Basolateral membrane expression of the Kir 2.3 channel is coordinated by PDZ interaction with Lin-7/CASK complex.
The basolateral membrane sorting determinant of an inwardly rectifying potassium channel, Kir 2.3, is comprised of a unique arrangement of trafficking motifs containing tandem, conceivably overlapping, biosynthetic targeting and PDZ-based signals. In the present study, we elucidate a mechanism by which a PDZ interaction coordinates one step in a basolateral membrane sorting program. In contrast to apical missorting of channels lacking the entire sorting domain, deletion of the PDZ binding motif caused channels to accumulate into an endosomal compartment. Here, we identify a new human ortholog of a Caenorhabditis elegans PDZ protein, hLin-7b, that interacts with the COOH-terminal tail of Kir 2.3 in renal epithelia. hLin-7b associates with the channel as a part of a multimeric complex on the basolateral membrane similar to a basolateral membrane complex in C. elegans vulva progenitor cells. Coexpression of hLin-7b with Kir 2.3 dramatically increases channel activity by stabilizing plasma membrane expression. The discovery identifies one component of the sorting machinery and provides evidence for a retention mechanism in a hierarchical basolateral trafficking program.
Olsen
Olav
O
Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Liu
Hui
H
Wade
James B
JB
Merot
Jean
J
Welling
Paul A
PA
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D019556:COS Cells; D029742:Caenorhabditis elegans Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002462:Cell Membrane / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology; D051528:Guanylate Kinases; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D014982:Xenopus laevis
D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; C099173:LIN-7 protein, C elegans; D008024:Ligands; D008565:Membrane Proteins; D015221:Potassium Channels; C106868:CASK kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; D011188:Potassium