Progranulin and EGFR modulate receptor-like tyrosine kinase sorting and stability in mesothelioma cells.

Progranulin is a growth factor with pro-tumorigenic activity. We recently demonstrated that in mesothelioma, progranulin regulates cell migration, invasion, adhesion, and in vivo tumor formation by modulating a complex signaling network involving multiple receptor tyrosine kinase (RTK)s. Progranulin biological activity relies on epidermal growth factor receptor (EGFR) and receptor-like tyrosine kinase (RYK), a co-receptor of the Wnt signaling pathway, which are both required for progranulin-induced downstream signaling. However, the molecular mechanism regulating the functional interaction among progranulin, EGFR, and RYK are not known. In this study, we demonstrated that progranulin directly interacted with RYK by specific enzyme-linked immunosorbent assay (ELISA) (KD = 0.67). Using immunofluorescence and proximity ligation assay, we further discovered that progranulin and RYK colocalized in mesothelioma cells in distinct vesicular compartments. Notably, progranulin-dependent downstream signaling was sensitive to endocytosis inhibitors, suggesting that it could depend on RYK or EGFR internalization. We discovered that progranulin promoted RYK ubiquitination and endocytosis preferentially through caveolin-1-enriched pathways, and modulated RYK stability. Interestingly, we also showed that in mesothelioma cells, RYK complexes with the EGFR, contributing to the regulation of RYK stability. Collectively, our results suggest a complex regulation of RYK trafficking/activity in mesothelioma cells, a process that is concurrently regulated by exogenous soluble progranulin and EGFR. NEW & NOTEWORTHY The growth factor progranulin has pro-tumorigenic activity. In mesothelioma, progranulin signaling is mediated by EGFR and RYK, a co-receptor of the Wnt signaling. However, the molecular mechanisms regulating progranulin action are not well defined. Here, we demonstrated that progranulin binds RYK and regulates its ubiquitination, internalization, and trafficking. We also uncovered a role for EGFR in modulating RYK stability. Overall, these results highlight a complex modulation of RYK activity by progranulin and EGFR in mesothelioma.

Progranulin Oncogenic Network in Solid Tumors.

Progranulin is a pleiotropic growth factor with important physiological roles in embryogenesis and maintenance of adult tissue homeostasis. While-progranulin deficiency is associated with a broad range of pathological conditions affecting the brain, such as frontotemporal dementia and neuronal ceroid lipofuscinosis, progranulin upregulation characterizes many tumors, including brain tumors, multiple myeloma, leiomyosarcoma, mesothelioma and epithelial cancers such as ovarian, liver, breast, bladder, adrenal, prostate and kidney carcinomas. The increase of progranulin levels in tumors might have diagnostic and prognostic significance. In cancer, progranulin has a pro-tumorigenic role by promoting cancer cell proliferation, migration, invasiveness, anchorage-independent growth and resistance to chemotherapy. In addition, progranulin regulates the tumor microenvironment, affects the function of cancer-associated fibroblasts, and modulates tumor immune surveillance. However, the molecular mechanisms of progranulin oncogenic function are not fully elucidated. In bladder cancer, progranulin action relies on the activation of its functional signaling receptor EphA2. Notably, more recent data suggest that progranulin can also modulate a functional crosstalk between multiple receptor-tyrosine kinases, demonstrating a more complex and context-dependent role of progranulin in cancer. Here, we will review what is currently known about the function of progranulin in tumors, with a focus on its molecular mechanisms of action and regulation.

Complexity of progranulin mechanisms of action in mesothelioma.

BACKGROUND: Mesothelioma is an aggressive disease with limited therapeutic options. The growth factor progranulin plays a critical role in several cancer models, where it regulates tumor initiation and progression. Recent data from our laboratories have demonstrated that progranulin and its receptor, EphA2, constitute an oncogenic pathway in bladder cancer by promoting motility, invasion and in vivo tumor formation. Progranulin and EphA2 are expressed in mesothelioma cells but their mechanisms of action are not well defined. In addition, there are no data establishing whether the progranulin/EphA2 axis is tumorigenic for mesothelioma cells. METHODS: The expression of progranulin in various mesothelioma cell lines derived from all major mesothelioma subtypes was examined by western blots on cell lysates, conditioned media and ELISA assays. The biological roles of progranulin, EphA2, EGFR, RYK and FAK were assessed in vitro by immunoblots, human phospho-RTK antibody arrays, pharmacological (specific inhibitors) and genetic (siRNAs, shRNAs, CRISPR/Cas9) approaches, motility, invasion and adhesion assays. In vivo tumorigenesis was determined by xenograft models. Focal adhesion turnover was evaluated biochemically using focal adhesion assembly/disassembly assays and immunofluorescence analysis with focal adhesion-specific markers. RESULTS: In the present study we show that progranulin is upregulated in various mesothelioma cell lines covering all mesothelioma subtypes and is an important regulator of motility, invasion, adhesion and in vivo tumor formation. However, our results indicate that EphA2 is not the major functional receptor for progranulin in mesothelioma cells, where progranulin activates a complex signaling network including EGFR and RYK. We further characterized progranulin mechanisms of action and demonstrated that progranulin, by modulating FAK activity, regulates the kinetic of focal adhesion disassembly, a critical step for cell motility. CONCLUSION: Collectively, our results highlight the complexity of progranulin oncogenic signaling in mesothelioma, where progranulin modulate functional cross-talks between multiple RTKs, thereby suggesting the need for combinatorial therapeutic approaches to improve treatments of this aggressive disease.

Imaging of neuralgic amyotrophy in the acute phase.

INTRODUCTION/AIMS: Hourglass-like constrictions (HGCs) occur in neuralgic amyotrophy (NA), but the earliest time at which they can be recognized by imaging is poorly understood. We aimed to determine the prevalence of abnormal imaging findings in the acute phase of NA. METHODS: Magnetic resonance neurography (MRN) and high-resolution ultrasound (US) examinations were performed at five sites. The investigation included 39 patients with acute NA who underwent imaging within 31 days of symptom onset. Correlation between imaging and electromyography (EMG) findings was measured. RESULTS: US was performed in 29 patients and MRN in 23; 16 patients underwent US only, 10 MRN only, and 13 had both. US and MRN showed nerve abnormalities within 1 mo from NA onset in 90% of patients. HGCs were found in 74% (29/39) of the patients: 4 within 1 wk, 8 within 2 wk, 5 within 3 wk, and 12 within 4 wk. The earliest HGC on US was found within 12 h, and on MRN within 3 days from symptom onset. MRN demonstrated a denervation edema pattern of affected muscles in 91% of the patients. The shortest time to observe an edema pattern on MRN was 8 days. EMG was performed in 30 patients and revealed fibrillation potentials in affected muscles in 22 (73%). A denervation edema pattern on MRN was significantly associated with the presence of HGCs both on MRN and US, and with fibrillation potentials on EMG. DISCUSSION: In the early phase of NA, US and MRN are useful diagnostic techniques for demonstrating nerve abnormalities.

Gantry-needle-target alignment technique for CT-guided needle approaches to the skull base and cranio-cervical junction.

PURPOSE: CT-guided percutaneous procedures involving the skull base and atlanto-axial cervical spine pose particular challenges due to high density of vital vascular and nervous structures and because the ideal needle trajectory often has a cranio-caudal obliquity different from the axial scan plane. We describe how the variable CT gantry tilt, combined with gantry-needle-target alignment technique, is used to obtain precise and safe needle placement in conventional and non-conventional approaches to the skull base and the atlanto-axial spine. METHODS: We retrospectively analyzed consecutive CT-guided needle accesses to the skull base and atlanto-axial spine performed for tissue sampling through fine-needle aspirates and core biopsies, cementoplasty of neoplastic lytic lesions of atlanto-axial spine, pain management injections, and dural puncture for cerebro-spinal fluid sampling. All the accesses were performed with the gantry-needle-target alignment technique. Procedural complications were recorded. RESULTS: Thirty-nine CT-guided procedures were analyzed. Paramaxillary approach was used in 15 cases, postero-lateral in 11, subzygomatic in 3. Nine non-conventional approach were performed: submastoid in 3 cases, suprazygomatic in 2, trans-nasal in 2, trans-mastoid in 1, and trans-auricular in 1. Two peri-procedural complications occurred: one asymptomatic and one resolved within 24 h. All the procedures were successfully completed with successful needle access to the target. CONCLUSION: The gantry tilt and gantry-needle-target alignment technique allows to obtain double-oblique needle accesses for CT-guided procedures involving the skull base and atlanto-axial cervical spine, minimizing uncertainty of needle trajectory and obtaining safe needle placement in conventional and non-conventional approaches.

RBL1/p107 Expression Levels Are Modulated by Multiple Signaling Pathways.

The members of the retinoblastoma (RB) protein family, RB1/p105, retinoblastoma-like (RBL)1/p107 and RBL2/p130 are critical modulators of the cell cycle and their dysregulation has been associated with tumor initiation and progression. The activity of RB proteins is regulated by numerous pathways including oncogenic signaling, but the molecular mechanisms of these functional interactions are not fully defined. We previously demonstrated that RBL2/p130 is a direct target of AKT and it is a key mediator of the apoptotic process induced by AKT inhibition. Here we demonstrated that RBL1/p107 levels are only minorly modulated by the AKT signaling pathway. In contrast, we discovered that RBL1/p107 levels are regulated by multiple pathways linked directly or indirectly to Ca2+-dependent signaling. Inhibition of the multifunctional calcium/calmodulin-dependent kinases (CaMKs) significantly reduced RBL1/p107 expression levels and phosphorylation, increased RBL1/p107 nuclear localization and led to cell cycle arrest in G0/G1. Targeting the Ca2+-dependent endopeptidase calpain stabilized RBL1/p107 levels and counteracted the reduction of RBL1/p107 levels associated with CaMKs inhibition. Thus, these novel observations suggest a complex regulation of RBL1/p107 expression involving different components of signaling pathways controlled by Ca2+ levels, including CaMKs and calpain, pointing out a significant difference with the mechanisms modulating the close family member RBL2/p130.

Chronic inflammatory demyelinating polyneuropathy with hypertrophic nerves.

We describe the distinctive features (with images and video) of a case of chronic inflammatory demyelinating polyneuropathy (CIDP) with giant nerves. The main clinical findings were insidious onset, gait ataxia and sensory symptoms. Electrodiagnostic studies showed very slow nerve conduction velocities, multiple conduction blocks, distal CMAP duration increase and absence of F-waves. The protein level in the cerebrospinal fluid was very high. Nerve ultrasound showed swelling of all peripheral nerves outside entrapment sites, with significant variability within different segments of the same nerve; nerves were massively enlarged (up to 10-fold normal values). Brain MRI showed hypertrophic cranial nerves, with gadolinium-enhancement. Spinal MRI showed hypertrophy of spinal roots and cauda equine, with gadolinium enhancement. Genetic test (PMP22 duplication/deletion, Whole Exome Sequencing panel for neuropathies) resulted negative. The patient had a relapsing-remitting course and responded to immunoglobulin treatment. In CIDP with hypertrophic nerves, there is discrepancy between severe nerve hypertrophy and mild clinical symptoms. Nerve enlargement seems inversely related to nerve conduction velocity and directly correlated with disease duration, but not associated with disease severity.

Negative allosteric modulators of metabotropic glutamate receptor 3 target the stem-like phenotype of glioblastoma.

Glioblastoma is an invariably deadly disease. A subpopulation of glioma stem-like cells (GSCs) drives tumor progression and treatment resistance. Two recent studies demonstrated that neurons form oncogenic glutamatergic electrochemical synapses with post-synaptic GSCs. This led us to explore whether glutamate signaling through G protein-coupled metabotropic receptors would also contribute to the malignancy of glioblastoma. We found that glutamate metabotropic receptor (Grm)3 is the predominantly expressed Grm in glioblastoma. Associations of GRM3 gene expression levels with survival are confined to the proneural gene expression subtype, which is associated with enrichment of GSCs. Using multiplexed single-cell qRT-PCR, GSC marker-based cell sorting, database interrogations, and functional assays in GSCs derived from patients' tumors, we establish Grm3 as a novel marker and potential therapeutic target in GSCs. We confirm that Grm3 inhibits adenylyl cyclase and regulates extracellular signal-regulated kinase. Targeting Grm3 disrupts self-renewal and promotes differentiation of GSCs. Thus, we hypothesize that Grm3 signaling may complement oncogenic functions of glutamatergic ionotropic receptor activity in neuroglial synapses, supporting a link between neuronal activity and the GSC phenotype. The novel class of highly specific Grm3 inhibitors that we characterize herein have been clinically tested as cognitive enhancers in humans with a favorable safety profile.

Endoglin and TGF-ß signaling in glioblastoma.

Microvascular proliferation is a key feature of glioblastoma and neovascularization has been implicated in tumor progression. Glioblastomas use pro-angiogenic factors such as vascular endothelial growth factor (VEGF) for new blood vessel formation. Yet, anti-VEGF therapy does not prolong overall survival so that alternative angiogenic pathways may need to be explored as drug targets. Both glioma cells and glioma-associated endothelial cells produce TGF-ß superfamily ligands which bind TGF-ß receptors (TGF-ßR). The TGF-ßR type III endoglin (CD105), is a marker of proliferating endothelium that has already been studied as a potential therapeutic target. We studied endoglin expression in glioblastoma tissue and in glioma-associated endothelial cells in a cohort of 52 newly diagnosed and 10 recurrent glioblastoma patients by immunohistochemistry and by ex vivo single-cell gene expression profiling of 6 tumors. Endoglin protein levels were similar in tumor stroma and endothelium and correlated within tumors. Similarly, endoglin mRNA determined by ex vivo single-cell gene expression profiling was expressed in both compartments. There was positive correlation between endoglin and proteins of TGF-ß superfamily signaling. No prognostic role of endoglin expression in either compartment was identified. Endoglin gene silencing in T98G glioma cells and in human cerebral microvascular endothelial cells (hCMEC) did not affect constitutive or exogenous TGF-ß superfamily ligand-dependent signaling, except for a minor facilitation of pSmad1/5 signaling in hCMEC. These observations challenge the notion that endoglin might become a promising therapeutic target in glioblastoma.

Peri-Aneurysmal Brain Edema in Native and Treated Aneurysms: The Role of Thrombosis.

Cerebral peri-aneurysmal edema (PE) is typically associated with giant partially-thrombosed aneurysms and less frequently with smaller aneurysms treated with endovascular embolization. An understanding of the pathophysiologic mechanism of PE is still limited. We report 3 cases of cerebral aneurysms associated with PE. We describe 2 cases of giant partially thrombosed aneurysms surrounded by vasogenic edema with apposition of an intramural and juxtamural thrombus. Our third case is a smaller aneurysm inciting vasogenic edema several years after coil embolization. Vessel-wall magnetic resonance imaging (MRI) showed avid wall enhancement and an enhancing thrombus embedded within the coils, reflecting inflammation of the aneurysm wall and proliferation of the vasa vasorum. Thrombosis within the aneurysmal sac and walls, both in native and treated aneurysms, may promote inflammatory changes and sustain the occurrence of PE. Vessel-wall MRI has a potential role in the evaluation process of this subgroup of aneurysms.

A tick cell line as a powerful tool to screen the antimicrobial susceptibility of the tick-borne pathogen Anaplasma marginale.

Anaplasma marginale is the causative agent of the severe bovine anaplasmosis. The tick Rhipicephalus microplus is one of the main vectors of A. marginale in tropical and subtropical regions of the world. After the tick bite, the bacterium invades and proliferates within the bovine erythrocytes leading to anemia, impairment of milk production and weight loss. In addition, infection can cause abortion and high mortality in areas of enzootic instability. Immunization with live and inactivated vaccines are employed to control acute bovine anaplasmosis. However, they do not prevent persistent infection. Consequently, infected animals, even if immunized, are still reservoirs of the bacterium and contribute to its dissemination. Antimicrobials are largely employed for the prophylaxis of bovine anaplasmosis. However, they are often used in sublethal doses which may select pre-existing resistant bacteria and induce genetic or phenotypic variations. Therefore, we propose a new standardized in vitro assay to evaluate the susceptibility of A. marginale strains to different antimicrobials. This tool will help health professionals to choose the more adequate treatment for each herd which will prevent the selection and spread of resistant strains. For that, we initially evaluated the antimicrobial susceptibility of two field isolates of A. marginale (Jaboticabal and Palmeira) infecting bovines. The least susceptible strain (Jaboticabal) was used for the standardization of an antimicrobial assay using a culture of Ixodes scapularis-derived tick cell line, ISE6. Results showed that enrofloxacin (ENRO) at 0.25, 1 or 4 µg/mL and oxytetracycline (OTC) at 4 or 16 µg/mL are the most efficient treatments, followed by OTC at 1 µg/mL and imidocarb dipropionate (IMD) at 1 or 4 µg/mL. In addition, this proposed tool has technical advantages compared to the previously established bovine erythrocyte culture. Thereby, it may be used to guide cattle farmers to the correct use of antimicrobials. The choice of the most suitable antimicrobial is essential to eliminate persistent infections, prevent the spread of resistant strains and help controlling of bovine anaplasmosis.

Cetacean movements in coastal waters of the southwestern Atlantic ocean / Movimentos de cetáceos pelas águas costeiras do sudoeste do oceano Atlântico

Abstract: Cetaceans were monitored along ca. 700 km of the southeast coast of Brazil (22°S to 25°S) from 1995 to 2014 using photo-identification. The objective of this study was to identify any presence of long-distance movements for monitored cetacean species and discuss implications. Data on long-range movements of four of the monitored species are presented after the analysis of 321,765 photographs taken for individual identification. Seven individuals from four populations of Guiana dolphins (Sotalia guianensis) considered resident to particular estuaries or bays were reported in dispersal involving movement between pairs of protected areas over long-range distances varying between 86 and 135 km. Three cataloged rough-toothed dolphins (Steno bredanensis), first seen in Guanabara Bay, Rio de Janeiro state (22°46'S) in November 2011, were sighted 240 km southwards as members of the same group in coastal waters of São Paulo state (23°46'S) in July 2014. Water depth for those sightings ranged from 16 to 52.7 m; local sightings of rough-toothed dolphins in Brazil have frequently been in shallow waters, but the species global distribution is usually associated with deeper waters. In a 27-day interval in the spring of 2012, a group of 16 orcas (Orcinus orca) travelled ca. 277 km in shallow coastal waters ranging from 20 to 30 m deep. Orcas are commonly observed between November and February in southeast Brazil, probably in search for prey. In summer months between 2012 and 2014, three Bryde's whales (Balaenoptera edeni) sighted in waters ranging from 14 to 49 m deep, moved between 218 and 327 km. Bryde's whales are usually found in local coastal waters where they spend summer months feeding on sardines. To date, these are the longest estimated movements reported to S. guianensis, S. bredanensis, O. orca and B. edeni in the Southwestern Atlantic Ocean.

Resumo: Cetáceos foram monitorados em cerca de 700 km da costa sudeste do Brasil (22°S a 25°S) entre 1995 e 2014 com o uso da fotoidentificação. O objetivo deste estudo foi de identificar quaisquer presenças de movimentos de longa distância de indivíduos das espécies monitoradas e discutir suas implicações. Dados de movimentos de longa distância de quatro das espécies monitoradas são apresentados após a análise de 321.765 fotos obtidas para identificações individuais. Sete indivíduos de quatro populações de boto-cinza (Sotalia guianensis) consideradas residentes a estuários e baías particulares foram reportados em movimentos de dispersão envolvendo pares de áreas protegidas em distâncias que variaram entre 86 e 135 km. Três golfinhos-de-dentes-rugosos (Steno bredanensis) catalogados e avistados primeiramente na Baía de Guanabara, Rio de Janeiro (22°46'S), em novembro de 2011, foram avistados 240 km mais ao sul como membros de um mesmo grupo nas águas costeiras do Estado de São Paulo (23°46'S) em julho de 2014. A profundidade da água onde essas avistagens aconteceram variou entre 16 e 52,7 m; avistagens de golfinhos-de-dentes-rugosos têm sido efetuadas em águas rasas na costa sudeste do Brasil, embora a distribuição global da espécie esteja associada a águas profundas. Em um intervalo de 27 dias na primavera de 2012, um grupo de 16 orcas (Orcinus orca) se desclocou cerca de 277 km em águas rasas variando entre 20 e 30 m. Orcas são comumente avistadas entre novembro e fevereiro no sudeste do Brasil, possivelmente em busca de presas. Nos meses de verão entre 2012 e 2014, três baleias-de-Bryde (Balaenoptera edeni) avistadas em águas de 14 a 49 m de profundidade, moveram-se entre 218 e 327 km. baleias-de-Bryde são encontradas em águas costeiras locais onde passam os meses de verão se alimentando de sardinhas. Até o presente momento, esses são os deslocamentos estimados como os de maiores distâncias observados para S. guianensis, S. bredanensis, O. orca and B. edeni no Atlântico Sudoeste.

TGF-ß induces oncofetal fibronectin that, in turn, modulates TGF-ß superfamily signaling in endothelial cells.

