Mutational analysis of P-glycoprotein: suppression of caspase activation in the absence of ATP-dependent drug efflux

Cell Death Differ. 2004 Sep;11(9):1028-37. doi: 10.1038/sj.cdd.4401440.


P-glycoprotein (P-gp) can induce multidrug resistance (MDR) through the ATP-dependent efflux of chemotherapeutic agents. We have previously shown that P-gp can inhibit nondrug apoptotic stimuli by suppressing the activation of caspases. To determine if this additional activity is functionally linked to ATP hydrolysis, we expressed wild-type and ATPase-mutant P-gp and showed that cells expressing mutant P-gp could not efflux chemotherapeutic drugs but remained relatively resistant to apoptosis. CEM lymphoma cells expressing mutant P-gp treated with vincristine showed a decrease in the fraction of cells with apoptotic morphology, cytochrome c release from the mitochondria and suppression of caspase activation, yet still accumulated in mitosis and showed a loss of clonogenic potential. The loss of clonogenicity in vincristine-treated cells expressing mutant P-gp was associated with accumulation of cells in mitosis and the presence of multinucleated cells consistent with mitotic catastrophe. The antiapoptotic effect of mutant P-gp was not affected by antibodies that inhibit the efflux function of the protein. These data are consistent with a dual activity model for P-gp-induced MDR involving both ATPase-dependent drug efflux and ATPase-independent inhibition of apoptosis. The structure-function analyses described herein provide novel insight into the mechanisms of action of P-gp in mediating MDR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics*
  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphate / metabolism*
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Apoptosis
  • Caspases / metabolism*
  • Cell Line
  • Cell Line, Tumor
  • Cell Membrane / metabolism
  • Cell Nucleus / metabolism
  • Cell Survival
  • Cytochromes c / metabolism
  • DNA Mutational Analysis
  • Drug Resistance, Multiple
  • Drug Resistance, Neoplasm
  • Enzyme Activation
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Hydrolysis
  • Hydroxamic Acids / pharmacology
  • Idarubicin / pharmacology
  • Lymphoma / drug therapy
  • Mitosis
  • Mutation
  • Retroviridae / genetics
  • Structure-Activity Relationship
  • Time Factors
  • Vincristine / pharmacology


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents
  • Antineoplastic Agents, Phytogenic
  • Hydroxamic Acids
  • oxamflatin
  • Green Fluorescent Proteins
  • Vincristine
  • Adenosine Triphosphate
  • Cytochromes c
  • Caspases
  • Adenosine Triphosphatases
  • Idarubicin