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Alpha (1,2) fucosylated glycoepitopes from invertebrates to humans
No full textGlycans participate in bio-communication, such as cell to cell recognition,
sperm-egg recognition and embryonic development because they have the
property of storing biological signals in forms that can be identified by other
biological systems, such as anti-glycan antibodies and glycan binding proteins
or lectins. Aberrant arise at the cell surface in many diseases, including
cancer, and altered carbohydrate moieties are indicated as mediators
of tumorigenicity and invasiveness. Alpha-L-fucopyranosyl residues are
immunodeterminant, playing an important role in the glyco-language; this is
especially true of residues alpha(1,2)-linked to a galactose, that frequently
exist as terminal modifications of N-glycans, O-glycans or glycolipids. The H
antigen is the product of the enzyme that adds fucose to galactose residues by
an alpha(1,2)-linkage. We report work in which we demonstrated the presence
and role of alpha(1,2)fucose-containing glycoepitopes in biocommunication
between egg and sperm in two invertebrate species, the tunicate Ciona
intestinalis and the mollusk Unio elongatulus. In the mollusk the structure
of the fucosylated epitopes involved in sperm recognition in the context of
the blood group H-antigen was confirmed by MS/MS data. Using an antibody
raised against the bio-communicating glycoprotein of the Unio oocyte, the
epitope of which was demonstrated to contain the alpha(1,2)fucosylated
O-glycans, we detected the same or a very similar epitope in nucleolin, a
protein expressed in highly proliferating and cancer cells in humans, known
to act as a shuttle between the cell surface and nucleus. We suggest that the
glycosylation machinery used to build up the alpha(1,2)fucosyl-containing
glycoepitope of the Unio egg, is re-stored in cancer cells
Expression of CD52 mRNA in the rat embryo
No full textCD52 is a leukocyte differentiation antigen first discovered in humans as expressed on the surface of lymphocytes,
monocytes and eosinophils. The human CD52 is found on chromosome 1, and two alleles are both known to be
reasonably common. A closely homologous gene has been identified in the cynomologous monkey and related
genes have been found in mouse, rat and dog. The role of CD52 in lymphocyte is still unclear but the anti-CD52
antibodies named CAMPATH-1 antibodies are largely used for therapy where depletion of lymphocytes is required.
In the past expression of the antigen on progenitors of leukocytes in bone marrow had been excluded, but recent
work indicates CD52 is highly expressed on cells with colony-forming and NOD/SCID (non-obese diabetic-severe
combined immunodeficiency)-engrafting capacities, both at the mRNA and membrane protein level. We have
investigated CD52 expression during development in rat embryos by in situ hybridization. We report here that
the antigen is highly expressed in the liver that is the major organ where multipotent hematopietic stem cells
differentiate but also in the splancnopleuric mesoderm, at early stages of embryo differentiation, where hematopietic
stem cells are suggested to arise. CD52+ cells were found in areas active in vasculogenesis at early embryo stages
and in the walls of the vessels in the liver at mid gestation. CD52+ cells were also found to emerge among c-Kit
positive cells
Vitelline coat of Unio elongatulus: II. Biochemical properties of the 220- and 180-kD components
No full textIn a previous study we found that two glycoproteins with apparent molecular weights of 220 kD and 180 kD account for 80-90% of the material dissolved from the vitelline coat of the egg of the bivalve mollusk, Unio elongatulus (Focarelli and Rosati, 1993: Mol Reprod Dev 35:44-51). In this study we isolated and purified these glycoproteins by electroelution. The two proteins differ in many respects: the 180-kD molecule is acidic in nature and highly heterogeneous, whereas the 220-kD protein is neutral and less heterogeneous. Both seem to have O- and N-linked oligosaccharide chains. The 180-kD protein contains 13-16% carbohydrate, whereas the 220-kD molecular contains only 7-8%. Amino acid analysis and peptide mapping also show that each protein represents a unique polypeptide chain
A fucose-containing O-glycoepitope on bovine and human nucleolin
No full textIn this paper, we demonstrate the existence and localization
of fucosyl-containing O-glycoforms of nucleolin in cultured
bovine endothelial cells (CVEC) and malignant cultured
human A431 cells. The tool for this discovery was an
antibody raised against gp273, a glycoprotein ligand for the
sperm–egg interaction in the mollusc bivalve Unio elongatulus.
