title: Rhodamine inhibitors of P-glycoprotein: an amide/thioamide "switch" for ATPase activity.
abstract: We have examined 46 tetramethylrosamine/rhodamine derivatives with structural diversity in the heteroatom of the xanthylium core, the amino substituents of the 3- and 6-positions, and the alkyl, aryl, or heteroaryl group at the 9-substituent. These compounds were examined for affinity and ATPase stimulation in isolated MDR3 CL P-gp and human P-gp-His(10), for their ability to promote uptake of calcein AM and vinblastine in multidrug-resistant MDCKII-MDR1 cells, and for transport in monolayers of MDCKII-MDR1 cells. Thioamide 31-S gave K(M) of 0.087 microM in human P-gp. Small changes in structure among this set of compounds affected affinity as well as transport rate (or flux) even though all derivatives examined were substrates for P-gp. With isolated protein, tertiary amide groups dictate high affinity and high stimulation while tertiary thioamide groups give high affinity and inhibition of ATPase activity. In MDCKII-MDR1 cells, the tertiary thioamide-containing derivatives promote uptake of calcein AM and have very slow passive, absorptive, and secretory rates of transport relative to transport rates for tertiary amide-containing derivatives. Thioamide 31-S promoted uptake of calcein AM and inhibited efflux of vinblastine with IC(50)'s of approximately 2 microM in MDCKII-MDR1 cells.
authors.affiliation: Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Gannon
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Holt
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Bennett
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Wetzel
authors.forename: Tip W
authors.initials: TW
authors.lastname: Loo
authors.forename: M Claire
authors.initials: MC
authors.lastname: Bartlett
authors.forename: David M
authors.initials: DM
authors.lastname: Clarke
authors.forename: Geri A
authors.initials: GA
authors.lastname: Sawada
authors.forename: J William
authors.initials: JW
authors.lastname: Higgins
authors.forename: Gregory
authors.initials: G
authors.lastname: Tombline
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Raub
authors.forename: Michael R
authors.initials: MR
authors.lastname: Detty
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors*; D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism*; D000577:Amides / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D004285:Dogs; D018432:Drug Resistance, Multiple; D005452:Fluoresceins / Q000493:pharmacokinetics; D006575:Heterocyclic Compounds, 3-Ring; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D012235:Rhodamines / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013854:Thioamides / Q000737:chemistry / Q000494:pharmacology*; D014747:Vinblastine / Q000493:pharmacokinetics
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000577:Amides; D005452:Fluoresceins; D006575:Heterocyclic Compounds, 3-Ring; D012235:Rhodamines; D013854:Thioamides; C412715:tetramethylrosamine; C085925:calcein AM; D014747:Vinblastine; D000251:Adenosine Triphosphatases