SDR9C7 catalyzes critical dehydrogenation of acylceramides for skin barrier formation

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Abstract

The corneocyte lipid envelope composed of covalently bound ceramides and fatty acids is important to the integrity of the permeability barrier in the stratum corneum, and its absence is a prime structural defect in various skin diseases associated with defective skin barrier function. SDR9C7 encodes a short chain dehydrogenase/reductase family 9C member 7 (SDR9C7) recently found mutated in ichthyosis. In a patient with SDR9C7 mutation and a mouse Sdr9c7 knockout model we show loss of covalent binding of epidermal ceramides to protein, a structural fault in the barrier. For reasons unresolved, protein binding requires lipoxygenase-catalyzed transformations of linoleic acid (18:2) esterified in ω-O-acylceramides. In Sdr9c7-/- epidermis, quantitative LC-MS assays revealed almost complete loss of a species of ω-O-acylceramide esterified with linoleate-9,10-trans-epoxy-11E-13-ketone; other acylceramides related to the lipoxygenase pathway were in higher abundance. Recombinant SDR9C7 catalyzed NAD+-dependent dehydrogenation of linoleate 9,10-trans-epoxy-11E-13-alcohol to the corresponding 13-ketone, while ichthyosis mutants were inactive. We propose, therefore, that the critical requirement for lipoxygenases and SDR9C7 is in producing acylceramide containing the 9,10-epoxy-11E-13-ketone, a reactive moiety known for its non-enzymatic coupling to protein. This suggests a mechanism for coupling of ceramide to protein and provides important insights into skin barrier formation and pathogenesis.

Authors

Takuya Takeichi, Tetsuya Hirabayashi, Yuki Miyasaka, Akane Kawamoto, Yusuke Okuno, Shijima Taguchi, Kana Tanahashi, Chiaki Murase, Hiroyuki Takama, Kosei Tanaka, William E. Boeglin, M. Wade Calcutt, Daisuke Watanabe, Michihiro Kono, Yoshinao Muro, Junko Ishikawa, Tamio Ohno, Alan R. Brash, Masashi Akiyama

KBTBD13 is an actin-binding protein that modulates muscle kinetics

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Abstract

The mechanisms that modulate the kinetics of muscle relaxation are critically important for muscle function. A prime example of the impact of impaired relaxation kinetics is nemaline myopathy caused by mutations in KBTBD13 (NEM6). In addition to weakness, NEM6 patients have slow muscle relaxation, compromising contractility and daily-life activities. The role of KBTBD13 in muscle is unknown, and the pathomechanism underlying NEM6 is undetermined. A combination of transcranial magnetic stimulation-induced muscle relaxation, muscle fiber- and sarcomere-contractility assays, low angle X-ray diffraction and super-resolution microscopy revealed that the impaired muscle relaxation kinetics in NEM6 patients are caused by structural changes in the thin filament, a sarcomeric microstructure. Using homology modeling, binding- and contractility assays with recombinant KBTBD13, novel Kbtbd13-knockout and Kbtbd13R408C-knockin mouse models and a GFP-labeled Kbtbd13- transgenic zebrafish model we discovered that KBTBD13 binds to actin – a major constituent of the thin filament - and that mutations in KBTBD13 cause structural changes impairing muscle relaxation kinetics. We propose that this actin-based impaired relaxation is central to NEM6 pathology.

Authors

Josine M. de Winter, Joery P. Molenaar, Michaela Yuen, Robbert van der Pijl, Shengyi Shen, Stefan Conijn, Martijn van de Locht, Menne Willigenburg, Sylvia J.P. Bogaards, Esmee S.B. van Kleef, Saskia Lassche, Malin Persson, Dilson E. Rassier, Tamar E. Sztal, Avnika A. Ruparelia, Viola Oorschot, Georg Ramm, Thomas E. Hall, Zherui Xiong, Christopher N. Johnson, Frank Li, Balazs Kiss, Noelia Lozano-Vidal, Reinier A. Boon, Manuela Marabita, Leonardo Nogara, Bert Blaauw, Richard J. Rodenburg, Benno Kϋsters, Jonne Doorduin, Alan H. Beggs, Henk Granzier, Ken Campbell, Weikang Ma, Thomas Irving, Edoardo Malfatti, Norma B. Romero, Robert J. Bryson-Richardson, Baziel G.M. van Engelen, Nicol C. Voermans, Coen A.C. Ottenheijm