Gene splicing profiles are frequently altered in cancer, and the splice variants of fibronectin (FN) that contain the extra-domains A (EDA) or B (EDB), referred to as EDA+FN or EDB+FN, are highly upregulated in tumor vasculature. Transforming growth factor ß (TGF-ß) signaling has been attributed a pivotal role in glioblastoma, with TGF-ß promoting angiogenesis and vessel remodeling. By using immunohistochemistry staining, we observed that the oncofetal FN isoforms EDA+FN and EDB+FN are expressed in glioblastoma vasculature. Ex vivo single-cell gene expression profiling of tumors by using CD31 and α-smooth muscle actin (αSMA) as markers for endothelial cells, and pericytes and vascular smooth muscle cells (VSMCs), respectively, confirmed the predominant expression of FN, EDA+FN and EDB+FN in the vascular compartment of glioblastoma. Specifically, within the CD31-positive cell population, we identified a positive correlation between the expression of EDA+FN and EDB+FN, and of molecules associated with TGF-ß signaling. Further, TGF-ß induced EDA+FN and EDB+FN in human cerebral microvascular endothelial cells and glioblastoma-derived endothelial cells in a SMAD3- and SMAD4-dependent manner. In turn, we found that FN modulated TGF-ß superfamily signaling in endothelial cells via the EDA and EDB, pointing towards a bidirectional influence of oncofetal FN and TGF-ß superfamily signaling.

Negative control of the HGF/c-MET pathway by TGF-ß: a new look at the regulation of stemness in glioblastoma.

Multiple target inhibition has gained considerable interest in combating drug resistance in glioblastoma, however, understanding the molecular mechanisms of crosstalk between signaling pathways and predicting responses of cancer cells to targeted interventions has remained challenging. Despite the significant role attributed to transforming growth factor (TGF)-ß family and hepatocyte growth factor (HGF)/c-MET signaling in glioblastoma pathogenesis, their functional interactions have not been well characterized. Using genetic and pharmacological approaches to stimulate or antagonize the TGF-ß pathway in human glioma-initiating cells (GIC), we observed that TGF-ß exerts an inhibitory effect on c-MET phosphorylation. Inhibition of either mitogen-activated protein kinase (MAPK)/ extracellular signal-regulated kinase (ERK) or phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) signaling pathway attenuated this effect. A comparison of c-MET-driven and c-MET independent GIC models revealed that TGF-ß inhibits stemness in GIC at least in part via its negative regulation of c-MET activity, suggesting that stem cell (SC) maintenance may be controlled by the balance between these two oncogenic pathways. Importantly, immunohistochemical analyses of human glioblastoma and ex vivo single-cell gene expression profiling of TGF-ß and HGF confirm the negative interaction between both pathways. These novel insights into the crosstalk of two major pathogenic pathways in glioblastoma may explain some of the disappointing results when targeting either pathway alone in human glioblastoma patients and inform on potential future designs on targeted pharmacological or genetic intervention.

Cutting Edge: ERK1 Mediates the Autocrine Positive Feedback Loop of TGF-ß and Furin in Glioma-Initiating Cells.

Glioblastoma is the most common and aggressive intrinsic brain tumor in adults. Self-renewing, highly tumorigenic glioma-initiating cells (GIC) have been linked to glioma invasive properties, immunomodulation, and increased angiogenesis, leading to resistance to therapy. TGF-ß signaling has been associated with the tumorigenic activity of GIC. TGF-ß is synthesized as a precursor molecule and proteolytically processed to the mature form by members of the family of the proprotein convertases subtilisin/kexin. In this study we report that furin is unique among the proprotein convertases subtilisin/kexin in being highly expressed in human GIC. Furin cleaves and promotes activation of pro-TGF-ß1 and pro-TGF-ß2, and TGF-ß2 in turn increases furin levels. Notably, TGF-ß2 controls furin activity in an ALK-5-dependent manner involving the ERK/MAPK pathway. We thus uncover a role of ERK1 in the regulation of furin activity by supporting a self-sustaining loop for high TGF-ß activity in GIC.

Programming of Intestinal Epithelial Differentiation by IL-33 Derived from Pericryptal Fibroblasts in Response to Systemic Infection.

The intestinal epithelium constitutes an efficient barrier against the microbial flora. Here, we demonstrate an unexpected function of IL-33 as a regulator of epithelial barrier functions. Mice lacking IL-33 showed decreased Paneth cell numbers and lethal systemic infection in response to Salmonella typhimurium. IL-33 was produced upon microbial challenge by a distinct population of pericryptal fibroblasts neighboring the intestinal stem cell niche. IL-33 programmed the differentiation of epithelial progenitors toward secretory IEC including Paneth and goblet cells. Finally, IL-33 suppressed Notch signaling in epithelial cells and induced expression of transcription factors governing differentiation into secretory IEC. In summary, we demonstrate that gut pericryptal fibroblasts release IL-33 to translate bacterial infection into an epithelial response to promote antimicrobial defense.