The physical association of protein kinase C theta with a lipid raft-associated inhibitor of kappa B factor kinase (IKK) complex plays a role in the activation of the NF-kappa B cascade by TCR and CD28.
We investigated the role of protein kinase C theta (PKCtheta) in the activation of the NF-kappaB cascade in primary human CD4(+) lymphocytes. Among six or so PKC isoforms expressed in T cells, only PKCtheta participates in the assembly of the supramolecular activation clusters at the contact site of the TCR with Ag. Signaling via both the TCR and CD28 is required for optimal activation of the multisubunit IkappaB kinase (IKK) complex in primary human T lymphocytes; this activation could be inhibited by a Ca(2+)-independent PKC isoform inhibitor, rottlerin. Moreover, endogenous PKCtheta physically associates with activated IKK complexes in CD3/CD28-costimulated primary CD4(+) T cells. The same set of stimuli also induced relocation of endogenous PKCtheta and IKKs to a GM1 ganglioside-enriched, detergent-insoluble membrane compartment in primary T cells. IKKs recruited to these lipid rafts were capable of phosphorylating a recombinant IkappaBalpha sustrate. Confocal microscopy further demonstrated that exogenously expressed PKCtheta and IKKss colocalize in the membrane of CD3/CD28-costimulated Jurkat T cells. Constitutively active but not kinase-inactive PKCtheta activated IKKbeta in Jurkat T cells. Expression of dominant-active PKCtheta also had stimulatory effects on the CD28 response element of the IL-2 promoter. Taken together, these data show that the activation of PKCtheta by the TCR and CD28 plays an important role in the assembly and activation of IKK complexes in the T cell membrane.
Khoshnan
A
A
Division of Clinical Immunology and Allergy, Department of Medicine, Center for Health Sciences, University of California, Los Angeles, CA 90095, USA.
Bae
D
D
Tindell
C A
CA
Nel
A E
AE
D018106:CD28 Antigens / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017252:CD3 Complex / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000276:immunology; D004791:Enzyme Inhibitors / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D051550:I-kappa B Kinase; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D019169:Jurkat Cells / Q000201:enzymology / Q000378:metabolism; D021962:Membrane Microdomains / Q000201:enzymology* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000276:immunology; D011493:Protein Kinase C / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D000074121:Protein Kinase C-theta; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D020218:Response Elements / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D016608:Talin / Q000378:metabolism
D018106:CD28 Antigens; D017252:CD3 Complex; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D016328:NF-kappa B; D011948:Receptors, Antigen, T-Cell; D016608:Talin; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta