Recently published - More

Abstract

Dickkopf1 (DKK1) is a secretory protein that antagonizes oncogenic Wnt signaling by binding to the Wnt coreceptor low-density lipoprotein receptor–related protein 6 (LRP6). DKK1 may also regulate its own signaling to promote cancer cell proliferation, but the mechanism is not understood. Here, we identified cytoskeleton-associated protein 4 (CKAP4) as a DKK1 receptor and evaluated CKAP4-mediated DKK1 signaling in cancer cell proliferation. We determined that DKK1 binds CKAP4 and LRP6 with similar affinity but interacts with these 2 receptors with different cysteine-rich domains. DKK1 induced internalization of CKAP4 in a clathrin-dependent manner, further supporting CKAP4 as a receptor for DKK1. DKK1/CKAP4 signaling activated AKT by forming a complex between the proline-rich domain of CKAP4 and the Src homology 3 domain of PI3K, resulting in proliferation of normal cells and cancer cells. Expression of DKK1 and CKAP4 was frequent in tumor lesions of human pancreatic and lung cancers, and simultaneous expression of both proteins in patient tumors was negatively correlated with prognosis and relapse-free survival. An anti-CKAP4 antibody blocked the binding of DKK1 to CKAP4, suppressed AKT activity in a human cancer cell line, and attenuated xenograft tumor formation in immunodeficient mice. Together, our results suggest that CKAP4 is a potential therapeutic target for cancers that express both DKK1 and CKAP4.

Authors

Hirokazu Kimura, Katsumi Fumoto, Kensaku Shojima, Satoshi Nojima, Yoshihito Osugi, Hideo Tomihara, Hidetoshi Eguchi, Yasushi Shintani, Hiroko Endo, Masahiro Inoue, Yuichiro Doki, Meinoshin Okumura, Eiichi Morii, Akira Kikuchi

×

Abstract

In humans, genetic variation of sortilin-related receptor, L(DLR class) A repeats containing (SORL1), which encodes the intracellular sorting receptor SORLA, is a major genetic risk factor for familial and sporadic forms of Alzheimer’s disease. Recent GWAS analysis has also associated SORL1 with obesity in humans and in mouse models, suggesting that this receptor may play a role in regulating metabolism. Here, using mouse models with genetic loss or tissue-specific overexpression of SORLA as well as data from obese human subjects, we observed a gene-dosage effect that links SORLA expression to obesity and glucose tolerance. Overexpression of human SORLA in murine adipose tissue blocked hydrolysis of triacylglycerides and caused excessive adiposity. In contrast, Sorl1 gene inactivation in mice accelerated breakdown of triacylglycerides in adipocytes and protected animals from diet-induced obesity. We then identified the underlying molecular mechanism whereby SORLA promotes insulin-induced suppression of lipolysis in adipocytes. Specifically, we determined that SORLA acts as a sorting factor for the insulin receptor (IR) that redirects internalized receptor molecules from endosomes to the plasma membrane, thereby enhancing IR surface expression and strengthening insulin signal reception in target cells. Our findings provide a molecular mechanism for the association of SORL1 with human obesity and confirm a genetic link between neurodegeneration and metabolism that converges on the receptor SORLA.

Authors

Vanessa Schmidt, Nadja Schulz, Xin Yan, Annette Schürmann, Stefan Kempa, Matthias Kern, Matthias Blüher, Matthew N. Poy, Gunilla Olivecrona, Thomas E. Willnow

×

Abstract

In Wilson disease (WD), functional loss of ATPase copper-transporting β (ATP7B) impairs biliary copper excretion, leading to excessive copper accumulation in the liver and fulminant hepatitis. Current US Food and Drug Administration– and European Medicines Agency–approved pharmacological treatments usually fail to restore copper homeostasis in patients with WD who have progressed to acute liver failure, leaving liver transplantation as the only viable treatment option. Here, we investigated the therapeutic utility of methanobactin (MB), a peptide produced by Methylosinus trichosporium OB3b, which has an exceptionally high affinity for copper. We demonstrated that ATP7B-deficient rats recapitulate WD-associated phenotypes, including hepatic copper accumulation, liver damage, and mitochondrial impairment. Short-term treatment of these rats with MB efficiently reversed mitochondrial impairment and liver damage in the acute stages of liver copper accumulation compared with that seen in untreated ATP7B-deficient rats. This beneficial effect was associated with depletion of copper from hepatocyte mitochondria. Moreover, MB treatment prevented hepatocyte death, subsequent liver failure, and death in the rodent model. These results suggest that MB has potential as a therapeutic agent for the treatment of acute WD.

Authors

Josef Lichtmannegger, Christin Leitzinger, Ralf Wimmer, Sabine Schmitt, Sabine Schulz, Yaschar Kabiri, Carola Eberhagen, Tamara Rieder, Dirk Janik, Frauke Neff, Beate K. Straub, Peter Schirmacher, Alan A. DiSpirito, Nathan Bandow, Bipin S. Baral, Andrew Flatley, Elisabeth Kremmer, Gerald Denk, Florian P. Reiter, Simon Hohenester, Friedericke Eckardt-Schupp, Norbert A. Dencher, Jerzy Adamski, Vanessa Sauer, Christoph Niemietz, Hartmut H.J. Schmidt, Uta Merle, Daniel Nils Gotthardt, Guido Kroemer, Karl Heinz Weiss, Hans Zischka

×

Abstract

Transplantation is the only cure for end-stage organ failure, but without immunosuppression, T cells rapidly reject allografts. While genetic disparities between donor and recipient are major determinants of the kinetics of transplant rejection, little is known about the contribution of environmental factors. Because colonized organs have worse transplant outcome than sterile organs, we tested the influence of host and donor microbiota on skin transplant rejection. Compared with untreated conventional mice, pretreatment of donors and recipients with broad-spectrum antibiotics (Abx) or use of germ-free (GF) donors and recipients resulted in prolonged survival of minor antigen–mismatched skin grafts. Increased graft survival correlated with reduced type I IFN signaling in antigen-presenting cells (APCs) and decreased priming of alloreactive T cells. Colonization of GF mice with fecal material from untreated conventional mice, but not from Abx-pretreated mice, enhanced the ability of APCs to prime alloreactive T cells and accelerated graft rejection, suggesting that alloimmunity is modulated by the composition of microbiota rather than the quantity of bacteria. Abx pretreatment of conventional mice also delayed rejection of major antigen–mismatched skin and MHC class II–mismatched cardiac allografts. This study demonstrates that Abx pretreatment prolongs graft survival, suggesting that targeting microbial constituents is a potential therapeutic strategy for enhancing graft acceptance.

Authors

Yuk Man Lei, Luqiu Chen, Ying Wang, Andrew T. Stefka, Luciana L. Molinero, Betty Theriault, Keston Aquino-Michaels, Ayelet S. Sivan, Cathryn R. Nagler, Thomas F. Gajewski, Anita S. Chong, Caroline Bartman, Maria-Luisa Alegre

×

Abstract

In HIV-1–infected patients, increased numbers of circulating CD8+ T cells are linked to increased risk of morbidity and mortality. Here, we identified a bystander mechanism that promotes CD8 T cell activation and expansion in untreated HIV-1–infected patients. Compared with healthy controls, untreated HIV-1–infected patients have an increased population of proliferating, granzyme B+, CD8+ T cells in circulation. Vβ expression and deep sequencing of CDR3 revealed that in untreated HIV-1 infection, cycling memory CD8 T cells possess a broad T cell repertoire that reflects the repertoire of the resting population. This suggests that cycling is driven by bystander activation, rather than specific antigen exposure. Treatment of peripheral blood mononuclear cells with IL-15 induced a cycling, granzyme B+ phenotype in CD8+ T cells. Moreover, elevated IL-15 expression in the lymph nodes of untreated HIV-1–infected patients correlated with circulating CD8+ T cell counts and was normalized in these patients following antiretroviral therapy. Together, these results suggest that IL-15 drives bystander activation of CD8+ T cells, which predicts disease progression in untreated HIV-1–infected patients and suggests that elevated IL-15 may also drive CD8+ T cell expansion that is linked to increased morbidity and mortality in treated patients.

Authors

Souheil-Antoine Younes, Michael L. Freeman, Joseph C. Mudd, Carey L. Shive, Arnold Reynaldi, Soumya Panigrahi, Jacob D. Estes, Claire Deleage, Carissa Lucero, Jodi Anderson, Timothy W. Schacker, Miles P. Davenport, Joseph M. McCune, Peter W. Hunt, Sulggi A. Lee, Sergio Serrano-Villar, Robert L. Debernardo, Jeffrey M. Jacobson, David H. Canaday, Rafick-Pierre Sekaly, Benigno Rodriguez, Scott F. Sieg, Michael M. Lederman

×

Abstract

Glioblastomas co-opt stem cell regulatory pathways to maintain brain tumor–initiating cells (BTICs), also known as cancer stem cells. NOTCH signaling has been a molecular target in BTICs, but NOTCH antagonists have demonstrated limited efficacy in clinical trials. Recombining binding protein suppressor of hairless (RBPJ) is considered a central transcriptional mediator of NOTCH activity. Here, we report that pharmacologic NOTCH inhibitors were less effective than targeting RBPJ in suppressing tumor growth. While NOTCH inhibitors decreased canonical NOTCH gene expression, RBPJ regulated a distinct profile of genes critical to BTIC stemness and cell cycle progression. RBPJ was preferentially expressed by BTICs and required for BTIC self-renewal and tumor growth. MYC, a key BTIC regulator, bound the RBPJ promoter and treatment with a bromodomain and extraterminal domain (BET) family bromodomain inhibitor decreased MYC and RBPJ expression. Proteomic studies demonstrated that RBPJ binds CDK9, a component of positive transcription elongation factor b (P-TEFb), to target gene promoters, enhancing transcriptional elongation. Collectively, RBPJ links MYC and transcriptional control through CDK9, providing potential nodes of fragility for therapeutic intervention, potentially distinct from NOTCH.

Authors

Qi Xie, Qiulian Wu, Leo Kim, Tyler E. Miller, Brian B. Liau, Stephen C. Mack, Kailin Yang, Daniel C. Factor, Xiaoguang Fang, Zhi Huang, Wenchao Zhou, Kareem Alazem, Xiuxing Wang, Bradley E. Bernstein, Shideng Bao, Jeremy N. Rich

×

Abstract

The severe liver pathology of untreated Wilson disease (WD) is associated with massive copper overload caused by mutations in a liver-specific copper-transporting ATPase, ATP7B. While early, presymptomatic detection and chelation with conventional copper-binding molecules enables effective and life-saving treatment, liver transplantation is the sole option currently available for those with advanced disease. In this issue of the JCI, Lichtmannegger, Leitzinger, and colleagues delineate the therapeutic effect of methanobactin (MB), a potent bacterial copper-binding protein, at three late stages of disease in a WD rat model. Their results suggest that a formal clinical trial of MB in human subjects with severe hepatic pathology caused by WD would be rational.

Authors

Stephen G. Kaler

×

Abstract

Targeting glioblastoma stem cells with γ-secretase inhibitors (GSIs) disrupts the Notch pathway and has shown some benefit in both pre-clinical models and in patients during phase I/II clinical trials. However, it is largely unknown why some glioblastoma (GBM) does not respond to GSI treatment. In this issue of the JCI, Xie et al. determined that GSI-resistant brain tumor–initiating cells (BTICs) from GBM express a higher level of the gene RBPJ, which encodes a mediator of canonical Notch signaling, compared to non-BTICs. Knockdown of RBPJ in BTICs decreased propagation in vitro and in vivo by inducing apoptosis. Interestingly, RBPJ was shown to regulate a different transcription program than Notch in BTICs by binding CDK9, thereby affecting Pol II–regulated transcript elongation. Targeting CDK9 or c-MYC, an upstream regulator of RBPJ, with small molecules also decreased BTIC propagation, and prolonged survival in mice bearing orthotopic GBM xenografts. This study not only provides a mechanism for GSI treatment resistance, but also identifies two potential therapeutic strategies to target GSI-resistant BTICs.

Authors

Xing Fan

×

Abstract

The secretory protein Dickkopf-1 (DKK-1) is a known Wnt antagonist and has been shown to suppress tumorigenesis in some cancer cells; however, it is also upregulated in many types of cancer and associated with poor prognosis. Wnt-independent mechanisms by which DKK-1 promotes cancer cell proliferation are not well understood. In this issue of the JCI, Kimura and colleagues demonstrate that DKK-1 interacts with cytoskeleton-associated protein 4 (CKAP4) to promote activation of AKT. They show that both DKK-1 and CKAP4 are frequently upregulated in pancreatic and lung cancers. Importantly, targeting this interaction with an anti-CKAP4 antibody prevented tumor formation in murine xenograft models. These results identify a previously unrecognized DKK-1–mediated pathway and suggest CKAP4 as a potential therapeutic target for certain cancers.

Authors

Dheeraj Bhavanasi, Kelsey F. Speer, Peter S. Klein

×

Abstract

Increasing evidence indicates that microbes have a large influence on immune function. Previous studies have linked pathogenic microorganisms with decreased allograft tolerance and subsequent rejection. In this issue of the JCI, Lei and colleagues demonstrate that commensal organisms also influence the host response to allograft transplantation. Using murine skin and cardiac transplant models, the authors demonstrate that allograft rejection is accelerated in mice with a normal microbiome compared with germ-free animals and antibiotic-treated mice. The increased graft rejection observed in conventional animals was due to enhanced T cell priming and was mediated through type I IFN. Together, these results suggest that altering a patient’s microbial community prior to transplant could improve allograft acceptance.

Authors

Mandy L. Ford

×




Advertisement

June 2016

126 6 cover

June 2016 Issue

On the cover:
Molecular mimicry promotes autoimmunity

On page 2191, Cole et al. present structural data for a specific human T cell receptor (TCR) clone from a type 1 diabetic patient that is known to mediate the destruction of insulin-expressing β cells. The cover image shows this TCR (green) interacting with a bacterial antigen (yellow sticks) presented by human leukocyte antigen A*0201 (purple).

×
Jci tm 2016 06

June 2016 JCI This Month

JCI This Month is a digest of the research, reviews, and other features published each month.

×

Review Series - More

Extracellular Vesicles

Series edited by Laurence Zitvogel

Cell-to-cell communication is an essential component in multicellular organisms, allowing for rapid, coordinated responses to changes within the environment. Classical signaling mediators include direct cell-cell contact as well as secreted factors, such as cytokines, metabolites, and hormones. In the past decade, extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, have emerged as important mediators of intercellular communication. EVs are double-membrane vesicles containing cargoes of multiple proteins, lipids, and nucleic acids, which are derived from their cells of origin, and EV cargoes can change depending on the status of their originating cells. Importantly, EVs are found in all body fluids and can carry their cargoes to distant sites within the body as well as neighboring cells. Reviews in this series discuss the role of EV-mediated signaling in physiological and pathophysiological conditions, including infection, host immune responses, and cancer. Additionally, these reviews cover the potential clinical use of EVs as therapeutics and diagnostic biomarkers.

×