[show abstract][hide abstract] ABSTRACT: Maintaining tolerance of T cells to self-antigens is essential to avoid autoimmune disease. How self-reactive T cells are kept functionally inactive is, however, unknown. In this study, we show that early growth response gene 2 (Egr-2), a zinc-finger transcription factor, is expressed in CD44(high) T cells and controls their proliferation and activation. In the absence of Egr-2, CD44(high), but not CD44(low) T cells, are hyperreactive and hyperproliferative in vivo. The accumulation of activated CD4(+)CD44(high) T cells leads to the development of a late onset lupuslike autoimmune disease characterized by the accumulation of interferon (IFN)-gamma and interleukin (IL)-17-producing CD4(+) T cells, loss of tolerance to nuclear antigens, massive infiltration of T cells into multiple organs and glomerulonephritis. We found that the expression of cyclin-dependent kinase inhibitor p21cip1 was impaired in Egr-2-deficient T cells, whereas the expression of IFN-gamma and IL-17 in response to T cell receptor ligation was significantly increased, suggesting that Egr-2 activates the expression of genes involved in the negative regulation of T cell proliferation and inflammation. These results demonstrate that Egr-2 is an intrinsic regulator of effector T cells and controls the expansion of self-reactive T cells and development of autoimmune disease.
Journal of Experimental Medicine 10/2008; 205(10):2295-307. · 13.21 Impact Factor
[show abstract][hide abstract] ABSTRACT: The suppressors of cytokine signaling (SOCS) family is thought to act largely as a negative regulator of signaling by cytokines and some growth factors. Surprisingly, the SOCS-6 transgenics had no significant defects in the cytokine signaling and hematopoietic system but displayed significant improvements in glucose metabolism. Insulin stimulation of Akt/protein kinase B was also potentiated. Biochemical analysis showed that, after insulin stimulation, SOCS-6 interacted with the monomeric p85 subunit of class-Ia phosphoinositide (PI) 3-kinase but not with p85/p110 dimers. Furthermore, SOCS-6 expression is transiently increased by serum and insulin in normal fibroblasts. However, both the mRNA and protein of SOCS-6 were rapidly degraded after induction by insulin. The degradation of the SOCS-6 protein was partially inhibited by a proteasome inhibitor, suggesting a proteasome-mediated degradation mechanism. In contrast, SOCS-6-associated p85 was not degraded and could be recruited to the newly synthesized SOCS-6 molecules in the presence of insulin, suggesting that SOCS-6 expression and its interaction with p85, but not the degradation, is regulated by insulin. The phenotype of SOCS-6 transgenic mice bears a striking resemblance to p85 knock-out mouse models in which glucose metabolism stimulated by insulin is significantly improved despite reduced activation of PI 3-kinase. This suggests that monomeric p85 might play a physiologically important role in attenuating signaling through PI 3-kinase-dependent pathways in unstimulated cells. Therefore, our results indicate that SOCS-6 may provide a dynamically regulated mechanism by which insulin can transiently overcome the negative effects that p85 monomers have on signaling via PI 3-kinase-dependent signaling pathways.
Journal of Biological Chemistry 09/2004; 279(33):34107-14. · 4.65 Impact Factor