<i>Rousseau and Weber: Two Studies in the Theory of Legitimacy</i>. J. G. Merquior

Merquior, José Guilherme

doi:10.1086/292451

Cited by 3 publications

(2 citation statements)

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“…In the presence of monensin, Galfll + 3GalNAc-Ser/Thr structures can clearly still be synthesized and can even be sialylated to some extent [40]. On the other hand, monensin completely blocks the GlcNAc: /31 + 4-galactosyltransferase 1401 which is a known marker for the truns Golgi [47] and an enzyme involved in the synthesis of complex-type N-glycans. However, it is not known at present whether the inhibition of /I1 + 4-galactosyltransferase activity by monensin is due to an effect on the enzyme itself or due to the inhibition of Golgi transport.…”

Section: Discussionmentioning

confidence: 99%

O‐Glycosylation of leukosialin in K562 cells

Piller

Klier

et al. 1989

European Journal of Biochemistry

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The O-glycosylation of leukosialin, a major sialoglycoprotein found on leukocytes, has been studied in the human erythroleukemic cell line K562. The appearance of its O-linked chains has been followed in pulse-chase experiments with [35S]methionine by immunoprecipitation with an anti-peptide antiserum as well as with a lectin from Sulvia sclureu seeds (SSA) specific for GalNAc-Ser/Thr and the peanut (Aruchis hypogueu) agglutinin (PNA) which recognizes GalPl -+ 3GalNAc-Ser/Thr structures. An O-glycan-free precursor was converted into the fully O-glycosylated mature form within the 1 O-min labeling period and no intermediates carrying only GalNAc-Ser/ Thr structures could be detected. The ionophore monensin was used in order to slow down intracellular traffic and thus O-glycan synthesis. The drug partly inhibited the transport from rough endoplasmic reticulum (RER) to the Golgi and also the cell-surface expression of leukosialin. It was found to have a marked effect on the synthesis of O-linked carbohydrate structures of leukosialin since the amount of O-glycans containing only GalNAc or NeuNAca2 + 6GalNAc was significantly increased after monensin treatment. Under these conditions the biosynthesis of the N-glycan on leukosialin was completely arrested in an endoglycosidase-H-sensitive step of processing, whereas the O-glycans already contained galactose and sialic acid although at a reduced level. On the other hand, the small amounts of leukosialin expressed on the cell surface of monensin-treated cells carried the same glycans as those remaining blocked inside the cell. In addition, immunocytochemical studies using SSA and PNA on untreated K562 cells suggested the absence of detectable amounts of GalNAc-Ser/Thr-bearing glycoproteins in the RER as well as in the Golgi. In contrast Galfll --f 3GalNAc structures could be detected on intracellular membranes which were tentatively identified as the cis-Golgi. Together these results lead us to the following conclusions: N-glycan transfer occurs in the RER before the initiation of O-glycans which takes place at the entrance of the protein into the Golgi; further elongation of O-glycans with galactose and sialic acid follows very rapidly, probably before the final processing of N-glycans to complex-type structures.Leukosialin is a major sialoglycoprotein present at the surface of human leukocytes 111. This glycoprotein has been shown to carry about 90 O-linked oligosaccharides attached to a polypeptide of about 52 kDa. It was found that human leukosialin also contains one N-linked chain. In addition, the structure of the O-linked oligosaccharides present on leukosialin has been determined in detail in different cell lines and was shown to be characteristic for each cell lineage and for a maturational stage in a given cell lineage [2]. In particular, leukosialin from K562 cells carries short and simple O-glycans and can thus serve as a model system to study O-glycosylation as well as the temporal relationship between 0-and Nglycosylation.

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Section: Discussionmentioning

confidence: 99%

O‐Glycosylation of leukosialin in K562 cells

Piller

Klier

et al. 1989

European Journal of Biochemistry

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“…The relative pool size of the 166000-M, polypeptide in the Mg2'-precipitated membrane fraction (Table 1) indicates that newly synthesized aminopeptidase N spends about one quarter to one third of its time prior to microvillar expression (15-20 min) in the mature state. This form is generated in the Golgi complex, probably in the trans cisternae of the organelle [20], and is therefore present in some Golgi-derived membranes as well as in transport vesicles en route to the plasma membrane. Involvement of the basolateral plasma membrane in the final transport of aminopeptidase N to the microvillar membrane would imply that a certain fraction of the 166000-Mr polypeptide in addition resides in membranes of basolateral origin.…”

Section: Evidence Against the Involvement Of The Hasolatrral Plasma Mmentioning

confidence: 99%

Biosynthesis of intestinal microvillar proteins. Evidence for an intracellular sorting taking place in, or shortly after, exit from the Golgi complex

Danielsen¹,

Cowell²

1985

Eur J Biochem

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Pig small intestinal mucosal explants, labelled with [35S]-methionine, were fractionated into Mg2+-precipitated (intracellular and basolaterdl) and microvillar membranes, and the orientation of newly synthesized aminopeptidase N (EC 3.4.1 1.2) in vesicles from the two fractions was studied by its accessibility to proteolytic cleavage. The mature polypeptide of M , 166000 from the latter fraction was cleaved by trypsin, proteinase K and papain, consistent with an extracellular location of the enzyme at its site of function. In contrast, both the mature form and the transient form of M , 140000 from the Mg2+-precipitated fraction were equally well protected from proteolytic cleavage (in the absence of Triton X-100). This indicates that the basolateral plasma membrane is unlikely to be involved in the post-Golgi transport of newly synthesized aminopeptidase N and suggests instead a direct delivery of the enzyme to the apical plasma membrane. A crude membrane preparation from labelled explants was used in immunoelectrophoretic purification of membranes to determine at what stage during intracellular transport newly synthesized microvillar enzymes are sorted, i. e., accumulated in areas of the membrane from where other proteins are excluded. The transient form of aminopeptidase N was only moderately enriched by immunopurification, using antibodies against different microvillar enzymes, but the mature form was enriched approximately 30-fold from explants, labelled for 30 min. This suggets that for microvillar enzymes, the aspects of sorting studied take place in, or shortly after exit from, the Golgi complex.

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Symbolic and Substantive Legitimation in Professional Practice

Richardson¹

1985

Canadian Journal of Sociology / Cahiers canadiens de sociologie

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Rousseau and Weber: Two Studies in the Theory of Legitimacy. J. G. Merquior

Cited by 3 publications

References 0 publications

O‐Glycosylation of leukosialin in K562 cells

O‐Glycosylation of leukosialin in K562 cells

Biosynthesis of intestinal microvillar proteins. Evidence for an intracellular sorting taking place in, or shortly after, exit from the Golgi complex

Symbolic and Substantive Legitimation in Professional Practice

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