Familial hypertrophic cardiomyopathy-linked alterations in Ca2+ binding of human cardiac myosin regulatory light chain affect cardiac muscle contraction.
The ventricular isoform of human cardiac regulatory light chain (HCRLC) has been shown to be one of the sarcomeric proteins associated with familial hypertrophic cardiomyopathy (FHC), an autosomal dominant disease characterized by left ventricular and/or septal hypertrophy, myofibrillar disarray, and sudden cardiac death. Our recent studies have demonstrated that the properties of isolated HCRLC could be significantly altered by the FHC mutations and that their detrimental effects depend upon the specific position of the missense mutation. This report reveals that the Ca(2+) sensitivity of myofibrillar ATPase activity and steady-state force development are also likely to change with the location of the specific FHC HCRLC mutation. The largest effect was seen for the two FHC mutations, N47K and R58Q, located directly in or near the single Ca(2+)-Mg(2+) binding site of HCRLC, which demonstrated no Ca(2+) binding compared with wild-type and other FHC mutants (A13T, F18L, E22K, P95A). These two mutants when reconstituted in porcine cardiac muscle preparations increased Ca(2+) sensitivity of myofibrillar ATPase activity and force development. These results suggest the importance of the intact Ca(2+) binding site of HCRLC in the regulation of cardiac muscle contraction and imply its possible role in the regulatory light chain-linked pathogenesis of FHC.
Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, Florida 33136, USA. dszczesna@med.miami.edu
Danuta
D
Szczesna-Cordary
Georgianna
G
Guzman
Shuk-Shin
SS
Ng
Jiaju
J
Zhao
D000251:Adenosine Triphosphatases / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D024741:Cardiomyopathy, Hypertrophic, Familial / Q000235:genetics* / Q000378:metabolism*; D002478:Cells, Cultured; D002942:Circular Dichroism; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009200:Myocardial Contraction; D018994:Myosin Light Chains / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms; D017386:Sequence Homology, Amino Acid; D013552:Swine
D018076:DNA, Complementary; D018994:Myosin Light Chains; D020033:Protein Isoforms; D000251:Adenosine Triphosphatases; D002118:Calcium