A cardiac myosin light chain kinase regulates sarcomere assembly in the vertebrate heart
Osamu Seguchi, Seiji Takashima, Satoru Yamazaki, Masanori Asakura,, Yoshihiro Asano, Yasunori Shintani, Masakatsu Wakeno, Tetsuo Minamino, Hiroya Kondo, Hidehiko Furukawa, Kenji Nakamaru, Asuka Naito,, Tomoko Takahashi, Toshiaki Ohtsuka, Koichi Kawakami, Tadashi Isomura,, Soichiro Kitamura, Hitonobu Tomoike, Naoki Mochizuki, Masafumi Kitakaze
Osamu Seguchi, Seiji Takashima, Satoru Yamazaki, Masanori Asakura,, Yoshihiro Asano, Yasunori Shintani, Masakatsu Wakeno, Tetsuo Minamino, Hiroya Kondo, Hidehiko Furukawa, Kenji Nakamaru, Asuka Naito,, Tomoko Takahashi, Toshiaki Ohtsuka, Koichi Kawakami, Tadashi Isomura,, Soichiro Kitamura, Hitonobu Tomoike, Naoki Mochizuki, Masafumi Kitakaze
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Research Article Cardiology

A cardiac myosin light chain kinase regulates sarcomere assembly in the vertebrate heart

Abstract

Marked sarcomere disorganization is a well-documented characteristic of cardiomyocytes in the failing human myocardium. Myosin regulatory light chain 2, ventricular/cardiac muscle isoform (MLC2v), which is involved in the development of human cardiomyopathy, is an important structural protein that affects physiologic cardiac sarcomere formation and heart development. Integrated cDNA expression analysis of failing human myocardia uncovered a novel protein kinase, cardiac-specific myosin light chain kinase (cardiac-MLCK), which acts on MLC2v. Expression levels of cardiac-MLCK were well correlated with the pulmonary arterial pressure of patients with heart failure. In cultured cardiomyocytes, knockdown of cardiac-MLCK by specific siRNAs decreased MLC2v phosphorylation and impaired epinephrine-induced activation of sarcomere reassembly. To further clarify the physiologic roles of cardiac-MLCK in vivo, we cloned the zebrafish ortholog z–cardiac-MLCK. Knockdown of z–cardiac-MLCK expression using morpholino antisense oligonucleotides resulted in dilated cardiac ventricles and immature sarcomere structures. These results suggest a significant role for cardiac-MLCK in cardiogenesis.

Authors

Osamu Seguchi, Seiji Takashima, Satoru Yamazaki, Masanori Asakura,, Yoshihiro Asano, Yasunori Shintani, Masakatsu Wakeno, Tetsuo Minamino, Hiroya Kondo, Hidehiko Furukawa, Kenji Nakamaru, Asuka Naito,, Tomoko Takahashi, Toshiaki Ohtsuka, Koichi Kawakami, Tadashi Isomura,, Soichiro Kitamura, Hitonobu Tomoike, Naoki Mochizuki, Masafumi Kitakaze

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Figure 5

Cardiac-MLCK is highly conserved in several vertebrates, including zebra­fish.

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Cardiac-MLCK is highly conserved in several vertebrates, including zebra...
(A) Cardiac-MLCK is evolutionarily conserved in vertebrates, including humans (Hu), dogs (Ca), mice (Mm), chickens (Gg), and zebrafish (z), with the highest degree of homology in the C-terminal portion of the serine/threonine kinase domain. Black backgrounds indicate identical amino acids. Amino acids in the ATP-binding region are shown in blue; those in the kinase active site are shown in red. (B–I) Whole-mount in situ hybridizations depict the expression of z–cardiac-MLCK (z-cMK) in zebrafish embryos hybridized with z–cardiac-MLCK–specific antisense probe (B, C, F, and G) or z–cardiac-MLCK sense probe (D, E, H, and I). At 24 hpf, z–cardiac-MLCK was expressed in heart precursor cells (arrow). At 48 hpf, z–cardiac-MLCK was selectively expressed in the heart (asterisks denote atrium [a] and ventricle [v]).