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At least 19 recordsLinked to original sources
PubMed1985

The calmodulin-dependent phosphorylation of cardiac myosin.

Cardiac myosin light chains are phosphorylated in vivo and in vitro. The enzyme myosin light-chain kinase, has been purified and found to be very specific for cardiac myosin light chains. Experiments with skinned cardiac fibers suggest that phosphorylation of myosin light chain-2-decreases ATP consumption, presumably by lowering the cross-bridge cycle. These results are discussed in this chapter.

Animals↗
PubMed1980

Localization of g2 light chain in the link between the heads and tail of cardiac myosin.

Cardiac myosin liberated 1.99 mol of acetate per mol after acid hydrolysis. The myosin subfragment-1, which cannot bind g2 light chain, liberated 0.85-1.16 mol of acetate per mol. On the other hand, negligible amounts of acetate could be detected from g1 and g2 light chains. The acetates, which were measured by a microenzymic method, were derived from the acetylated N-terminal of the heavy chain. It was concluded that g2 light chain is bound to the C-terminal region of subfragment-1, which is the link between the heads and tail of myosin.

Acetates↗
PubMed2000

Reactivity of rheumatic fever and scarlet fever patients' sera with group A streptococcal M protein, cardiac myosin, and cardiac tropomyosin: a retrospective study.

Archived sera (collected in 1946) from acute rheumatic fever (ARF) and untreated scarlet fever and/or pharyngitis patients were reacted with streptococcal M protein, cardiac myosin, and cardiac tropomyosin. Except for very low levels to tropomyosin, antibodies to other antigens were not elevated in the sera of ARF patients relative to those of non-ARF patients, even though there was roughly equivalent exposure to group A streptococci. This suggests that antibodies to these molecules may not play a central role in the induction of ARF.

Acute Disease↗
PubMed1975

Effect of the thyroid state on the enzymatic characteristics of cardiac myosin. A difference in behavior of rat and rabbit cardiac myosin.

The effect of thyroid state on the activity of myosin adenosinetriphosphatase (ATPase) was examined in the rat and the rabbit. Cardiac myosin from thyroxine-treated rabbits showed enzymatic properties characterized by high Ca2plus-activated ATPase activity, low activation energy, lower rate of inactivation at alkaline pH, and no activation by N-ethylmaleimide compared with the same properties in the normal rabbit; thyroidectomy did not affect the enzymatic properties of rabbit cardiac myosin. These findings suggest a difference in the myosin molecule at or near the active site, involving some sulfhydryl groups, between hyperthyroid and euthyroid rabbits. However, rat cardiac myosin showed a pattern of activity in the euthyroid state similar to that of the hyperthyroid rabbit and changed to the euthyroid type after thyroidectomy. These changes were specific for cardiac myosin, since no change was observed in skeletal myosin. It is unlikely that there are major differences in the myosin molecule associated with the two types of activity, since similar proportion and amino acid composition of the subunits of cardiac myosin were observed in the different thyroid states. Thus, we concluded that the administration of thyroxine to the rabbit stimulates the synthesis of new cardiac myosin with altered enzymatic properties and that synthesis of this type of cardiac myosin is maintained by the normal level of thyroid hormone in the rat.

Adenosine Triphosphatases↗
PubMed2006

A molecular screening strategy based on beta-myosin heavy chain, cardiac myosin binding protein C and troponin T genes in Italian patients with hypertrophic cardiomyopathy.

BACKGROUND: Mutations causing hypertrophic cardiomyopathy (HCM) have been described in nine different genes of the sarcomere. Three genes account for most known mutations: beta-myosin heavy chain (MYH7), cardiac myosin binding protein C (MYBPC3) and cardiac troponin T (TNNT2). Their prevalence in Italian HCM patients is unknown. Thus, we prospectively assessed a molecular screening strategy of these three genes in a consecutive population with HCM from two Italian centres. METHODS: Comprehensive screening of MYBPC3, MYH7 and TNNT2 was performed in 88 unrelated HCM patients by denaturing high-performance liquid chromatography and automatic sequencing. RESULTS: We identified 32 mutations in 50 patients (57%); 16 were novel. The prevalence rates for MYBPC3, MYH7 and TNNT2 were 32%, 17% and 2%, respectively. MYBPC3 mutations were 18, including two frameshift, five splice-site and two nonsense. All were 'private' except insC1065 and R502Q, present in three and two patients, respectively. Moreover, E258K was found in 14% of patients, suggesting a founder effect. MYH7 mutations were 12, all missense; seven were novel. In TNNT2, only two mutations were found. In addition, five patients had a complex genotype [i.e. carried a double MYBPC3 mutation (n = 2), or were double heterozygous for mutations in MYBPC3 and MYH7 (n = 3)]. CONCLUSIONS: The first comprehensive evaluation of MYBPC3, MYH7 and TNNT2 in an Italian HCM population allowed a genetic diagnosis in 57% of the patients. These data support a combined analysis of the three major sarcomeric genes as a rational and cost-effective initial approach to the molecular screening of HCM.

Cardiomyopathy, Hypertrophic↗
PubMed1997

Molecular mimicry between cardiac myosin and Trypanosoma cruzi antigen B13: identification of a B13-driven human T cell clone that recognizes cardiac myosin.

Previous reports from our group have demonstrated the association of molecular mimicry between cardiac myosin and the immunodominant Trypanosoma cruzi protein B13 with chronic Chagas' disease cardiomyopathy at both the antibody and heart-infiltrating T cell level. At the peripheral blood level, we observed no difference in primary proliferative responses to T. cruzi B13 protein between chronic Chagas' cardiopathy patients, asymptomatic chagasics and normal individuals. In the present study, we investigated whether T cells sensitized by T. cruzi B13 protein respond to cardiac myosin. T cell clones generated from a B13-stimulated T cell line obtained from peripheral blood of a B13-responsive normal donor were tested for proliferation against B13 protein and human cardiac myosin. The results showed that one clone responded to B13 protein alone and the clone FA46, displaying the highest stimulation index to B13 protein (SI = 25.7), also recognized cardiac myosin. These data show that B13 and cardiac myosin share epitopes at the T cell level and that sensitization of a T cell with B13 protein results in response to cardiac myosin. It can be hypothesized that this also occurs in vivo during T. cruzi infection which results in heart tissue damage in chronic Chagas' disease cardiomyopathy.

Animals↗
PubMed1979

Thyroid hormone stimulates synthesis of a cardiac myosin isozyme. Comparison of the two-two-dimensional electrophoretic patterns of the cyanogen bromide peptides of cardiac myosin heavy chains from euthyroid and thyrotoxic rabbits.

The CNBr peptides of [14C]carboxymethylated cardiac myosin heavy chains from euthyroid and thyrotoxic rabbits have been compared using a two-dimensional electrophoretic system. The results indicated that there were extensive differences in the peptide "maps" of these heavy chains, which included differences in the distribution of radiolabeled thiol peptides. Also, the patterns of heavy chain peptides from the cardiac myosins have been compared with those produced by the heavy chain myosin isozymes from skeletal muscles. Peptide maps of heavy chains from red skeletal muscle myosin closely resembled the pattern of peptides found with cardiac myosin heavy chains from euthyroid rabbits. However, peptide maps of heavy chains from white skeletal muscle myosin were dissimilar to those of the cardiac myosin isozymes. We conclude that thyroxine administration stimulates the synthesis of a cardiac myosin isozyme with a heavy chain primary structure which is different from either of the skeletal muscle myosin isozymes.

Adenosine Triphosphatases↗
PubMed1978

Detection of serum cardiac myosin light chains in acute experimental myocardial infarction: radioimmunoassay of cardiac myosin light chains.

To develop a more specific plasma test for myocardial infarction, antibodies specific for cardiac myosin light chains (CM-LC) were elicited that showed less than 3% cross-reactivity with skeletal muscle light chains. These antibodies were used to develop a radioimmunoassay for CM-LC that had a sensitivity of 20 ng (+/- 4 SD; P less than 0.001). Normal dog plasma showed no measurable concentrations of CM-LC (n = 6). Plasma samples from 10 dogs with experimental myocardial infarction produced by persistent left anterior descending coronary artery (LAD) occlusion were obtained at 0, 2, 4, 6, 24, 48 and 72 hours. CM-LC were first detectable in all 10 animals 6 hours after occlusion (97.98 +/- 14 ng/ml [mean +/- SEM]; P less than 0.001). Maximal CM-LC levels were usually obtained between 24 and 48 hours. Sham-operated open chest dogs (0--48 hours, n = 3) showed no measurable CM-LC in the plasma samples. Another group of 10 dogs were subjected to 5 hours of LAD occlusion, followed by reperfusion. In four dogs, CM-LC were detectable as early as 1 hour after reperfusion (81.88 +/- 37.75 ng/ml serum). Sera from all 10 dogs showed elevated levels of CM-LC (199.75 +/- 24.0 ng/ml) by 24 hours. Peak CM-LC concentrations were obtained in five dogs at 24 hours (247.0 +/- 35.28 ng/ml) and in another dog at 120 hours (245 ng/ml). Histochemical infarct size was determined to be 0.5--10% of the left ventricular mass at seven days by triphenyltetrazolium chloride staining. The specificity and sensitivity of this radioimmunoassay for detection of CM-LC, unique proteins to the heart, may be valuable in the diagnosis of myocardial infarction.

