SAP97 interacts with Kv1.5 in heterologous expression systems.
PDZ domain-containing proteins such as SAP97 and ZO-1 have been implicated in the targeting and clustering of ion channels. We have explored the interactions of these polypeptides with a cardiac voltage-gated potassium channel. Immunocytochemistry in cardiac myocytes revealed colocalization of SAP97 and Kv1.5, both at the intercalated disks and the lateral membranes. Transient transfection experiments in COS-7 cells revealed that SAP97 and Kv1.5 polypeptides formed perinuclear clustered complexes that could be coimmunoprecipitated. Mutation of the three COOH-terminal amino acid residues of Kv1.5 (T-D-L to A-A-A) abolished these interactions. Whereas in most COS-7 cells the SAP97-Kv1.5 complexes were retained in the ER, functional analyses in Xenopus oocytes showed that Kv1.5-encoded outward potassium currents were augmented by coexpression with SAP97. By contrast, cotransfected ZO-1 and Kv1.5 polypeptides in COS-7 cells could not be coprecipitated nor did the coinjection of ZO-1 augment the Kv1.5-encoded currents in oocytes. Collectively, our results suggest that SAP97 may play an important role in the modulation of Kv1.5 channel function in cardiac myocytes.
Murata
M
M
Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Buckett
P D
PD
Zhou
J
J
Brunner
M
M
Folco
E
E
Koren
G
G
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D007150:Immunohistochemistry; D051666:Kv1.5 Potassium Channel; D008565:Membrane Proteins / Q000032:analysis; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology; D010750:Phosphoproteins / Q000032:analysis; D015221:Potassium Channels / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D014162:Transfection; D014981:Xenopus; D029867:Xenopus Proteins; D062826:Zonula Occludens-1 Protein
D048868:Adaptor Proteins, Signal Transducing; C501119:Dlg1 protein, rat; C496983:Kcna5 protein, rat; D051666:Kv1.5 Potassium Channel; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C569045:TJP1 protein, Xenopus; C569044:Tjp1 protein, rat; D029867:Xenopus Proteins; D062826:Zonula Occludens-1 Protein