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  • 1
    ISSN: 1432-1424
    Keywords: aminopeptidase ; brush border ; cell polarity ; intracellular transport ; membrane biogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In vivo pulse-chase labeling of rabbit jejunum loops was used in conjunction with subcellular fractionation and quantitative immunoprecipitation to determine whether or not the newly synthesized aminopeptidase N transits through the basolateral membrane before it reaches the apical brush border, its final localization. The kinetics of the arrival of the newly synthesized enzyme in the Golgi complex, basolateral and brush border membrane fractions strongly suggest that on leaving the Golgi aminopeptidase N is transiently integrated into the basolateral domain before reaching the brush border.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1424
    Keywords: aminopeptidase N ; enterocyte ; cell polarity ; fluorometry ; biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A fast and easy procedure is proposed for preparing concomitantly from the same sample of intestinal mucosa of A+ rabbits, four fractions high enriched in the brush-border and basolateral plasma membrane domains, rough endoplasmic reticulum, and smooth endoplasmic reticulum plus Golgi apparatus membranes, respectively. This is the first time the technique of flow fluorometry has been applied to characterize the brush-border and basolateral membrane fractions using polyclonal or monoclonal antibodies against antigens common to or specific for these two plasma membrane domains. This technique definitely proves the presence of aminopeptidase in at least 60% of the basolateral membrane vesicles, where its level is about 4.5% of that in the brush-border membrane vesicles. The endoglycosidase H-sensitive intermediate of glycosylation of aminopeptidase N in the steady state is accumulated in both the rough and smooth endoplasmic reticulum membranes. Although the rough membrane is more extensive it contains only about 40% of this transient form.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 83 (1985), S. 139-146 
    ISSN: 1432-1424
    Keywords: intestine ; aminopeptidase N ; biosynthesis ; glycoproteins ; A antigenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A papain treatment at 15°C and pH 7.3 of a microsomal fraction from rabbit enterocytes quantitatively releases the aminopeptidase N integrated in the plasma membranes without solubilizing the enzyme integrated in the intracellular membranes. Working on A+ rabbits, characterized by the presence on the brush-border hydrolases of glycans corresponding to the human blood group A-determinant structure, it was possible to separate the intracellular aminopeptidase into two major molecular forms with or without these determinants. The molecular form devoid of human blood group A antigenicity corresponds to the only stable intermediate of glycosylation, bearing N-linked high mannose oligosaccharides. This endoglycosidase H-sensitive form is fully active and represents in the steady state about 1% of the total cellular aminopeptidase. It contains a cytoplasmic sequence of about 3000 daltons that has not yet been detected in the mature form. The A antigenicity is acquired simultaneously with processing of high mannose glycans to complex glycans. Pulse chase labeling of jejunum loops with [35S]-methionine showed that the complete processing of the transient form synthesized during 10 min takes 1 hr. During the last 30 min of processing, all the newly transformed molecules are transported to the plasma membrane.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Aminopeptidase N ; Blood group A ; antigenicity ; Digestive tract ; Digestive glands ; Liver ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cellular localization of an aminopeptidase N homologous to the brush-border intestinal enzyme and that of human blood group A-substances were investigated using the immunofluorescence technique on thin frozen sections (200 nm) of the digestive tract and associated glands of A+ and A− rabbits. Aminopeptidase N was found to be a common specific marker of both the apical region of plasma membrane of acinar cells in submaxillary and parotid glands and pancreas and the brush border of jejunum and colon absorbing cells. In hepatocytes, the enzyme was localized in the sinusoidal domains. Soluble A-substances were present in mucus secretory granules of intestinal goblet cells and those of stomach and gall bladder mucous cells. In contrast, the mucous acini of sublingual and submaxillary glands were devoid of A-antigenicity. The columnar cells of striated ducts of these glands exhibited A-antigenicity. Soluble A-substances were also found in zymogen granules of parotid and pancreas acinar cells and those of stomach chief cells. Moreover, in all cells secreting A-substances, and in the non-secreting absorbing intestinal cells, the glycoproteins of the plasma membrane bore A-determinants. Aminopeptidase N was one of the membrane-bound glycoproteins that bore A-determinants in cells that expressed A-antigenicity.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0878
    Keywords: (Na++K+)-ATPase ; Membrane markers ; Monoclonal antibody ; Ouabain ; Enzyme inhibition ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The antigen detected by the rat anti-mouse monoclonal antibody (m Ab), anti-BSP-3, has been initially described as a brain cell-surface protein. Evidence is presented that this m Ab recognizes mouse (Na++K+)-ATPase (ATP phosphohydrolase, E.C.3.6.1.3). The antigen, purified from mouse brain by means of affinity chromatography, migrated in SDS-polyacrylamide gels in the form of two polypeptide chains of 100000 and 48000 molecular weight, which could be shown to react with subunit-specific polyclonal antisera against ATPase in immunoblotting experiments. Purified BSP-3 antigen was bound to the specific (Na++K+)-ATPase inhibitor ouabain. Finally, the anti-BSP-3 m Ab was capable of immunoprecipitating the ATPase activity of a microsomal fraction from mouse kidney. The m Ab was used to study the localization of (Na++K+)-ATPase in different organs of the mouse. It stained the basolateral plasma membranes of polarized cells in immunofluorescence experiments, while the entire cell surface of unpolarized cells was labeled. Interestingly, several cell types did not react with the m Ab, indicating a possible heterogeneity of ATPases. Such a m Ab could prove to be a useful tool for studying localization, structure and function of (Na++K+)-ATPase.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0878
    Keywords: Aminopeptidase ; Thyroid ; Thyroid cell ; Membrane marker ; Polarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An aminopeptidase N has been detected by immunofluorescence in the apical plasma membrane of porcine thyroid cells, facing the follicular lumen. Freshly isolated cells obtained by tissue trypsinization, lose their polarity and exhibit a homogeneous enzyme distribution over the whole plasma membrane. In thyrotropin-stimulated cultured cells organized into follicles, the enzyme is localized in the apical cell pole. In monolayer cells, on the other hand, the enzyme is distributed over the whole surface facing the medium. In both types of cultures fluorescence is also observed in intracytoplasmic organelles. In vivo, aminopeptidase is a marker of the apical part of the thyroid plasma membrane, but its in vitro localization depends upon cell differentiation related to the culture conditions.
    Type of Medium: Electronic Resource
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