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D Eichinger

Publications and source records attributed to D Eichinger.

26 records · Page 2Linked to original sources
PubMed1994

Structural and functional properties of Trypanosoma trans-sialidase.

Sialic acids and sialidases play important roles in cellular interactions and modulate the recognition of pathogenic microbes by mammalian host cells. Protozoan parasites of the genus Trypanosoma express a unique sialic acid-metabolizing enzyme. This enzyme, named trans-sialidase (TS), catalyzes the transfer of sialic acids from host glycoconjugates to acceptor molecules of the parasite plasma membrane. In African trypanosomes, the agents of sleeping sickness, TS is found only in forms developing within the insect vector, and the enzyme sialylates the major surface protein. In Trypanosoma cruzi, the causative agent of Chagas' disease in Central and South America, TS is expressed both in the insect and mammalian forms of the parasite. The T. cruzi enzyme has been biochemically characterized, and the gene encoding the enzyme has been cloned. The enzyme sialylates abundant mucin-like molecules present on the surface of the parasite. Several lines of evidence suggest that TS and sialic acid acceptors on the surface of T. cruzi participate in host-parasite interactions and mediate the initial stages of the trypanosomes' invasion of host cells.

Amino Acid Sequence↗
PubMed1993

Trypanosoma cruzi trans-sialidase and cell invasion.

Trypanosoma cruzi does not synthesize sialic acid but does contain a trans-sialidase, an enzyme capable of transferring sialic acid between host glycoconjugates and the parasite. Sialic acids are negatively charged carbohydrates attached to the terminal non-reducing end of glycoproteins and glycolipids, and their presence can dramatically influence many cell-surface recognition processes. Since sialic acids have been implicated in several ligand-receptor interactions, including the interaction of pathogenic viruses, bacteria and protozoans with their hosts, the expression of trans-sialidase and the acquisition of sialic acid by T. cruzi may be relevant to the interaction of the parasite with the host, and consequently may influence the pathobiology of Chagas disease. In this review, Sergio Schenkman and Daniel Eichinger discuss recent data about the structure and function of T. cruzi trans-sialidase.

Journal Article↗
PubMed1992

Only some members of a gene family in Trypanosoma cruzi encode proteins that express both trans-sialidase and neuraminidase activities.

Trypomastigotes, the blood stage form of the human parasite Trypanosoma cruzi, contain an enzyme on their surface, trans-sialidase, which catalyses the transfer of sialic acid from host glycoconjugates to acceptors on its own cell surface. At least a subset of the sialic acid-bearing acceptor molecules are involved in parasite invasion of host cells, an essential step in the life cycle of the parasite. Another trypomastigote surface enzyme that affects host cell invasion is neuraminidase and recent evidence suggests that both trans-sialidase and neuraminidase activities may be expressed by the same proteins on the parasite surface. We describe here the isolation and expression of several members of a trans-sialidase--neuraminidase gene family from T.cruzi. One of the isolated genes does indeed encode a protein with both trans-sialidase and neuraminidase activities, while other members of the gene family encode closely related proteins that express neither enzymatic activity. Chimeric protein constructs combining different portions of active and inactive genes identified a region of the gene necessary for enzymatic activity. Sequence analysis of this portion of the gene revealed a limited number of amino acid differences between the predicted active and inactive gene products.

Amino Acid Sequence↗
PubMed1988

The Saccharomyces cerevisiae genome contains functional and nonfunctional copies of transposon Ty1.

Saccharomyces cerevisiae Ty elements are transposons closely related to retroviruses. The DNA sequence of a functional Ty element (TyH3) is presented. The long terminal repeat sequences are different, suggesting that TyH3 is a recombinant Ty element. A chromosomal Ty element near the LYS2 gene, Ty173, was found to be nonfunctional, even though it has no detectable insertions or deletions. The defect in Ty173 transposition is caused by a missense mutation giving rise to a Leu-to-Ile substitution in the TYB (pol) open reading frame. Several chromosomal Ty elements carry this lesion in their DNA, indicating that nonfunctional Ty elements are common in the yeast genome.

Amino Acid Sequence↗
PubMed1982

The murine sex-limited protein (Slp): reassessment of its sex limitation.

Previous studies in which an alloantiserum was used to measure Slp levels indicated that in certain inbred strains of mice (Slpa), this protein was sex-limited, that is, present only in males. We raised several monoclonal antibodies directed against different epitopes of Slp and used them to develop a sensitive two-site immunoradiometric assay. Using this assay we detected Slp in serum of all Slpa females previously thought to be phenotypically negative. The levels of Slp in these females are about 0.2 to 4% of that of the males of the same inbred strain. The molecule found in serum of females was isolated by affinity chromatography and was found to have the characteristic three-chain structure of male Slp. These findings establish that the presence of Slp in Slpa females is the rule rather than the exception. Quantitative differences similar in magnitude to those found between males and females were also detected among Slpa males; i.e., Sd males have about 100 times more Slp than Sp males. The mechanisms by which androgens determine the extensive quantitative male-female differences, and by which the S region determines large variations among Slpa males, are unknown.

Animals↗
PubMed1981

A simplified two-dimensional electrophoretic technique.

The two-dimensional electrophoretic O'Farrell technique can be simplified in terms of effort and equipment. This simplification derives mainly from the fact that the first dimension (isoelectric focusing) is run in a vertical slab gel. Since all tracks are cast in a single template, a reproducible and uniform first dimension is obtained, allowing easy and accurate comparison among tracks after standard staining and/or radioautographic procedures. After the first dimension, the focused tracks are cut and, following equilibration, simply laid on top of the second dimensional slab gel, whose spacers are 0.1 mm thicker than those used in the first separation. Thus, basically the same equipment can be used for both dimensions. This modified technique has been experimentally validated since it has allowed the detection of structural variants of two proteins related to the mouse complement system, namely, the fourth component and the sex-limited protein.

Animals↗
PubMedDate not supplied

A role for a galactose lectin and its ligands during encystment of Entamoeba.

In the life cycle of Entamoeba parasites alternate between the colon-dwelling trophozoite and the infectious cyst forms. The physiologic stimuli that trigger differentiation of trophozoites into cysts remain undefined. On the surface of the human-infecting Entamoeba, parasites express a galactose/N-acetylgatactosamine (gal/galNAc)-binding lectin, which plays demonstrated roles in contact-dependent lysis of target cells and resistance to host complement. Using a reptilian parasite, Entamoeba invadens, to study cyst formation in vitro, we found that efficient encystation was dependent on the presence of gal-terminated ligands in the induction medium. Precise concentration ranges of several gal-terminated ligands, such as asialofetuin, gal-bovine serum albumin (gal-BSA), and mucin, functioned in encystation medium to stimulate differentiation. Greater than 10 mM levels of free gal inhibited the amoeba aggregation that precedes encystation and prevented formation of mature cysts. Inhibitory levels of gal also prevented the up-regulation of genes which normally occurs at 24 h of encystation. The surface of Entamoeba invadens was found to express a gal lectin which has a heterodimeric structure similar to that of Entamoeba histolytica. The 30 kDa light subunit (LGL) of the E. invadens lectin is similar in overall size and sequence to the LGL of E. histolytica. The heavy subunits, however, differ in size, have an identical spacing of cysteines in their extracellular domains, and have highly conserved C-terminal transmembrane and cytoplasmic domains. These results suggest a new role for the Entamoeba gal lectins in monitoring the concentrations of gal ligands in the colon and contributing to stimuli that induce encystment.

Animals↗