George Tsokos, MD, Laboratory
The Tsokos laboratory is engaged in cutting-edge research into immune cell signaling and gene transcription in human SLE as well as mechanisms of tissue injury. By exploring the molecular origin of the multiple immune cell abnormalities in SLE, the lab is helping to identify novel biomarkers for the diagnosis of the disease and therapeutic targets.
Studies on SLE T cell signaling
SLE T cells express decreased increased T cell receptor (TCR)-mediated early signaling response. Lipid rafts are aggregated on the surface membrane of T cells while the TCR is rewired with the FcRgamma chain assuming the function of the zeta chain. Additional signaling molecules are present in the lipid rafts including Syk and the adhesion molecule CD44 which signals though pERM. pERM is phosphorylated by Rho kinase. Reconstitution of the missing CD3zeta chain, inhibition of its degradation, inhibition of Syk or Rho kinase activity all result in normalization of T cell effector function.
Studies on the decreased production of interleukin-2 (IL-2) in human SLE T cells
We have established that decreased transcriptional activity of the IL-2 promoter leads to decreased production of IL-2 by SLE T cells. We have found that the suppressor CREMalpha is expressed in increased amounts in SLE T cells and binds to the IL-2 promoter. After binding, CREMalpha recruits HDAC1, which deacetylates histones and confers a "closed" chromatin structure. CREMalpha activation and binding to the IL-2 promoter was found to be caused by CaMKIV which is also increased in SLE T cells. In parallel studies we found that SLE T cells express increased amounts of PP2Ac which dephosphorylates CREB and thus deprives the IL-2 promoter of a putative transcriptional enhancer. We use lupus-prone mice to carry our preclinical studies and we engineer genetically lupus-prone animals (e.g. MRL/ lprCamkiv-/-) to confirm findings in patients with SLE and better dissect the involved mechanisms.
IL23/IL17 axis in SLE
Double negative (CD3+CD4-CD8-) T cells are expanded in SLE patients and we found to produce IL-17 and more interestingly to populate the kidneys of patients with lupus nephritis. In humans, double negative T cells appear to arise from CD8+ cells and in mice they expand under the influence of IL23. Ongoing studies in humans and in genetically engineered mice will determine the origin, developmental requirements and pathogenicity of double negative cells.
Development of T cell-based biomarkers for SLE
While performing our studies we have identified markers that we plan to develop as biomarkers. Specifically, aggregated lipid rafts on the surface membrane of SLE T cells represent a disease specific and highly sensitive phenomenon. Expression of aggregated lipid rafts and molecules that are included in the rafts, such as FcRgamma, Syk, CD44, and complement components, is being studied with a goal of using them as disease biomarkers.
Tissue Injury Program
We have demonstrated, using a mouse model of mesenteric ischemia/reperfusion (I/R) model that autoantibodies such, as anti-DNA, cardiolipin, histones and RNP, infused in mice resistant to RI, Rag1-/-, do not cause any tissue injury unless the mice undergo I/R. We have shown that these antibodies bind to neoantigens expressed on IR-stressed tissues, activate complement and execute pathology. The goal of these studies is to decipher mechanisms of tissue injury and develop approaches to limit damage.
1. Ubiquitination Regulates Expression of the Serine/Arginine-rich Splicing Factor 1 (SRSF1) in Normal and Systemic Lupus Erythematosus (SLE) T Cells. Moulton VR, Gillooly AR, Tsokos GC. J Biol Chem. 2014 Feb 14;289(7):4126-34.
2. Deletion of microRNA-155 reduces autoantibody responses and alleviates lupus-like disease in the Faslpr mouse. Thai TH, Patterson HC, Pham DH, Kis-Toth K, Kaminski DA, Tsokos GC. Proc Natl Acad Sci U S A. 2013 Dec 10; 110(50):20194-9.
3. cAMP-responsive Element Modulator a (CREMa) trans-Represses the Transmembrane Glycoprotein CD8 and Contributes to the Generation of CD3+CD4-CD8- T Cells in Health and Disease. Hedrich CM, Rauen T, Crispin JC, Koga T, Ioannidis C, Zajdel M, Kyttaris VC, Tsokos GC. J Biol Chem. 2013 Nov 1; 288(44):31880-7.
4. Spleen Tyrosine Kinase (Syk) Regulates Systemic Lupus Erythematosus (SLE) T Cell Signaling. Grammatikos AP, Ghosh D, Devlin A, Kyttaris VC, Tsokos GC. PLoS One. 2013; 8(8):e74550.
