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J D Guitton

Publications and source records attributed to J D Guitton.

16 recordsLinked to original sources
PubMed1997

Interaction of human angiogenin with copper modulates angiogenin binding to endothelial cells.

Angiogenin is a potent inducer of blood-vessel formation with ribonucleolytic activity. Angiogenin binds to high affinity endothelial cell receptors and with lower affinity to extracellular matrix components. Here we report the effect of copper and zinc on these interactions. There was a 4.3-fold increase in angiogenin binding to calf pulmonary artery endothelial cells in the presence of Cu2+ in vitro. A 3.8-fold increase was observed with Zn2+, whereas Ni2+, Co2+, or Li+ had no effect. Specific angiogenin binding to the lower affinity matrix sites was increased by 2.7- and 1.9-fold in the presence of Cu2+ and Zn2+ respectively. Metal ion affinity chromatography and atomic absorption spectrometry were used to show the direct interaction of angiogenin with copper and zinc ions. Angiogenin bound 2.4 mol of copper per mole of protein. We suggest that copper, a modulator of angiogenesis in vivo, may be involved in the regulation of the biological activity of angiogenin.

Angiogenesis Inducing Agents↗
PubMed1997

Synthesis and conformational analysis of peptide inhibitors of farnesyltransferase.

Farnesylation of the ras oncogene product by Farnesyl Transferase (FTase) is known to be a critical step in cell transformation leading to uncontrolled proliferation. The peptide CysValTicMet is a potent FTase inhibitor, but its degradation by amino-peptidases and its only weak internalization into cells make it a bad candidate for a future cancer drug. We have prepared improved CysValTicMet analogues using several approaches: (i) amino terminal modifications or introduction of pseudopeptides or non-natural amino acids to increase proteolytic stability, (ii) introduction of hydrophobic aliphatic chains to increase cell internalization and metabolic stability and (iii) transformation into prodrugs. Additionally, we have carried out comparative conformational analysis studies by molecular dynamics of some of the here presented peptides and of our recently described peptidomimetic inhibitors of FTase.

Alkyl and Aryl Transferases↗
PubMed1996

Blockage of urokinase receptor reduces in vitro the motility and the deformability of endothelial cells.

The binding of urokinase (u-PA) to its cell surface receptor (u-PAR) is critical for tumor cell invasion. Here, we report that the distribution of this binding by a u-PAR antagonist ATF-HSA inhibits in vitro the motility of endothelial cells in a dose-dependent manner. This inhibition was also observed when the cells were first stimulated with potent angiogenic factors, including bFGF or VEGF. [3H]thymidine incorporation assay demonstrated that ATF-HSA did not affect the cell proliferation. ATF-HSA was more potent than plasmin inhibitors, suggesting that it exerts its effects not solely by inhibiting the remodeling of the extracellular matrix. In fact, analysis of the cell shape change during migration revealed for the first time that its effect is related to a decrease in cell deformability. These results suggest that u-PAR antagonist may be a new approach to control angiogenesis.

Aprotinin↗
PubMed1994

Blockage of the urokinase receptor on the cell surface: construction and characterization of a hybrid protein consisting of the N-terminal fragment of human urokinase and human albumin.

Receptor-bound urokinase is likely to be a crucial determinant in both tumor invasion and angiogenesis. We report here that a yeast-derived genetic conjugate between human serum albumin and the 1-135 N-terminal residues of urokinase (u-PA) competitively inhibits the binding of exogenous and endogenous u-PA to its cell-anchored receptor (u-PAR). This hybrid molecule (ATF-HSA) also inhibits in vitro pro-urokinase-dependent plasminogen activation in the presence of u-PAR bearing cells. These effects are probably responsible for the observed in vitro inhibition of tumor cell invasion in a reconstituted basement membrane extract (Matrigel).

Cell Line↗
PubMed1994

Solution structure of RP 71955, a new 21 amino acid tricyclic peptide active against HIV-1 virus.

The structure of RP 71955, a new tricyclic 21 amino acid peptide active against human immunodeficiency virus 1, was determined. Its amino acid composition was inferred from the results of fast atom bombardment mass spectrometry, nuclear magnetic resonance, Raman spectroscopy, and amino acid analysis. Its sequence could not be determined classically, using Edman degradation, given the lack of a free terminal NH2. It was deduced from the interpretation of interresidue nuclear Overhauser effects and confirmed by the sequencing of peptides obtained by limited chemical hydrolysis. It was found to be CLGIGSCNDFAGCGYAVVCFW. An internal amide bond between the NH2 of C1 and the gamma-COOH of D9 was observed, as well as two disulfide bridges, one between C1 and C13 and one between C7 and C19. The three-dimensional structure of RP 71955 was determined from nuclear magnetic resonance derived constraints using distance geometry, restrained molecular dynamics, nuclear Overhauser effect back calculation, and an iterative refinement using a full relaxation matrix approach. Analogies between the structure of RP 71955 and some functional domains of gp41, the transmembrane protein of human immunodeficiency virus 1, suggest hypotheses concerning the mode of action of RP 71955.

Amino Acid Sequence↗
PubMed1993

Interleukin-1 beta-specific partial agonists defined by site-directed mutagenesis studies.

Monocyte-derived interleukin 1 (IL-1) mediates a wide range of biological effects including destruction of the cartilage matrix in articular diseases such as rheumatoid and osteoarthritis. To elucidate further the relationships between protein structure and biological activities, we have analyzed the sequence of several IL-1 polypeptides using the algorithm of Parker, the hydrophobic cluster analysis method and published structural data. This led us to identify several residues that seemed to be strictly topologically conserved, with respect to identifiable secondary structures features, although this was not readily apparent from sequence alignments. We performed site-directed mutagenesis on some of these conserved residues, as well as on those predicted to occur in external loops of the polypeptide. Human IL-1 beta mutant polypeptides were expressed in Escherichia coli in soluble form and purified to homogeneity by anion-exchange and gel-filtration chromatography. Their biological effects (binding to EL4-6.1 murine thymocytes, Raji human B cells and rabbit chondrocytes cells, lymphocyte activation, neutral protease induction, proteoglycan degradation and synthesis) have been determined. Among the 20 IL-1 beta mutant polypeptides we present here, four showed a markedly reduced activity in cartilage matrix assays without any significant change in their binding to the cartilage matrix cells (chondrocytes). Furthermore, some of these mutants were specific partial agonists of the effects of IL-1 on connective tissue since they have a low affinity for thymocytes.

Amino Acid Sequence↗
PubMed1989

Specific binding of angiogenin to calf pulmonary artery endothelial cells.

Specific binding of angiogenin (ANG) to calf pulmonary artery endothelial cells was demonstrated. Cellular binding at 4 degrees C of 125I-labeled human recombinant ANG was time and concentration dependent, reversible, and saturable in the presence of increasing amounts of the unlabeled molecules. The interaction was shown to be specific since a large excess of unlabeled ANG reduced labeled ANG binding by 80%, whereas similar doses of RNase A, a structurally related protein, had no effect. Scatchard analyses of binding data revealed two apparent components. High-affinity sites with an apparent dissociation constant of 5 x 10(-9) M were shown to represent cell-specific interactions. The second component, comprising low-affinity/high-capacity sites with an apparent dissociation constant of 0.2 x 10(-6) M, was essentially associated with pericellular components. High-affinity ANG binding sites varied with cell density and were found on other endothelial cells from bovine aorta, cornea, and adrenal cortex capillary but not on Chinese hamster lung fibroblasts. Divalent copper, a modulator of angiogenesis, was found to induce a severalfold increase in specific cell-bound radioactivity. Placental ribonuclease inhibitor, a tight-binding inhibitor of both ribonucleolytic and angiogenic activities of ANG, abolished 125I-labeled human recombinant ANG binding only in the absence of copper.

Angiogenesis Inducing Agents↗
PubMed1987

Chemical synthesis of a gene coding for human angiogenin, its expression in Escherichia coli and conversion of the product into its active form.

A synthetic gene coding for human angiogenin was synthesized by solid support phosphoramidite chemistry as eight long oligodeoxynucleotides which were subsequently assembled and cloned in Escherichia coli. The gene was designed to use codons found in highly expressed E. coli proteins. A pBR322-derived expression vector was constructed containing the E. coli trp promoter, the ribosome-binding site of the bacteriophage lambda cII gene, the angiogenin coding sequence, and the transcription terminator region of the E. coli rrnB operon. Under tryptophan deprivation, angiogenin was strongly expressed in E. coli cells at a yield of 5-10% of total protein. The eukaryotic protein was found to be insoluble but could be easily renatured and purified. The purified angiogenin was demonstrated to be active as an angiogenic factor and exhibited a characteristic RNase activity.

Amino Acid Sequence↗
PubMed1984

An abnormal plasma antithrombin with no apparent affinity for heparin.

Congenital antithrombin abnormality was found in several members of a French family. No history of thrombotic episodes was associated with this abnormality. Plasma antithrombin concentration as well as the rate of thrombin inactivation by defibrinated plasma in the absence of heparin were normal. However, the heparin cofactor activity was decreased by about 50% in plasma of affected patients. Accordingly, about half the amount of plasma antithrombin did not bind to gel bound heparin. Moreover the crossed immunoelectrophoretic pattern in the presence of heparin demonstrated two peaks of antithrombin, the slower one migrating as normal antithrombin when heparin was omitted from the first agarose gel. It was concluded that molecular alteration of the antithrombin molecule seemed to affect only the heparin binding site thus preventing from any rate enhancement of thrombin inactivation.

Antithrombin III Deficiency↗
PubMed1984

Distribution of non-enzymatically bound glucose in in vivo and in vitro glycosylated type I collagen molecules.

Non-enzymatic glycosylation of collagen occurs both in vivo during diabetes and in vitro after incubation with glucose. Glycosylated collagen exhibits altered physicochemical and biological properties which could explain some of the complications of diabetes. To provide a mechanistic explanation of this modification the localization of bound glucose was investigated using NaB[3H]H4 reduction and CNBr cleavage. Glucose fixation is distributed mainly on the alpha 1CB6 peptide after in vitro glycosylation whereas this distribution occurs less specifically during diabetes. It is concluded that fibrillogenesis alteration of in vitro glycosylated collagen is related to glucose fixation on free epsilon NH2 sites normally implied in intermolecular interactions.

Animals↗
PubMed1984

Influence of in vitro non-enzymatic glycosylation on the physicochemical parameters of type I collagen.

In vitro non-enzymatic condensation of glucose on acid soluble collagen is shown not to affect the molecular structure and stability as evaluated both by circular dichroism and differential spectrometry. Viscometric studies demonstrate a lowering in intermolecular interactions; whereas the hydrodynamic volume remains unaffected by nonenzymatic glycosylation. alpha 2(I) collagen chains exhibit a modified electrophoretic mobility previously found in collagen of diabetic rats; this peculiar behavior is discussed in terms of lowered hydrophobicity due to addition of hydrophilic groups from glucose. The lowered formation of hydrophobic areas, evaluated from the fluorescence emission of diphenylhexatriene, indicates that non-enzymatic glycosylation is able to influence the close packing of collagen fibers.

Animals↗
PubMed1983

Non enzymatic glycosylation increases platelet aggregating potency of collagen from placenta of diabetic human beings.

Pepsin extracted collagen and an acid soluble glycoprotein were purified from placentas of normal and diabetic human beings. Diabetic samples exhibit a significant increase in ketoamine-linked glucose whereas both amino acid and carbohydrate composition were unaffected. This excess non enzymatic condensation of glucose on free amino-groups was found to increase platelet aggregating potency of these proteins independently of any modification in fiber morphology.

Amino Acids↗
PubMed1983

Nonenzymatic glycosylation of collagen in diabetes: incidence on increased normal platelet aggregation.

The effect of normal and nonenzymatically glycosylated rat type I acid-soluble collagen on normal human platelets was investigated. Glycosylated collagen was obtained either after in vitro incubation with glucose or from rats made diabetic by streptozotocin. The amount of nonenzymatically bound glucose was as follows: normal 2.3, diabetic 7.6 and in vitro glycosylated collagen 9.0 nmol/mg. When investigated under conditions leading to identical diameters and molecular packings for all the samples, the aggregation potency was markedly stronger for diabetic and glycosylated collagens than for normal ones. These results show the potential role of this posttranslational modification of collagen which can be considered as a risk factor in the thrombotic pathogeny of diabetes.

Animals↗
PubMed1981

Effects of in vitro N-glucosylation on type-I collagen fibrillogenesis.

Acid-soluble collagen from rat tail tendon was glucosylated in vitro and fibrillogenesis parameters were determined first at 35 degrees C then at 4 degrees C. Increased lag phase and half time were shown to be related to the amount of non-enzymatically bound glucose, probably due to a decrease of hydrophobic interactions at this early stage of fibril formation. The absence of intermolecular cross-links and the partial redissolution of fibrils of 4 degrees C, as investigated both by turbidimetry and electron microscopy, suggests a defect in the maturation process in glucosylated collagen fibrils.

Animals↗