| Autor: |
Zamofing, D., Rossier, B. C., Geering, K. |
| Zdroj: |
Journal of Membrane Biology; August 1988, Vol. 104 Issue: 1 p69-79, 11p |
| Abstrakt: |
Summary No functional role could yet be established for the glycosylated ß-subunit of the Na,K-ATPase. In this study, we describe the intracellular processing of the ß-subunit as a glycoprotein in toad bladder cells and the consequences of its structural perturbation with glycosylation inhibitors on the cellular expression of the a- and ß-subunits and on the structural and functional maturation of the enzyme. Controlled trypsinolysis of homogenates from pulse-labeled cells reveals that the ß-subunit is subjected to glycosylation-dependent structural rearrangements during its intracellular routing. Inhibition of correct terminal glycosylation of the ß-subunit with deoxynojirimycin or swainsonine has no effect on the trypsin sensitivity of the a-subunit, its ability to perform cation-dependent conformation changes or the cellular Na,K-ATPase activity. Acquisition of core-sugars is sufficient for the enzyme to assume its catalytic functions. On the other hand, complete inhibition of glycosylation with tunicamycin leads to a destabilization of both the ß- and the a-subunits as judged by their higher trypsin sensitivity. In addition, tunicamycin treatment results in a decrease of the amount of newly synthesized ß- and a-subunit indicating that a glycoprotein, possibly the ß-subunit itself, plays a role in the efficient accumulation of the a-subunit in the endoplasmic reticulum. |
| Databáze: |
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