Acetyltransferase; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D002117:Calcitriol; D003474:Curcumin