Biosynthesis and transport of lysosomal alpha-glucosidase in the human colon carcinoma cell line Caco-2 : secretion from the apical surface

Klumperman, J. and Fransen, J. A. and Boekestijn, T. C. and Oude Elferink, R. P. and Matter, K. and Hauri, H. P. and Tager, J. M. and Ginsel, L. A.. (1991) Biosynthesis and transport of lysosomal alpha-glucosidase in the human colon carcinoma cell line Caco-2 : secretion from the apical surface. Journal of cell science, Vol. 100, H. 2. pp. 339-347.

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Official URL: http://edoc.unibas.ch/dok/A5257807

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The human adenocarcinoma cell line Caco-2 was used for studies on the biosynthesis and transport of lysosomal acid alpha-glucosidase in polarized epithelial cells. Metabolic labelling revealed that in Caco-2 cells alpha-glucosidase is synthesized as a precursor form of 110 x 10(3) Mr. This form is converted into a precursor of slightly higher Mr (112 x 10(3)) by the addition of complex oligosaccharide chains. Via an intermediate form of 95 x 10(3) Mr, this precursor is processed into a mature form of 76 x 10(3) Mr. Combination of metabolic labelling with subcellular fractionation showed that the 112 x 10(3) Mr precursor of alpha-glucosidase is transported to the lysosomes. However, the same form is secreted into the culture medium (20% of newly synthesized enzyme after 4 h of chase). Immunoprecipitation of alpha-glucosidase from culture medium derived from either the apical or basolateral site of radiolabelled Caco-2 cells, showed that 70-80% of the total amount of precursor form present in the medium is secreted from the apical membrane. Measurement of enzyme activities also showed that alpha-glucosidase, unlike other lysosomal enzymes, is mainly secreted via the apical pathway. Furthermore, immunocytochemistry showed the presence of a precursor form of alpha-glucosidase on the apical, but not the basolateral, membrane of the Caco-2 cells. We conclude that alpha-glucosidase is, unlike all other secretory proteins studied so far, secreted preferentially from the apical membrane of Caco-2 cells.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Pharmacology/Neurobiology (Hauri)
UniBasel Contributors:Hauri, Hans-Peter
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Company of Biologists
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:20
Deposited On:22 Mar 2012 13:19

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