Short-Interfering RNA-Mediated Lck Knockdown Results in Augmented Downstream T Cell Responses

Methi T, Ngai J, Mahic M, Amarzguioui M, Vang T and Tasken K
Source: J Immunol
Publication Date: (2005)
Issue: 175(11): 7398-7406
Research Area:
Immunotherapy / Hematology
Cells used in publication:
T cell, human peripheral blood unstim.
Species: human
Tissue Origin: blood
Nucleofector® I/II/2b
The Src family kinase Lck is essential for T cell Ag receptor-mediated signaling. In this study, we report the effects of acute elimination of Lck in Jurkat TAg and primary T cells using RNA interference mediated by short-interfering RNAs. In cells with Lck knockdown (kd), proximal TCR signaling was strongly suppressed as indicated by reduced zeta-chain phosphorylation and intracellular calcium mobilization. However, we observed sustained and elevated phosphorylation of ERK1/2 in Lck kd cells 30 min to 2 h after stimulation. Downstream effects on immune function as determined by activation of a NFAT-AP-1 reporter, and TCR/CD28-stimulated IL-2 secretion were strongly augmented in Jurkat and primary T cells, respectively. As expected, overexpression of SHP-1 in Jurkat cells inhibited TCR-induced NFAT-AP-1 activation, but this effect could be overcome by simultaneous kd of Lck. Furthermore, acute elimination of Lck also suppressed TCR-mediated activation of SHP-1, suggesting the possible role of SHP-1 in a negative feedback loop originating from Lck. This report underscores Lck as an important mediator of proximal TCR signaling, but also indicates a suppressive role on downstream immune function.