Activation of mammalian target of rapamycin controls the loss of TCRzeta in lupus T cells through HRES-1/Rab4-regulated lysosomal degradation.
Persistent mitochondrial hyperpolarization (MHP) and enhanced calcium fluxing underlie aberrant T cell activation and death pathway selection in systemic lupus erythematosus. Treatment with rapamycin, which effectively controls disease activity, normalizes CD3/CD28-induced calcium fluxing but fails to influence MHP, suggesting that altered calcium fluxing is downstream or independent of mitochondrial dysfunction. In this article, we show that activity of the mammalian target of rapamycin (mTOR), which is a sensor of the mitochondrial transmembrane potential, is increased in lupus 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 CD4(+) lupus 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 overexpression was also inversely correlated with diminished TCRzeta protein levels. Pull-down studies revealed a direct interaction of HRES-1/Rab4 with CD4 and TCRzeta. Importantly, the deficiency of the TCRzeta chain and of Lck and the compensatory up-regulation of FcepsilonRIgamma and Syk, which mediate enhanced calcium fluxing in lupus T cells, were reversed in patients treated with rapamcyin in vivo. Knockdown of HRES-1/Rab4 by small interfering RNA and inhibitors of lysosomal function augmented TCRzeta protein levels in vitro. The results suggest that activation of mTOR causes the loss of TCRzeta in lupus T cells through HRES-1/Rab4-dependent lysosomal degradation.
Fernandez
David R
DR
Division of Rheumatology, Department of Medicine, State University of New York, Syracuse, NY 13210, USA.
Telarico
Tiffany
T
Bonilla
Eduardo
E
Li
Qing
Q
Banerjee
Sanjay
S
Middleton
Frank A
FA
Phillips
Paul E
PE
Crow
Mary K
MK
Oess
Stefanie
S
Muller-Esterl
Werner
W
Perl
Andras
A
D000293:Adolescent; D000328:Adult; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008180:Lupus Erythematosus, Systemic / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018613:Microscopy, Confocal; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011494:Protein Kinases / Q000276:immunology* / Q000378:metabolism; D034741:RNA, Small Interfering; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020123:Sirolimus / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases; D014162:Transfection; D020695:rab4 GTP-Binding Proteins / Q000276:immunology* / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000096:biosynthesis
D007166:Immunosuppressive Agents; D034741:RNA, Small Interfering; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D009569:Nitric Oxide; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020695:rab4 GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D020123:Sirolimus