5. T Cell CD3ζ Deficiency Enables Multiorgan Tissue Inflammation. Deng GM, Beltran J, Chen C, Terhorst C, Tsokos GC. J Immunol. 2013 Oct 1; 191(7):3563-7.
6. R-spondin3 prevents mesenteric ischemia/reperfusion-induced tissue damage by tightening endothelium and preventing vascular leakage. Kannan L, Kis-Toth K, Yoshiya K, Thai TH, Sehrawat S, Mayadas TN, Dalle Lucca JJ, Tsokos GC. Proc Natl Acad Sci U S A. 2013 Aug 27; 110(35):14348-53.
7. Treatment with anti-interleukin 23 antibody ameliorates disease in lupus-prone mice. Kyttaris VC, Kampagianni O, Tsokos GC. Biomed Res Int. 2013; 2013:861028.
8. New therapeutics in systemic lupus erythematosus. Paz Z, Tsokos GC. Curr Opin Rheumatol. 2013 May; 25(3):297-303.
9. Brief Report: Increased expression of a short splice variant of CTLA-4 exacerbates lupus in MRL/lpr mice. Ichinose K, Zhang Z, Koga T, Juang YT, Kis-Tóth K, Sharpe AH, Kuchroo V, Crispín JC, Tsokos GC. Arthritis Rheum. 2013 Mar; 65(3):764-9.
10. Splicing factor SF2/ASF rescues IL-2 production in T cells from systemic lupus erythematosus patients by activating IL-2 transcription. Moulton VR, Grammatikos AP, Fitzgerald LM, Tsokos GC. Proc Natl Acad Sci USA. 2013 Jan 29;110(5):1845-50. doi: 10.1073/pnas.1214207110. Epub 2013 Jan. 14.
11. Increased Expression of a short splice variant of CTLA-4 exacerbates lupus in MRL/lpr mice. Ichinose K, Koga T, Juang YT, Kis-Toth K, Sharpe AH, Kuchroo V, Crispin JC, Tsokos GC. Arthritis Rheum. 2012 Nov 30. doi: 10.1002/art.37790.
12. Interleukin-2 in systemic autoimmunity hits the micro way. Tsokos GC, Thai TH. Arthritis Rheum. 2012 Nov;64(11):3494-7. doi: 10.1002/art.34597.
13. cAMP response element modulator α controls IL2 and IL17A expression during CD4 lineage commitment and subset distribution in lupus. Hedrich CM, Crispin JC, Rauen T, Ioannidis C, Apostolidis SA, Lo MS, Kyttaris VC, Tsokos GC. Proc Natl Acad Sci USA. 2012 Oct 9;109(41):16606-11. doi: 10.1073/pnas.1210129109. Epub 2012 Sep 26.
14. Calcium/calmodulin-dependent protein kinase IV suppresses IL-2 production and regulatory T cell activity in lupus. Koga T, Ichinose K, Mizui M, Crispin JC, Tsokos GC. J Immunol. 2012 Oct 1;189(7):3490-6. Epub 2012 Aug 31.
15. The role of platelet factor 4 in local and remote tissue damage in a mouse model of mesenteric ichemia/reperfusion injury. Lapchak PH, Ioannou A, Rani P, Lieberman LA, Yoshiya K, Kannan L, Dalle Lucca JJ, Kowalska MA, Tsokos GC. PLoS One. 2012;7(7):e39934. doi: 10.1371/journal.pone.0039934.
Members of the Tsokos Laboratory
Vasileios C. Kyttaris, MD
Vaishali Moulton, MD, PhD
Lakshmi Kannan, PhD
Katalin Kis-Toth, PhD
Gelareh Atefi, MD
Sean Bradley, PhD
Denis Comte, MD
Hong Dai, PhD
Trevor Davis, MD
Irina Gavanescu-Stockton, PhD, MD
Mayya Geha, MD
Jonathan Hausmann, MD
Fan He, MD, PhD
Maria Iliou, PhD
Maria Karampetsou, MD, PhD
Isaac Kasper, MD
Michihito Kono, MD, PhD
Hao Li, PhD
Mindy Lo, MD, PhD
Naoya Matsumoto, PhD, MD
Kamalpreet Nagpal, PhD
Kotaro Otomo, MD, PhD
Esra Ozcan, MD
Ziv Paz, MD
Abel Suárez-Fueyo, PhD
Nobuya Yoshida, MD, PhD
Michele Finnell, ANP
Noe Rodriguéz-Rodriguéz, MS
Christina Ioannidis, BS – Lab Manager
Michael Mosho, BS