Kv4 potassium channels form a tripartite complex with the anchoring protein SAP97 and CaMKII in cardiac myocytes.
Membrane-associated guanylate kinase (MAGUK) proteins are major determinants of the organization of ion channels in the plasma membrane in various cell types. Here, we investigated the interaction between the MAGUK protein SAP97 and cardiac Kv4.2/3 channels, which account for a large part of the outward potassium current, I(to), in heart. We found that the Kv4.2 and Kv4.3 channels C termini interacted with SAP97 via a SAL amino acid sequence. SAP97 and Kv4.3 channels were colocalized in the sarcolemma of cardiomyocytes. In CHO cells, SAP97 clustered Kv4.3 channels in the plasma membrane and increased the current independently of the presence of KChIP and dipeptidyl peptidase-like protein-6. Suppression of SAP97 by using short hairpin RNA inhibited I(to) in cardiac myocytes, whereas its overexpression by using an adenovirus increased I(to). Kv4.3 channels without the SAL sequence were no longer regulated by Ca2+/calmodulin kinase (CaMK)II inhibitors. In cardiac myocytes, pull-down and coimmunoprecipitation assays showed that the Kv4 channel C terminus, SAP97, and CaMKII interact together, an interaction suppressed by SAP97 silencing and enhanced by SAP97 overexpression. In HEK293 cells, SAP97 silencing reproduced the effects of CaMKII inhibition on current kinetics and suppressed Kv4/CaMKII interactions. In conclusion, SAP97 is a major partner for surface expression and CaMKII-dependent regulation of cardiac Kv4 channels.
El-Haou
Saïd
S
UMRS-956, Faculté de Médecine Pierre-Marie Curie, 91 Boulevard de l'Hôpital, 75013 Paris, France.
Balse
Elise
E
Neyroud
Nathalie
N
Dilanian
Gilles
G
Gavillet
Bruno
B
Abriel
Hugues
H
Coulombe
Alain
A
Jeromin
Andreas
A
Hatem
Stéphane N
SN
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D016466:CHO Cells; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D000074288:Discs Large Homolog 1 Protein; D006801:Humans; D051605:Kv Channel-Interacting Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000235:genetics / Q000378:metabolism*; D051672:Shal Potassium Channels / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; C501119:Dlg1 protein, rat; D051605:Kv Channel-Interacting Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D051672:Shal Potassium Channels; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2