Protein Kinase C (PKC) and PKC Are the Major PKC Isotypes Involved in TCR Down-Regulation

Authors:
von Essen M, Nielsen MW, Bonefeld CM, Boding L, Larsen JM, Leitges M, Baier G, Odum N, Geisler C
In:
Source: J Immunol
Publication Date: (2006)
Issue: 176(12): 7502-10
Research Area:
Immunotherapy / Hematology
Cells used in publication:
Jurkat
Species: human
Tissue Origin: blood
T cell, human peripheral blood unstim.
Species: human
Tissue Origin: blood
T cell, human stim.
Species: human
Tissue Origin: blood
Jurkat-modified
Species: human
Tissue Origin:
Platform:
Nucleofectorâ„¢ I/II/2b
Abstract
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.