IMR Press / FBE / Volume 3 / Issue 4 / DOI: 10.2741/E344

Frontiers in Bioscience-Elite (FBE) is published by IMR Press from Volume 13 Issue 2 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article

Intercalated Disc-Associated Protein, mXin-alpha, influences surface expression of ITO currents in ventricular myocytes 

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1 Institute of Physiology, National Defense Medical Center, Taipei, Taiwan, ROC
2 Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan, ROC
3 Department of Biomedical Engineering, National Defense Medical Center, Taipei, Taiwan, ROC
4 Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC
5 Department of Biology, University of Iowa, Iowa City, IA, U.S.A.

*Author to whom correspondence should be addressed.

Academic Editor: Jim Jung-Ching Lin

Front. Biosci. (Elite Ed) 2011, 3(4), 1425–1442; https://doi.org/10.2741/E344
Published: 1 June 2011
Abstract

Mouse Xin-alpha (mXin-alpha) encodes a Xin repeat-containing, actin-binding protein localized to the intercalated disc (ICD). Ablation of mXin-alpha progressively leads to disrupted ICD structure, cardiac hypertrophy and cardiomyopathy with conduction defects during adulthood. Such conduction defects could be due to ICD structural defects and/or cell electrophysiological property changes. Here, we showed that despite the normal ICD structure, juvenile mXina-null cardiomyocytes (from 3~4-week-old mice) exhibited a significant reduction in the transient outward K+ current (ITO), similar to adult mutant cells. Juvenile but not adult mutant cardiomyocytes also had a significant reduction in the delayed rectifier K+ current. In contrast, the mutant adult ventricular myocytes had a significant reduction in the inward rectifier K+ current (IK1) on hyperpolarization. These together could account for the prolongation of action potential duration (APD) and the ease of developing early afterdepolarization observed in juvenile mXin-alpha-null cells. Interestingly, juvenile mXin-alpha-null cardiomyocytes had a notable decrease in the amplitude of intracellular Ca2+ transient and no change in the L-type Ca2+ current, suggesting that the prolonged APD did not promote an increase in intracellular Ca2+ for cardiac hypertrophy. Juvenile mXin-alpha-null ventricles had reduced levels of membrane-associated Kv channel interacting protein 2, an auxiliary subunit of ITO, and filamin, an actin cross-linking protein. We further showed that mXin-alpha interacted with both proteins, providing a novel mechanism for ITO surface expression.

Keywords
Developmental Changes
Electrophysiology
KChIP2
transient outward K+ current
L-type Ca2+ current
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