The function and immunological properties of gp273
mainly depend on clustered Lewis-like, fucose-containing
O-glycans. Here an anti-gp273 antibody was used to evaluate
whether glycoepitopes similar to those of gp273 are part
of potential ligands of selectins in endothelial cells.We found
that anti-gp273 strongly and exclusively interacted with a
110 kDa protein in CVEC and A431 tumor cells. After partial
purification, mass spectrometry identified the protein
as nucleolin. This was confirmed by comparing anti-gp273
and anti-nucleolin antibody immunoblotting after nucleolin
depletion.We confirmed that anti-gp273 binding to nuclear
and extranuclear nucleolin was against a fucose-containing
O-glycoepitope by immunoblot analysis of the protein after
chemically removing O-glycans and by lectin-blot analysis
of control and nucleolin-depleted samples. Using anti-gp273
IgG, we detected nucleolin on the plasma membrane and
cytoplasm. O-glycosylation may regulate the plethora of
functions in which nucleolin is involved
CD52, an intriguing antigen of the human sperm surface
No full textCD52 is the product of a single gene on chromosome 1, first characterized as a human leukocyte differentiation antigen expressed on the surface of lymphocytes and monocytes and then identified in the epithelial cells of epididymal corpus and cauda and in the deferent ducts. Sperm also have this antigen, acquiring it as they pass through the epididymis. The precursor of CD52 is 61 amino acids long, but the mature antigen, that serves as backbone for N-glycosylation and a final GPI-anchor, only contains 12 amino acids. O-linked oligosaccharide chains are also bound to certain glycoforms of this complex antigen. The first and most commonly used anti-CD52 monoclonal antibody, termed CAMPATH-1, generated in the immune system, interacts with the last three amino acids and the first part of GPI, and recognizes CD52 on leukocytes, epididymal cells and sperm. Other antibodies such as S19 and Mab H6-3C4 react only with CD52 carbohydrate epitopes specific to the reproductive system. We generated a polyclonal antibody that mainly recognizes CD52 glycoforms containing O-linked oligosaccharide chains. We called this antibody anti-gp20 because it was raised against a 20 kDa sialylglycoprotein, homologous to CD52, recovered as sole radiolabelled glycoprotein after radiolabelling surface sialic acid residues of capacitated human sperm. Anti-gp20 revealed that the O-glycan-containing glycoform in capacitated sperm differs from the other CD52 glycoforms in localization on the surface and microdomain segregation. This does not occur on leukocytes and freshly ejaculated sperm. Since this form specifically localizes in the equatorial region of sperm capacitated in vitro and anti-gp20 impairs sperm penetration of denuded hamster eggs, a role in sperm-egg fusion has been suggested for it. The capacity of CD52 to form a complex with semenogelin I recently indicated that the antigen also has a role in semen clot formation and liquefaction
The Spermatozoon of Arthropoda. XXVI. The spermatozoon of Isoptera, Embioptera and Dermaptera
No full textThe spermatozoon of Reticulitermes and Calotermes appear highly evolved, and at the same time simplified. Both sperm types are devoid of acrosome. The role of the Golgi apparatus seems to be exclusively for the elaboration of the plasma membrane of mature sperms. The mitochondria are few and round, and have cristae of conventional type. The flagellum is absent. Even in the mature sperm, 2 centrioles are found, but no flagellar structures appear. No other structures are to be seen in substitution for the flagellum in Reticulitermes, while the mature sperm of Calotermes has retained a manchette of perinuclear microtubules projected outwards inside the characteristics festoons of the plasma membrane. characteristic might be interpreted as substitutes for the flagellum. In Calotermes lysosomes appear to digest large areas of the cytoplasm. The study of the sperm of Embioptera and Dermaptera demonstrates that the typical orthopteroid sperm type resembles the sperm type of most pterygota insects in having a 3 layered acrosome complex, a fusiform nucleus, a large centriole adjunct, 2 mitochondrial derivatives partly or entirely full of crystalline material and a 9 + 9 + 2 axoneme. In single lines of evolution within the orthopteroid orders this sperm type is simplified: the acrosome layers are fewer (Embioptera, Phasmida, Termites), the mitochondria also fewer or missing (Termites, Phasmida) and the flagellum is lacking (Termites)
Identification of a novel, alpha2-fucosylation-dependent uptake system in highly proliferative cells.
No full textIn this paper we describe a new structure present in highly proliferative cells and absent in cells with normal growth potential. We used cultured bovine venular endothelial cells (CVEC) as examples of high proliferation, and dermal fibroblasts of a primary culture as examples of normal proliferation. The structure, consisting of tubules radiating from the nuclear region to the tips of cell protrusions, was revealed by its strong positivity to the fucose-binding lectin from Lotus (LTL) that prefers glycans with alpha-1,2-linked fucose. Another fucose-binding lectin that prefers glycans with alpha-1,6-linked fucose was instead found to localize glycans exclusively in Golgi complexes. LTL binding sites were also found at the surface of CVEC in a restricted region close to the nucleus. The role of alpha-1,2-linked fucose in forming or maintaining the tubules was confirmed by the fact that down-regulation of the fucosyltransferases FUT1 and FUT2 resulted in disappearance of the tubular structure. LTL also proved able to penetrate the cells through the tubular structures up to the nuclear region and to inhibit proliferation. Endostatin was also found to massively penetrate the cells in the tubular structures in control cells but not in FUT1/2 depleted cells. In cells of a first passage primary culture of dermal fibroblasts the tubular LTL-positive structure was absent as well as the LTL-positive sites at the external surface, and both fucose-binding lectins were found to exclusively localize glycans in Golgi complexes. Tubules were again found progressively in fibroblasts derived from repeated passages, where faster growing cells predominate. Disappearance of LTL-positivity in Golgi complexes paralleled appearance of LTL-positive tubules. The role of Golgi complexes in forming the tubules is discussed
Identification and characterization of a 38 kDa glycoprotein functionally associated with mating activity of Paramecium primaurelia
No full textIn Paramecium primaurelia mating interactions take place immediately after mixing mating-competent cells of opposite mating types. The cells clump in clusters (mating reaction) and then separate in pairs. Previous results have
shown that sialic acid-containing glycoconjugates are present on the cell surface and are involved in mating-cell
pairing. In order to identify the sialic acid-containing glycoprotein(s), we first metabolically radiolabelled non-mating competent cells with D-[6-3H]galactose, and then analyzed the radiolabelled proteins by anion exchange
chromatography. We characterized a 38 kDa (gp38) sialic acid-containing glycoprotein and raised the corresponding
polyclonal antibody by means of which we localized the antigen at the level of the oral region of non-mating competent cells and on the ciliary surface of mating-competent cells. Immunoblot analysis of the ciliary protein
fraction showed that the anti-gp38 serum interacted with a 38 kDa protein in both mating types I and II cells. We also
demonstrated the functional activity of gp38 in the mating reaction by means of anti-gp38 antibody competition
assays
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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