U3-1402 sensitizes HER3-expressing tumors to PD-1 blockade by immune activation

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Abstract

Immunotherapy targeting programmed cell death-1 (PD-1) induces durable antitumor efficacy in many types of cancer. However, such clinical benefit is limited because of the insufficient reinvigoration of antitumor immunity with the drug alone; therefore, rational therapeutic combinations are required to improve its efficacy. In our preclinical study, we evaluated the antitumor effect of U3-1402, a human epidermal growth factor receptor 3 (HER3)–targeting antibody-drug conjugate, and its potential synergism with PD-1 inhibition. Using a syngeneic mouse tumor model that is refractory to anti–PD-1 therapy, treatment with U3-1402 exhibited an obvious antitumor effect via direct lysis of tumor cells. Disruption of tumor cells by U3-1402 enhanced the infiltration of innate and adaptive immune cells. Chemotherapy with exatecan derivative (Dxd: the drug payload of U3-1402) revealed that the enhanced antitumor immunity produced by U3-1402 was associated with the induction of alarmins including HMGB-1 via tumor-specific cytotoxicity. Notably, U3-1402 significantly sensitized the tumor to PD-1 blockade, as a combination of U3-1402 and the PD-1 inhibitor significantly enhanced antitumor immunity. Further, clinical analyses indicated that tumor-specific HER3 expression was frequently observed in patients with PD-1 inhibitor–resistant solid tumors. Overall, U3-1402 is a promising candidate as a partner of immunotherapy for such patients.

Authors

Koji Haratani, Kimio Yonesaka, Shiki Takamura, Osamu Maenishi, Ryoji Kato, Naoki Takegawa, Hisato Kawakami, Kaoru Tanaka, Hidetoshi Hayashi, Masayuki Takeda, Naoyuki Maeda, Takashi Kagari, Kenji Hirotani, Junji Tsurutani, Kazuto Nishio, Katsumi Doi, Masaaki Miyazawa, Kazuhiko Nakagawa

β1-integrin- and K_V1.3 channel-dependent signaling stimulates glutamate release from Th17 cells

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Abstract

While the impact of T helper 17 (Th17) cells in autoimmunity is undisputable, their pathogenic effector mechanism is still enigmatic. We have discovered SNARE complex proteins in Th17 cells enabling a vesicular glutamate release pathway inducing local intracytoplasmic calcium release and subsequent damage in neurons. This pathway is glutamine dependent and triggered by binding of β1-integrin to VCAM-1 on neurons in inflammatory context. Glutamate secretion could be blocked by inhibiting either glutaminase or KV1.3 channels, known to be linked to integrin expression and highly expressed on stimulated T cells. While KV1.3 is not expressed in the CNS tissue, intrathecal administration of a KV1.3 channel blocker or a glutaminase inhibitor ameliorated disability in experimental neuroinflammation. In humans, T cells from multiple sclerosis patients secreted higher levels of glutamate, and cerebrospinal fluid glutamine levels were increased. Altogether, our findings demonstrate that β1-integrin- and KV1.3 channel-dependent signaling stimulates glutamate release from Th17 cells upon direct cell-cell contact between Th17 cells and neurons.

Authors

Katharina Birkner, Beatrice Wasser, Tobias Ruck, Carine Thalman, Dirk Luchtman, Katrin Pape, Samantha Schmaul, Lynn Bitar, Eva-Maria Krämer-Albers, Albrecht Stroh, Sven G. Meuth, Frauke Zipp, Stefan Bittner

Antigen-loaded monocyte administration induces potent therapeutic anti-tumor T cell responses

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Abstract

Efficacy of dendritic cell (DC) cancer vaccines is classically thought to depend on their antigen-presenting cell (APC) activity. Studies show, however, that DC vaccine priming of cytotoxic T lymphocytes (CTL) requires the activity of endogenous DC, suggesting that exogenous DC stimulate anti-tumor immunity by transferring antigen (Ag) to endogenous DC. Such Ag transfer functions are most commonly ascribed to monocytes, implying that undifferentiated monocytes would function equally well as a vaccine modality and need not be differentiated to DC to be effective. Here, we used several murine cancer models to test the anti-tumor efficacy of undifferentiated monocytes loaded with protein or peptide Ag. Intravenously injected monocytes displayed anti-tumor activity superior to DC vaccines in several cancer models, including aggressive intracranial glioblastoma. Ag-loaded monocytes induced robust CTL responses via Ag transfer to splenic CD8+ DC in a manner independent of monocyte APC activity. Ag transfer required cell-cell contact and the formation of connexin 43-containing gap junctions between monocytes and DC. These findings demonstrate the existence of an efficient gap junction-mediated Ag transfer pathway between monocytes and CD8+ DC and suggest that administration of tumor Ag-loaded undifferentiated monocytes may serve as a simple and efficacious immunotherapy for the treatment of human cancers.

