Project description:DUSP22 (also named JKAP) is a dual-specificity phosphatase that inhibits T cell activation. Here we identified the E3 ubiquitin ligase UBR2 as an upstream activator of Lck during T-cell activation. JKAP dephosphorylated UBR2 at two residues, leading to ubiquitin-mediated UBR2 degradation. The SCF (SKP1-CUL1-βTrCP) complex induced UBR2 Lys48-linked ubiquitination at three lysine residues. Moreover, single-cell RNA sequencing analysis and UBR2 knockout showed that UBR2 increased proinflammatory cytokines. Remarkably, UBR2 induced Lys63-linked ubiquitination of Lck at two lysine residues and subsequent Lck Tyr394 phosphorylation/activation in TCR signaling. Conversely, TCR-induced Lck activation and JKAP knockout-enhanced inflammatory phenotypes were attenuated by UBR2 knockout. Consistently, the UBR2- Lck interaction and Lck Lys63-linked ubiquitination were induced in peripheral blood T cells of human SLE patients. Collectively, UBR2 protein stability and UBR2-induced Lck ubiquitination/activation are inhibited by JKAP, leading to attenuation of T-cell activation and T-cell-mediated inflammation.
Project description:DUSP22 (also named JKAP) is a dual-specificity phosphatase that inhibits T cell activation. Here we identified the E3 ubiquitin ligase UBR2 as an upstream activator of Lck during T-cell activation. JKAP dephosphorylated UBR2 at two residues, leading to ubiquitin-mediated UBR2 degradation. The SCF (SKP1-CUL1-βTrCP) complex induced UBR2 Lys48-linked ubiquitination at three lysine residues. Moreover, single-cell RNA sequencing analysis and UBR2 knockout showed that UBR2 increased proinflammatory cytokines. Remarkably, UBR2 induced Lys63-linked ubiquitination of Lck at two lysine residues and subsequent Lck Tyr394 phosphorylation/activation in TCR signaling. Conversely, TCR-induced Lck activation and JKAP knockout-enhanced inflammatory phenotypes were attenuated by UBR2 knockout. Consistently, the UBR2- Lck interaction and Lck Lys63-linked ubiquitination were induced in peripheral blood T cells of human SLE patients. Collectively, UBR2 protein stability and UBR2-induced Lck ubiquitination/activation are inhibited by JKAP, leading to attenuation of T-cell activation and T-cell-mediated inflammation.
Project description:DUSP22 (also named JKAP) is a dual-specificity phosphatase that inhibits T cell activation. Here we identified the E3 ubiquitin ligase UBR2 as an upstream activator of Lck during T-cell activation. JKAP dephosphorylated UBR2 at two residues, leading to ubiquitin-mediated UBR2 degradation. The SCF (SKP1-CUL1-βTrCP) complex induced UBR2 Lys48-linked ubiquitination at three lysine residues. Moreover, single-cell RNA sequencing analysis and UBR2 knockout showed that UBR2 increased proinflammatory cytokines. Remarkably, UBR2 induced Lys63-linked ubiquitination of Lck at two lysine residues and subsequent Lck Tyr394 phosphorylation/activation in TCR signaling. Conversely, TCR-induced Lck activation and JKAP knockout-enhanced inflammatory phenotypes were attenuated by UBR2 knockout. Consistently, the UBR2- Lck interaction and Lck Lys63-linked ubiquitination were induced in peripheral blood T cells of human SLE patients. Collectively, UBR2 protein stability and UBR2-induced Lck ubiquitination/activation are inhibited by JKAP, leading to attenuation of T-cell activation and T-cell-mediated inflammation.
