Nck-mediated recruitment of BCAP to the BCR regulates the PI(3)K-Akt pathway in B cells.

The adaptor Nck links receptor signaling to cytoskeleton regulation. Here we found that Nck also controlled the phosphatidylinositol-3-OH kinase (PI(3)K)-kinase Akt pathway by recruiting the adaptor BCAP after activation of B cells. Nck bound directly to the B cell antigen receptor (BCR) via the non-immunoreceptor tyrosine-based activation motif (ITAM) phosphorylated tyrosine residue at position 204 in the tail of the immunoglobulin-α component. Genetic ablation of Nck resulted in defective BCR signaling, which led to hampered survival and proliferation of B cells in vivo. Indeed, antibody responses in Nck-deficient mice were also considerably impaired. Thus, we demonstrate a previously unknown adaptor function for Nck in recruiting BCAP to sites of BCR signaling and thereby modulating the PI(3)K-Akt pathway in B cells.

Kinase-independent function of E-type cyclins in liver cancer.

E-type cyclins (cyclins E1 and E2) are components of the core cell cycle machinery and are overexpressed in many human tumor types. E cyclins are thought to drive tumor cell proliferation by activating the cyclin-dependent kinase 2 (CDK2). The cyclin E1 gene represents the site of recurrent integration of the hepatitis B virus in the pathogenesis of hepatocellular carcinoma, and this event is associated with strong up-regulation of cyclin E1 expression. Regardless of the underlying mechanism of tumorigenesis, the majority of liver cancers overexpress E-type cyclins. Here we used conditional cyclin E knockout mice and a liver cancer model to test the requirement for the function of E cyclins in liver tumorigenesis. We show that a ubiquitous, global shutdown of E cyclins did not visibly affect postnatal development or physiology of adult mice. However, an acute ablation of E cyclins halted liver cancer progression. We demonstrated that also human liver cancer cells critically depend on E cyclins for proliferation. In contrast, we found that the function of the cyclin E catalytic partner, CDK2, is dispensable in liver cancer cells. We observed that E cyclins drive proliferation of tumor cells in a CDK2- and kinase-independent mechanism. Our study suggests that compounds which degrade or inhibit cyclin E might represent a highly selective therapeutic strategy for patients with liver cancer, as these compounds would selectively cripple proliferation of tumor cells, while sparing normal tissues.

Impact of loss-of-function mutations at the RNF43 locus on colorectal cancer development and progression.

RNF43 mutations are frequently detected in colorectal cancer cells and lead to a loss of function of the ubiquitin E3 ligase. Here, we investigated the clinical significance of RNF43 mutations in a large Japanese cohort and the role of RNF43 at various stages of colorectal cancer development and progression. Mutation analysis of the RNF43 gene locus with pyrosequencing technology detected RNF43 hotspot mutations in one (0.88%) of 113 colorectal polyp cases and in 30 (6.45%) of 465 colorectal cancer cases. Moreover, patients with colorectal cancer harbouring mutated RNF43 experienced a higher recurrence rate than those harbouring non-mutated RNF43. In addition, the growth of RNF43 wild-type colorectal cancer cell lines was significantly increased by RNF43 silencing. We generated Rnf43 knockout mice in a C57BL/6 N background by using the CRISPR-Cas9 system. Although intestinal organoids from Rnf43 knockout mice did not show continuous growth in the absence of R-spondin, an azoxymethane/dextran sodium sulphate mouse model demonstrated that tumours were markedly larger in Rnf43 knockout mice than in wild-type mice. These findings provide evidence that Wnt signalling activation by RNF43 mutations during the tumourigenic stage enhances tumour growth and promotes a high recurrence rate in colorectal cancer patients. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Reduced Erg Dosage Impairs Survival of Hematopoietic Stem and Progenitor Cells.

