Selective Lentiviral Gene Delivery to CD133-Expressing Human Glioblastoma Stem Cells
N. Sumru Bayin
Aram S. Modrek
Christian J. Buchholz
Moses V. Chao
Dimitris G. Placantonakis
- Glioblastoma multiforme (GBM) is a deadly primary brain malignancy. Glioblastoma stem cells (GSC), which have the ability to self-renew and differentiate into tumor lineages, are believed to cause tumor recurrence due to their resistance to current therapies. A subset of GSCs is marked by cell surface expression of CD133, a glycosylated pentaspan transmembrane protein. The study of CD133-expressing GSCs has been limited by the relative paucity of genetic tools that specifically target them. Here, we present CD133-LV, a lentiviral vector presenting a single chain antibody against CD133 on its envelope, as a vehicle for the selective transduction of CD133-expressing GSCs. We show that CD133-LV selectively transduces CD133+ human GSCs in dose-dependent manner and that transduced cells maintain their stem-like properties. The transduction efficiency of CD133-LV is reduced by an antibody that recognizes the same epitope on CD133 as the viral envelope and by shRNA-mediated knockdown of CD133. Conversely, the rate of transduction by CD133-LV is augmented by overexpression of CD133 in primary human GBM cultures. CD133-LV selectively transduces CD133-expressing cells in intracranial human GBM xenografts in NOD.SCID mice, but spares normal mouse brain tissue, neurons derived from human embryonic stem cells and primary human astrocytes. Our findings indicate that CD133-LV represents a novel tool for the selective genetic manipulation of CD133-expressing GSCs, and can be used to answer important questions about how these cells contribute to tumor biology and therapy resistance.
A negative feedback modulator of antigen processing evolved from a frameshift in the cowpox virus genome
Agnes I. Wycisk
Peter U. Mayerhofer
- Abstract: Coevolution of viruses and their hosts represents a dynamic molecular battle between the immune system and viral factors that mediate immune evasion. After the abandonment of smallpox vaccination, cowpox virus infections are an emerging zoonotic health threat, especially for immunocompromised patients. Here we delineate the mechanistic basis of how cowpox viral CPXV012 interferes with MHC class I antigen processing. This type II membrane protein inhibits the coreTAP complex at the step after peptide binding and peptide-induced conformational change, in blocking ATP binding and hydrolysis. Distinct from other immune evasion mechanisms, TAP inhibition is mediated by a short ER-lumenal fragment of CPXV012, which results from a frameshift in the cowpox virus genome. Tethered to the ER membrane, this fragment mimics a high ER-lumenal peptide concentration, thus provoking a trans-inhibition of antigen translocation as supply for MHC I loading. These findings illuminate the evolution of viral immune modulators and the basis of a fine-balanced regulation of antigen processing.
Author Summary: Virus-infected or malignant transformed cells are eliminated by cytotoxic T lymphocytes, which recognize antigenic peptide epitopes in complex with major histocompatibility complex class I (MHC I) molecules at the cell surface. The majority of such peptides are derived from proteasomal degradation in the cytosol and are then translocated into the ER lumen in an energy-consuming reaction via the transporter associated with antigen processing (TAP), which delivers the peptides onto MHC I molecules as final acceptors. Viruses have evolved sophisticated strategies to escape this immune surveillance. Here we show that the cowpox viral protein CPXV012 inhibits the ER peptide translocation machinery by allosterically blocking ATP binding and hydrolysis by TAP. The short ER resident active domain of the viral protein evolved from a reading frame shift in the cowpox virus genome and exploits the ER-lumenal negative feedback peptide sensor of TAP. This CPXV012-induced conformational arrest of TAP is signaled by a unique communication across the ER membrane to the cytosolic motor domains of the peptide pump. Furthermore, this study provides the rare opportunity to decipher on a molecular level how nature plays hide and seek with a pathogen and its host.
Characterization of the two isoforms of cbb3-type cytochrome c oxidase from Pseudomonas stutzeri ZoBell
- Heme-copper oxidases (HCOs) are the terminal enzymes of the aerobic respiratory chain in the inner mitochondrial membrane or the plasma membrane in many prokaryotes. These multi-subunit membrane protein complexes catalyze the reduction of oxygen to water, coupling this exothermic reaction to the establishment of an electrochemical proton gradient across the membrane in which they are embedded. The energy stored in the electrochemical proton gradient is used e.g. by the FOF1-ATP synthase to generate ATP from ADP and inorganic phosphate. The superfamily of HCOs is phylogenetically classified into three major families: A, B and C. The A-family HCOs, represented by the well-studied aa3-type cytochrome c oxidases (aa3-CcOs), are found in mitochondria and many bacteria. The B-family of HCOs contains a number of bacterial and archaeal oxidases. The C-family comprises only the cbb3-type cytochrome c oxidase (cbb3-CcO) and is most distantly related to the mitochondrial respiratory oxidases.
