Protein kinase A regulates expression of p27(kip1) and cyclin D3 to suppress proliferation of leukemic T cell lines.
Peripheral homeostasis and tolerance requires the suppression or removal of excessive or harmful T lymphocytes. This can occur either by apoptosis through active antigen-induced death or cytokine withdrawal. Alternatively, T cell activation can be suppressed by agents that activate the cAMP-dependent protein kinase (PKA) signaling pathway, such as prostaglandin E2. Stimulation of PKA inhibits lymphocyte proliferation and immune effector functions. Here we have investigated the mechanism by which activation of PKA induces inhibition of proliferation in human leukemic T cell lines. Using a variety of agents that stimulate PKA, we can arrest Jurkat and H9 leukemic T cells in the G(1) phase of the cell cycle, whereas cell viability is hardly affected. This G(1) arrest is associated with an inhibition of cyclin D/Cdk and cyclin E/Cdk kinase activity. Interestingly, expression of cyclin D3 is rapidly reduced by PKA activation, whereas expression of the Cdk inhibitor p27(kip1) is induced. Ectopic expression of cyclin D3 can override the growth suppression induced by PKA activation to some extent, indicating that growth inhibition of leukemic T cells by PKA activation is partially dependent on down-regulation of cyclin D3 expression. Taken together our data suggest that immunosuppression by protein kinase A involves regulation of both cyclin D3 and p27(kip1) expression.
van Oirschot
B A
BA
Jordan Laboratory for Hemato-Oncology, G03-647, Utrecht Medical Center, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
Stahl
M
M
Lens
S M
SM
Medema
R H
RH
D017209:Apoptosis; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002455:Cell Division; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism* / Q000502:physiology*; D056743:Cyclin D3; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006801:Humans; D019169:Jurkat Cells; D007938:Leukemia / Q000201:enzymology*; D010766:Phosphorylation; D015398:Signal Transduction; D013997:Time Factors; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
C534696:CCND3 protein, human; D018797:Cell Cycle Proteins; D056743:Cyclin D3; D016213:Cyclins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases