The Overexpression of S105N Mutant Rad Leads Intracellular Ca2+ Overload Via Up-Regulation of Cardiac Ryanodine Receptor Activity

Hiroyuki Yamakawa, Mitsushige Murata, Hirotaka Yada, Mika Mizusawa, Shugo Tohyama, Yasuyuki Ohgino, Shinsuke Yuasa, Shinji Makino, Motoaki Sano, Keiichi Fukuda, Tomoyuki Suzuki, Kaichiro Kamiya

Research output: Contribution to journalArticle


Background: The ras-related small G-protein Rad was originally identified from skeletal muscle of patients with type 2 diabetes mellitus. We have recently reported that Rad plays a critical role in generating arrhythmias. The study was aimed to elucidate the role of Rad in intracellular calcium homeostasis. Methods and Reslts: We developed the transgenic mice that overexpress S105N mutant Rad driven by α-myosin heavy chain promoter. We mesure intracellular Ca concentration ([Ca2+]I) from isolated cardiomyocytes by confocal microscopy. The amplitude of [Ca2+]I transient was significantly increased in S105N-Rad-TG cardiomyocytes, compared with littermate. Furthermore, the Ca2+ sparks and the spontaneous Ca2+ waves occurred with greater frequency in S105N-Rad-TG cells, implicating the enhanced activity of SERCA. We recorded L-type calcium currents (ICa-L) and action potentials (APs) from isolated cardiomyocytes using whole cell patch-clamp technique. The peak ICa-L was dramatically larger in the S105N-Rad-TG cells than in littermate. Early afterdepolarization (EAD) and delayed afterdepolarization (DAD) were frequently observed in S105N-Rad-TG. Then, the phosphorylation of RYR2 at Ser2809 and PKA was significantly enhanced in S105N-Rad-TG by Western blot. Conclusions: Our results provided the first evidence that Rad might regulate RYR2 activity possibly via downstream of PKA signaling pathway.

Original languageEnglish
Pages (from-to)275
Number of pages1
JournalJournal of Arrhythmia
Issue number4
Publication statusPublished - 2011



  • Ca homeostasis
  • delayed afterdepolarization (DAD)
  • small G protein

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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