J Immunol. 2004 Jun 15;172(12):7324-34. Related Articles, Links
A Novel Role for p21-Activated Protein Kinase 2 in T Cell Activation.
Chu PC, Wu J, Liao XC, Pardo J, Zhao H, Li C, Mendenhall MK, Pali E, Shen M, Yu S, Taylor VC, Aversa G, Molineaux S, Payan DG, Masuda ES.
Rigel, Inc., South San Francisco, CA 94080; and.
To identify novel components of the TCR signaling pathway, a large-scale retroviral-based functional screen was performed using CD69 expression as a marker for T cell activation. In addition to known regulators, two truncated forms of p21-activated kinase 2 (PAK2), PAK2DeltaL(1-224) and PAK2DeltaS(1-113), both lacking the kinase domain, were isolated in the T cell screen. The PAK2 truncation, PAK2DeltaL, blocked Ag receptor-induced NFAT activation and TCR-mediated calcium flux in Jurkat T cells. However, it had minimal effect on PMA/ionomycin-induced CD69 up-regulation in Jurkat cells, on anti-IgM-mediated CD69 up-regulation in B cells, or on the migratory responses of resting T cells to chemoattractants. We show that PAK2 kinase activity is increased in response to TCR stimulation. Furthermore, a full-length kinase-inactive form of PAK2 blocked both TCR-induced CD69 up-regulation and NFAT activity in Jurkat cells, demonstrating that kinase activity is required for PAK2 function downstream of the TCR. We also generated a GFP-fused PAK2 truncation lacking the Cdc42/Rac interactive binding region domain, GFP-PAK2(83-149). We show that this construct binds directly to the kinase domain of PAK2 and inhibits anti-TCR-stimulated T cell activation. Finally, we demonstrate that, in primary T cells, dominant-negative PAK2 prevented anti-CD3/CD28-induced IL-2 production, and TCR-induced CD40 ligand expression, both key functions of activated T cells. Taken together, these results suggest a novel role for PAK2 as a positive regulator of T cell activation. |
