Most overweight individuals do not develop diabetes due to compensatory islet responses to restore glucose homeostasis. Therefore, regulatory pathways that promote β-cell compensation are potential targets for treatment of diabetes. The melastatin transient receptor potential 7 protein (TRPM7), harboring a cation channel and a serine/threonine kinase, has been implicated in controlling cell growth and proliferation. Here, we report that selective deletion of Trpm7 in β-cells disrupts insulin secretion and leads to progressive glucose intolerance. We indicate that the diminished insulinotropic response in β-cell-specific Trpm7 knockout mice is caused by decreased insulin production due to an impaired enzymatic activity of this protein. Accordingly, high-fat fed mice with a genetic loss of TRPM7 kinase activity (Trpm7R/R) display a marked glucose intolerance accompanied by hyperglycemia. These detrimental glucoregulatory effects are engendered by reduced compensatory β-cell responses due to mitigated AKT/ERK signaling. Collectively, our data identify TRPM7 kinase as a novel regulator of insulin synthesis, β-cell dynamics, and glucose homeostasis under obesogenic diet.
Noushafarin Khajavi, Andreas Beck, Klea Ricku, Philipp Beyerle, Katharina Jacob, Sabrina F. Syamsul, Anouar Belkacemi, Peter S. Reinach, Pascale C.F. Schreier, Houssein Salah, Tanja Popp, Aaron Novikoff, Andreas Breit, Vladimir Chubanov, Timo D. Müller, Susanna Zierler, Thomas Gudermann
In the progression phase of idiopathic pulmonary fibrosis (IPF) the normal alveolar structure of the lung is lost and replaced by remodeled fibrotic tissue and by bronchiolized cystic airspaces. Although these are characteristic features of IPF, knowledge of specific interactions between these pathological processes is limited. Here, the interaction of lung epithelial and lung mesenchymal cells was investigated in a co–culture model of human primary airway epithelial cells (EC) and lung fibroblasts (FB). Single–cell RNA sequencing (sc–RNA–seq) revealed that the starting EC population was heterogenous and enriched for cells with a basal cell signature. Furthermore, fractions of the initial EC and FB cell populations adopted distinct pro–fibrotic cell differentiation states upon co-cultivation, resembling specific cell populations that were previously identified in lungs of IPF patients. Transcriptomic analysis revealed active nuclear factor NF–kappa–B (NF–κB) signaling early in the co–cultured EC and FB cells and the identified NF–κB expression signatures were also found in “HAS1 High FB” and “PLIN2+ FB” populations from IPF patient lungs. Pharmacological blockade of NF–κB signaling attenuated specific phenotypic changes of EC and prevented FB–mediated interleukin–6 (IL6), interleukin–8 (IL–8) and C–X–C motif chemokine ligand 6 (CXCL6) cytokine secretion, as well as collagen alpha–1(I) chain (COL1A1) and alpha–smooth muscle actin (α–SMA) accumulation. Thus, we identified NF–κB as a potential mediator, linking epithelial pathobiology with fibrogenesis.
Patrick Sieber, Anny Schäfer, Raphael Lieberherr, Silvia L Caimi, Urs Lüthi, Jesper Ryge, Jan H. Bergmann, Francois Le Goff, Manuel Stritt, Peter Blattmann, Bérengère Renault, Patrick Rammelt, Bruno Sempere, Diego Freti, Rolf Studer, Eric S. White, Magdalena Birker-Robaczewska, Maxime Boucher, Oliver Nayler
NK cell deficiencies (NKD) are a type of primary immune deficiency in which the major immunologic abnormality affects NK cell number, maturity, or function. Since NK cells contribute to immune defense against virally infected cells, patients with NKD experience higher susceptibility to chronic, recurrent, and fatal viral infections. An individual with recurrent viral infections and mild hypogammaglobulinemia was identified to have an X-linked damaging variant in the transcription factor gene ELF4. The variant does not decrease expression but disrupts ELF4 protein interactions and DNA binding, reducing transcriptional activation of target genes and selectively impairing ELF4 function. Corroborating previous murine models of ELF4 deficiency (Elf4–/–) and using a knockdown human NK cell line, we determined that ELF4 is necessary for normal NK cell development, terminal maturation, and function. Through characterization of the NK cells of the proband, expression of the proband’s variant in Elf4–/– mouse hematopoietic precursor cells, and a human in vitro NK cell maturation model, we established this ELF4 variant as a potentially novel cause of NKD.
Sandra Andrea Salinas, Emily M. Mace, Matilde I. Conte, Chun Shik Park, Yu Li, Joshua I. Rosario-Sepulveda, Sanjana Mahapatra, Emily K. Moore, Evelyn R. Hernandez, Ivan K. Chinn, Abigail E. Reed, Barclay J. Lee, Alexander Frumovitz, Richard A. Gibbs, Jennifer E. Posey, Lisa R. Forbes Satter, Akaluck Thatayatikom, Eric J. Allenspach, Theodore G. Wensel, James R. Lupski, H. Daniel Lacorazza, Jordan S. Orange
Mitochondria are dynamic organelles responsible for energy production and many processes central to cellular function. Alterations in mitochondrial function is associated with human fibrotic lung diseases, including idiopathic pulmonary fibrosis (IPF). Pulmonary fibrosis is characterized by stiffening of the extracellular matrix (ECM). Fibroblasts migrate in the direction of greater stiffness, a phenomenon termed durotaxis. The mechanically guided fibroblast migration could be a crucial step in the progression of lung fibrosis. In this study, we identified mitochondria as an important mechanotransducer at the intersection between extracellular mechanical signals and durotactic lung fibroblast migration. Primary human lung fibroblasts sense increasing matrix stiffness with a change of mitochondrial dynamics in favor of mitochondrial fission and increased production of ATP. Mitochondria polarize in the direction of a physiologically relevant stiffness gradient, with conspicuous localization to the leading edge, primarily lamellipodia and filopodia, of migrating lung fibroblasts. Matrix stiffness-regulated mitochondrial fission and durotactic lung fibroblast migration are mediated by a DRP1/MFF-dependent pathway. Importantly, we found that the DRP1/MFF pathway is activated in fibrotic lung myofibroblasts in both human IPF and bleomycin-induced mouse lung fibrosis. Our findings suggest that energy-producing mitochondria need to be sectioned via fission and repositioned in durotactic lung fibroblasts to meet the higher energy demand. This represents a new mechanism through which mitochondria may contribute to the progression of fibrotic lung diseases. Inhibition of durotactic migration of lung fibroblasts may play an important role in preventing the progression of IPF.
Ting Guo, Chun-sun Jiang, Shan-Zhong Yang, Yi Zhu, Chao He, A. Brent Carter, Veena B. Antony, Hong Peng, Yong Zhou
Progressive fibrosis and maladaptive organ repair result in significant morbidity and millions of premature deaths annually. Senescent cells accumulate with aging and after injury and are implicated in organ fibrosis, but the mechanisms by which senescence influences repair are poorly understood. Using 2 murine models of injury and repair, we show that obstructive injury generated senescent epithelia, which persisted after resolution of the original injury, promoted ongoing fibrosis, and impeded adaptive repair. Depletion of senescent cells with ABT-263 reduced fibrosis in reversed ureteric obstruction and after renal ischemia/reperfusion injury. We validated these findings in humans, showing that senescence and fibrosis persisted after relieved renal obstruction. We next characterized senescent epithelia in murine renal injury using single-cell RNA-Seq. We extended our classification to human kidney and liver disease and identified conserved profibrotic proteins, which we validated in vitro and in human disease. We demonstrated that increased levels of protein disulfide isomerase family A member 3 (PDIA3) augmented TGF-β–mediated fibroblast activation. Inhibition of PDIA3 in vivo significantly reduced kidney fibrosis during ongoing renal injury and as such represented a new potential therapeutic pathway. Analysis of the signaling pathways of senescent epithelia connected senescence to organ fibrosis, permitting rational design of antifibrotic therapies.
Eoin D. O’Sullivan, Katie J. Mylonas, Rachel Bell, Cyril Carvalho, David P. Baird, Carolynn Cairns, Kevin M. Gallagher, Ross Campbell, Marie Docherty, Alexander Laird, Neil C. Henderson, Tamir Chandra, Kristina Kirschner, Bryan Conway, Gry H. Dihazi, Michael Zeisberg, Jeremy Hughes, Laura Denby, Hassan Dihazi, David A. Ferenbach
Human NK cell deficiency (NKD) is a primary immunodeficiency in which the main clinically relevant immunological defect involves missing or dysfunctional NK cells. Here, we describe a familial NKD case in which 2 siblings had a substantive NKD and neutropenia in the absence of other immune system abnormalities. Exome sequencing identified compound heterozygous variants in Go-Ichi-Ni-San (GINS) complex subunit 4 (GINS4, also known as SLD5), an essential component of the human replicative helicase, which we demonstrate to have a damaging impact upon the expression and assembly of the GINS complex. Cells derived from affected individuals and a GINS4-knockdown cell line demonstrate delayed cell cycle progression, without signs of improper DNA synthesis or increased replication stress. By modeling partial GINS4 depletion in differentiating NK cells in vitro, we demonstrate the causal relationship between the genotype and the NK cell phenotype, as well as a cell-intrinsic defect in NK cell development. Thus, biallelic partial loss-of-function mutations in GINS4 define a potentially novel disease-causing gene underlying NKD with neutropenia. Together with the previously described mutations in other helicase genes causing NKD, and with the mild defects observed in other human cells, these variants underscore the importance of this pathway in NK cell biology.
Matilde I. Conte, M. Cecilia Poli, Angelo Taglialatela, Giuseppe Leuzzi, Ivan K. Chinn, Sandra A. Salinas, Emma Rey-Jurado, Nixa Olivares, Liz Veramendi-Espinoza, Alberto Ciccia, James R. Lupski, Juan Carlos Aldave Becerra, Emily M. Mace, Jordan S. Orange
One of the least-investigated areas of brain pathology research is glycosylation, which is a critical regulator of cell surface protein structure and function. β-Galactoside α2,6-sialyltransferase (ST6GAL1) is the primary enzyme that α2,6 sialylates N-glycosylated proteins destined for the plasma membrane or secretion, thereby modulating cell signaling and behavior. We demonstrate a potentially novel, protumorigenic role for α2,6 sialylation and ST6GAL1 in the deadly brain tumor glioblastoma (GBM). GBM cells with high α2,6 sialylation exhibited increased in vitro growth and self-renewal capacity and decreased mouse survival when orthotopically injected. α2,6 Sialylation was regulated by ST6GAL1 in GBM, and ST6GAL1 was elevated in brain tumor-initiating cells (BTICs). Knockdown of ST6GAL1 in BTICs decreased in vitro growth, self-renewal capacity, and tumorigenic potential. ST6GAL1 regulates levels of the known BTIC regulators PDGF Receptor β (PDGFRB), Activated Leukocyte Cell Adhesion Molecule, and Neuropilin, which were confirmed to bind to a lectin-recognizing α2,6 sialic acid. Loss of ST6GAL1 was confirmed to decrease PDGFRB α2,6 sialylation, total protein levels, and the induction of phosphorylation by PDGF-BB. Thus, ST6GAL1-mediated α2,6 sialylation of a select subset of cell surface receptors, including PDGFRB, increases GBM growth.
Sajina GC, Kaysaw Tuy, Lucas Rickenbacker, Robert Jones, Asmi Chakraborty, C. Ryan Miller, Elizabeth A. Beierle, Vidya Sagar Hanumanthu, Anh N. Tran, James A. Mobley, Susan L. Bellis, Anita B. Hjelmeland
Intercellular communication is critical for homeostasis in mammalian systems, including the gastrointestinal (GI) tract. Exosomes are nanoscale lipid extracellular vesicles that mediate communication between many cell types. Notably, the roles of immune cell exosomes in regulating GI homeostasis and inflammation are largely uncharacterized. By generating mouse strains deficient in cell-specific exosome production, we demonstrate deletion of the small GTPase Rab27A in CD11c+ cells exacerbated murine colitis, which was reversible through administration of DC-derived exosomes. Profiling RNAs within colon exosomes revealed a distinct subset of miRNAs carried by colon- and DC-derived exosomes. Among antiinflammatory exosomal miRNAs, miR-146a was transferred from gut immune cells to myeloid and T cells through a Rab27-dependent mechanism, targeting Traf6, IRAK-1, and NLRP3 in macrophages. Further, we have identified a potentially novel mode of exosome-mediated DC and macrophage crosstalk that is capable of skewing gut macrophages toward an antiinflammatory phenotype. Assessing clinical samples, RAB27A, select miRNAs, and RNA-binding proteins that load exosomal miRNAs were dysregulated in ulcerative colitis patient samples, consistent with our preclinical mouse model findings. Together, our work reveals an exosome-mediated regulatory mechanism underlying gut inflammation and paves the way for potential use of miRNA-containing exosomes as a novel therapeutic for inflammatory bowel disease.
