One in five, more than 50 million Americans are affected by autoimmune diseases (American Autoimmune Related Diseases Association, www.aarda.org). The diseases are due to a failure in suppressing self-reactive/autoimmune immune cells, a process called immune tolerance. However, it has been an unsolved immunological puzzle about how the autoreactive immune cells are tolerized in mammals. Our research goals are to solve this puzzle and to identify the therapeutic molecular targets for the treatment of autoimmune diseases particularly of rheumatoid arthritis (RA) and type 1 diabetes (T1D).
In our laboratory, we use genetic, proteomic, molecular biology and immunological approaches to dissect the molecular networks underlying the regulation of immune response and autoimmunity. Several specific genes that are critical for immune regulation and autoimmune diseases have been identified in our laboratory. Small molecules that modulate the functions of these newly identified genes can potentially be used to treat type 1 diabetes and rheumatoid arthritis.
The current ongoing research projects, in my laboratory are:
1. Sirt1, a type III histone deacetylase, is required for immune tolerance.
We recently found that the type III histone deacetylase, Sirt1, negatively regulates T-cell activation and is required for peripheral T-cell tolerance. Genetically disruption of Sirt1 expression in mice results in abnormally increased T-cell activation and a breakdown of CD4+ T-cell tolerance. As a consequence, Sirt1-/- mice develop spontaneous autoimmune disease. Our findings indicate that Sirt1 is a negative regulator of T-cell activation and is required for peripheral T-cell tolerance (Journal of Clinical Investigation, 2009, In press).
2. The ubiquitin E3 ligase, Synoviolin, is a therapeutic target for rheumatoid arthritis.
RA is characterized by the activation of self-reactive immune cells, leukocyte infiltration, hyper-proliferation of synovial cells and bone destruction. The hyper-proliferation of synovial tissues results in direct invasions and destruction of the bone and cartilage and causes the disease. Therefore, we are aiming to understand how the over-growth of synovial cells is triggered and to develop a therapeutic approach for the treatment of RA by suppressing synovial cell growth. Synoviolin, a RING finger-containing E3 ubiquitin ligase, has been recently found as a rheumatoid factor that causes the overgrowth of synovial cells. My laboratory has recently found that proinflammatory cytokines upregulate SYVN expression in synovial fibroblasts (Arthritis Res Ther.2006). We further demonstrated that SYVN inhibits the apoptosis of synovial cells by directly targeting IRE1 for ubiquitination during arthritis development (EMBO reports, 2008).
We are currently investigating the molecular mechanisms by which SYVN regulates synovial cell proliferation, and using small RNA interference (siRNA) strategy to inhibit SYVN in mice joint for the treatment of arthritis. (is supported by an NIH R21 and the Arthritis Foundation grants).
3. The tyrosine kinase c-Abl in T-cell differentiation and allergic lung inflammation.
One in six Americans suffers from the allergic inflammatory lung disease such as asthma, an incurable allergic disease. T helper type 2 (Th2) cells are crucial for causing the disease. The molecular mechanisms that mediate naïve CD4+ T cells, after stimulated by specific antigens, differentiate into Th1 or Th2 are still poorly understood. We have demonstrated that loss of the functions of c-Abl, a Src family tyrosine kinase, skews CD4+ T cells to Th2 differentiation, and that c-Abl-/- mice are more susceptible to experimental asthma. We further demonstrated that c-Abl is a tyrosine kinase of T-bet, a Th1-lineage-specific transcription factor. c-Abl-mediated phosphorylation regulates the promoter-binding activity of T-bet during T-cell differentiation. The molecular mechanisms by which c-Abl in T cell differentiation are under further investigation (is supported by an NIH R21 grant).
