TY - JOUR
T1 - N-glycosylation and deletion mutants of the human MDR1 P-glycoprotein
AU - Schinkel, A. H.
AU - Kemp, S.
AU - Dollé, M.
AU - Rudenko, G.
AU - Wagenaar, E.
PY - 1993
Y1 - 1993
N2 - 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
AB - 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
M3 - Article
C2 - 8096511
SN - 0021-9258
VL - 268
SP - 7474
EP - 7481
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 10
ER -