Activation of mTOR controls the loss of TCRζ in lupus T cells through HRES-1/Rab4-regulated lysosomal degradation

CD3-positive T cells were negatively isolated from 10 SLE patients and 9 healthy controls without SLE. All of the SLE samples and control samples were compared with one another to identify baseline differences in expression due to the disease. Next, T cell preparations from 4 of the control subjects were stimulated with either Nitric Oxide (NOC-18) 600 uM for 24hr or stimulated through CD3/CD28 for 24hr to determine which genes were responsive to these signaling mechanisms. Here, we show that activity of the mammalian target of rapamycin (mTOR), which is a sensor of the mitochondrial transmembrane potential, is increased in SLE T cells. Activation of mTOR was inducible by NO, a key trigger of MHP which in turn enhanced the expression of HRES-1/Rab4, a small GTPase that regulates recycling of surface receptors through early endosomes. Expression of HRES-1/Rab4 was increased in SLE T cells and, in accordance with its dominant impact on the endocytic recycling of CD4, it was inversely correlated with diminished CD4 expression. HRES-1/Rab4 over-expression was also inversely correlated with diminished TCRζ protein levels. Combined with follow up studies, these results suggest that activation of mTOR causes the loss of TCRζ in lupus T cells through HRES-1/Rab4-dependent lysosomal degradation. 10 replicate T cell samples from SLE (Lupus) patients 9 replicate T cell samples from healthy control (BC) subjects 4 replicate Nitric Oxide (NOC-18) stimulated T cell samples from 4 of the control subjects 4 replicate CD3/CD28 stimulated T cell samples from 4 of the control subjects