Identification of a new co-factor, MOG1, required for the full function of cardiac sodium channel Nav 1.5.
The cardiac sodium channel Nav 1.5 is essential for the physiological function of the heart and contributes to lethal cardiac arrhythmias and sudden death when mutated. Here, we report that MOG1, a small protein that is highly conserved from yeast to humans, is a central component of the channel complex and modulates the physiological function of Nav 1.5. The yeast two-hybrid screen identified MOG1 as a new protein that interacts with the cytoplasmic loop II (between transmembrane domains DII and DIII) of Nav 1.5. The interaction was further demonstrated by both in vitro glutathione S-transferase pull-down and in vivo co-immunoprecipitation assays in both HEK293 cells with co-expression of MOG1 and Nav1.5 and native cardiac cells. Co-expression of MOG1 with Nav1.5 in HEK293 cells increased sodium current densities. In neonatal myocytes, overexpression of MOG1 increased current densities nearly 2-fold. Western blot analysis revealed that MOG1 increased cell surface expression of Nav1.5, which may be the underlying mechanism by which MOG1 increased sodium current densities. Immunostaining revealed that in the heart, MOG1 was expressed in both atrial and ventricular tissues with predominant localization at the intercalated discs. In cardiomyocytes, MOG1 is mostly localized in the cell membrane and co-localized with Nav1.5. These results indicate that MOG1 is a critical regulator of sodium channel function in the heart and reveal a new cellular function for MOG1. This study further demonstrates the functional diversity of Nav1.5-binding proteins, which serve important functions for Nav1.5 under different cellular conditions.
Wu
Ling
L
Department of Molecular Cardiology, Lerner Research Institute, Center for Cardiovascular Genetics, Tausig Cancer Center, Cleveland Clinic, Cleveland, Ohio 44195, USA.
Yong
Sandro L
SL
Fan
Chun
C
Ni
Ying
Y
Yoo
Shin
S
Zhang
Teng
T
Zhang
Xianqin
X
Obejero-Paz
Carlos A
CA
Rho
Hyun-Jin
HJ
Ke
Tie
T
Szafranski
Przemyslaw
P
Jones
Stephen W
SW
Chen
Qiuyun
Q
Wang
Qing Kenneth
QK
D000818:Animals; D000831:Animals, Newborn; D004594:Electrophysiology / Q000379:methods; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D006321:Heart / Q000502:physiology; D006801:Humans; D051379:Mice; D008808:Mice, Inbred CBA; D008954:Models, Biological; D009124:Muscle Proteins / Q000737:chemistry*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D015222:Sodium Channels / Q000737:chemistry*; D020798:Two-Hybrid System Techniques; D020931:ran GTP-Binding Protein / Q000737:chemistry / Q000502:physiology*
D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human; C568321:Scn5a protein, mouse; D015222:Sodium Channels; D005982:Glutathione Transferase; C498735:RANGNRF protein, human; C498736:Rangnrf protein, mouse; D020931:ran GTP-Binding Protein