SAP97 increases Kv1.5 currents through an indirect N-terminal mechanism.
The functional interaction of the voltage-gated potassium channel hKv1.5 with the PDZ domain containing protein SAP97 has been investigated. In marked contrast with the known dependence of SAP97-induced Kv1 potassium current down-regulation on the channel C-termini, SAP97 increased hKv1.5 current through an indirect interaction with the Kv1.5 N-terminus. Deletion of the Kv1.5 N-terminus eliminated the SAP97-mediated increase in potassium currents whereas deletion of the channel's C-terminal PDZ binding motif had no effect. In contrast with other Kv1-SAP97 interactions, no physical interaction could be detected in vivo or in vitro between the two proteins. The proteins did not co-localize in cardiac myocytes nor did they co-immunoprecipitate from transfected HEK cells. Yeast two-hybrid experiments also failed to detect any interaction between the two proteins, but in one experiment of six, Kv1.5 co-immunoprecipitated very inefficiently with SAP97 from rat ventricular myocytes. Thus, we conclude that the influence of SAP97 on Kv1.5 potassium current levels is dependent upon a novel regulatory mechanism.
Eldstrom
Jodene
J
Department of Physiology, University of British Columbia, 2146 Health Sciences Mall, V6T 1Z3, Vancouver, BC, Canada.
Choi
Woo Sung
WS
Steele
David F
DF
Fedida
David
D
D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D002460:Cell Line; D000074288:Discs Large Homolog 1 Protein; D006321:Heart / Q000502:physiology; D006325:Heart Atria; D006352:Heart Ventricles; D006801:Humans; D051666:Kv1.5 Potassium Channel; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism; D015221:Potassium Channels / Q000302:isolation & purification / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; C496981:KCNA5 protein, human; D051666:Kv1.5 Potassium Channel; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins