Early events of human T lymphocyte activation are associated with type I protein kinase A activity.
Human T lymphocytes possess both the type I and II isozymes of protein kinase A (PKA). The type I (PKA-I) isozyme is predominantly associated with the plasma membrane, whereas the type II (PKA-II) isozyme is primarily localized to the cytosol. Because the functions of both PKA-I and PKA-II isozymes in the biochemical events of T lymphocyte activation have not been clearly elucidated, we tested the hypothesis that very early events of normal human T lymphocyte activation are mediated by the PKA-I and/or PKA-II isozyme(s). Fresh normal human T cells and a normal human CD4+ T cell line (GK606) activated with anti-CD3-epsilon and recombinant interleukin 1 alpha (rIL-1 alpha) exhibited a peak six- to sevenfold increase of PKA phosphotransferase activity at 5 min that returned to baseline by 60 min. Similarly, both fresh T cells and the T cell line activated by phorbol myristate acetate and ionomycin demonstrated a peak eightfold increase of PKA activity by 15 min that returned toward baseline by 60 min. Chromatographic separation of the PKA isozymes and quantification of phosphotransferase activities after T cell activation by either agonist pair showed preferential activation of the PKA-I isozyme, resulting in a significant reduction in the ratio of PKA-I to PKA-II isozyme activity from 3.1:1-6.2:1 to 1.1:1-3.2:1. PKA-I isozyme activation resulted in the release of free catalytic (C) subunit, an increase in C subunit phosphotransferase activity, and the phosphorylation of T cell plasma membrane-associated proteins, p14, p17, p20, p21, p38, and p48. However, activation of the PKA-I isozyme did not appear to be required for the transcription of IL-2 mRNA, an event necessary for mitosis. These data indicate that ligand-induced T cell activation is associated with rapid activation of the PKA-I, but not PKA-II, isozyme that results in phosphorylation of plasma membrane-associated proteins. The involvement of the PKA-I isozyme during the very early events of T cell activation suggests that this isozyme may be an antigen- or mitogen-stimulated protein kinase.
Laxminarayana
D
D
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Berrada
A
A
Kammer
G M
GM
D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D017252:CD3 Complex / Q000276:immunology / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000031:analogs & derivatives; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000187:drug effects; D008969:Molecular Sequence Data; D010766:Phosphorylation; D013601:T-Lymphocytes / Q000201:enzymology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors
D017252:CD3 Complex; D007375:Interleukin-1; D007527:Isoenzymes; D013873:Thionucleotides; C014308:adenosine 5'-phosphorothioate; D000249:Adenosine Monophosphate; D015759:Ionomycin; D000242:Cyclic AMP; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate