Pompe disease (PD) is a severe neuromuscular disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). PD is currently treated with enzyme replacement therapy (ERT) with intravenous infusions of recombinant human GAA (rhGAA). Although the introduction of ERT represents a breakthrough in the management of PD, the approach suffers from several shortcomings. Here, we developed a mouse model of PD to compare the efficacy of hepatic gene transfer with adeno-associated virus (AAV) vectors expressing secretable GAA with long-term ERT. Liver expression of GAA results in enhanced pharmacokinetics and uptake of the enzyme in peripheral tissues compared to ERT. Combination of gene transfer with pharmacological chaperones boosts GAA bioavailability, resulting in improved rescue of the PD phenotype. Scale-up of hepatic gene transfer to non-human primates also successfully results in enzyme secretion in blood and uptake in key target tissues, supporting the ongoing clinical translation of the approach.

Abstract Cancer cells evade destruction by co-opting checkpoint signaling in the immune system. Therapeutics aimed at preventing this, such as anti-PD1 and anti-CTLA4 antibodies, promote cytotoxic T lymphocyte (CTL)-mediated antitumor immune responses against advanced solid tumors. Harnessing the antitumor activity of CTLs, and that of their innate counterpart natural killer (NK) cells, is a promising approach. Activation of CTLs and NK cells is tightly regulated. CTLs require costimulatory signals, such as CD28, for robust activation. NK cell activation can be kept in check by a variety of inhibitory receptors, such as those of the TAM tyrosine kinase receptor family. Ultimately, these signaling events are orchestrated by the ubiquitin signaling system. One ubiquitin ligase in particular, Cbl-b (Casitas B-lineage lymphoma proto-oncogene b), is a negative regulator of both CTL and NK cell activation. In T cells, Cbl-b attenuates TCR signaling by negatively regulating several downstream signaling components, enforcing the requirement for costimulation. In NK cells, Cbl-b regulates TAM receptor internalization at the plasma membrane via ubiquitylation, and this process is important in enabling inhibitory signaling via the TAM receptors. Accordingly, mice deficient in active Cbl-b exhibit hyper-responsive immunity and reject a variety of implanted metastatic and nonmetastatic tumors. Outgrowth of spontaneous tumors in these mice is also significantly delayed. This tumor resistance is mediated by activated CD8+ T cells and NK cells. Thus, Cbl-b is a promising target for developing small-molecule cancer immunotherapy agents. Using proprietary HTS technologies, Progenra has discovered novel and selective Cbl-b inhibitors that decrease ubiquitylation of TAM receptor family members (Tyro3). These inhibitors also promote CD3-mediated activation of T cells in a CD28-independent manner, markedly increasing proliferation, IL-2 secretion, and TNFα production in T cells. Additionally, these Cbl-b inhibitors increase NK cell activation (as measured by IFNγ and degranulation) in ex vivo assays. ADME/DMPK as well as in vivo efficacy data will be discussed. These molecules are expected to synergize with other approved immunotherapy agents. Citation Format: Christopher Riling, Ivan Sokirniy, Brigid Cunnion, Emily Todd, Michael Mattern, Jian Wu, Taku Kambayashi, Suresh Kumar. Small-molecule Cbl-b inhibitors as novel intracellular checkpoint inhibitors for cancer immunotherapy [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A206.

Janus kinase 2 (JAK2) is a central kinase in hematopoietic stem/progenitor cells (HSPCs), and its uncontrolled activation is a prominent oncogenic driver of hematopoietic neoplasms. However, molecular mechanisms underlying the regulation of JAK2 have remained elusive. Here we report that the Casitas B-cell lymphoma (CBL) family E3 ubiquitin ligases down-regulate JAK2 stability and signaling via the adaptor protein LNK/SH2B3. We demonstrated that depletion of CBL/CBL-B or LNK abrogated JAK2 ubiquitination, extended JAK2 half-life, and enhanced JAK2 signaling and cell growth in human cell lines as well as primary murine HSPCs. Built on these findings, we showed that JAK inhibitor (JAKi) significantly reduced aberrant HSPCs and mitigated leukemia development in a mouse model of aggressive myeloid leukemia driven by loss of Cbl and Cbl-b Importantly, primary human CBL mutated (CBLmut ) leukemias exhibited increased JAK2 protein levels and signaling and were hypersensitive to JAKi. Loss-of-function mutations in CBL E3 ubiquitin ligases are found in a wide range of myeloid malignancies, which are diseases without effective treatment options. Hence, our studies reveal a novel signaling axis that regulates JAK2 in normal and malignant HSPCs and suggest new therapeutic strategies for treating CBLmut myeloid malignancies.

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. Jak1 degradation is aborted in activated T cells that lack Ndfips. In wild-type cells, Jak1 degradation lessens CD4+ cell sensitivity to cytokines during TCR stimulation, while in Ndfip-deficient cells cytokine responsiveness persists, promoting increased expansion and survival of pathogenic effector T cells. Thus, Ndfip1/Ndfip2 regulate the cross talk between the T-cell receptor and cytokine signalling pathways to limit inappropriate T-cell responses.

The approval by the FDA and clinical use of immune checkpoint inhibitors, such as anti-PD1 and anti-CTLA4 antibodies, that activate cytotoxic T lymphocyte (CTL) mediated anti-tumor immune responses against advanced solid tumors has resulted in a paradigm shift in cancer therapy. Antitumor activity of CTLs and NK cells is tightly regulated by intracellular signaling events orchestrated by the ubiquitin signaling system. In particular, Cbl-b (Casitas B-lineage lymphoma proto-oncogene b), a RING finger E3-ubiquitin ligase primarily expressed in immune cells, acts as an intracellular checkpoint and a master negative regulator of both CTLs and NK cells. Accordingly, Cbl-b-/- mice have been observed to reject a variety of implanted metastatic and non-metastatic tumors and to delay significantly the outgrowth of spontaneous tumors; these observed antitumor effects were seen to be mediated by activated CD8+ T cells and NK cells. Based on the overwhelming evidence supporting the role of Cbl-b in immune suppression, this ubiquitin conjugating enzyme is considered a novel target for developing small molecule cancer immunotherapy agents. Using proprietary high throughput screening technologies, Progenra identified novel, selective Cbl-b inhibitors that were shown to decrease ubiquitination of substrates such as TAM receptor kinases (Tyro3) and to activate T cells (as judged by increased IL-2 production) and NK cells (as judged by increased IFNγ production and degranulation) in ex vivo functional assays. ADME/DMPK evaluation and in vivo efficacy of selected Cbl-b inhibitors will be discussed in relation to the therapeutic utility of this class of small molecule agent, which is expected to potentiate the anticancer effects of approved immunotherapy agents. Citation Format: Saket Agarwal, Jian Wu, Chris Riling, Matthew Kodrasov, Joseph Weinstock, Ivan Sokirniy, Michael Mattern, Taku Kambayashi, Suresh Kumar. Cbl-b inhibitors as novel intra-cellular checkpoint inhibitors for cancer immunotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2228.

Abstract Ubiquitylation tunes signaling pathways in stimulated T cells to regulate activation and function. We have found that, in vitro, Nedd4-family interacting protein 1 (Ndfip1) and Ndfip2 activate Nedd4-family catalytic E3 ligases with known roles in T cells. Ndfip1 negatively regulates T cell activation and Th2 polarization, but the in vivo role of Ndfip2 is unknown. We generated Ndfip2-/- mice and found that Ndfip2 is not a prominent negative regulator of T cell activation or Th2 polarization. However, loss of Ndfip2 exacerbates the inflammatory Ndfip1-/- phenotype, suggesting that Ndfip2 dampens inflammation. We generated mixed fetal liver chimeras and found that Ndfip1/Ndfip2 deficiency leads to T cell intrinsic hyperactivity. To identify signaling pathways affected by loss of Ndfips, we used semiquantitative proteomics to compare stimulated control and knockout CD4+ T cells. Pathway analysis revealed increased MEK1 activity in knockout cells, which was confirmed by observing increased ERK phosphorylation in stimulated Ndfip1/Ndfip2 deficient CD4+ T cells. To identify aberrant ubqiuitylation of proteins upstream of ERK, we have taken a quantitative proteomic approach, using Tandem Ubiquitin Binding Entities (TUBEs) to enrich for polyubiquitylated proteins in isotope labeled control and Ndfip deficient CD4+ T cells. This approach has yielded several potential targets of Ndfip-dependent ubiquitylation in CD4+ T cells that are currently under investigation.

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. Our data reveal how these two regulatory processes are linked functionally. In the absence of Ndfip1, the Nedd4 family member Itch can bind an E2 but cannot accept ubiquitin onto its catalytic cysteine. This is because Itch is autoinhibited by an intramolecular interaction between its HECT (homologous to the E6-AP carboxy terminus domain) and two central WW domains. Ndfip1 binds these WW domains to release the HECT, allowing trans-thiolation and Itch catalytic activity. This molecular switch also regulates the closely related family member WWP2. Importantly, multiple PY motifs are required for Ndfip1 to activate Itch, functionally distinguishing Ndfips from single PY-containing substrates. These data establish a novel mechanism for control of the function of a subfamily of Nedd4 E3 ligases at the level of E2-E3 trans-thiolation.

Abstract Ubiquitylation tunes signaling pathways in stimulated T cells to regulate activation and function. Catalytic E3 ubiquitin ligases, like Itch, have known roles in these processes. We have found that Nedd4-family interacting protein 1 (Ndfip1) and Ndfip2 promote ubiquitin charging of Itch, a requisite step in protein ubiquitylation. In vitro, Ndfip1 and Ndfip2 have overlapping function. In vivo, Ndfip1 negatively regulates T cell activation and Th2 polarization. The in vivo role of Ndfip2 is unknown. To investigate this, we generated Ndfip2-/- mice. We found that, unlike Ndfip1, Ndfip2 is not a prominent negative regulator of T cell activation or Th2 polarization. However, loss of Ndfip2 exacerbates the inflammatory Ndfip1-/- phenotype, suggesting that, like Ndfip1, Ndfip2 dampens inflammatory processes. Our data indicate a T cell intrinsic role for Ndfips in limiting T cell activation and function, as Ndfip1/Ndfip2 DKO CD4+ T cells in mixed fetal liver chimeras are more activated and produce more cytokine than WT CD4+ T cells in the same host. In vitro coculture of naïve WT and DKO CD4+ T cells supports that Ndfip deficient T cells have increased viability and proliferative capacity. These results suggest that Ndfip1 and Ndfip2 together limit T cell survival and proliferation downstream of TCR engagement. We are taking a quantitative proteomic approach to identify ubiquitylation pathways engaged during TCR stimulation that are nucleated by Ndfip-E3 ligase interactions.

E3 ubiquitin ligases tune signaling pathways in activated T cells to regulate differentiation and cytokine production. Nedd4-family ligases have distinct roles in these processes. These ligases often function with adaptors, which have been shown to aid binding to substrates and/or E2 enzymes. We have found that Nedd4-family interacting protein 1 (Ndfip1) and Ndfip2 promote Nedd4-family E3 ligase catalytic activity by a new mechanism. Our in vitro studies also indicate that Ndfip1 and Ndfip2 have overlapping function. In vivo, Ndfip1 negatively regulates T cell activation and TH2 cytokine production. The in vivo function of Ndfip2 is unknown; therefore, we generated Ndfip2-/- mice. Our studies revealed that, unlike Ndfip1, Ndfip2 is not a prominent negative regulator of T cell activation or TH2 polarization. However, loss of Ndfip2 exacerbated the inflammatory Ndfip1-/- phenotype. This suggested that, like Ndfip1, Ndfip2 limits inflammation. Supporting this, using a T cell transfer model of colitis, we found that transfer of doubly deficient T cells caused more severe disease compared to transfer of Ndfip1-/- T cells. These data indicate that Ndfip2 negatively regulates effector cell function following activation. We have now tested the effects of Ndfip2 deficiency on distinct cellular subsets in models of both acute and chronic inflammatory bowel disease. These studies suggest that Ndfip1 and Ndfip2 are pleiotropic modulators of inflammation.

Recent population-based studies of expecting mothers identified a unique profile of immune markers that are associated with an increased risk of having a child diagnosed with autism spectrum disorder (ASD). This immune profile, including increased levels of maternal and placental interleukin (IL)-4 and IL-5, is consistent with an immune response found in an allergic-asthma phenotype. Allergies and asthma reflect an imbalance in immune responses including polarization towards T-helper type 2 (TH2) responses, with both genetic susceptibility and environmental factors affecting this T-cell polarization. Mouse strains provide a known and controlled source of genetic diversity to explore the role of genetic predisposition on environmental factors. In particular, the FVB background exhibits a skew towards TH2-mediated allergic-asthma response in traditional models of asthma whereas the C57 strain exhibits a more blunted TH2 polarized phenotype resulting in an attenuated allergic-asthma response. C57BL/6J (C57) and the sighted FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant (FVB/Ant) lines were selected based on their characteristic high sociability and differing sensitivity to TH2-mediated stimuli. Based on the distinct allergy-sensitive immune responses of these two strains, we hypothesized that unique developmental consequences would occur in offspring following maternal allergy-asthma exposure. Female C57 and FVB/Ant dams were primed/sensitized with an exposure to ovalbumin (OVA) before pregnancy, then exposed to either aerosolized OVA or PBS-vehicle throughout gestation. Sera from pregnant dams were analyzed for changes in cytokine profiles using multiplex-arrays and offspring were assessed for changes in autism-like behavioral responses. Analysis of maternal sera revealed elevated IL-4 and IL-5 in OVA-treated dams of both strains but only C57 mice expressed increased levels of IL-1β, IL-6, TNFα, and IL-17. Behavioral assessments revealed strain-dependent changes in juvenile reciprocal social interaction in offspring of maternal allergic asthma dams. Moreover, mice of both strains showed decreased repetitive grooming and increased marble burying behavior when born to OVA-exposed dams. Together, these findings support the important role genetic predisposition plays in the effects of maternal immune activation and underscore differences in ASD-like behavioral outcomes across mouse strains.

Ndfip1 is an adaptor protein that regulates the E3 ubiquitin ligase Itch. Ndfip1 promotes Itch ubiquitination of JunB, a transcription factor involved in TH2 differentiation. Ndfip1-/- mice develop a TH2-mediated inflammatory disease in the skin and lungs. We now show that Ndfip1-/- mice also develop gastrointestinal (GI) inflammation, characterized by the infiltration of eosinophils. The GI inflammation is accompanied by weight loss and premature death. We have found that Ndfip1-/- T cells are both necessary and sufficient to recruit eosinophils into the GI tract. Furthermore, we have found that IL-5 plays a major role in disease induction. Ndfip1-/- mice show increased IL-5 levels in the blood and Ndfip1-/- T cells secrete IL-5 when activated ex vivo. Taken together, our results indicate that the eosinophilic inflammation of the GI track in Ndfip1-/- mice is caused by T cell activation and consequent secretion of IL-5. A similar mechanism could lead to Inflammatory Bowel Disease (IBD) in humans, in particular, TH2-mediated forms of the disease. Single Nucleotide Polymorphisms (SNPs) were analyzed within the Ndfip1 gene. Comparing patient populations with or without IBD, significant differences were found (p-value <0.001) in several SNPs. Thus, Ndfip1-/- mice are a novel genetic model of TH2-driven gastrointestinal inflammatory disease that could provide novel insights into IBD. NIH training grant: T Lymphocyte Development and Activation.