4. The roles of FoxP3 in regulatory T cells.
Regulatory T cells (Tregs) have been shown to play a crucial role in maintaining self-tolerance and suppressing autoimmunity. The forkhead transcription factor, FoxP3, is a key molecule necessary and sufficient for Tregs development and function. However, the molecular mechanisms by which FoxP3 regulates the phenotypic (anergic) and the functional (suppressive) characteristics of Tregs are not well defined. We have found that FoxP3 maintains the anergic feature of Treg by suppressing both the transcriptional activity and promoter DNA-binding of AP-1. These findings uncover one of the mechanisms underlying how FoxP3 maintains the unresponsiveness of Tregs (Blood, 2008). Our laboratory is currently further investigating the roles of FoxP3 in Treg functions (is supported by an NIH RO3 grant).
5. Ubiquitination in aging and autoimmunity.
Aging is still a biological mystery. Our laboratory has recently found that a RING (really interesting new gene) finger-containing E3 ubiquitin ligase regulates the lifespan of C. elegans. We thus named this E3 ubiquitin ligase as RLE-1 (regulation of longevity by E3) (Developmental Cell, 2007). RLE-1 is an evolutionally conserved E3 ubiquitin ligase from yeast to humans, and is recently found to be involved in immune regulation. We are currently developing genetically modified mouse model to study the regulatory functions of RLE-1 in immune regulation and in aging. (an NSF grant was scored as very good, re-submission are under preparation).
6. Novel MicroRNAs in immune tolerance and autoimmunity.
MicroRNAs have emerged as key regulators for many, if not all, biological functions and their dysregulations are involved in many human diseases. Using a microarray approach, we have recently identified several microRNAs specifically involved in immune tolerance. Our laboratory is currently investigating how microRNAs regulate immune tolerance and whether the misregulated microRNA functions are involved in autoimmune diseases by generating genetically modified mouse models.
Overall, our studies have demonstrated that immune tolerance can by regulated by multiple mechanisms, such as epigenetics, protein post-translational modification and microRNAs. Our continued efforts will lead to a better understanding of immune responses and autoimmunity. We hope that our efforts will also help the cure/prevention of some types of autoimmune diseases in humans.
Selected Publications:
Zhang, J.P., Lee, S.M., Gao, B., McBurny, M.W., Chen, A and Fang, D. The type III histone deacetylase, Sirt1, is required for peripheral T cell tolerance. Journal of Clinical Investigation. In press.
An Chen, Beixue Gao, Jingping Zhang, Tamara McEwen, Shui Q. Ye, Donna Zhang and Deyu Fang. The HECT-type E3 ubiquitin ligase AIP2 inhibits activation-induced T cell death by catalyzing EGR2 ubiquitination. Molecular and Cellular Biology. 2009, In press.
Chen, M., Sun, Z., Wang, X.J., Fang, D. and Zhang, D.D. The antioxidant function of p21Cip1/WAF1 is mediated through upregulation of Nrf2. Molecular Cell, 2009. In press.
Lee, S.M., Gao. B, Calhoun, K and Fang, D. Decreased FoxP3 gene expression in the nasalsecretions from patients with allergic rhinitis. Otolaryngology, 2009 Feb;140(2):197-201.
Li, H., Peng Liu, Javier Cepeda, Fang D, Blaine Easley, Brett Simon, Li Q Zhang and Shui Q Ye. Augmentation of Pulmonary Epithelial Cell IL-8 Expression and Permeability by Pre-B-cell Colony Enhancing Factor. Journal of Inflammation, 2008, 22;5:15.
Gao, B., Lee, S.M., Chen, A., Zhang, J.P., Kannan, K., Ortmann, R. O and Fang, D. Synoviolin promotes IRE1 ubiquitination and degradation in synovial fibroblasts from mice with collagen-induced arthritis. EMBO reports, 2008, 12(2):235-46.
Lee, S.M., Gao, B. and Fang, D. FoxP3 maintains Treg unresponsiveness by selectively inhibiting the promoter DNA-binding activity of AP-1. Blood, 2008, 111(7):3599-606.
Li, W., Gao, B., Lee, S. M., Bennett, K and Fang, D. RLE-1, a novel E3 ubiquitin ligase, regulates C. elegans aging by catalyzing DAF-16 polyubiquitination. Developmental Cell. 2007, Feb;12(2):235-46.
