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: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: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: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:T cell antigen receptor (TCR) signaling depends upon the kinases Lck and Zap70. Lck phosphorylates the TCR, facilitating Zap70 recruitment to the stimulated TCR. Lck also phosphorylates Zap70, relieving its auto-inhibition and activating its catalytic domain. Zap70 then phosphorylates the critical adaptors LAT and SLP76 which serve to nucleate key effector molecules required for downstream responses. However, mechanisms facilitating the interaction of Zap70 with its substrates have not been described. We report an evolutionarily conserved proline-rich motif in LAT is important for Zap70-induced phosphorylation of LAT and downstream signaling. This LAT proline-rich motif associated with the Lck SH3 domain, thereby facilitating Zap70-mediated phosphorylation of LAT and downstream functions. Our results suggest Lck orchestrates multiple steps in TCR signaling including the newly described facilitation of the interaction of Zap70 with its substrate LAT. This previously unrecognized feature of TCR proximal signaling may contribute to the development of more immunomodulatory therapies.
Project description:Ubiquitination is crucial for the dynamic regulation of diverse signaling pathways. To
enhance understanding of ubiquitination mediated signaling, we generated a new class
of bispecific antibodies which combine recognition of ubiquitination substrates and
specific polyubiquitin linkages. RIP1-K63 or RIP1-linear (Lin) linkage polyubiquitin
bispecific antibodies can detect linkage-specific RIP1 ubiquitination in cells and in
tissues, and also reveal RIP1 ubiquitination by immunofluorescence. In a similar
fashion, RIP2 ubiquitination with K63 or linear linkages can be specifically detected with
RIP2-K63 and RIP2-Lin bispecific antibodies. Furthermore, using RIP2-K63 and RIP2-
Lin bispecific antibodies we examined IBD patient samples and found prominent K63-
linked and linear RIP2 ubiquitination in ulcerative colitis and Crohn's disease patient
samples. We also developed a bispecific antibody (K63-Lin) that can simultaneously
recognize K63-linked and linear ubiquitination in a variety of signaling pathways.
Collectively, these bispecific antibodies provide a novel conceptual paradigm for
potential future development of inflammatory markers.
Project description:FKBP51 is an immunophilin with a relevant role in sustaining cancer cell growth and aggressiveness, particularly in melanoma. Thanks to its scaffold and isomerase activities, mediated by its TPR and FK1 domains, respectively, FKBP51 participates in several signaling pathways. Akt is a serine-threonine kinase that is constitutively active in many tumors with a role in cancer growth and resistance. FKBP51 forms a complex with Akt and PH-domain leucine-rich repeat protein phosphatase (PHLPP), which is reported to deactivate Akt. The effect of FKBP51 on Akt activation is far from being fully elucidated and opposite data emerge from literature. We recently identified a spliced FKBP51 isoform. In this paper, we interrogated the two FKBP51 isoforms in the regulation of Akt activation and the underlying mechanisms. Our finding shows that the pAkt levels were upregulated by the canonical but not the spliced FKBP51. We show that the TPR domain mediates Akt-K63-ubiquitination, an essential aspect of Akt activation. The spliced FKBP51s, lacking such domain, could not link K63-Ub residues to Akt. Unexpectedly, PHLPP silencing did not foster phosphorylation of Akt, and its overexpression even induced phosphorylation of Akt. Our finding shows that PHLPP stabilizes levels of the E3-ubiquitin ligase TRAF6, a known FKBP51 interactor. We observed an increased K63-ubiquitination of Akt upon PHLPP overexpression. A mass spectrometry-based proteome profile of melanoma cells highlighted a relevant role for such phosphatase in improving oncogenic hallmarks, first, cell proliferation. In conclusion, we show that canonical FKBP51 promotes Akt activation by serving as a scaffold to build the macro complex deputed to Akt ubiquitination and phosphorylation. The short FKBP51 isoform, even if it retains the ability to bind to Akt, cannot support Akt phosphorylation, being unable to engage K63-ubiquitin.
Project description:The antiapoptotic Bcl-2 family member Bfl-1 is upregulated in many human tumors in which NF-kB is implicated, and contributes significantly to tumor cell survival and chemoresistance. We previously found that NF-kB induces transcription of bfl-1, and that the Bfl-1 protein is also regulated by the ubiquitin-proteasome. However little is known of the role that dysregulation of Bfl-1 turnover plays in cancer. We found that ubiquitination-resistant mutants of Bfl-1 display increased stability and greatly accelerate tumor formation in a mouse model of leukemia/lymphoma. Gene expression profiling revealed that tyrosine kinase Lck is highly upregulated and activated in these tumors compared to the parental cells, as were several genes in the RANK signaling pathway, and leads to activation of the IKK, Akt and Erk signaling pathways, which are key mediators in cancer. Tumor assays with cells coexpressing constitutively active Lck with Bfl-1, or with tumor-derived cells following shRNA-mediated Lck knockdown, unveiled functional cooperation between Bfl-1 and Lck in leukemia/lymphomagenesis. These data demonstrate that ubiquitination is a critical mechanism for regulating Bfl-1 function, and suggest that mutations in bfl-1 or in the signaling pathways that control its ubiquitination may predispose to cancer. Additionally since bfl-1 is upregulated in many human hematopoietic tumors, these data suggest that strategies to promote Bfl-1 ubiquitination may improve therapy in drug-resistant tumors. FL5.12 pro-B cells were stably transfected with Bfl-1DC and p53DD (Parental - P) and injected i.v. into nude mice. The spleens were harvested from three independent mice that developed leukemia/lymphoma (T1, T2, and T3). To identify the changes in gene expression that occurred during tumorigenesis, RNA was isolated from the parental cell line (P) and from three independent splenic tumors (T) and hybridized to Affymetrix Mouse Genome 430A_2.0 arrays. The analysis was performed in duplicate.