title: PDZK1 regulates breast cancer resistance protein in small intestine.
abstract: Transporter adaptor protein PDZK1 regulates several influx transporters for xenobiotics and nutrients in small intestine, and their expression on the apical membrane is diminished in pdzk1 gene knockout [pdzk1(-/-)] mice. In the present study, we initially attempted to use pdzk1(-/-) mice to functionally identify influx transporters responsible for intestinal absorption of cimetidine. Contrary to our expectation, the plasma concentration of cimetidine after oral administration to pdzk1(-/-) mice was higher than that in wild-type mice, and the double peaks of plasma concentration found in wild-type mice were not observed in pdzk1(-/-) mice. Western blot analysis of intestinal brush-border membranes revealed that expression of breast cancer resistance protein (BCRP) but not of P-glycoprotein is reduced in pdzk1(-/-) mice. This result was compatible with the reduction of apical localization of BCRP in pdzk1(-/-) mice assessed by immunohistochemical analysis. Transcellular transport of cimetidine in the basal-to-apical direction in Madin-Darby canine kidney II (MDCKII) cells stably expressing both BCRP and PDZK1 (MDCKII/BCRP/PDZK1) was higher than that in MDCKII cells stably expressing BCRP (MDCKII/BCRP) cells. Moreover, MDCKII/BCRP/PDZK1 cells are more resistant than MDCKII/BCRP cells to the cytotoxicity of the anticancer agent 7-ethyl-10-hydroxycamptothecin (SN-38), which is a substrate of BCRP. These results were consistent with the higher expression of BCRP on apical membranes in MDCKII/BCRP/PDZK1 cells. Pull-down and immunoprecipitation studies revealed a physical interaction between BCRP and PDZK1. Taken together, these findings demonstrate that PDZK1 plays a pivotal role in the apical localization of BCRP. This is the first identification of a regulatory protein that physically interacts with and regulates BCRP in small intestine in vivo.
authors.affiliation: Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Shimizu
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sugiura
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Wakayama
authors.forename: Ai
authors.initials: A
authors.lastname: Kijima
authors.forename: Noritaka
authors.initials: N
authors.lastname: Nakamichi
authors.forename: Shoichi
authors.initials: S
authors.lastname: Iseki
authors.forename: David L
authors.initials: DL
authors.lastname: Silver
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kato
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000284:Administration, Oral; D000818:Animals; D001692:Biological Transport; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D002927:Cimetidine / Q000097:blood / Q000494:pharmacology; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D000077146:Irinotecan; D007668:Kidney / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D054730:Protein Interaction Domains and Motifs
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C501412:Abcg2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C514896:PDZK1 protein, mouse; D000077146:Irinotecan; D002927:Cimetidine; D002166:Camptothecin