Kaylyn M. Bauer, Morgan C. Nelson, William W. Tang, Tyson R. Chiaro, D. Garrett Brown, Arevik Ghazaryan, Soh-Hyun Lee, Allison M. Weis, Jennifer H. Hill, Kendra A. Klag, Van B. Tran, Jacob W. Thompson, Andrew G. Ramstead, Josh K. Monts, James E. Marvin, Margaret Alexander, Warren P. Voth, W. Zac Stephens, Diane M. Ward, Aaron C. Petrey, June L. Round, Ryan M. O’Connell
The individual contribution of specific myeloid subsets such as CD1c+ conventional dendritic cells (cDC) to perpetuation of Rheumatoid Arthritis (RA) pathology remains unclear. In addition, the specific innate sensors driving pathogenic activation of CD1c+ cDCs in RA patients and their functional implications have not been characterized. Here, we assessed phenotypical, transcriptional and functional characteristics of CD1c+ and CD141+ cDCs and monocytes from the blood and synovial fluid of RA patients. Increased levels of CCR2 and the IgG receptor CD64 on circulating CD1c+ cDC associated with the presence of this DC subset in the synovial membrane in RA patients. Moreover, synovial CD1c+ cDCs are characterized by increased expression of proinflammatory cytokines and high abilities to induce pathogenic IFNγ+IL-17+ CD4+ T cells in vitro. Finally, we identified the crosstalk between Fcγ Receptors and NLRC4 as a new potential molecular mechanism mediating pathogenic activation, CD64 upregulation and functional specialization of CD1c+ cDCs in response to dsDNA-IgG in RA patients.
Cristina Delgado-Arévalo, Marta Calvet-Mirabent, Ana Triguero-Martinez, Enrique Vázquez de Luis, Alberto Benguría-Filippini, Raquel Largo, Diego Calzada-Fraile, Olga Popova, Ildefonso Sánchez-Cerrillo, Ilya Tsukalov, Roberto Moreno-Vellisca, Hortensia de la Fuente, Gabriel Herrero-Beaumont, Almudena R. Ramiro, Francisco Sánchez-Madrid, Santos Castañeda, Ana Dopazo, Isidoro González-Álvaro, Enrique Martin-Gayo
No disease-modifying drug exists for osteoarthritis (OA). Despite success in animal models, candidate drugs continue to fail in clinical trials due to the unmapped interpatient heterogeneity and disease complexity. We have utilized a single-cell cytometry-by-time-of-flight (cyTOF) based platform to precisely outline the effects of candidate drugs on human OA chondrocytes. OA chondrocytes harvested from patients undergoing total knee arthroplasty were treated with two drugs, an NF-κB pathway inhibitor, BMS-345541, and a chondroinductive small molecule, Kartogenin, that showed preclinical success in animal models for OA. cyTOF conducted with 30 metal isotope-labeled antibodies parsed the effects of the drugs on inflammatory, senescent, and chondroprogenitor populations. The NF-κB pathway inhibition decreased the expression of NF-κB, HIF2A and iNOS in multiple chondrocyte clusters and significantly depleted four p16ink4a expressing senescent populations including NOTCH1+STRO1+ chondroprogenitors. While Kartogenin also affected select p16ink4a expressing senescent clusters, there was a less discernible effect on chondroprogenitor populations. Overall, BMS-345541 elicited a uniform drug response in all patients while only a few responded to Kartogenin. These studies demonstrate that a single-cell cyTOF-based drug screening platform can provide insights into patient response assessment and their stratification.
Neety Sahu, Fiorella C. Grandi, Nidhi Bhutani
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