Project description:DUSP22 (also named JKAP) is a dual-specificity phosphatase that inhibits T cell activation. Here we identified the E3 ubiquitin ligase UBR2 as an upstream activator of Lck during T-cell activation. JKAP dephosphorylated UBR2 at two residues, leading to ubiquitin-mediated UBR2 degradation. The SCF (SKP1-CUL1-βTrCP) complex induced UBR2 Lys48-linked ubiquitination at three lysine residues. Moreover, single-cell RNA sequencing analysis and UBR2 knockout showed that UBR2 increased proinflammatory cytokines. Remarkably, UBR2 induced Lys63-linked ubiquitination of Lck at two lysine residues and subsequent Lck Tyr394phosphorylation/activation in TCR signaling. Conversely, TCR-induced Lck activation and JKAP knockout-enhanced inflammatory phenotypes were attenuated by UBR2 knockout. Consistently, the UBR2-Lck interaction and Lck Lys63-linked ubiquitination were induced in peripheral blood T cells of human SLE patients. Collectively, UBR2 protein stability and UBR2-induced Lck ubiquitination/activation are inhibited by JKAP, leading to attenuation of T-cell activation and T-cell-mediated inflammation.
Project description:While Lck has been widely recognized to play a pivotal role in the initiation of the T cell receptor (TCR) signaling pathway, an understanding of the precise regulation of Lck in T cells upon TCR activation remains elusive. Investigation of protein-protein interaction (PPI) using proximity labeling techniques such as TurboID has the potential to provide valuable molecular insights into Lck regulatory networks. By expressing Lck-TurboID in Jurkat T cells, we have uncovered a dynamic, short-range Lck protein interaction network upon 30 minutes of TCR stimulation. In this novel application of TurboID, we detected 27 TCR stimulation-induced Lck-proximal interactors in living T cells, including both bona fide and uncanonical Lck interactors, validating the discovery power of this tool. Our results revealed previously unappreciated Lck PPI which may be associated with cytoskeletal rearrangement, ubiquitination of TCR signaling proteins, activation of the MAPK cascade, coalescence of the LAT signalosome, and formation of the immunological synapse. In this study, we demonstrated for the first time in immune cells and for the kinase Lck that TurboID can be utilized to unveil PPI dynamics in living cells at a time scale consistent with TCR signaling.
Project description:Skeletal muscle wasting results from numerous conditions, such as sarcopenia, glucocorticoid therapy or intensive care. It prevents independent living in the elderly, predisposes to secondary diseases, and ultimately reduces lifespan. There is no approved drug therapy and the major causative mechanisms are not fully understood. Dual specificity phosphatase 22 (DUSP22) is a pleiotropic signaling molecule that plays important roles in immunity and cancer. However, the role of DUSP22 in skeletal muscle wasting is unknown. In this study, DUSP22 was found to be upregulated in sarcopenia patients and models of skeletal muscle wasting. DUSP22 knockdown or pharmacological inhibition with BML-260 prevented multiple forms of muscle wasting. Mechanistically, targeting DUSP22 suppressed FOXO3a, a master regulator of skeletal muscle wasting, via downregulation of the stress-activated kinase JNK, which occurred independently of aberrant Akt activation. DUSP22 targeting was also effective in human skeletal muscle cells undergoing atrophy. In conclusion, phosphatase DUSP22 is a novel target for preventing skeletal muscle wasting and BML-260 is a therapeutically effective small molecule inhibitor. The DUSP22-JNK-FOXO3a axis could be exploited to treat sarcopenia or related aging disorders.
Project description:Signaling through the T cell antigen receptor is essential for the formation of regulatory T (Treg) cells in the thymus and for their involvement in antigen-directed suppression of immune responses. Using a conditional null allele of the gene encoding p56Lck we show here that T cell antigen receptor (TCR) signaling is also essential for sustaining the phenotype and homeostasis of Treg cells. Inactivation of p56Lck in Treg cells resulted in large-scale changes in their gene expression profile, blocked their capacity to suppress responses, inhibited their proliferation, and caused them to redistribute in the body. The results make clear multiple aspects of the Treg cell phenotype that are dependent on a sustained capacity to respond through their TCRs. Keywords: Genetic deficiency of p56lck Two-condition experiment: wild-type memory or regulatory T cells versus lck-deficient memory or regulatory T cells.
