PDZ-binding and di-hydrophobic motifs regulate distribution of Kir4.1 channels in renal cells.
It was shown previously that the carboxyl-terminal cytoplasmic portion of Kir4.1 determines the localization of basolateral K+ channel in renal distal tubules, which is composed from the assembly of Kir4.1 and Kir5.1. For clarifying the signals for this localization, specific sequence motifs of Kir4.1 were sought. In HEK293T cells, where Kir4.1 showed linear expression on the cell surface, disruption of the carboxyl-terminal PDZ-binding motif induced mostly clustered distribution but did not reduce whole-cell channel activity. Point mutation analysis revealed that serine377 in this motif was responsible for the surface vicinity expression. Disruption of the di-hydrophobic array of valine333/valine334 induced diffuse cytoplasmic distribution and diminished channel activity. Both valine333 and valine334 contributed to this effect. In contrast to the di-hydrophobic motifs of other membrane proteins that facilitate the sorting, valine333/valine334 supported the cell-surface retention. Because both the PDZ-binding and di-hydrophobic motifs participated in the basolateral expression of both Kir4.1 homomer and Kir5.1/Kir4.1 heteromer in MDCK cells, they are thought to be responsible for the localization of basolateral K+ channel in renal distal tubules.
Tanemoto
Masayuki
M
Division of Nephrology, Hypertension, and Endocrinology, Department of Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-cho, Aoba-ku, Sendai 980-8574, Japan. mtanemoto-tky@umin.ac.jp
Abe
Takaaki
T
Ito
Sadayoshi
S
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000098854:Kcnj10 Channel
D000098854:Kcnj10 Channel; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins