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Functional interaction of Junctophilin 2 with small‐ conductance Ca 2+ ‐activated potassium channel subtype 2( SK 2) in mouse cardiac myocytes
Author(s) -
Fan H. K.,
Luo T. X.,
Zhao W. D.,
Mu Y. H.,
Yang Y.,
Guo W. J.,
Tu H. Y.,
Zhang Q.
Publication year - 2018
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/apha.12986
Subject(s) - myocyte , intracellular , gene knockdown , microbiology and biotechnology , potassium channel , extracellular , cardiac action potential , biology , ion channel , sk channel , biophysics , chemistry , electrophysiology , biochemistry , neuroscience , repolarization , gene , receptor
Abstract Aim Junctophilins ( JP s), a protein family of the junctional membrane complex, maintain the close conjunction between cell surface and intracellular membranes in striate muscle cells mediating the crosstalk between extracellular Ca 2+ entry and intracellular Ca 2+ release. The small‐conductance Ca 2+ ‐activated K + channels are activated by the intracellular calcium and play an essential role in the cardiac action potential profile. Molecular mechanisms of regulation of the SK channels are still uncertain. Here, we sought to determine whether there is a functional interaction of junctophilin type 2 ( JP 2) with the SK channels and whether JP 2 gene silencing might modulate the function of SK channels in cardiac myocytes. Methods Association of JP 2 with SK 2 channel in mouse heart tissue as well as HEK 293 cells was studied using in vivo and in vitro approaches. si RNA knockdown of JP 2 gene was assessed by real‐time PCR . The expression of proteins was analysed by Western blotting. Ca 2+ ‐activated K + current ( I K,Ca ) in infected adult mouse cardiac myocytes was recorded using whole‐cell voltage‐clamp technique. The intracellular Ca 2+ transient was measured using an IonOptix photometry system. Results We showed for the first time that JP 2 associates with the SK 2 channel in native cardiac tissue. JP 2, via the membrane occupation and recognition nexus ( MORN motifs) in its N‐terminus, directly interacted with SK 2 channels. A colocalization of the SK 2 channel with its interaction protein of JP 2 was found in the cardiac myocytes. Moreover, we demonstrated that JP 2 is necessary for the proper cell surface expression of the SK 2 channel in HEK 293. Functional experiments indicated that knockdown of JP 2 caused a significant decrease in the density of I K,Ca and reduced the amplitude of the Ca 2+ transient in infected cardiomyocytes. Conclusion The present data provide evidence that the functional interaction between JP 2 and SK 2 channels is present in the native mouse heart tissue. Junctophilin 2, as junctional membrane complex ( JMC ) protein, is an important regulator of the cardiac SK channels.