Endothelium-dependent and -independent relaxation and VASP serines 157/239 phosphorylation by cyclic nucleotide-elevating vasodilators in rat aorta
- Endothelium-dependent vasodilation is thought to be mediated primarily by the NO/cGMP signaling pathway whereas cAMP-elevating vasodilators are considered to act independent of the endothelial cell layer. However, recent functional data suggest that cAMP-elevating vasodilators such as β-receptor agonists, adenosine or forskolin may also be endothelium-dependent. Here we used functional and biochemical assays to analyze endothelium-dependent, cGMP- and cAMP-mediated signaling in rat aorta. Acetylcholine and sodium nitroprusside (SNP) induced a concentration-dependent relaxation of phenylephrine-precontracted aorta. This response was reflected by the phosphorylation of the vasodilator-stimulated phosphoprotein (VASP), a validated substrate of cGMP- and cAMP-dependent protein kinases (cGK, cAK), on Ser157 and Ser239. As expected, the effects of acetylcholine were endothelium-dependent. However, relaxation induced by the β-receptor agonist isoproterenol was also almost completely impaired after endothelial denudation. At the biochemical level, acetylcholine- and isoproterenol-evoked cGK and cAK activation, respectively, as measured by VASP Ser239 and Ser157 phosphorylation, was strongly diminished. Furthermore, the effects of isoproterenol were repressed by eNOS inhibition when endothelium was present. We also observed that the relaxing and biochemical effects of forskolin were at least partially endothelium-dependent. We conclude that cAMP-elevating vasodilators, i.e. isoproterenol and to a lesser extent also forskolin, induce vasodilation and concomitant cyclic nucleotide protein kinase activation in the vessel wall in an endothelium-dependent way.
The NO/cGMP pathway inhibits Rap1 activation in human platelets via cGMP-dependent protein kinase I
- The NO/cGMP signalling pathway strongly inhibits agonist-induced platelet aggregation. However, the molecular mechanisms involved are not completely defined.We have studied NO/cGMP effects on the activity of Rap1, an abundant guanine-nucleotidebinding protein in platelets. Rap1-GTP levels were reduced by NO-donors and activators of NO-sensitive soluble guanylyl cyclase. Four lines of evidence suggest that NO/cGMP effects are mediated by cGMP-dependent protein kinase (cGKI): (i) Rap1 inhibition correlated with cGKI activity as measured by the phosphorylation state ofVASP, an established substrate of cGKI, (ii) 8-pCPT-cGMP, a membrane permeable cGMP-analog and activator of cGKI, completely blocked Rap1 activation, (iii) Rp- 8pCPT-cGMPS, a cGKI inhibitor, reversed NO effects and (iv) expression of cGKI in cGKI-deficient megakaryocytes inhibited Rap1 activation. NO/cGMP/cGKI effects were independent of the type of stimulus used for Rap1 activation.Thrombin-,ADPand collagen-induced formation of Rap1-GTP in platelets as well as turbulence-induced Rap1 activation in megakaryocytes were inhibited. Furthermore, cGKI inhibited ADP-induced Rap1 activation induced by the G a i -coupled P2Y12 receptor alone, i.e. independently of effects on Ca2+-signalling. From these studies we conclude that NO/cGMP inhibit Rap1 activation in human platelets and that this effect is mediated by cGKI. Since Rap1 controls the function of integrin a IIbß 3 , we propose that Rap1 inhibition might play a central role in the anti-aggregatory actions of NO/cGMP.
Synthesis of new 1,2,3-triazol-4-yl-quinazoline nucleoside and acyclonucleoside analogues
Joachim W. Engels
Hassan B. Lazrek
- In this study, we describe the synthesis of 1,4-disustituted-1,2,3-triazolo-quinazoline ribonucleosides or acyclonucleosides by means of 1,3-dipolar cycloaddition between various O or N-alkylated propargyl-quinazoline and 1'-azido-2',3',5'-tri-O-benzoylribose or activated alkylating agents under microwave conditions. None of the compounds selected showed significant anti-HCV activity in vitro.
Phase Ib study evaluating a self-adjuvanted mRNA cancer vaccine (RNActive®) combined with local radiation as consolidation and maintenance treatment for patients with stage IV non-small cell lung cancer
Sven D. Koch
Altered mucosal immune response after acute lung injury in a murine model of Ataxia Telangiectasia
Su Youn Kim
Antigenic and 3D structural characterization of soluble X4 and hybrid X4-R5 HIV-1 Env trimers
Correlative light- and electron microscopy with chemical tags
Margot P. Scheffer
Erin M. Schuman
Achilleas S. Frangakis
- Correlative microscopy incorporates the specificity of fluorescent protein labeling into high-resolution electron micrographs. Several approaches exist for correlative microscopy, most of which have used the green fluorescent protein (GFP) as the label for light microscopy. Here we use chemical tagging and synthetic fluorophores instead, in order to achieve protein-specific labeling, and to perform multicolor imaging. We show that synthetic fluorophores preserve their post-embedding fluorescence in the presence of uranyl acetate. Post-embedding fluorescence is of such quality that the specimen can be prepared with identical protocols for scanning electron microscopy (SEM) and transmission electron microscopy (TEM); this is particularly valuable when singular or otherwise difficult samples are examined. We show that synthetic fluorophores give bright, well-resolved signals in super-resolution light microscopy, enabling us to superimpose light microscopic images with a precision of up to 25 nm in the x-y plane on electron micrographs. To exemplify the preservation quality of our new method we visualize the molecular arrangement of cadherins in adherens junctions of mouse epithelial cells.