Josette Lamy

Octamerization Enables Soluble CD46 Receptor To Neutralize Measles Virus In Vitro and In Vivo

ABSTRACT A chimeric fusion protein encompassing the CD46 ectodomain linked to the C-terminal part of the C4b binding protein (C4bp) α chain (sCD46-C4bpα) was produced in eukaryotic cells. This protein, secreted as a disulfide-linked homo-octamer, was recognized by a panel of anti-CD46 antibodies with varying avidities. Unlike monomeric sCD46, the octameric sCD46-C4bpα protein was devoid of complement regulatory activity. However, sCD46-C4bpα was able to bind to the measles virus hemagglutinin protein expressed on murine cells with a higher avidity than soluble monomeric sCD46. Moreover, the octameric sCD46-C4bpα protein was significantly more efficient than monomeric sCD46 in inhibiting virus binding to CD46, in blocking virus induced cell-cell fusion, and in neutralizing measles virus in vitro. In addition, the octameric sCD46-C4bpα protein, but not the monomeric sCD46, fully protected CD46 transgenic mice against a lethal intracranial measles virus challenge.

Immunological correlates between the multiple hemocyanin subunits of Limulus polyphemus and Tachypleus tridentatus

Abstract The 60 S hemocyanins of the horseshoe crabs, Limulus polyphemus and Tachypleus tridentatus, are of interest as models of how structurally diverse subunits interact in the assembly of high molecular weight proteins. Subunit diversity is a general characteristic in hemocyanins of the Chelicerates (horseshoe crabs, spiders, and scorpions) and is expressed to a lesser extent in hemocyanins of the crustaceans (crabs, shrimp, and lobsters). In order to better characterize the hemocyanins of Limulus and Tachypleus, their subunits were fractionated by ion-exchange and thin-layer gel chromatography. Immunological techniques were used extensively in isolation and characterization of the subunits. Both hemocyanins yield six chromatographic zones at pH 8.9. The Limulus pattern is due to the existence of seven monomers and a heterodimer. The heterodimer contains one additional monomer for a total of eight distinct subunits. Limulus monomer IIA is antigenically related to IIIa but is antigenically deficient. Dissociation of Tachypleus hemocyanin at pH 8.9 yields five monomers and a heterodimer that contains two additional monomers. One monomer in the dimeric component of Limulus hemocyanin is antigenically related to a monomer of the dimeric component of Tachypleus and the other two monomers in the dimers are antigenically identical. It is proposed that dimeric components link the hexameric “building blocks” of the Chelicerate hemocyanins and thus play specific functional and structural roles.

Immunological correlates between multiple isolated subunits of Androctonus australis and Limulus polyphemus hemocyanins: an evolutionary approach.

Immunological cross-reactivities between isolated subunits of the scorpion Androctonus australis (Aa) and of the horseshoe crab Limulus polyphemus (Lp) hemocyanins were studied using subunit-specific antibodies prepared through immunoadsorption to pure immobilized subunits. Rocket immunoelectrophoreses of the various subunits of both hemocyanins were carried out at constant antigen concentration against the various subunit-specific antibody preparations. Then the data were analyzed through factorial correspondence analysis and compared to the respective intramolecular locations of the subunits in both hemocyanins. The results show that the dimeric subunits located in the central part of each (4 X 6)meric structure (Aa whole molecule and Lp half molecule) were strongly preserved. In addition, the (8 X 6)mer-forming subunit of Lp hemocyanin (LpIV) and the subunit occupying the same intramolecular position in Aa hemocyanin (Aa5A) were also strongly preserved. Besides the strong antigenic relatedness, less pronounced crossed immunoprecipitations or no precipitation at all were observed between subunits with homologous positions suggesting a minor structural and/or functional roles for these subunits. All the antigen-antibody combinations leading to an absence of immunoprecipitation were screened for the presence of soluble immunocomplexes by radioimmunological tests. In all cases, soluble immunocomplexes were observed. These results suggest the following evolution scenario. First, the central dimeric subunits, responsible of the dodecamer aggregation (Aa3C and 5B and LpV and VI) were already differentiated when Merostomata diverged from Arachnida. Second, the differentiation of the (8 X 6)mer-forming subunit occurred in the Merostomata ramification in a preserved subunit already possessing a functional advantage. Third, the differentiation of subunits Aa3A and Aa3B recently occurred in the scorpion ramification.

Ultrastructure of 16 S substances obtained by reassociation using different combinations of three isolated subunits of scorpion hemocyanin (Androctonus australis garzonii)

Different combinations of three subunits of Androctonus australis hemocyanin, isolated by the method of Lamy et al. (1976) and treated with divalent cations at pH 7.5, give reassociation products which, after isolation by thin layer gel chromatography, permit the determination of the subunit composition and the ultrastructure. Subunit 4 as well as its binary and ternary compositions containing subunit 2 give intermediate products. Hexamers corresponding to ternary mixtures are more stable than the others and tend to adhere to each other in twos or threes.

Crystals of the carboxyl-terminal functional unit from Octopus dofleini hemocyanin

The carboxyl-terminal oxygen-binding unit of the polypeptide from Octopus dofleini hemocyanin has been crystallized in a form suitable for three-dimensional X-ray analysis. This proteolytic fragment has a molecular weight of 47 kDa and reversibly binds O2 while exhibiting a slight Bohr effect. Two types of crystals have been grown. Type I crystals, currently under analysis, belong to the orthorhombic space group P2(1)2(1)2(1) and have unit cell dimensions of 92.6 A x 167.4 A x 59.2 A. A composition of two protein molecules per asymmetric unit and 50% solvent content is consistent with a self-rotation function that identifies a non-crystallographic 2-fold axis of symmetry relating these molecules. Diffraction extending beyond 1.9 A Bragg spacings can be detected with synchrotron X-radiation.

Preliminary Results on the Structure of Octopus Dofleini Hemocyanin

The hemocyanin of Octopus dofleini has provided an excellent model for the study of the behavior of multi-subunit proteins (1–3). Sedimentation experiments indicated that the native molecule (Mr = 3.6 × 106, S20,w =51S) is a decamer of polypeptide chains (Mr = 3.6 × 105, S20,w = 11.1S). Preliminary electrophoretic studies suggested that there might be only a single kind of polypeptide chain, making this structure simpler than that of most molluscan hemocyanins. Furthermore, the molecular weight of the subunit is smaller than that of gastropod hemocyanins, suggesting that it might contain fewer than eight oxygen binding domains. We report here on our investigations of the structure of O. dofleini hemocyanin.

Réversibilité des signes biologiques de cirrhose chez l'alcoolique chronique a la suite du sevrage

Abstract In cases of chronic alcoholism without clinical signs of cirrhosis, after one year of alcohol-free diet the IgA level decreases significantly (85 subjects under study). This decrease is more important when the initial increase was higher. On the contrary, when alcoholic consumption continues, the IgA level increases significantly (45 subjects under study). The increase or decrease of the IgA level might be correlated to the mesenchyme inflammation of the liver.

Intramolecular location of the subunits of androctonus australis hemocyanin

Arthropod hemocyanins (Hc) are large molecular mass, copper containing respiratory proteins made up of polypeptide chains with M, 70 000-95 000. The complexity of the molecule varies with the species but it is generally accepted that the more complex structures arose by successive dimerisations of a minimal structural unit, often designated as hexamer (1 X 6 mer), constituted of 6 polypeptide chains. In the scorpion Androctonus australis, 8 subunits [I], with different N-terminal amino acid sequences [2] constitute the 34 S (4 X 6 mer) native Hc. The number of copies of each chain being known [3], the next step in the determination of the quaternary structure is the intramolecular location of each subunit. This papel reports how the immunological recognition of the subunits in the native molecule was used to approach the problem of their intramolecular location.

Hyperhaptoglobinemie des alcooliques chroniques

Abstract Chronic alcoholics exhibit a high serum haptoglobin level at an average of 2.21 g/l. In almost 50% of them serum haptoglobin values are higher than the upper limit (2.3 g/l) of the 99% confidence interval of controls. This hyper-haptoglobinaemia persists after a 3-months temperance cure and is not lowered by corticotherapy. These results can be compared to the lasting, corticoid-resistant hyper-haptoglobinaemia described by Jayle as a sign of a precoronary condition.

Molecular immunoelectron microscopy and image processing: An approach to epitope mapping on high molecular weight proteins

ULTRASTRUCTURE OF ACCESSORY ADRENOCORTICAL NODULES IN WlSTAR RATS. Anna S. BELLONI ( 1 ) , Francesco MUSAJO (2) , Giuseppina MAZZOCCHI (1) and Gastone G. NUSSDORFER ( 1 ) . (1) Department o f Anatomy and (2) 2nd S u r g i c a l C l i n i c , U n i v e r s i t y o f Padua, I t a l y . More than 70% o f b i l a t e r a l l y a d r e n a l e c t o m i z e d Wis t a r r a t s s u r v i v e and w i t h i n t h r e e months deve lop one o r two consp icuous a d r e n o c o r t i c a l nodules (2-3 mm in d i a m e t e r ) , which, thouEh d i s p l a y i n g an obvious histoloEical zonation, are not associated with chromaffin tissue. Middle and inner cells of the nodules are similar to zona fasciculata (ZF) and zona reticularis elements of the adult rat adrenal Eland, res pectively. Middle cells show numerous round mitochondria with vesicular cristae, while inner cells con tain ovoid mitochondria with tubule-convolute cristae. Both cell types possess abundant smooth endopla smic reticulum and few lipid droplets, as well as a very elaborated microvillous system. Conversely, outer (subcapsular) cells of the accessory nodules do not resemble lena Elomerulosa (ZG) elements, since they display ovoid mitochondria with vesicular cristae instead of elonEated orEanelles with tubu lo-laminar cristae. Moreover, morphometry shows that their volume is about two-fold that of the true ZG cells (1400 um3 versus 700 um3). These morpholoEical data accord well with the fact that basal plasm8 concentration of aldosterone, at variance with that of corticosterone, remains very low three months after bilateral adrenalectomy. The lack of differentiated ZG cells in the accessory adrenocortical nod ules could be explained by the very elevated blood level of ACTH (about 5-times hiEher than in shamoperated rats), in fact, chronic ACTH hypersecretion is known to transform ZG cells into ZF elements (i). Some lines of evidence suEEest the existence of a paracrine control of adrenal zona corticalis by zona medullaris (i). We think that accessory adrenocortical nodules, lackinE zona medullaris, could be a Eood experimental model to Eain insiEht into this problem.