SGK1 inhibition attenuated the action potential duration in patient- and genotype-specific re-engineered heart cells with congenital long QT syndrome

Figures

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  Figure 1. The action potential duration and serum and glucocorticoid regulated kinase-1 activity are increased in SCN5A-P1332L induced pluripotent stem cell–derived cardiomyocytes (iPSC-CMs) compared with isogenic control (IC) iPSC-CMs. A: Representative tracings (left) of action potential from SCN5A-P1332L (P1332L) (black line) and IC (gray line) iPSC-CMs. The raw tracings were recorded using a fluorescent voltage dye, FluoVolt. Quantification (right) of action potential duration at 90% repolarization (APD90) of SCN5A-P1332L and IC iPSC-CMs. B: Representative immunoblots of protein lysates of SCN5A-P1332L and IC iPSC-CMs probed for phospho (Ser9)-glycogen synthase kinase beta (p-GSK3β), total GSK3β (T-GSK3β), and GAPDH as a loading control (left). Quantification of band intensity on the immunoblot (right). Protein levels were normalized to GAPDH, and data were expressed as fold change relative to IC.

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  Figure 2. Action potential duration–shortening effects of a novel serum and glucocorticoid regulated kinase-1 (SGK1) inhibitor compound in long QT syndrome type 3 induced pluripotent stem cell–derived cardiomyocytes (iPSC-CMs). A: Representative tracings (left) of action potential from SCN5A-P1332L iPSC-CMs after 4-hour treatment with mexiletine (MEX) and a novel SGK1 inhibitor, SGK1-I1. The black, gray, and red lines indicated tracing of action potential of dimethyl sulfoxide (DMSO), 10 μM MEX, and 30 nM SGK1-I1, paced at a frequency of 1 Hz, respectively. Quantification (right) of action potential duration at 90% repolarization (APD90) of SCN5A-P1332L iPSC-CMs after compound treatment. The dotted line indicates the APD90 of isogenic control iPSC-CMs at baseline. B: Representative tracings (left) of action potential from SCN5A-R1623Q iPSC-CMs after 4-hour treatment with MEX and SGK1-I1. The black, gray, and red lines indicated tracing of the action potential of DMSO, 10 μM MEX, and 3 nM SGK1-I1, paced at a frequency of 1 Hz, respectively. Quantification (right) of APD90 of SCN5A-R1623Q iPSC-CMs after compound treatment.

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  Figure 3. Action potential duration–shortening effects of a novel serum and glucocorticoid regulated kinase-1 (SGK1) inhibitor compound in long QT syndrome type 1 and type 2 induced pluripotent stem cell–derived cardiomyocytes (iPSC-CMs). A: Representative tracings (left) of action potential from KCNQ1-V254M iPSC-CMs after 4-hour treatment with mexiletine (MEX) and an SGK1 inhibitor, SGK1-I1. The black, gray, and red lines indicated tracing of action potential of dimethyl sulfoxide (DMSO), 10 μM MEX, and 100 nM SGK1-I1, paced at a frequency of 1 Hz, respectively. Quantification (right) of action potential duration at 90% repolarization (APD90) of KCNQ1-V254M iPSC-CMs after compound treatment. B: Representative tracings (left) of action potential from KCNH2-G604S iPSC-CMs after 4-hour treatment with MEX and SGK1-I1. The black, gray, and red lines indicated tracing of action potential of DMSO, 10 μM MEX, and 30 nM SGK1-I1, paced at a frequency of 1 Hz, respectively. Quantification (right) of APD90 of KCNH2-G604S iPSC-CMs after compound treatment.