title: The PDZ domain protein PDZK1 interacts with human peptide transporter PEPT2 and enhances its transport activity.
abstract: The proton-coupled peptide transporter PEPT2 (SLC15A2) mediates the high-affinity low-capacity transport of small peptides as well as various oral peptide-like drugs in the kidney. In contrast to its well-characterized transport properties, there is less information available on its regulatory mechanism, although the interaction of PEPT2 to the PDZ (PSD-95, DglA, and ZO-1)-domain protein PDZK1 has been preliminarily reported. To examine whether PDZK1 is a physiological partner of PEPT2 in kidneys, we started from a yeast two-hybrid screen of a human kidney cDNA library with the C-terminus of PEPT2 (PEPT2 C-terminus (PEPT2-CT)) as bait. We could identify PDZK1 as one of the positive clones. This interaction requires the PDZ motif of PEPT2-CT detected by a yeast two-hybrid assay, in vitro binding assay and co-immunoprecipitation. The binding affinities of second and third PDZ domains of PDZK1 to PEPT2-CT were measured by surface plasmon resonance. Co-immunoprecipitation using human kidney membrane fraction and localization of PEPT2 in renal apical proximal tubules revealed the physiological meaning of this interaction in kidneys. Furthermore, we clarified the mechanism of enhanced glycylsarcosine (Gly-Sar) transport activity in PEPT2-expressing HEK293 cells after the PDZK1 coexpression. This augmentation was accompanied by a significant increase in the V(max) of Gly-Sar transport via PEPT2 and it was also associated with the increased surface expression level of PEPT2. These results indicate that the PEPT2-PDZK1 interaction thus plays a physiologically important role in both oligopeptide handling as well as peptide-like drug transport in the human kidney.
authors.affiliation: Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Noshiro
authors.forename: N
authors.initials: N
authors.lastname: Anzai
authors.forename: T
authors.initials: T
authors.lastname: Sakata
authors.forename: H
authors.initials: H
authors.lastname: Miyazaki
authors.forename: T
authors.initials: T
authors.lastname: Terada
authors.forename: H J
authors.initials: HJ
authors.lastname: Shin
authors.forename: X
authors.initials: X
authors.lastname: He
authors.forename: D
authors.initials: D
authors.lastname: Miura
authors.forename: K
authors.initials: K
authors.lastname: Inui
authors.forename: Y
authors.initials: Y
authors.lastname: Kanai
authors.forename: H
authors.initials: H
authors.lastname: Endou
mesh_terms: D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D015723:Gene Library; D006801:Humans; D007150:Immunohistochemistry; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary; D020349:Surface Plasmon Resonance; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; C484659:PDZK1 protein, human; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2