Clustering and enhanced activity of an inwardly rectifying potassium channel, Kir4.1, by an anchoring protein, PSD-95/SAP90.
An inwardly rectifying potassium channel predominantly expressed in glial cells, Kir4.1/KAB-2, has a sequence of Ser-Asn-Val in its carboxyl-terminal end, suggesting a possible interaction with an anchoring protein of the PSD-95 family. We examined the effects of PSD-95 on the distribution and function of Kir4.1 in a mammalian cell line. When Kir4.1 was expressed alone, the channel immunoreactivity was distributed homogeneously. In contrast, when co-expressed with PSD-95, prominent clustering of Kir4.1 in the cell membrane occurred. Kir4.1 was co-immunoprecipitated with PSD-95 in the co-expressed cells. Glutathione S-transferase-fusion protein of COOH terminus of Kir4.1 bound to PSD-95. These interactions disappeared when the Ser-Asn-Val motif was deleted. The magnitude of whole-cell Kir4.1 current was increased by 2-fold in cells co-expressing Kir4.1 and PSD-95 compared with cells expressing Kir4. 1 alone. SAP97, another member of the PSD-95 family, showed similar effects on Kir4.1. Furthermore, we found that Kir4.1 as well as SAP97 distributed not diffusely but clustered in retinal glial cells. Therefore, PSD-95 family proteins may be a physiological regulator of the distribution and function of Kir4.1 in glial cells.
Horio
Y
Y
Department of Pharmacology II, Faculty of Medicine, Osaka University, Suita, Osaka 565, Japan.
Hibino
H
H
Inanobe
A
A
Yamada
M
M
Ishii
M
M
Tada
Y
Y
Satoh
E
E
Hata
Y
Y
Takai
Y
Y
Kurachi
Y
Y
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002460:Cell Line; D000074288:Discs Large Homolog 1 Protein; D000076122:Disks Large Homolog 4 Protein; D005786:Gene Expression Regulation; D018014:Gene Transfer Techniques; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D017136:Ion Transport; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D051381:Rats
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; C501444:DLG4 protein, human; D000074288:Discs Large Homolog 1 Protein; D000076122:Disks Large Homolog 4 Protein; C501119:Dlg1 protein, rat; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C033652:postsynaptic density proteins