CRL4b Inhibition Ameliorates Experimental Autoimmune Encephalomyelitis Progression.

Multiple sclerosis, and its murine model experimental autoimmune encephalomyelitis (EAE), is a neurodegenerative autoimmune disease of the CNS characterized by T cell influx and demyelination. Similar to other autoimmune diseases, therapies can alleviate symptoms but often come with side effects, necessitating the exploration of new treatments. We recently demonstrated that the Cullin-RING E3 ubiquitin ligase 4b (CRL4b) aided in maintaining genome stability in proliferating T cells.

B cell expression of E3 ubiquitin ligase Cul4b promotes chronic gammaherpesvirus infection .

The human gammaherpesviruses Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus are etiologic agents of numerous B cell lymphomas. A hallmark of gammaherpesvirus infection is their ability to establish lifelong latency in B cells. However, the specific mechanisms that mediate chronic infection in B cells remain elusive.

c-Myc uses Cul4b to preserve genome integrity and promote antiviral CD8 T cell immunity.

During infection, virus-specific CD8 T cells undergo rapid bursts of proliferation and differentiate into effector cells that kill virus-infected cells and reduce viral load. This rapid clonal expansion can put T cells at significant risk for replication-induced DNA damage. Here, we find that c-Myc links CD8 T cell expansion to DNA damage response pathways though the E3 ubiquitin ligase, Cullin 4b (Cul4b).

The ubiquitin ligase Cul5 regulates CD4 T cell fate choice and allergic inflammation.

Antigen encounter directs CD4 T cells to differentiate into T helper or regulatory cells. This process focuses the immune response on the invading pathogen and limits tissue damage. Mechanisms that govern T helper cell versus T regulatory cell fate remain poorly understood.

The E3 ubiquitin ligase Cul4b promotes CD4+ T cell expansion by aiding the repair of damaged DNA.

The capacity for T cells to become activated and clonally expand during pathogen invasion is pivotal for protective immunity. Our understanding of how T cell receptor (TCR) signaling prepares cells for this rapid expansion remains limited. Here we provide evidence that the E3 ubiquitin ligase Cullin-4b (Cul4b) regulates this process.

Itch attenuates CD4 T-cell proliferation in mice by limiting WBP2 protein stability.

To mount an antipathogen response, CD4 T cells must undergo rapid cell proliferation; however, poorly controlled expansion can result in diseases such as autoimmunity. One important regulator of T-cell activity is the E3 ubiquitin ligase Itch. Itch deficient patients suffer from extensive autoinflammation.

Itch regulation of innate and adaptive immune responses in mice and humans.

The E3 ubiquitin ligase Itch has long been appreciated to be a critical suppressor of inflammation, first identified as a regulator of Th2 differentiation and lung inflammation. Recent studies have revealed novel roles for this protein in mouse and human disease, and it is now clear that Itch also limits the function of other lymphocytes, innate immune cells, and nonhematopoietic cells to regulate immunity. In addition to Th2 cells, Itch also regulates Th17 and regulatory T cells.

An Integrated Strategy for Identifying Targets of Ubiquitin-Mediated Degradation in CD4+ T Cells.

Ubiquitination is a crucial component of many immune processes. While ubiquitin-mediated degradation is essential to T cell activation via T cell receptor signaling, the specific E3 ligases and substrates involved are not well-understood. Here, we describe a strategy integrating RNA, protein, and posttranslational modification datasets to identify targets of ubiquitin-mediated degradation.

The E3 ubiquitin ligase Itch restricts antigen-driven B cell responses.

The E3 ubiquitin ligase Itch regulates antibody levels and prevents autoimmune disease in humans and mice, yet how Itch regulates B cell fate or function is unknown. We now show that Itch directly limits B cell activity. While Itch-deficient mice displayed normal numbers of preimmune B cell populations, they showed elevated numbers of antigen-experienced B cells.

Regulation of autoimmune disease by the E3 ubiquitin ligase Itch.

Itch is a HECT type E3 ubiquitin ligase that is required to prevent the development of autoimmune disease in both mice and humans. Itch is expressed in most mammalian cell types, and, based on published data, it regulates many cellular pathways ranging from T cell differentiation to liver tumorigenesis. Since 1998, when Itch was first discovered, hundreds of publications have described mechanisms through which Itch controls various biologic activities in both immune and non-immune cells.

Integrative proteomics reveals an increase in non-degradative ubiquitylation in activated CD4 T cells.

Despite gathering evidence that ubiquitylation can direct non-degradative outcomes, most investigations of ubiquitylation in T cells have focused on degradation. Here, we integrated proteomic and transcriptomic datasets from primary mouse CD4 T cells to establish a framework for predicting degradative or non-degradative outcomes of ubiquitylation. Di-glycine remnant profiling was used to reveal ubiquitylated proteins, which in combination with whole-cell proteomic and transcriptomic data allowed prediction of protein degradation.

Ndfip Proteins Target Robo Receptors for Degradation and Allow Commissural Axons to Cross the Midline in the Developing Spinal Cord.

Commissural axons initially respond to attractive signals at the midline, but once they cross, they become sensitive to repulsive cues. This switch prevents axons from re-entering the midline. In insects and mammals, negative regulation of Roundabout (Robo) receptors prevents premature response to the midline repellant Slit.

Ndfip1 restricts mTORC1 signalling and glycolysis in regulatory T cells to prevent autoinflammatory disease.

Foxp3 T regulatory (T) cells suppress immune cell activation and establish normal immune homeostasis. How T cells maintain their identity is not completely understood. Here we show that Ndfip1, a coactivator of Nedd4-family E3 ubiquitin ligases, is required for T cell stability and function.

Aberrant Th2 inflammation drives dysfunction of alveolar macrophages and susceptibility to bacterial pneumonia.

The ubiquitin ligase, Itch, is required to prevent autoinflammatory disease in mice and humans. Itch-deficient mice develop lethal pulmonary inflammation characterized by the production of Th2 cytokines (for example, interleukin-4 (IL-4)); however, the contribution of Itch to immune defense against respiratory pathogens has not been determined. We found that Itch-deficient mice were highly susceptible to intranasal infection with the respiratory pathogen Klebsiella pneumoniae.

Ndfip1 restricts Th17 cell potency by limiting lineage stability and proinflammatory cytokine production.

While Th17 cells can protect against colonization by pathogenic organisms, they also have the potential to become pathogenic and promote autoimmune and inflammatory diseases. Mechanisms that control their pathogenic potential remain poorly understood. Here we show that Ndfip1, a co-activator of the E3 ubiquitin ligase Itch, restricts the frequency and pathogenicity of Th17 cells.

Ubiquitin Ligases and Deubiquitinating Enzymes in CD4+ T Cell Effector Fate Choice and Function.

The human body is exposed to potentially pathogenic microorganisms at barrier sites such as the skin, lungs, and gastrointestinal tract. To mount an effective response against these pathogens, the immune system must recruit the right cells with effector responses that are appropriate for the task at hand. Several types of CD4(+) T cells can be recruited, including Th cells (Th1, Th2, and Th17), T follicular helper cells, and regulatory T cells.

Ndfip-mediated degradation of Jak1 tunes cytokine signalling to limit expansion of CD4+ effector T cells.

Nedd4 family E3 ubiquitin ligases have been shown to restrict T-cell function and impact T-cell differentiation. We show here that Ndfip1 and Ndfip2, activators of Nedd4 family ligases, together limit accumulation and function of effector CD4+ T cells. Using a three-part proteomics approach in primary T cells, we identify stabilization of Jak1 in Ndfip1/2-deficient T cells stimulated through the TCR.

CD11b+Ly6G+ cells inhibit tumor growth by suppressing IL-17 production at early stages of tumorigenesis.

Neutrophils are important innate immune cells involved in microbial clearance at the sites of infection. However, their role in cancer development is unclear. We hypothesized that neutrophils mediate antitumor effects in early tumorigenesis.

Ubiquitylation as a Rheostat for TCR Signaling: From Targeted Approaches Toward Global Profiling.

T cell receptor (TCR) signaling must be precisely tuned to limit collateral damage and prevent reactivity to self, while still allowing robust protective immune responses that control pathogen invasion. One process that can be used to promote, modify, or terminate TCR signaling is ubiquitylation. During ubiquitylation, ubiquitin is covalently attached to target proteins through a multistep process, in which E3 ubiquitin ligases promote the formation of ubiquitin chains on selected substrates.

Itch WW Domains Inhibit Its E3 Ubiquitin Ligase Activity by Blocking E2-E3 Ligase Trans-thiolation.

Nedd4-family E3 ubiquitin ligases regulate an array of biologic processes. Autoinhibition maintains these catalytic ligases in an inactive state through several mechanisms. However, although some Nedd4 family members are activated by binding to Nedd4 family-interacting proteins (Ndfips), how binding activates E3 function remains unclear.

Increased peripheral IL-4 leads to an expanded virtual memory CD8+ population.

Memory-phenotype CD8(+) T cells can arise even in the absence of overt Ag stimulation. Virtual memory (VM) CD8(+) T cells are CD8(+) T cells that develop a memory phenotype in the periphery of wild-type mice in an IL-15-dependent manner. Innate CD8(+) T cells, in contrast, are memory-phenotype CD8(+) T cells that develop in the thymus in response to elevated thymic IL-4.

The microbiota regulates neutrophil homeostasis and host resistance to Escherichia coli K1 sepsis in neonatal mice.

Neonatal colonization by microbes, which begins immediately after birth, is influenced by gestational age and the mother's microbiota and is modified by exposure to antibiotics. In neonates, prolonged duration of antibiotic therapy is associated with increased risk of late-onset sepsis (LOS), a disorder controlled by neutrophils. A role for the microbiota in regulating neutrophil development and susceptibility to sepsis in the neonate remains unclear.

E3-ubiquitin ligase Nedd4 determines the fate of AID-associated RNA polymerase II in B cells.

Programmed mutagenesis of the immunoglobulin locus of B lymphocytes during class switch recombination (CSR) and somatic hypermutation requires RNA polymerase II (polII) transcription complex-dependent targeting of the DNA mutator activation-induced cytidine deaminase (AID). AID deaminates cytidine residues on substrate sequences in the immunoglobulin (Ig) locus via a transcription-dependent mechanism, and this activity is stimulated by the RNA polII stalling cofactor Spt5 and the 11-subunit cellular noncoding RNA 3'-5' exonucleolytic processing complex RNA exosome. The mechanism by which the RNA exosome recognizes immunoglobulin locus RNA substrates to stimulate AID DNA deamination activity on its in vivo substrate sequences is an important question.

Ndfip1 enforces a requirement for CD28 costimulation by limiting IL-2 production.

Although the pathways that permit IL-2 production and the full activation of T cells upon Ag encounter are fairly well defined, the negative regulatory circuits that limit these pathways are poorly understood. In this study, we show that the E3 ubiquitin ligase adaptor Ndfip1 directs one such negative regulatory circuit. T cells lacking Ndfip1 produce IL-2, upregulate IL-2Rα, and proliferate, in the absence of CD28 costimulation.