Project description:Treatment of MV4;11 cells with CU-T12-9 increased ubiquitination of c-Myc compared to control and correspondingly resulted in reduced K148 acetylation. Chromatin immunoprecipitation coupled to high-throughput sequencing (Chip-Seq) revealed a significant loss of c-Myc occupancy in the genome following TLR1/2 activation with CU-T12-9. As expected, diminished c-Myc binding resulted in gene downregulation of well-establish c-Myc targets. These findings suggest that TLR-mediated K63-linked ubiquitination of c-Myc at K148 inhibits activation of c-Myc by interfering with its acetylation at the same residue.
Project description:Lymphocyte-specific protein tyrosine kinase (Lck) is crucial for signaling from the T cell receptor (TCR) and is controlled through tyrosine phosphorylations. Phosphorylated Tyr505 (pTyr505) promotes a closed, inactive conformation of Lck, while pTyr394 is critical for kinase activity. Additionally, pTyr192 has been suggested to regulate Lck activity by changing the specificity of the Lck Src-homology 2 (SH2) domain and/or by affecting Lck association with CD45 thus drastically increasing pTyr505. However, little is known about how pTyr192 affects endogenously expressed Lck. Here we used CRISPR/Cas9 genome editing to generate Jurkat cell lines expressing Lck Glu192 mimicking Lck pTyr192, or Lck Phe192 mimicking unphosphorylated Lck Tyr192. We confirmed that Lck Glu192 is hyperphosphorylated on Tyr505, possibly explaining reduced association of Lck Glu192 with prototypic Lck-SH2 ligands. To isolate the effect of Lck Tyr192 mutations from the effect on Lck pTyr505, we subsequently generated Jurkat cells doubly mutated on Lck Tyr192 and Lck Tyr505. Both Lck Phe192/Phe505 and Lck Glu192/Phe505 mutants co-precipitated similar amounts of binding partners. Moreover, both mutants displayed hyperphosphorylation of Tyr394. Our results indicate that CD45 is the main phosphatase controlling Lck pTyr394 in steady-state T cells. Additionally, our data demonstrate that the prototypic specificity of the Lck SH2 domain (owned by the Lck Phe192 mutants) promotes transphosphorylation of Tyr394. These observations pinpoint the fundamental role of Tyr192 in regulation of Lck activity and simultaneously reveal the most potent Lck mutants so far described
Project description:The Foxp3 transcription factor is a crucial determinant of both regulatory T (TREG) cell development and their functional maintenance. Appropriate modulation of tolerogenic immune responses therefore requires tight regulation of Foxp3 transcriptional output, and this involves both transcriptional and post-translational regulation. Here, we show that during T cell activation, phosphorylation of Foxp3 in TREG cells can be regulated by a TGFβ Activated Kinase 1 (TAK1)-Nemo Like Kinase (NLK) signaling pathway. NLK interacts with Foxp3 in TREG cells and directly phosphorylates Foxp3 on multiple serine residues. This phosphorylation results in stabilization of Foxp3 protein levels by preventing association with the STUB1 E3-ubiquitin protein ligase, resulting in both reduced ubiquitination and proteasome-mediated degradation. Conditional TREG cell NLK-knockout (NLKTREG) results in decreased TREG cell-mediated immunosuppression in vivo and NLK-deficient TREG cell animals develop more severe experimental autoimmune encephalomyelitis. Our data suggest a molecular mechanism, in which stimulation of TCR-mediated signaling can induce a TAK1-NLK pathway to sustain Foxp3 transcriptional activity through stabilization of protein levels, thereby maintaining TREG cell suppressive function. Pharmacological manipulation of this phosphorylation-ubiquitination axis may provide therapeutic opportunities for regulating TREG cell function, for example during cancer immunotherapy.