Authors

Min-Nung Huang, Lowell T. Nicholson, Kristen A. Batich, Adam M. Swartz, David Kopin, Sebastian Wellford, Vijay K. Prabhakar, Karolina Woroniecka, Smita K. Nair, Peter E. Fecci, John H. Sampson, Michael D. Gunn

Effects of maternal iron status on placental and fetal iron homeostasis

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Abstract

Iron deficiency is common worldwide and is associated with adverse pregnancy outcomes. The increasing prevalence of indiscriminate iron supplementation during pregnancy also raises concerns about the potential adverse effects of iron excess. We examined how maternal iron status affects the delivery of iron to the placenta and fetus. Using mouse models, we documented maternal homeostatic mechanisms which protect the placenta and fetus from maternal iron excess. We determined that under physiological conditions or in iron deficiency, fetal and placental hepcidin does not regulate fetal iron endowment. With maternal iron deficiency, critical transporters mediating placental iron uptake (transferrin receptor 1, TFR1) and export (ferroportin, FPN) were strongly regulated. In mice, not only was TFR1 increased but FPN was surprisingly decreased to preserve placental iron, in the face of fetal iron deficiency. In human placentas from pregnancies with mild iron deficiency, TFR1 was increased but without a change in FPN. However, induction of more severe iron deficiency in human trophoblast in vitro resulted in the regulation of both TFR1 and FPN, similarly to the mouse model. This placental adaptation prioritizing placental iron is mediated by the iron-regulatory protein 1 and is important for the maintenance of mitochondrial respiration, thus ultimately protecting the fetus from the potentially dire consequences of generalized placental dysfunction.

Authors

Veena Sangkhae, Allison L. Fisher, Shirley Wong, Mary Dawn Koenig, Lisa Tussing-Humphreys, Alison Chu, Melisa Lelić, Tomas Ganz, Elizabeta Nemeth

SIV-specific CD8⁺ T cells are clonotypically distinct across lymphoid and mucosal tissues

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Abstract

CD8+ T cell responses are necessary for immune control of simian immunodeficiency virus (SIV). However, the key parameters that dictate antiviral potency remain elusive, conceivably because most studies to date have been restricted to analyses of circulating CD8+ T cells. We conducted a detailed clonotypic, functional, and phenotypic survey of SIV-specific CD8+ T cells across multiple anatomical sites in chronically infected rhesus macaques with high (> 10,000 copies/mL plasma) or low burdens of viral RNA (< 10,000 copies/mL plasma). No significant differences in response magnitude were identified across anatomical compartments. Rhesus macaques with low viral loads (VLs) harbored higher frequencies of polyfunctional CXCR5+ SIV-specific CD8+ T cells in various lymphoid tissues and higher proportions of unique Gag-specific CD8+ T cell clonotypes in the mesenteric lymph nodes relative to rhesus macaques with high VLs. In addition, public Gag-specific CD8+ T cell clonotypes were more commonly shared across distinct anatomical sites than the corresponding private clonotypes, which tended to form tissue-specific repertoires, especially in the peripheral blood and the gastrointestinal tract. Collectively, these data suggest that functionality and tissue localization are important determinants of CD8+ T cell-mediated efficacy against SIV.

