Posttranslational modifications of proteins within T cell receptor signaling cascades allow T lymphocytes to initiate a rapid but appropriate immune response such as the production of cytokines. We have previously demonstrated a key role for arginine methylation in regulating T helper cell cytokine expression, including IFNg and IL-4, the signature Th1 and Th2 cytokines, respectively. Th1/Th2 and the recently identified Th17 cell subsets have been associated with susceptibility to malignant, infectious, allergic, and autoimmune diseases. The improper development of Th1 and Th17 cells can lead to autoimmunity, while an overreactive Th2 cells can lead to allergy and asthma. Because of their distinct roles in immune function, it is important that the development and activity of Th subsets be tightly regulated. Indeed these discrete subsets antagonize the maturation and behavior of each other in the immune response. Thus, manipulation of the Th subsets provides an intriguing avenue of therapy.
     Arginine methylation of the amino-terminus of the NFAT cofactor NIP45 by Protein Arginine Methyltransferase (PRMT) 1 augmented its interaction with NFAT and resulted in elevated cytokine production. Covalent modification of NIP45 by arginine methylation is a novel mechanism of regulating the expression of NFAT-dependent cytokine genes. Until recently, arginine methylation had been thought to be a permanent mark as no demethylase had been identified. Peptidylarginine deiminases (PAD) hydrolyze arginine residues within proteins to create the non-native amino acid citrulline. By creating the citrulline residue in histone proteins, PAD4 was shown to be capable of removing methyl groups from monomethylated arginines and of preventing methylation of arginine residues. We have found that PAD4 negatively regulates the interaction between NIP45 and NFAT and, thus, represses NFAT-driven cytokine transcription. Indeed, RNAi mediated knockdown of PAD4 expression in Th2 cells leads to elevated IL-4 production. Interestingly, a PAD4 variant is associated with rheumatoid arthritis (RA) in a Japanese population. Many autoantibodies in RA are directed against citrullinated proteins. It has been proposed that PAD4 is linked to RA because PAD4 citrullination of peptides leads to a breakdown in tolerance to self-antigens. Our data suggests that PAD4 may also influence RA development through regulation of the cytokine milieu.
     Based on these observations, our lab focus is to elucidate the role of PRMT and PAD family members in T helper cell cytokine production. To assess the importance of PRMT and PAD family members, we are analyzing the effects of RNAi-mediated knockdown, genetic ablation, and chemical targeting of PRMTs and PAD family members in T helper cell function both in vitro and in vivo, particularly in murine autoimmune models. We are investigating upstream regulators of the PADs and PRMTs by identifying posttranslational modifications of these enzymes and interacting proteins. Furthermore, we are identifying new substrates of these enzymes using mass spectrometry.  Our research has identified a unique contribution of the PRMT and PAD family members in T cell function and possibly provides new therapeutic targets, particularly for autoimmunity.

Selected Publications

Mowen K.A. and Glimcher L. H. (2004) Signaling Pathways in Th2 Development. Immunological Reviews. 202:203.

Mowen K.A., Schurter B.T., Fathman J., David M, and Glimcher L. H. (2004) . Arginine Methylation of NIP45 Modulates Cytokine Gene Expression in Effector T Lymphocytes. Molecular Cell. 15:559.

Rengarajan J., Mowen K., McBride K. D., Smith E. D., Singh H., and Glimcher L. H. (2002). Interferon regulatory factor (IRF4) interacts with NFATc2 to modulate IL-4 gene expression. J Exp Med. 195:1003-1012.

Mowen, KA and David M. (2001). Analysis of  protein arginine methylation and protein arginine methyltransferase activity. Sci STKE. Jul 31;2001 (93).

Blesofsky, WA, Mowen K., Arduini RM, Baker DP, Murphy MA, Bowtell DD, David M. (2001). Regulation of STAT protein synthesis by c-Cbl. Oncogene. 20:7326-7333.

Mowen KA, and David, M. (2001). Cytokine activation of transcription. Genet Engineering, Principles and Methods. Ed. J. K. Setlow, Kluwer Academic/Plenum Press.

Lieberson R., Mowen KA,  McBride, KD, Leautaud, V, Zhang X, Suh WK, Wu L, and Glimcher, LH. (2001). Tumor necrosis factor receptor-associated (TRAF)2 represses the T helper cell type 2 response through interaction with NFAT-interacting protein (NIP45). J Exp Med. 194:89-98.

Mowen K., Tang J., Zhu W., Schurter B T, Shuai K, Herschman H., and David M.  (2001) Arginine Methylation of STAT1 modulates IFNa/b  induced Transcription. Cell. 104:731-741.

Mowen K., and David, M. (2000). Regulation of STAT1 Nuclear Export by Jak1. Mol Cell Biol. 20:7273-7281.

Mowen K. and David M. (1998). Role of the STAT1-SH2 Domain and STAT2 in the Activation and Nuclear Translocation of STAT1. JBC. 273:30073-30076.

Navarro L., Mowen K., Rodems S., Weaver B., Reich, N., Spector S., and David M. (1998).  Cytomegalovirus Activates Interferon Immediate-Early Response Gene Expression and an Interferon Regulatory Factor 3 – Containing Interferon Stimulated Response Element-Binding Complex. MCB 18: 3796-3802.

Huggenvik, J., Michelson, R. J., Collard M.W., Ziemba A. J., Gurley P., and Mowen K. A. (1998). Characterization of a Nuclear Deformed Epidermal Autoregulatory Factor-1 (DEAF-1) Related (NUDR) Transcriptional Regulator Protein. Mol. Endo. 12: 1619-1639.