Protein kinase C (PKC) alpha and PKC theta are the major PKC isotypes involved in TCR down-regulation.
It is well known that protein kinase C (PKC) plays an important role in regulation of TCR cell surface expression levels. However, eight different PKC isotypes are present in T cells, and to date the particular isotype(s) involved in TCR down-regulation remains to be identified. The aim of this study was to identify the PKC isotype(s) involved in TCR down-regulation and to elucidate the mechanism by which they induce TCR down-regulation. To accomplish this, we studied TCR down-regulation in the human T cell line Jurkat, in primary human T cells, or in the mouse T cell line DO11.10 in which we either overexpressed constitutive active or dominant-negative forms of various PKC isotypes. In addition, we studied TCR down-regulation in PKC knockout mice and by using small interfering RNA-mediated knockdown of specific PKC isotypes. We found that PKCalpha and PKCtheta were the only PKC isotypes able to induce significant TCR down-regulation. Both isotypes mediated TCR down-regulation via the TCR recycling pathway that strictly depends on Ser(126) and the di-leucine-based receptor-sorting motif of the CD3gamma chain. Finally, we found that PKCtheta was mainly implicated in down-regulation of directly engaged TCR, whereas PKCalpha was involved in down-regulation of nonengaged TCR.
von Essen
Marina
M
Institute of Medical Microbiology and Immunology, University of Copenhagen, Denmark.
Nielsen
Martin W
MW
Bonefeld
Charlotte M
CM
Boding
Lasse
L
Larsen
Jeppe M
JM
Leitges
Michael
M
Baier
Gottfried
G
Odum
Niels
N
Geisler
Carsten
C
D020816:Amino Acid Motifs; D000818:Animals; D017252:CD3 Complex / Q000502:physiology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D006801:Humans; D006825:Hybridomas; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019169:Jurkat Cells; D007930:Leucine / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051571:Protein Kinase C-alpha / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000074121:Protein Kinase C-theta; D034741:RNA, Small Interfering / Q000494:pharmacology; D011948:Receptors, Antigen, T-Cell / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*
D017252:CD3 Complex; C452842:CD3 antigen, gamma chain; D007527:Isoenzymes; D034741:RNA, Small Interfering; D011948:Receptors, Antigen, T-Cell; C496630:Prkca protein, mouse; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D000074121:Protein Kinase C-theta; D007930:Leucine