Beta-alanine containing peptides: a novel molecular tool for the design of gamma-turns.

In the present paper we describe the synthesis, purification, single crystal x-ray analysis, and solution conformational characterization of the cyclic tetrapeptide cyclo-(L-Pro-beta-Ala-L-Pro-beta-Ala). This peptide was synthesized by classical solution methods and the cyclization of the free tetrapeptide was accomplished in good yields in diluted methylene chloride solution using N,N-dicyclohexyl-carbodiimide (DCCI). The compound crystallizes in the orthorombic space group P2(1)2(1)2(1) from ethyl acetate. All peptide bonds are trans. The molecular conformation is stabilized by two intramolecular hydrogen bonds between the CO and NH groups of the two beta-alanine residues. These hydrogen bonds take place in a C7 structure in which both proline residues occupy the 2 position of an inverse gamma-turn. The two beta-alanine residues have a typical folded conformation (around the C alpha-C beta bond) observed in other cyclic peptides containing this residue. A detailed 1H-nmr analysis in CD3CN solution has been carried out. The molecule assumes a twofold symmetry in solution with a molecular conformation consistent with that observed in the solid state.     

Meiotic transmission of T-DNA genes inArabidopsis thaliana plants and their expression after 5-azacytidine treatment

Arabidopsis thaliana tumors were induced by octopine strain ofAgrobacterium tumefaciens B6S3 and its derivatives with modified T-DNA. Flowering shoots appeared sponta-neously onin vitro cultivated tumors and set seeds. R₁ and R₂ progeny of octopine synthesizing plants segregated in opine synthesis activities 3:1 and 15:1. Octopine synthase activity showed absolute linkage with agropine synthesis in most lines. In R₃ and R₄ progenies, the fraction of octopine synthase and agropine synthesis positive plants was lower than expected, but Mendelian segregation was restored if plants were cultivated on medium with 5-azacytidine. The most probable mechanism of disapearance of opine synthesis is cytosine methylation. The effect of 5-azacytidine lasted for at least next two generations.     

The in vitro adherence of murine eosinophils, neutrophils and non-induced and induced macrophages to infective larvae of Toxocara canis (Nematoda, Ascarididae)

Infective larvae of the parasite nematode Toxocara canis were incubated in vitro with murine eosinophils, neutrophils and non-induced and induced macrophages. The interactions between the different types of cells and the worms were observed in the presence or absence of immune mouse serum and/or complement. Cells showed considerable differences in the manner, duration and outcome of this interaction. Despite the adhesion of cells to the larvae of T. canis, there was no evidence of damage to the worms. Scanning and transmission electron microscopic observations suggest that the cells adhere to the cuticular surface via an electron-dense material. This material might play a protective role against the helmintotoxic capacity of the inflammatory cells.     

Iso-FRET: an isothermal competition assay to analyze quadruplex formation in vitro

Algorithms have been widely used to predict G-quadruplexes (G4s)-prone sequences. However, an experimental validation of these predictions is generally required. We previously reported a high-throughput technique to evidence G4 formation in vitro called FRET-MC. This method, while convenient and reproducible, has one known weakness: its inability to pin point G4 motifs of low thermal stability. As such quadruplexes may still be biologically relevant if formed at physiological temperature, we wanted to develop an independent assay to overcome this limitation. To this aim, we introduced an isothermal version of the competition assay, called iso-FRET, based on a duplex-quadruplex competition and a well-characterized bis-quinolinium G4 ligand, PhenDC3. G4-forming competitors act as decoys for PhenDC3, lowering its ability to stabilize the G4-forming motif reporter oligonucleotide conjugated to a fluorescence quencher (37Q). The decrease in available G4 ligand concentration restores the ability of 37Q to hybridize to its FAM-labeled short complementary C-rich strand (F22), leading to a decrease in fluorescence signal. In contrast, when no G4-forming competitor is present, PhenDC3 remains available to stabilize the 37Q quadruplex, preventing the formation of the F22 + 37Q complex. Iso-FRET was first applied to a reference panel of 70 sequences, and then used to investigate 23 different viral sequences.     

Nuclear localization of TRK-A in liver cells

The liver represents a site of expression of neurotrophins and their receptors. We have characterized the expression and intracellular localization of the nerve growth factor (NGF) receptor, Trk-A, in liver cells in vivo and in vitro. In both normal and fibrotic liver tissue, Trk-A immunostaining was present in different cell types, including parenchymal cells and cells of the inflammatory infiltrate. In hepatocytes and activated stellate cells (HSC), Trk-A showed a predominant nuclear localization, both in the presence and absence of injury. In cultured HSC, Trk-A was found to be functional, because exposure of the cells to recombinant NGF resulted in stimulation of cell migration and activation of intracellular signaling pathways, including Ras-ERK and PI3K/Akt. Remarkably, in cultured HSC, Trk-A staining was found constitutively in the nucleus. In these cells, Trk-A could be stained only by antibodies directed against the intracellular domain but not by those recognizing the extracellular portion of Trk-A suggesting that the intracellular portion of the receptor is the major determinant of nuclear Trk-A staining. In contrast to HSC, freshly isolated hepatocytes did not show any nuclear localization of the intracellular portion of Trk-A. In pheocromocytoma cells, nuclear staining for Trk-A was not present in conditions of serum deprivation, but could be induced by exposure to NGF or to a mixture of soluble mediators. We conclude that nuclear localization of the intracellular domain of Trk-A is observed constitutively in liver cells such as HSC, while in other cell types it could be induced in response to soluble factors.     

Proteomic profiling of the hypothalamus in two mouse models of narcolepsy

Narcolepsy is a disabling neurological disorder of sleepiness linked to the loss of neurons producing orexin neuropeptides in the hypothalamus. Two well‐characterized phenotypic mouse models of narcolepsy, loss‐of‐function (orexin‐knockout), and progressive loss of orexin (orexin/ataxin‐3) exist. The open question is whether the proteomics signatures of the hypothalamus would be different between the two models. To address this gap, we utilized a label‐free proteomics approach and conducted a hypothalamic proteome analysis by comparing each disease model to that of wild type. Following data processing and statistical analysis, 14 484 peptides mapping to 2282 nonredundant proteins were identified, of which 39 proteins showed significant differences in protein expression across groups. Altered proteins in both models showed commonalties in pathways for mitochondrial dysfunction and neuronal degeneration, as well as altered proteins related to inflammatory demyelination, insulin resistance, metabolic responses, and the dopaminergic and monoaminergic systems. Model‐specific alterations in insulin degraded enzyme (IDE) and synaptosomal‐associated protein‐25 were unique to orexin‐KO and orexin/ataxin‐3, respectively. For both models, proteomics not only identified clinically suspected consequences of orexin loss on energy homeostasis and neurotransmitter systems, but also identified commonalities in inflammation and degeneration despite the entirely different genetic basis of the two mouse models.     

Effect of CMV-immunoglobulins (cytotect biotest) prophylaxis on CMV pneumonia after lung transplantation

Lung transplant (LT) recipients among solid organ transplant recipients are at high risk for cytomegalovirus (CMV) infections. We evaluated the effect of CMV-Immunoglobulins (CMV-IG) (Cytotect Biotest) on CMV pneumonia diagnosed in 303 follow-up transbronchial biopsies (TBB) of lung transplant recipients. 24 patients (control group, 155 TBB from 1999 to 2002) received acyclovir for 24 months and 33 recipients (study group, 148 TBB from 2003 to 2008) received a combined CMV prophylaxis consisting of CMV-IG (Cytotect Biotest) for 12 months and a short Ganciclovir or Valganciclovir therapy from 21th to 42th postoperative day followed by acyclovir up to 24 months. In our study the percentage of pneumonia at first month TBB was similar in the study group vs the control group, 9.1% (3/33) vs 8.3% (2/24), p=0.9 ns, but after the first month the percentage was significantly lower in the study group in the first year at follow-up TBB, 1% (1/99) vs 6.4% (5/78), p=0.048, and in first two years follow-up TBB, 0.8% (1/122) vs 6.5% 8/124), p=0.018 (Statistical analysis: Chi-square test for proportion differences). Our data suggest a strong efficacy of CMV-IG prophylaxis in reducing CMV pneumonia after first month in lung transplant recipients.     

Lysosomal fusion and SNARE function are impaired by cholesterol accumulation in lysosomal storage disorders

The function of lysosomes relies on the ability of the lysosomal membrane to fuse with several target membranes in the cell. It is known that in lysosomal storage disorders (LSDs), lysosomal accumulation of several types of substrates is associated with lysosomal dysfunction and impairment of endocytic membrane traffic. By analysing cells from two severe neurodegenerative LSDs, we observed that cholesterol abnormally accumulates in the endolysosomal membrane of LSD cells, thereby reducing the ability of lysosomes to efficiently fuse with endocytic and autophagic vesicles. Furthermore, we discovered that soluble N‐ethylmaleimide‐sensitive factor attachment protein (SNAP) receptors (SNAREs), which are key components of the cellular membrane fusion machinery are aberrantly sequestered in cholesterol‐enriched regions of LSD endolysosomal membranes. This abnormal spatial organization locks SNAREs in complexes and impairs their sorting and recycling. Importantly, reducing membrane cholesterol levels in LSD cells restores normal SNARE function and efficient lysosomal fusion. Our results support a model by which cholesterol abnormalities determine lysosomal dysfunction and endocytic traffic jam in LSDs by impairing the membrane fusion machinery, thus suggesting new therapeutic targets for the treatment of these disorders.     

The interaction between nesprins and sun proteins at the nuclear envelope is critical for force transmission between the nucleus and cytoskeleton

Maintaining physical connections between the nucleus and the cytoskeleton is important for many cellular processes that require coordinated movement and positioning of the nucleus. Nucleo-cytoskeletal coupling is also necessary to transmit extracellular mechanical stimuli across the cytoskeleton to the nucleus, where they may initiate mechanotransduction events. The LINC (Linker of Nucleoskeleton and Cytoskeleton) complex, formed by the interaction of nesprins and SUN proteins at the nuclear envelope, can bind to nuclear and cytoskeletal elements; however, its functional importance in transmitting intracellular forces has never been directly tested. This question is particularly relevant since recent findings have linked nesprin mutations to muscular dystrophy and dilated cardiomyopathy. Using biophysical assays to assess intracellular force transmission and associated cellular functions, we identified the LINC complex as a critical component for nucleo-cytoskeletal force transmission. Disruption of the LINC complex caused impaired propagation of intracellular forces and disturbed organization of the perinuclear actin and intermediate filament networks. Although mechanically induced activation of mechanosensitive genes was normal (suggesting that nuclear deformation is not required for mechanotransduction signaling) cells exhibited other severe functional defects after LINC complex disruption; nuclear positioning and cell polarization were impaired in migrating cells and in cells plated on micropatterned substrates, and cell migration speed and persistence time were significantly reduced. Taken together, our findings suggest that the LINC complex is critical for nucleo-cytoskeletal force transmission and that LINC complex disruption can result in defects in cellular structure and function that may contribute to the development of muscular dystrophies and cardiomyopathies.