Authors

Carly E. Starke, Carol L. Vinton, Kristin Ladell, James E. McLaren, Alexandra M. Ortiz, Joseph C. Mudd, Jacob K. Flynn, Stephen H. Lai, Fan Wu, Vanessa M. Hirsch, Samuel Darko, Daniel C. Douek, David A. Price, Jason M. Brenchley

Mycobacterium tuberculosis Programs Mesenchymal Stem Cells to Establish Dormancy and Persistence

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Abstract

Tuberculosis (TB) remains a major infectious disease worldwide. TB treatment displays a bi-phasic bacterial clearance, in which the majority of bacteria clear within the first month of treatment, but residual bacteria remains non-responsive to treatment and eventually may become resistant. Here, we have shown that Mycobacterium tuberculosis (M.tb) is taken up by mesenchymal stem cells (MSCs), where it established dormancy and became highly non-responsive to isoniazid, a major constituent of Directly Observed Treatment Short-course (DOTS). Dormant M.tb induced quiescence in MSCs and promoted their long-term survival. Unlike macrophages, where M.tb resides in early-phagosomal compartments, in MSCs the majority of bacilli were found in the cytosol, where they promoted rapid lipid-synthesis, hiding within lipid-droplets. Inhibition of lipid-synthesis prevented dormancy and sensitized the organisms to isoniazid. Thus, we have established that M.tb gains dormancy in MSCs, which thus serve as a long-term natural-reservoir of dormant M.tb. Interestingly, in the murine-model of TB, induction of autophagy eliminated M.tb from MSCs and consequently, the addition of rapamycin to an isoniazid treatment regimen successfully attained sterile clearance and prevented disease reactivation.

Authors

Samreen Fatima, Shashank Shivaji Kamble, Ved Prakash Dwivedi, Debapriya Bhattacharya, Santosh Kumar, Anand Ranganathan, Luc Van Kaer, Sujata Mohanty, Gobardhan Das

Oral ferroportin inhibitor ameliorates ineffective erythropoiesis in a model of β-thalassemia

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Abstract

β-thalassemia is a genetic anemia caused by partial or complete loss of β-globin synthesis leading to ineffective erythropoiesis and RBCs with short life-span. Currently, there is no efficacious oral medication modifying anemia for patients with beta-thalassemia. The inappropriately low levels of the iron regulatory hormone hepcidin enable excessive iron absorption by ferroportin, the unique cellular iron exporter in mammals, leading to organ iron overload and associated morbidities. Correction of unbalanced iron absorption and recycling by induction of hepcidin synthesis or treatment with hepcidin mimetics ameliorates β-thalassemia. However, hepcidin modulation or replacement strategies currently in clinical development all require parenteral drug administration. We identified oral ferroportin inhibitors by screening a library of small molecular weight compounds for modulators of ferroportin internalization. Restricting iron availability by VIT-2763, the first clinical stage oral ferroportin inhibitor, ameliorated anemia and the dysregulated iron homeostasis in the Hbbth3/+ mouse model of beta-thalassemia intermedia. VIT-2763 not only improved erythropoiesis but also corrected the proportions of myeloid precursors in spleens of Hbbth3/+ mice. VIT-2763 is currently developed as an oral drug targeting ferroportin for the treatment of β-thalassemia.

Authors

Vania Manolova, Naja Nyffenegger, Anna Flace, Patrick Altermatt, Ahmet Varol, Cédric Doucerain, Hanna Sundstrom, Franz Dürrenberger

Targetable cellular signaling events mediate vascular pathology in vascular Ehlers-Danlos syndrome

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Abstract

Vascular Ehlers-Danlos syndrome (vEDS) is an autosomal-dominant connective tissue disorder caused by heterozygous mutations in the COL3A1 gene, which encodes the pro-alpha 1 chain of collagen III. Loss of structural integrity of the extracellular matrix is believed to drive the signs and symptoms of this condition, including spontaneous arterial dissection and/or rupture, the major cause of mortality. We created two mouse models of vEDS that carry heterozygous mutations in Col3a1 that encode glycine substitutions analogous to those found in patients, and showed that signaling abnormalities in the PLC/IP3/PKC/ERK pathway (phospholipase C/inositol 1,4,5-triphosphate/protein kinase C/extracellular signal-regulated kinase) are major mediators of vascular pathology.Treatment with pharmacologic inhibitors of ERK1/2 or PKC-beta prevented death due to spontaneous aortic rupture. Additionally, we found that pregnancy- and puberty-associated accentuation of vascular risk, also seen in vEDS patients, is rescued by attenuation of oxytocin and androgen signaling, respectively. Taken together, our results provide evidence that targetable signaling abnormalities contribute to the pathogenesis of vEDS, highlighting unanticipated therapeutic opportunities.

Authors

Caitlin J. Bowen, Juan Francisco Calderón Giadrosic, Zachary Burger, Graham Rykiel, Elaine C. Davis, Mark R. Helmers, Kelly Benke, Elena Gallo MacFarlane, Harry C. Dietz