title: Molecular mechanism of inward rectifier potassium channel 2.3 regulation by tax-interacting protein-1.
abstract: Inwardly rectifying potassium channel 2.3 (Kir2.3) is specifically targeted on the basolateral membranes of epithelial and neuronal cells, and it thus plays an important role in maintaining potassium homeostasis. Tax-interacting protein-1 (TIP-1), an atypical PDZ-domain-containing protein, binds to Kir2.3 with a high affinity, causing the intracellular accumulation of Kir2.3 in cultured epithelial cells. However, the molecular basis of the TIP-1/Kir2.3 interaction is still poorly understood. Here, we present the crystal structure of TIP-1 in complex with the C-terminal Kir2.3-peptide (residues 436-445) to reveal the molecular details of the interaction between them. Moreover, isothermal titration calorimetry experiments show that the C-terminal Kir2.3-peptide binds much more strongly to TIP-1 than to mammalian Lin-7, indicating that TIP-1 can compete with mammalian Lin-7 to uncouple Kir2.3 from its basolateral membrane anchoring complex. We further show that the phosphorylation/dephosphorylation of Ser443 within the C-terminal Kir2.3 PDZ-binding motif RRESAI dynamically regulates the Kir2.3/TIP-1 association in heterologous HEK293T cells. These data suggest that TIP-1 may act as an important regulator for the endocytic pathway of Kir2.3.
authors.affiliation: Tianjin Key Laboratory of Protein Science, College of Life Science, Nankai University, Tianjin 300071, China.
authors.forename: Xiaojie
authors.initials: X
authors.lastname: Yan
authors.forename: Hao
authors.initials: H
authors.lastname: Zhou
authors.forename: Jinxiu
authors.initials: J
authors.lastname: Zhang
authors.forename: Chaowei
authors.initials: C
authors.lastname: Shi
authors.forename: Xingqiao
authors.initials: X
authors.lastname: Xie
authors.forename: Yinan
authors.initials: Y
authors.lastname: Wu
authors.forename: Changlin
authors.initials: C
authors.lastname: Tian
authors.forename: Yuequan
authors.initials: Y
authors.lastname: Shen
authors.forename: Jiafu
authors.initials: J
authors.lastname: Long
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D018360:Crystallography, X-Ray; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005972:Glutaminase / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D008954:Models, Biological; D008958:Models, Molecular; D010766:Phosphorylation; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C099489:KCNJ4 protein, human; D024661:Potassium Channels, Inwardly Rectifying; C421249:TAX1BP3 protein, human; D017868:Cyclic AMP-Dependent Protein Kinases; D005972:Glutaminase