A single serine in the carboxyl terminus of cardiac essential myosin light chain-1 controls cardiomyocyte contractility in vivo.
Although it is well known that mutations in the cardiac essential myosin light chain-1 (cmlc-1) gene can cause hypertrophic cardiomyopathy, the precise in vivo structural and functional roles of cMLC-1 in the heart are only poorly understood. We have isolated the zebrafish mutant lazy susan (laz), which displays severely reduced contractility of both heart chambers. By positional cloning, we identified a nonsense mutation within the zebrafish cmlc-1 gene to be responsible for the laz phenotype, leading to expression of a carboxyl-terminally truncated cMLC-1. Whereas complete loss of cMLC-1 leads to cardiac acontractility attributable to impaired cardiac sarcomerogenesis, expression of a carboxyl-terminally truncated cMLC-1 in laz mutant hearts is sufficient for normal cardiac sarcomerogenesis but severely impairs cardiac contractility in a cell-autonomous fashion. Whereas overexpression of wild-type cMLC-1 restores contractility of laz mutant cardiomyocytes, overexpression of phosphorylation site serine 195-deficient cMLC-1 (cMLC-1(S195A)) does not reconstitute cardiac contractility in laz mutant cardiomyocytes. By contrast, introduction of a phosphomimetic amino acid on position 195 (cMLC-1(S195D)) rescues cardiomyocyte contractility, demonstrating for the first time an essential role of the carboxyl terminus and especially of serine 195 of cMLC-1 in the regulation of cardiac contractility.
Meder
Benjamin
B
Department of Medicine III, University of Heidelberg, Heidelberg, Germany.
Laufer
Christina
C
Hassel
David
D
Just
Steffen
S
Marquart
Sabine
S
Vogel
Britta
B
Hess
Alexander
A
Fishman
Mark C
MC
Katus
Hugo A
HA
Rottbauer
Wolfgang
W
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018389:Codon, Nonsense; D005038:Ethylnitrosourea / Q000633:toxicity; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D006321:Heart / Q000187:drug effects / Q000196:embryology*; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D053580:Muscle Strength; D009153:Mutagens / Q000633:toxicity; D009200:Myocardial Contraction / Q000235:genetics; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D018994:Myosin Light Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D012518:Sarcomeres / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine; D013997:Time Factors; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C532158:Cmlc1 protein, zebrafish; D018389:Codon, Nonsense; D009153:Mutagens; D018994:Myosin Light Chains; D029961:Zebrafish Proteins; D012694:Serine; D005038:Ethylnitrosourea