Cyclic AMP inhibits translation of cyclin D3 in T lymphocytes at the level of elongation by inducing eEF2-phosphorylation.
The purpose of the present study was to understand the mechanism by which activated protein kinase A (PKA) leads to down-regulation of cyclin D3 in lymphocytes. By using Jurkat cells as a model system, we have been able to demonstrate that cyclin D3 is reduced at the level of translation by inhibition of elongation. One of the important factors involved in translational elongation is the eukaryotic elongation factor 2 (eEF2). eEF2 promotes translation in its unphosphorylated form, and we observed a rapid phosphorylation of the eEF2-protein upon forskolin treatment. When using specific inhibitors of the eEF2-kinase prior to forskolin treatment, we were able to inhibit the increased phosphorylation of eEF2. Furthermore, inhibition of eEF2-kinase prevented the forskolin-mediated down-regulation of cyclin D3. Taken together, it appears that activation of PKA in Jurkat cells reduces the expression of cyclin D3 at the level of translational elongation by increasing the phosphorylation of eEF2 and thereby inhibiting its activity.
Gutzkow
Kristine B
KB
Institute of Medical Biochemistry, University of Oslo, PO Box 1112, Blindern, N-0317, Oslo, Norway.
Låhne
Hege U
HU
Naderi
Soheil
S
Torgersen
Knut Martin
KM
Skålhegg
Bjørn
B
Koketsu
Mamoru
M
Uehara
Yoshimasa
Y
Blomhoff
Heidi Kiil
HK
D015152:Blotting, Northern; D015153:Blotting, Western; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D056743:Cyclin D3; D016213:Cyclins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004261:DNA Replication / Q000187:drug effects; D015536:Down-Regulation; D054736:Elongation Factor 2 Kinase; D005434:Flow Cytometry / Q000379:methods; D016193:G1 Phase / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D009025:Morpholines / Q000494:pharmacology; D016566:Organoselenium Compounds / Q000494:pharmacology; D010441:Peptide Chain Elongation, Translational / Q000502:physiology; D020652:Peptide Elongation Factor 2 / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011132:Polyribosomes / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D016160:Retinoblastoma Protein / Q000187:drug effects / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection
C405507:4-ethyl-4-hydroxy-2-(4-tolyl)-4H-5,6-dihydro-1,3-selenazine; C534696:CCND3 protein, human; D002867:Chromones; D056743:Cyclin D3; D016213:Cyclins; D009025:Morpholines; D016566:Organoselenium Compounds; D020652:Peptide Elongation Factor 2; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D005576:Colforsin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D003513:Cycloheximide; D000242:Cyclic AMP; C517689:EEF2K protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D054736:Elongation Factor 2 Kinase; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha