Biochemical basis of polyvalency as a strategy for enhancing the efficacy of P-glycoprotein (ABCB1) modulators: stipiamide homodimers separated with defined-length spacers reverse drug efflux with greater efficacy.
Human P-glycoprotein (Pgp) is as an ATP-dependent efflux pump for a variety of chemotherapeutic drugs. The aim of this study is to evaluate whether Pgp modulators can be engineered to exhibit high-affinity binding using polyvalency. Five bivalent homodimeric polyenes based on stipiamide linked with polyethylene glycol ethers in the range of 3-50 A were synthesized and quantitatively characterized for their effect on Pgp function. The stipiamide homodimers displaced [(125)I]iodoarylazidoprazoin (IAAP), an analogue of the Pgp substrate prazosin. A minimal spacer of 11 A is necessary for inhibition of IAAP labeling, beyond which there is an inverse correlation between the length of the spacer and the IC(50) for the displacement of IAAP. ATP hydrolysis by Pgp on the other hand is stimulated by the dimers with spacers of up to 22 A, whereas dimers with longer spacers inhibit ATP hydrolysis. Finally, the homodimers reverse Pgp-mediated drug efflux in intact cells overexpressing Pgp, and 11 A is a threshold beyond which the effectiveness of the homodimers increases exponentially and levels off at 33 A. We demonstrate that dimerization and identification of an optimal spacer length increase by 11-fold the affinity of stipiamide, and this is reflected in the efficacy with which Pgp-mediated drug efflux is reversed. These results suggest that polyvalency could be a useful strategy for the development of more potent Pgp modulators.
Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4254, USA.
Zuben E
ZE
Sauna
Merritt B
MB
Andrus
Timothy M
TM
Turner
Suresh V
SV
Ambudkar
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000037:antagonists & inhibitors / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D001692:Biological Transport; D001896:Boron Compounds / Q000378:metabolism; D019281:Dimerization; D004337:Drug Carriers / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007457:Iodine Radioisotopes / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D019920:Photoaffinity Labels / Q000378:metabolism; D011090:Polyenes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D011224:Prazosin / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism
C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D001386:Azides; D001896:Boron Compounds; D004337:Drug Carriers; D005452:Fluoresceins; D007457:Iodine Radioisotopes; D019920:Photoaffinity Labels; D011090:Polyenes; C069644:stipiamide; C085925:calcein AM; C017040:8-azidoadenosine 5'-triphosphate; D000255:Adenosine Triphosphate; C041552:azidoprazosin; D011224:Prazosin