ERG, an ETS family transcription factor frequently overexpressed in human leukemia, has been implicated as a key regulator of hematopoietic stem cells. However, how ERG controls normal hematopoiesis, particularly at the stem and progenitor cell level, and how it contributes to leukemogenesis remain incompletely understood. Using homologous recombination, we generated an Erg knockdown allele (Ergkd ) in which Erg expression can be conditionally restored by Cre recombinase. Ergkd/kd animals die at E10.5-E11.5 due to defects in endothelial and hematopoietic cells, but can be completely rescued by Tie2-Cre-mediated restoration of Erg in these cells. In Ergkd/+ mice, ∼40% reduction in Erg dosage perturbs both fetal liver and bone marrow hematopoiesis by reducing the numbers of Lin- Sca-1+ c-Kit+ (LSK) hematopoietic stem and progenitor cells (HSPCs) and megakaryocytic progenitors. By genetic mosaic analysis, we find that Erg-restored HSPCs outcompete Ergkd/+ HSPCs for contribution to adult hematopoiesis in vivo. This defect is in part due to increased apoptosis of HSPCs with reduced Erg dosage, a phenotype that becomes more drastic during 5-FU-induced stress hematopoiesis. Expression analysis reveals that reduced Erg expression leads to changes in expression of a subset of ERG target genes involved in regulating survival of HSPCs, including increased expression of a pro-apoptotic regulator Bcl2l11 (Bim) and reduced expression of Jun. Collectively, our data demonstrate that ERG controls survival of HSPCs, a property that may be used by leukemic cells. Stem Cells 2017;35:1773-1785.

ZNRF3 promotes Wnt receptor turnover in an R-spondin-sensitive manner.

R-spondin proteins strongly potentiate Wnt signalling and function as stem-cell growth factors. Despite the biological and therapeutic significance, the molecular mechanism of R-spondin action remains unclear. Here we show that the cell-surface transmembrane E3 ubiquitin ligase zinc and ring finger 3 (ZNRF3) and its homologue ring finger 43 (RNF43) are negative feedback regulators of Wnt signalling. ZNRF3 is associated with the Wnt receptor complex, and inhibits Wnt signalling by promoting the turnover of frizzled and LRP6. Inhibition of ZNRF3 enhances Wnt/ß-catenin signalling and disrupts Wnt/planar cell polarity signalling in vivo. Notably, R-spondin mimics ZNRF3 inhibition by increasing the membrane level of Wnt receptors. Mechanistically, R-spondin interacts with the extracellular domain of ZNRF3 and induces the association between ZNRF3 and LGR4, which results in membrane clearance of ZNRF3. These data suggest that R-spondin enhances Wnt signalling by inhibiting ZNRF3. Our study provides new mechanistic insights into the regulation of Wnt receptor turnover, and reveals ZNRF3 as a tractable target for therapeutic exploration.

Tumour suppressor RNF43 is a stem-cell E3 ligase that induces endocytosis of Wnt receptors.

LGR5+ stem cells reside at crypt bottoms, intermingled with Paneth cells that provide Wnt, Notch and epidermal growth factor signals. Here we find that the related RNF43 and ZNRF3 transmembrane E3 ubiquitin ligases are uniquely expressed in LGR5+ stem cells. Simultaneous deletion of the two genes encoding these proteins in the intestinal epithelium of mice induces rapidly growing adenomas containing high numbers of Paneth and LGR5+ stem cells. In vitro, growth of organoids derived from these adenomas is arrested when Wnt secretion is inhibited, indicating a dependence of the adenoma stem cells on Wnt produced by adenoma Paneth cells. In the HEK293T human cancer cell line, expression of RNF43 blocks Wnt responses and targets surface-expressed frizzled receptors to lysosomes. In the RNF43-mutant colorectal cancer cell line HCT116, reconstitution of RNF43 expression removes its response to exogenous Wnt. We conclude that RNF43 and ZNRF3 reduce Wnt signals by selectively ubiquitinating frizzled receptors, thereby targeting these Wnt receptors for degradation.

Nck influences preosteoblastic/osteoblastic migration and bone mass.

Migration of the cells in osteoblastic lineage, including preosteoblasts and osteoblasts, has been postulated to influence bone formation. However, the molecular bases that link preosteoblastic/osteoblastic cell migration and bone formation are incompletely understood. Nck (noncatalytic region of tyrosine kinase; collectively referred to Nck1 and Nck2) is a member of the signaling adaptors that regulate cell migration and cytoskeletal structures, but its function in cells in the osteoblastic lineage is not known. Therefore, we examined the role of Nck in migration of these cells. Nck is expressed in preosteoblasts/osteoblasts, and its knockdown suppresses migration as well as cell spreading and attachment to substrates. In contrast, Nck1 overexpression enhances spreading and increases migration and attachment. As for signaling, Nck double knockdown suppresses migration toward IGF1 (insulin-like growth factor 1). In these cells, Nck1 binds to IRS-1 (insulin receptor substrate 1) based on immunoprecipitation experiments using anti-Nck and anti-IRS-1 antibodies. In vivo, Nck knockdown suppresses enlargement of the pellet of DiI-labeled preosteoblasts/osteoblasts placed in the calvarial defects. Genetic experiments indicate that conditional double deletion of both Nck1 and Nck2 specifically in osteoblasts causes osteopenia. In these mice, Nck double deficiency suppresses the levels of bone-formation parameters such as bone formation rate in vivo. Interestingly, bone-resorption parameters are not affected. Finally, Nck deficiency suppresses repair of bone injury after bone marrow ablation. These results reveal that Nck regulates preosteoblastic/osteoblastic migration and bone mass.

Targeting NCK-Mediated Endothelial Cell Front-Rear Polarity Inhibits Neovascularization.

BACKGROUND: Sprouting angiogenesis is a key process driving blood vessel growth in ischemic tissues and an important drug target in a number of diseases, including wet macular degeneration and wound healing. Endothelial cells forming the sprout must develop front-rear polarity to allow sprout extension. The adaptor proteins Nck1 and 2 are known regulators of cytoskeletal dynamics and polarity, but their function in angiogenesis is poorly understood. Here, we show that the Nck adaptors are required for endothelial cell front-rear polarity and migration downstream of the angiogenic growth factors VEGF-A and Slit2. METHODS AND RESULTS: Mice carrying inducible, endothelial-specific Nck1/2 deletions fail to develop front-rear polarized vessel sprouts and exhibit severe angiogenesis defects in the postnatal retina and during embryonic development. Inactivation of NCK1 and 2 inhibits polarity by preventing Cdc42 and Pak2 activation by VEGF-A and Slit2. Mechanistically, NCK binding to ROBO1 is required for both Slit2- and VEGF-induced front-rear polarity. Selective inhibition of polarized endothelial cell migration by targeting Nck1/2 prevents hypersprouting induced by Notch or Bmp signaling inhibition, and pathological ocular neovascularization and wound healing, as well. CONCLUSIONS: These data reveal a novel signal integration mechanism involving NCK1/2, ROBO1/2, and VEGFR2 that controls endothelial cell front-rear polarity during sprouting angiogenesis.

Oxidant stress evoked by pacemaking in dopaminergic neurons is attenuated by DJ-1.

Parkinson's disease is a pervasive, ageing-related neurodegenerative disease the cardinal motor symptoms of which reflect the loss of a small group of neurons, the dopaminergic neurons in the substantia nigra pars compacta (SNc). Mitochondrial oxidant stress is widely viewed as being responsible for this loss, but why these particular neurons should be stressed is a mystery. Here we show, using transgenic mice that expressed a redox-sensitive variant of green fluorescent protein targeted to the mitochondrial matrix, that the engagement of plasma membrane L-type calcium channels during normal autonomous pacemaking created an oxidant stress that was specific to vulnerable SNc dopaminergic neurons. The oxidant stress engaged defences that induced transient, mild mitochondrial depolarization or uncoupling. The mild uncoupling was not affected by deletion of cyclophilin D, which is a component of the permeability transition pore, but was attenuated by genipin and purine nucleotides, which are antagonists of cloned uncoupling proteins. Knocking out DJ-1 (also known as PARK7 in humans and Park7 in mice), which is a gene associated with an early-onset form of Parkinson's disease, downregulated the expression of two uncoupling proteins (UCP4 (SLC25A27) and UCP5 (SLC25A14)), compromised calcium-induced uncoupling and increased oxidation of matrix proteins specifically in SNc dopaminergic neurons. Because drugs approved for human use can antagonize calcium entry through L-type channels, these results point to a novel neuroprotective strategy for both idiopathic and familial forms of Parkinson's disease.

Regulation of the VHL/HIF-1 pathway by DJ-1.

DJ-1 (PARK7) is a gene linked to autosomal recessive Parkinson disease (PD). We showed previously that DJ-1 loss sensitizes neurons in models of PD and stroke. However, the biochemical mechanisms underlying this protective role are not completely clear. Here, we identify Von Hippel Lindau (VHL) protein as a critical DJ-1-interacting protein. We provide evidence that DJ-1 negatively regulates VHL ubiquitination activity of the α-subunit of hypoxia-inducible factor-1 (HIF-1α) by inhibiting HIF-VHL interaction. Consistent with this observation, DJ-1 deficiency leads to lowered HIF-1α levels in models of both hypoxia and oxidative stress, two stresses known to stabilize HIF-1α. We also demonstrate that HIF-1α accumulation rescues DJ-1-deficient neurons against 1-methyl-4-phenylpyridinium-induced toxicity. Interestingly, lymphoblast cells extracted from DJ-1-related PD patients show impaired HIF-1α stabilization when compared with normal individuals, indicating that the DJ-1-VHL link may also be relevant to a human context. Together, our findings delineate a model by which DJ-1 mediates neuronal survival by regulation of the VHL-HIF-1α pathway.

Lipocalin 2 regulates brown fat activation via a nonadrenergic activation mechanism.

In this study, we report that lipocalin 2 (Lcn2), a recently characterized adipokine/cytokine, is a novel regulator of brown adipose tissue (BAT) activation by modulating the adrenergic independent p38 MAPK-PGC-1α-UCP1 pathway. Global Lcn2 knock-out (Lcn2(-/-)) mice have defective BAT thermogenic activation caused by cold stimulation and decreased BAT activity under high fat diet-induced obesity. Nevertheless, Lcn2(-/-) mice maintain normal sympathetic nervous system activation as evidenced by normal catecholamine release and lipolytic activity in response to cold stimulation. Further studies showed that Lcn2 deficiency impairs peroxisomal and mitochondrial oxidation of lipids and attenuates cold-induced Pgc1a and Ucp1 expression and p38 MAPK phosphorylation in BAT. Moreover, in vitro studies showed that Lcn2 deficiency reduces the thermogenic activity of brown adipocytes. Lcn2(-/-) differentiated brown adipocytes have significantly decreased expression levels of brown fat markers, decreased p38 MAPK phosphorylation, and decreased mitochondrial oxidation capacity. However, Lcn2(-/-) brown adipocytes have normal norepinephrine-stimulated p38 MAPK and hormone-sensitive lipase phosphorylation and Pgc1a and Ucp1 expression, suggesting an intact ß-adrenergic signaling activation. More intriguingly, recombinant Lcn2 was able to significantly stimulate p38 MAPK phosphorylation in brown adipocytes. Activating peroxisome proliferator-activated receptor γ, a downstream effector of PGC-1α, by thiazolidinedione administration fully reverses the BAT function of Lcn2(-/-) mice. Our findings provide evidence for the novel role Lcn2 plays in oxidative metabolism and BAT activation via an adrenergic independent mechanism.

A36-dependent actin filament nucleation promotes release of vaccinia virus.

Cell-to-cell transmission of vaccinia virus can be mediated by enveloped virions that remain attached to the outer surface of the cell or those released into the medium. During egress, the outer membrane of the double-enveloped virus fuses with the plasma membrane leaving extracellular virus attached to the cell surface via viral envelope proteins. Here we report that F-actin nucleation by the viral protein A36 promotes the disengagement of virus attachment and release of enveloped virus. Cells infected with the A36(YdF) virus, which has mutations at two critical tyrosine residues abrogating localised actin nucleation, displayed a 10-fold reduction in virus release. We examined A36(YdF) infected cells by transmission electron microscopy and observed that during release, virus appeared trapped in small invaginations at the plasma membrane. To further characterise the mechanism by which actin nucleation drives the dissociation of enveloped virus from the cell surface, we examined recombinant viruses by super-resolution microscopy. Fluorescently-tagged A36 was visualised at sub-viral resolution to image cell-virus attachment in mutant and parental backgrounds. We confirmed that A36(YdF) extracellular virus remained closely associated to the plasma membrane in small membrane pits. Virus-induced actin nucleation reduced the extent of association, thereby promoting the untethering of virus from the cell surface. Virus release can be enhanced via a point mutation in the luminal region of B5 (P189S), another virus envelope protein. We found that the B5(P189S) mutation led to reduced contact between extracellular virus and the host membrane during release, even in the absence of virus-induced actin nucleation. Our results posit that during release virus is tightly tethered to the host cell through interactions mediated by viral envelope proteins. Untethering of virus into the surrounding extracellular space requires these interactions be relieved, either through the force of actin nucleation or by mutations in luminal proteins that weaken these interactions.

Concurrent deletion of cyclin E1 and cyclin-dependent kinase 2 in hepatocytes inhibits DNA replication and liver regeneration in mice.

UNLABELLED: The liver has a strong regenerative capacity. After injury, quiescent hepatocytes can reenter the mitotic cell cycle to restore tissue homeostasis. This G(0) /G(1) -S cell-cycle transition of primed hepatocytes is regulated by complexes of cyclin-dependent kinase 2 (Cdk2) with E-type cyclins (CcnE1 or CcnE2). However, single genetic ablation of either E-cyclin or Cdk2 does not affect overall liver regeneration. Here, we systematically investigated the contribution of CcnE1, CcnE2, and Cdk2 for liver regeneration after partial hepatectomy (PH) by generating corresponding double- and triple-knockout (KO) mouse mutants. We demonstrate that conditional deletion of Cdk2 alone in hepatocytes resulted in accelerated induction of CcnE1, but otherwise normal initiation of S phase in vivo and in vitro. Excessive CcnE1 did not contribute to a noncanonical kinase activity, but was located at chromatin together with components of the pre-replication complex (pre-RC), such as the minichromosome maintenance (MCM) helicase. Concomitant ablation of Cdk2 and CcnE1 in hepatocytes caused a defect in pre-RC formation and further led to dramatically impaired S-phase progression by down-regulation of cyclin A2 and cell death in vitro and substantially reduced hepatocyte proliferation and liver regeneration after PH in vivo. Similarly, combined loss of CcnE1 and CcnE2, but also the Cdk2/CcnE1/CcnE2 triple KO in liver, significantly inhibited S-phase initiation and liver mass reconstitution after PH, whereas concomitant ablation of CcnE2 and Cdk2 had no effect. CONCLUSION: In the absence of Cdk2, CcnE1 performs crucial kinase-independent functions in hepatocytes, which are capable of driving MCM loading on chromatin, cyclin A2 expression, and S-phase progression. Thus, combined inactivation of Cdk2 and CcnE1 is the minimal requirement for blocking S-phase machinery in vivo.

The role of lipocalin-2 in liver regeneration.

BACKGROUND & AIMS: Various immune mediators such as interleukin-6 (IL-6) have been implicated in the process of liver regeneration. Lipocalin-2 (LCN2) has been recently characterized as a prototypic immune mediator produced by various cell types being involved mainly in host defence. In addition, numerous studies have demonstrated its clinical value as a biomarker. This study aimed at defining the role of LCN2 in liver regeneration. METHODS: We studied LCN2 expression in wild-type mice in a model of partial hepatectomy (PH). Furthermore, we evaluated liver regeneration after PH in LCN-deficient mice compared to littermate controls. Serum levels of LCN2 were assessed in a small group of patients undergoing hepatic resection. RESULTS: LCN2 is dramatically induced in livers and sera of wild-type mice after PH, whereas liver LCN2-receptor expression was decreased. Sham operations did not affect hepatic and serum LCN2 expression. Although LCN2-deficient mice exhibited increased baseline liver expression indices, LCN2-deficient mice did not differ from wild-type mice with respect to hepatic proliferation suggesting that this molecule is not involved in hepatic repair. Only serum IL-1ß levels were slightly lower in LCN(-/-) mice, whereas IL-6 serum levels did not differ between various tested animal groups. In humans undergoing hepatic resection, LCN2 levels increased significantly within 24 h following surgery. CONCLUSIONS: LCN2, although massively induced in mice after PH, is not relevant in murine hepatic regeneration. Further, human studies have to define whether LCN2 could evolve as biomarker after liver surgery.

Phenotypic polarization of activated astrocytes: the critical role of lipocalin-2 in the classical inflammatory activation of astrocytes.

Astrocytes provide structural and functional support for neurons, as well as display neurotoxic or neuroprotective phenotypes depending upon the presence of an immune or inflammatory microenvironment. This study was undertaken to characterize multiple phenotypes of activated astrocytes and to investigate the regulatory mechanisms involved. We report that activated astrocytes in culture exhibit two functional phenotypes with respect to pro- or anti-inflammatory gene expression, glial fibrillary acidic protein expression, and neurotoxic or neuroprotective activities. The two distinct functional phenotypes of astrocytes were also demonstrated in a mouse neuroinflammation model, which showed pro- or anti-inflammatory gene expression in astrocytes following challenge with classical or alternative activation stimuli; similar results were obtained in the absence of microglia. Subsequent studies involving recombinant lipocalin-2 (LCN2) protein treatment or Lcn2-deficient mice indicated that the pro- or anti-inflammatory functionally polarized phenotypes of astrocytes and their intracellular signaling pathway were critically regulated by LCN2 under in vitro and in vivo conditions. Astrocyte-derived LCN2 promoted classical proinflammatory activation of astrocytes but inhibited IL-4-STAT6 signaling, a canonical pathway involved in alternative anti-inflammatory activation. Our results suggest that the secreted protein LCN2 is an autocrine modulator of the functional polarization of astrocytes in the presence of immune or inflammatory stimuli and that LCN2 could be targeted therapeutically to dampen proinflammatory astrocytic activation and related pathologies in the CNS.

Deficiency of hyccin, a newly identified membrane protein, causes hypomyelination and congenital cataract.

We describe a new autosomal recessive white matter disorder ('hypomyelination and congenital cataract') characterized by hypomyelination of the central and peripheral nervous system, progressive neurological impairment and congenital cataract. We identified mutations in five affected families, resulting in a deficiency of hyccin, a newly identified 521-amino acid membrane protein. Our study highlights the essential role of hyccin in central and peripheral myelination.

Acute white matter injury after experimental subarachnoid hemorrhage: potential role of lipocalin 2.

BACKGROUND AND PURPOSE: White matter injury occurs after subarachnoid hemorrhage (SAH) and has not been well studied. In this study, we investigated acute white matter injury in a mouse SAH model and the role of lipocalin 2 (LCN2) in that injury. METHODS: SAH was induced by endovascular perforation in wild-type (WT) or LCN2 knockout (LCN2-/-) mice. Sham WT mice underwent the same procedure without perforation. MRI was performed 24 hours after SAH and the volumes of the T2-hyperintensity in white matter were measured. Immunohistochemistry was performed to determine white matter injury. RESULTS: Mortality rates and SAH severity were not significantly different between WT and LCN2-/- animals. T2-hyperintensity in the white matter was observed in all WT animals at 24 hours after SAH (6.1±2.7 versus 0.06±0.07 mm3 in sham; P<0.001), and the volume of T2-hyperintensity tended to correlate with SAH severity (r=0.30; P=0.055). In WT animals with SAH, numerous LCN2-positive cells were observed in white matter. In contrast, LCN2-/- animals scarcely developed white matter T2-hyperintensity after SAH (0.5±0.5 mm3; P<0.001, versus WT). Markers of axonal damage and myelin degradation were increased in white matter after SAH in WT compared with those in LCN2-/- animals (P<0.05). CONCLUSIONS: SAH results in an acute white matter injury at 24 hours in mice, and LCN2 plays an important role in SAH-induced white matter injury.

DJ-1 deficiency triggers microglia sensitivity to dopamine toward a pro-inflammatory phenotype that is attenuated by rasagiline.

DJ-1 is an oxidative stress sensor that localizes to the mitochondria when the cell is exposed to oxidative stress. DJ-1 mutations that result in gene deficiency are linked to increased risk of Parkinson's disease (PD). Activation of microglial stress conditions that are linked to PD may result in neuronal death. We postulated that DJ-1 deficiency may increase microglial neurotoxicity. We found that down-regulation of DJ-1 in microglia using an shRNA approach increased cell sensitivity to dopamine as measured by secreted pro-inflammatory cytokines such as IL-1ß and IL-6. Furthermore, we discovered that DJ-1-deficient microglia had increased monoamine oxidase activity that resulted in elevation of intracellular reactive oxygen species and nitric oxide leading to increased dopaminergic neurotoxicity. Rasagaline, a monoamine oxidase inhibitor approved for treatment of PD, reduced the microglial pro-inflammatory phenotype and significantly reduced neurotoxicity. Moreover, we discovered that DJ-1-deficient microglia have reduced expression of triggering receptor expressed on myeloid cells 2 (TREM2), previously suggested as a risk factor for pro-inflammation in neurodegenerative diseases. Further studies of DJ-1-mediated cellular pathways in microglia may contribute useful insights into the development of PD providing future avenues for therapeutic intervention

Lipocalin 2 deficiency dysregulates iron homeostasis and exacerbates endotoxin-induced sepsis.

Various states of inflammation, including sepsis, are associated with hypoferremia, which limits iron availability to pathogens and reduces iron-mediated oxidative stress. Lipocalin 2 (Lcn2; siderocalin, 24p3) plays a central role in iron transport. Accordingly, Lcn2-deficient (Lcn2KO) mice exhibit elevated intracellular labile iron. In this study, we report that LPS induced systemic Lcn2 by 150-fold in wild-type mice at 24 h. Relative to wild-type littermates, Lcn2KO mice were markedly more sensitive to endotoxemia, exhibiting elevated indices of organ damage (transaminasemia, lactate dehydrogenase) and increased mortality. Such exacerbated endotoxemia was associated with substantially increased caspase-3 cleavage and concomitantly elevated immune cell apoptosis. Furthermore, cells from Lcn2KO mice were hyperresponsive to LPS ex vivo, exhibiting elevated cytokine secretion. Additionally, Lcn2KO mice exhibited delayed LPS-induced hypoferremia despite normal hepatic hepcidin expression and displayed decreased levels of the tissue redox state indicators cysteine and glutathione in liver and plasma. Desferroxamine, an iron chelator, significantly protects Lcn2KO mice from LPS-induced toxicity, including mortality, suggesting that Lcn2 may act as an antioxidant in vivo by regulating iron homeostasis. Thus, Lcn2-mediated regulation of labile iron protects the host against sepsis. Its small size and simple structure may make Lcn2 a deployable treatment for sepsis.

CDK8 is a colorectal cancer oncogene that regulates beta-catenin activity.

Aberrant activation of the canonical WNT/beta-catenin pathway occurs in almost all colorectal cancers and contributes to their growth, invasion and survival. Although dysregulated beta-catenin activity drives colon tumorigenesis, further genetic perturbations are required to elaborate full malignant transformation. To identify genes that both modulate beta-catenin activity and are essential for colon cancer cell proliferation, we conducted two loss-of-function screens in human colon cancer cells and compared genes identified in these screens with an analysis of copy number alterations in colon cancer specimens. One of these genes, CDK8, which encodes a member of the mediator complex, is located at 13q12.13, a region of recurrent copy number gain in a substantial fraction of colon cancers. Here we show that the suppression of CDK8 expression inhibits proliferation in colon cancer cells characterized by high levels of CDK8 and beta-catenin hyperactivity. CDK8 kinase activity was necessary for beta-catenin-driven transformation and for expression of several beta-catenin transcriptional targets. Together these observations suggest that therapeutic interventions targeting CDK8 may confer a clinical benefit in beta-catenin-driven malignancies.