von Essen Marina, Nielsen Martin W, Bonefeld Charlotte M, Boding Lasse, Larsen Jeppe M, Leitges Michael, Baier Gottfried, Odum Niels, Geisler Carsten
Institute of Medical Microbiology and Immunology, University of Copenhagen, Denmark.
J Immunol. 2006 Jun 15;176(12):7502-10. doi: 10.4049/jimmunol.176.12.7502.
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.
众所周知，蛋白激酶C（PKC）在调节TCR细胞表面表达水平中发挥重要作用。然而，T细胞中存在八种不同的PKC亚型，迄今为止，参与TCR下调的具体亚型仍有待确定。本研究的目的是确定参与TCR下调的PKC亚型，并阐明它们诱导TCR下调的机制。为实现这一目标，我们在人T细胞系Jurkat、原代人T细胞或小鼠T细胞系DO11.10中研究了TCR下调情况，在这些细胞系中我们过表达了各种PKC亚型的组成型活性或显性负性形式。此外，我们在PKC基因敲除小鼠中以及通过使用小干扰RNA介导的特定PKC亚型敲低来研究TCR下调。我们发现PKCalpha和PKCtheta是仅有的能够诱导显著TCR下调的PKC亚型。这两种亚型均通过严格依赖于Ser(126)和CD3γ链基于双亮氨酸的受体分选基序的TCR再循环途径介导TCR下调。最后，我们发现PKCtheta主要参与直接结合的TCR的下调，而PKCalpha则参与未结合的TCR的下调。
