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The phosphatase DUSP22/JKAP inhibits UBR2-mediated K63-ubiquitination and activation of Lck in TCR signaling

ABSTRACT: 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.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: ying chun shih

LAB HEAD: Tse-Hua Tan

PROVIDER: PXD043457 | Pride | 2024-01-04

REPOSITORIES: pride

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Project description:Classical Hodgkin lymphoma (cHL) is one of the most common malignant lymphomas. It is characterized by the presence of rare Hodgkin and Reed/Sternberg (HRS) cells embedded in an extensive inflammatory infiltrate. Constitutive activation of nuclear factor-kappaB (NF-kappaB) in HRS cells which transcriptionally regulates expression of multiple anti-apoptotic factors and pro-inflammatory cytokines plays a central role in the pathogenesis of cHL (1, 2). In non-stimulated condition, NF-kappaB proteins are rendered inactive by binding to their inhibitors (IkappaB s), which sequester them in the cytoplasm. Stimulation of multiple receptors activates the IkappaB kinase (IKK) complex that phosphorylates IkappaB at two specific serine residues, followed by its ubiquitination and proteasomal degradation, thereby releasing NF-kappaB proteins and allowing their nuclear translocation (3). Recently, two studies provided further insights into the molecular mechanisms of IKK activation upon TNF stimulation (4, 5). Activation of the IKK complex and subsequent NF-kappaB activation requires Lys63 polyubiquitination of RIP1, a kinase which is recruited to the receptor upon TNF stimulation. IKK-ï§ï (NEMO), the regulatory subunit of the IKK complex, specifically recognizes these Lys63-linked polyubiquitins attached to RIP1 and thereby activates IKK and NF-kappaB (4, 5). A20 is an ubiquitin-modifying enzyme that inhibits NF-kappaB activation in succession of tumor necrosis factor (TNF) receptor and Toll-like receptor induced signals (6-8). This enzyme removes Lys63 linked ubiquitin chains from RIP1 and adds Lys48 polyubiquitins to RIP1, thereby targeting this factor for proteasomal degradation, thus explaining the molecular mechanism of NF-kappaB inhibition by A20 (6). A20 likely inhibits NF-kappaB acitivity also by additional means, including interaction with TRAF1 and TRAF2 (9). SNP 6.0 array (Affymetrix) analyses were performed according to the manufacturer's directions on DNA extracted from three Hodgkin cell lines (L1236, HDLM-2, U-HO1), HapMap samples included in the Genotyping Console Software 3.0 were used as references.

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.

			Action	DRS
	B_1.csv	Csv
	B_10.csv	Csv
	B_10_220414.mgf	Mgf
	B_10_220414.raw	Raw
	B_11.csv	Csv

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The phosphatase DUSP22/JKAP inhibits UBR2-mediated K63-ubiquitination and activation of Lck in TCR signaling

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