@article{0c44c8d3ce0244f5968bdb057f7222e1,
title = "Altered Cell surface glycoproteins in phytohemagglutinin-resistant mutants of Chinese hamster ovary cells",
abstract = "Purified membranes from surface-labelled phytohemagglutinin-resistant (PhaR) and wild-type chinese hamster ovary cells have been analysed by sodium dodecyl sulphate gel electrophoresis. Gel patterns were compared for cells labelled via galactose oxidase and B3H4 or lactoperoxidase and radioactive iodide. The results suggest that PhaR cells are altered in the carbohydrate portion of a number of their membrane glycoproteins.",
author = "Juliano, {R. L.} and Pamela Stanley",
note = "Funding Information: These surface-labelling experiments have provided futher information on the nature of the alteration(s) at the plasma membrane of Pha R CHO cells. The results of galactose oxidase-B3H4 surface-labelling clearly show that Pha R cells possess few available ultimate and penultimate surface galactose residues compared with wild-type CHO cells. The glycoproteins which do label in Pha~membranes may represent a subset of wild-type glycoproteins which are not affected by the mutation to phytohemagglutinin-resistance. These membrane mutants therefore provide unique biological material for experiments designed to analyze the surface architecture of mammalian cells. By contrast, Pha R and wild-type cells label to a similar extent by lactoperoxidase iodination, but many of the species from Pha R membranes appear to migrate with a decreased molecular weight. There is evidence that the major surface components in CHO cells which label via the galactose method are also those which label via the lactoperoxidase method (Juliano and Behar-Bannelier, submitted for publication). Therefore, glycoproteins and proteins in wild-type membranes are also available for enzymic iodination in Pha R cells but that the glycoproteins in Pha R cells, being significantly less glycosylated, migrate more rapidly in dodecyl sulfate gels. This interpretation is supported by recent experiments in our laboratory which show that both Pha R clones Pro-Pha R 1-1 and Gat-Pro÷2 Pha R 1 possess very little activity (~< 5% that present in wild-type cell extracts) of a specific glycosyl transferase which transfers N-acetylglucosamine (GlcNAc) to terminal a-mannose residues (Stanley, Narasimhan, Schachter and Simino-vitch, manuscript in preparation). If the phytohemagglutinin receptor in CHO cells is similar to that characterized from human red blood cells \[7\] a predicted consequence of this enzyme lesion would be that cell glycoproteins containing the a-mannose-GlcNAc sequence would be incompletely glycosylated. It has recently been shown that Ricinus communis-resistant CHO cells also possess very low activity for the GlcNAc-transferase, absent in PhaRceUs and that glycoproteins in crude membrane extracts from these cells appear to migrate with a decreased molecular weight in dodecyl sulfate gels \[8\]. The availability of membrane mutants will greatly facilitate the study of membrane structure and function in mammalian cells. It is of interest that the independently isolated Pha R clones Pro-Pha R 1-1 and Gat-Pro÷2 - PhaR1 appear to differ in the exposure of their surface glycoproteins (Fig. 1), despite both having lost the activity of the same specific glycosyl transferase. Further comparisons such as these are now possible since a number of phenotypically distinct lectin-resistant cells have recently been isolated in our laboratory (Stanley, Caillibot and Siminovitch, manuscript in preparation). The authors wish to acknowledge the expert technical assistance of Ms M. Behar-Bannelier and Ms Wendy MacDougall. We are also grateful for the advice of Dr L. Siminovitch in the preparation of the manuscript. This work was supported by the Medical Research Council of Canada and by the National Cancer Institute. P.S. is post-doctoral fellow of The Medical Research Coucil of Canada.",
year = "1975",
month = may,
day = "6",
doi = "10.1016/0005-2736(75)90332-6",
language = "English (US)",
volume = "389",
pages = "401--406",
journal = "BBA - Biomembranes",
issn = "0005-2736",
publisher = "Elsevier",
number = "2",
}