Characterization of prenylcysteines that interact with P-glycoprotein and inhibit drug transport in tumor cells.
Prenylcysteine methyl esters that represent the C-terminal structures of prenylated proteins demonstrate specific substrate-like interactions with P-glycoprotein (Zhang, L., Sachs, C. W., Fine, R. L., and Casey, P. J. (1994) J. Biol. Chem. 269, 15973-15976). The simplicity of these compounds provides a unique system for probing the structural specificity of P-glycoprotein substrates. We have further assessed the structural elements of prenylcysteines involved in the interaction with P-glycoprotein. Carboxyl group methylation, a modification in many prenylated proteins, plays an essential role of blocking the negative charge at the free carboxylate. Substitution of the methyl ester with a methyl amide or simple amide does not change the ability of the molecule to stimulate P-glycoprotein ATPase activity, but substitution with a glycine is not tolerated unless the carboxyl group of glycine is methylated. The presence of a nitrogen atom, which is found in many P-glycoprotein substrates and modifiers, is also essential for prenylcysteines to interact with P-glycoprotein. The structure at the nitrogen atom can, however, influence the type of interaction. Acetylation of the free amino group of prenylcysteine/results in a significant loss in the ability of prenylcysteines to stimulate P-glycoprotein ATPase activity. Instead, certain acetylated prenylcysteines behave as inhibitors of this activity. In studies using MDR1-transfected human breast cancer cells, the acetylated prenylcysteine analogs inhibit P-glycoprotein-mediated drug transport and enhance the steady-state accumulation of [3H]vinblastine, [3H]colchicine, and [3H]taxol. These inhibitors do not, however, affect drug accumulation in parental cells. These studies provide a novel approach for designing P-glycoprotein inhibitors that could prove effective in reversing the phenotype of multidrug resistance in tumor cells.
Zhang
L
L
Department of Molecular Cancer Biology and Biochemistry, Durham Veterans Affairs Medical Center, Duke University Medical Center, Durham, North Carolina 27710, USA.
Sachs
C W
CW
Fu
H W
HW
Fine
R L
RL
Casey
P J
PJ
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001943:Breast Neoplasms; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology*; D018432:Drug Resistance, Multiple / Q000235:genetics; D005260:Female; D006801:Humans; D007700:Kinetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D018411:Spodoptera; D013329:Structure-Activity Relationship; D014162:Transfection; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases; D003545:Cysteine