Alpha1 catalytic subunit of AMPK modulates contractile function of cardiomyocytes through phosphorylation of troponin I.
OBJECTIVE
The specific role of AMPKα1 or AMPKα2 in mediating cardiomyocyte contractile function remains elusive. The present study investigated how AMPK activation modulates the contractility of isolated cardiomyocytes.


METHODS
Mechanical properties and intracellular Ca(2+) properties were measured in isolated cardiomyocytes. The stress signaling was evaluated using western blot and immunoprecipitation analysis.


RESULTS
AMPK activator, A-769662 induced maximal velocity of shortening (+dL/dt) and relengthening (-dL/dt), peak height and peak shortening (PS) amplitude in both WT and AMPKα2 KO cardiomyocytes, but did not affect time-to-90% relengthening (TR90). AMPK KD cardiomyocytes demonstrated contractile dysfunction compared with cardiomyocytes from WT and AMPKα2 KO hearts. However, the rise of intracellular Ca(2+) levels as well as intracellular ATP levels has no significant difference among WT, AMPKα2 KO and AMPK KD groups with and without the presence of A-769662. Besides, WT, AMPKα2 KO and AMPK KD group displayed a phosphorylated AMPK and downstream acetyl-CoA carboxylase (ACC) phosphorylation. Interestingly, A-769662 also triggered troponin I (cTnI) phosphorylation at Ser(149) site which is related to contractility of cardiomyocytes. Furthermore, the immunoprecipitation analysis revealed that AMPKα1 of cardiomyocytes was phosphorylated by A-769662.


CONCLUSIONS
This is the first study illustrating that activation of AMPK plays a significant role in mediating the contractile function of cardiomyocytes using transgenic animal models. AMPK activator facilitates the contractility of cardiomyocytes via activating AMPKα1 catalytic subunit. The phosphorylation of cTnI by AMPK could be a factor attributing to the regulation of contractility of cardiomyocytes.
Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo - State University of New York, Buffalo, NY, United States.
Si
S
Chen
Department of Cardiovascular Surgery, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China.
Ping
P
Zhu
Department of Cardiovascular Surgery, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China.
Hui-Ming
HM
Guo
Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin - Madison, WI, United States.
Raquel Sancho
RS
Solis
Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo - State University of New York, Buffalo, NY, United States.
Yanqing
Y
Wang
Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo - State University of New York, Buffalo, NY, United States.
Yina
Y
Ma
Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo - State University of New York, Buffalo, NY, United States.
Jinli
J
Wang
Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo - State University of New York, Buffalo, NY, United States.
Junjie
J
Gao
Department of Cardiovascular Surgery, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China.
Ji-Mei
JM
Chen
Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin - Madison, WI, United States.
Ying
Y
Ge
Department of Cardiovascular Surgery, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China. Electronic address: zhuangjianzggd@yahoo.cn.
Jian
J
Zhuang
Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo - State University of New York, Buffalo, NY, United States. Electronic address: jli23@buffalo.edu.
Ji
J
Li
D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D001713:Biphenyl Compounds; D015151:Immunoblotting; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D011753:Pyrones / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013876:Thiophenes / Q000494:pharmacology; D019210:Troponin I / Q000378:metabolism*
D001713:Biphenyl Compounds; D011753:Pyrones; D013876:Thiophenes; D019210:Troponin I; D055372:AMP-Activated Protein Kinases; C512408:4-hydroxy-3-(4-(2-hydroxyphenyl)phenyl)-6-oxo-7H-thieno(2,3-b)pyridine-5-carbonitrile
AMPK; Contractile function; Troponin I