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SAP97 increases Kv1.5 currents through an indirect N‐terminal mechanism
Author(s) -
Eldstrom Jodene,
Choi Woo Sung,
Steele David F,
Fedida David
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)00668-9
Subject(s) - pdz domain , potassium channel , immunoprecipitation , biophysics , chemistry , hek 293 cells , myocyte , microbiology and biotechnology , transfection , in vivo , c terminus , voltage gated potassium channel , in vitro , biology , biochemistry , amino acid , genetics , gene
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.