Dual-Specificity Phosphatase 14 (DUSP14/MKP6) Negatively Regulates TCR Signaling by Inhibiting TAB1 Activation

Abstract

T cell activation is dependent upon phosphorylation of MAPKs, which play a critical role in the regulation of immune responses. Dual-specificity phosphatase 14 (DUSP14; also known as MKP6) is classified as a MAPK phosphatase. The in vivo functions of DUSP14 remain unclear. Thus, we generated DUSP14-deficient mice and characterized the roles of DUSP14 in T cell activation and immune responses. DUSP14 deficiency in T cells resulted in enhanced T cell proliferation and increased cytokine production upon T cell activation. DUSP14 directly interacted with TGF-β–activated kinase 1 (TAK1)-binding protein 1 (TAB1) and dephosphorylated TAB1 at Ser438, leading to TAB1–TAK1 complex inactivation in T cells. The phosphorylation levels of the TAB1–TAK1 complex and its downstream molecules, including JNK and IκB kinase, were enhanced in DUSP14-deficient T cells upon stimulation. The enhanced JNK and IκB kinase activation in DUSP14-deficient T cells was attenuated by TAB1 short hairpin RNA knockdown. Consistent with that, DUSP14-deficient mice exhibited enhanced immune responses and were more susceptible to experimental autoimmune encephalomyelitis induction. Thus, DUSP14 negatively regulates TCR signaling and immune responses by inhibiting TAB1 activation.

JNK Signaling: Regulation and Functions Based on Complex Protein-Protein Partnerships

“…However, the results of comparison of MKP1 with MKP5 (by evaluating the levels of individual MAPK activities in MKP1 Ϫ/Ϫ versus MKP5 Ϫ/Ϫ mice) suggest that MKP5 is more important for JNK1 dephosphorylation (75) while MKP1 is likely more critical for p38␣ inactivation, at least in macrophages (85). Other members of the dual-specificity phosphatase family may also regulate JNK pathways by acting on upstream signaling proteins, such as the Tab1/TAK1 complex (86) or the focal adhesion kinase (87). Depending on their targets, the latter phosphatases can either inhibit (MKP6/DUSP14) or activate (MKP-x/DUSP22) JNK signaling (87)(88)(89).…”

Induction of DUSP14 ubiquitination by PRMT5‐mediated arginine methylation

“…If TAB1 (55 kDa) is not detected in the coimmunoprecipitation assays (17), it is likely that TAB1 is not properly separated from the Ig heavy chain in the immunoblot. In fact, a direct interaction of DUSP14 with TAB1, but not with TAK1, has been demonstrated using purified proteins and Alpha technology/protein-protein interaction assays (PerkinElmer, Waltham, MA, USA) (13) as well as in situ proximity ligation assay (PLA) (in this report). DUSP14 is also reported to directly interact with TAK1 in the pull-down assay using immunopurified proteins (18); however, DUSP14- and TAK1-immunopurified complexes may contain coimmunoprecipitated TAB1 proteins.…”

“…Myc-DUSP14, Flag-DUSP14, Flag-DUSP14 (C111S) mutant, Flag-TAB1, Flag-TAK1 (13), Flag-DUSP14 (K103R) mutant (19), and Flag-TRAF2 plasmids (20) were previously described. Human DUSP14 cDNA was used for these DUSP14 constructs.…”

“…DUSP14 is also reported to directly interact with TAK1 in the pull-down assay using immunopurified proteins (18); however, DUSP14- and TAK1-immunopurified complexes may contain coimmunoprecipitated TAB1 proteins. DUSP14 indirectly interacts with TAK1 through TAB1 (13). Thus, DUSP14 inhibits T-cell activation during TCR signaling by dephosphorylating TAB1, leading to inactivation of TAK1, IKK, and JNK (13).…”

“…DUSP14 indirectly interacts with TAK1 through TAB1 (13). Thus, DUSP14 inhibits T-cell activation during TCR signaling by dephosphorylating TAB1, leading to inactivation of TAK1, IKK, and JNK (13). We further demonstrated that DUSP14 is Lys63-linked ubiquitination by the E3 ligase TNF receptor associated factor (TRAF)2, and this modification stimulates its phosphatase activity (19).…”