N-glycosylation and deletion mutants of the human MDR1 P-glycoprotein

Alfred H. Schinkel, Stephan Kemp, Martijn Dollé, Gabrielle Rudenko, Els Wagenaar

Research output: Contribution to journalArticlepeer-review

183 Scopus citations


P-glycoproteins are heavily glycosylated plasma membrane proteins, which confer multidrug resistance by pumping a range of different drugs from the cell. To investigate the significance of the conserved N-glycosylation sites present in the putative first extracellular loop of P-glycoproteins, we mutated one, two, or all three of these sites present in the human MDR1 P-glycoprotein. We also deleted a stretch of 20 amino acids, containing two of the three N-glycosylation sites. The effects of these mutations were studied by transfection into drug-sensitive cells. In vincristine-resistant transfected clones selected for similar steady state levels of membrane-bound P-glycoprotein, the absence of N-glycosylation did not alter the level or pattern of (cross-)resistance. However, the absence of N-glycosylation sites drastically reduced the efficiency with which drug-resistant clones could be generated. These findings suggest that N-glycosylation contributes to proper routing or stability of P-glycoprotein but not to drug transport per se. The deletion mutants demonstrated a clearly decreased and altered drug resistance pattern, even with a high level of P-glycoprotein in the plasma membrane. This, and possibly the observed lack of glycosylation of the remaining intact glycosylation sequence, suggests a constrained P-glycoprotein structure. Our findings support the current model for P-glycoprotein structure.

Original languageEnglish (US)
Pages (from-to)7474-7481
Number of pages8
JournalJournal of Biological Chemistry
Issue number10
StatePublished - Apr 5 1993
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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