title: Direct interaction between protein kinase C theta (PKC theta) and 14-3-3 tau in T cells: 14-3-3 overexpression results in inhibition of PKC theta translocation and function.
abstract: Recent studies have documented direct interactions between 14-3-3 proteins and several oncogene and proto-oncogene products involved in signal transduction pathways. Studies on the effects of 14-3-3 proteins on protein kinase C (PKC) activity in vitro have reported conflicting results, and previous attempts to demonstrate a direct association between PKC and 14-3-3 were unsuccessful. Here, we examined potential physical and functional interactions between PKC theta, a Ca(2+)-independent PKC enzyme which is expressed selectively in T lymphocytes, and the 14-3-3 tau isoform in vitro and in intact T cells. PKC theta and 14-3-3 tau coimmunoprecipitated from Jurkat T cells, and recombinant 14-3-3 tau interacted directly with purified PKC theta in vitro. Transient overexpression of 14-3-3 tau suppressed stimulation of the interleukin 2 (IL-2) promoter mediated by cotransfected wild-type or constitutively active PKC theta, as well as by endogenous PKC in ionomycin- and/or phorbol ester-stimulated cells. This did not represent a general inhibition of activation events, since PKC-independent (but Ca(2+)-dependent) activation of an IL-4 promoter element was not inhibited by 14-3-3 tau under similar conditions. Overexpression of wild-type 14-3-3 tau also inhibited phorbol ester-induced PKC theta translocation from the cytosol to the membrane in Jurkat cells, while a membrane-targeted form of 14-3-3 tau caused increased localization of PKC theta in the particulate fraction in unstimulated cells. Membrane-targeted 14-3-3 tau was more effective than wild-type 14-3-3 tau in suppressing PKC theta-dependent IL-2 promoter activity, suggesting that 14-3-3 tau inhibits the function of PKC theta not only by preventing its translocation to the membrane but also by associating with it. The interaction between 14-3-3 and PKC theta may represent an important general mechanism for regulating PKC-dependent signals and, more specifically, PKC theta-mediated functions during T-cell activation.
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
authors.forename: N
authors.initials: N
authors.lastname: Meller
authors.forename: Y C
authors.initials: YC
authors.lastname: Liu
authors.forename: T L
authors.initials: TL
authors.lastname: Collins
authors.forename: N
authors.initials: N
authors.lastname: Bonnefoy-Bérard
authors.forename: G
authors.initials: G
authors.lastname: Baier
authors.forename: N
authors.initials: N
authors.lastname: Isakov
authors.forename: A
authors.initials: A
authors.lastname: Altman
mesh_terms: D048948:14-3-3 Proteins; D015153:Blotting, Western; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000096:biosynthesis; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis / Q000235:genetics; D015759:Ionomycin / Q000494:pharmacology; D007527:Isoenzymes / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D019169:Jurkat Cells; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011493:Protein Kinase C / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D016324:Sequence Tagged Sites; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase
chemical_list: D048948:14-3-3 Proteins; D007376:Interleukin-2; D007527:Isoenzymes; C000715470:MAS1 protein, human; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011994:Recombinant Proteins; D015759:Ionomycin; D014446:Tyrosine 3-Monooxygenase; D015500:Chloramphenicol O-Acetyltransferase; D005982:Glutathione Transferase; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D013755:Tetradecanoylphorbol Acetate