Selective modulation of protein kinase C-theta during T-cell activation.
Every cell contains many families of protein kinases, and may express several structurally related yet genetically distinct kinases of each family. The activity of the serine/threonine protein kinase C (PKC) enzymes has long been implicated in T-cell activation, but it is not known which members of the PKC family regulate the T-cell response to foreign antigens. The activation of T cells by antigen-presenting cells (APCs) is spatially restricted to their site of contact, where receptors on the T cells engage their counter-receptors on the APCs. We used this localized engagement to identify, at the single-cell level, intracellular proteins involved in the activation process. By digital immunofluorescence microscopy, we localized six isoforms of PKC in antigen-specific T-cell clones activated by APCs. Surprisingly, only PKC-theta translocated to the site of cell contact. Accordingly, in vitro kinase activity assays of PKC immunoprecipitates from the conjugates of T cells and APCs showed a selective increase in the activity of PKC-theta, indicating that the translocated enzyme is active. Several modes of partial T-cell activation that failed to cause PKC-theta translocation also failed to cause T-cell proliferation, further suggesting the involvement of PKC-theta in T-cell activation.
Monks
C R
CR
Division of Basic Sciences, National Jewish Center for Immunology, Denver, Colorado 80206, USA.
Kupfer
H
H
Tamir
I
I
Barlow
A
A
Kupfer
A
A
D000938:Antigen-Presenting Cells / Q000276:immunology; D001692:Biological Transport; D002460:Cell Line; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism*; D008213:Lymphocyte Activation; D008856:Microscopy, Fluorescence; D011493:Protein Kinase C / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D014407:Tumor Cells, Cultured
D007527:Isoenzymes; D011948:Receptors, Antigen, T-Cell; D011493:Protein Kinase C