Acute Disease↗
PubMed2000

Chronic myocarditis induced by T cells reactive to a single cardiac myosin peptide: persistent inflammation, cardiac dilatation, myocardial scarring and continuous myocyte apoptosis.

Recent recognition that an autoimmune myocarditis may precede, and result in, dilated cardiomyopathy has focused attention on immune mechanisms of myocardial injury. In this paper, we describe a model of chronic autoimmune myocarditis in the Lewis rat. The production of myocarditis has been previously described by this group and in brief is accomplished by a single tail vein infusion of activated T cells specific for a 17-amino acid peptide from rat cardiac myosin. In this report, animals were followed for approximately 6 months post-T-cell infusion. Hearts from animals which received cardiac myosin specific T cells all showed extensive fibrosis associated with ongoing inflammation. Apoptosis, identified by TdT-mediated dUTP nick end labelling (TUNEL), was identified as a mode of myocyte death in hearts with acute and chronic myocarditis but not in age- and sex-matched controls. Immunohistochemistry was used to characterize the immune infiltrate and adhesion molecules in hearts with chronic myocarditis and these findings were compared to hearts with acute myocarditis. We propose that this rat model of chronic myocarditis mimics human disease, since inflammation results in ventricular dilatation and myocyte hypertrophy reminiscent of dilated cardiomyopathy. This model offers potential for further investigation of immune, functional and possible therapeutic aspects of autoimmune related cardiomyopathies.

Adoptive Transfer↗
PubMed2001

A peptide fragment of beta cardiac myosin heavy chain (beta-CMHC) can provoke autoimmune myocarditis as well as the corresponding alpha cardiac myosin heavy chain (alpha-CMHC) fragment.

The validity of the general belief that alpha cardiac myosin heavy chain (alpha-CMHC) is primarily responsible for causing experimental autoimmune myocarditis because of the more profound tolerance induction to beta-CMHC due to its expression during the embryonic stage has been examined. In order to completely avoid cross-contamination among components of the two myosin heavy chains, recombinant myosin fragments were synthesized in Escherichia coli using cDNA fragments of rat alpha- and beta-CMHC cloned by reverse transcription polymerase chain reaction (RT-PCR). Two fragments corresponding to amino acid residues 1107-1164 derived from alpha- and beta-heavy chains were equally capable of provoking severe myocarditis in Lewis rats when immunized in complete Freund's adjuvant. No significant differences in the severity, as judged from histological scoring, were observed between the diseases induced by the two different peptide fragments, indicating conclusively that beta-CMHC is as pathogenic as alpha-CMHC.

Amino Acid Sequence↗
PubMed1977

Studies on adenosine triphosphatase activity of rat cardiac myosin in isoproterenol-induced cardiac hypertrophy.

Ca2+- and K+ -activated ATPase activity of cardiac myosin from normal and hypertrophied rat hearts was investigated. Cardiac hypertrophy was induced by isoproterenol treatment. A nearly 40% increase in heart mass was seen after seven consecutive days of isoproterenol injection (5 mg/kg) as determined by either heart weight expressed as per cent of body weight or by dry heart weight and total protein content. The measurement of ATP hydrolysis revealed that cardiac myosin from isoproterenol-treated rats had a significant decrease (P less than 0.01) in Ca2+-activated ATPase activity at low ionic strength (0.05 M KCl) in the presence of 5 and 10 mM Ca2+. In contrast, in a high ionic strength medium (0.50 M KCl) the K+- and Ca2+-activated ATPase activity of myosin prepared from hypertrophied myocardium remained unchanged. Comparative analysis of protein present in the light chains of myosin showed no alteration in the proportion of LC1 to LC2 in the myosin from hypertrophied hearts, however, a decrease in the absorption of myosin in the u.v. region was observed. On the basis of our results one can hypothesize that there may be some conformational change in the myosin molecule from hypertrophied myocardium, thereby modifying both Ca2+-sensitivity and ATPase activity at a low KCl concentration.

Animals↗
PubMed1985

Biochemical characteristics of cardiac myosin: the pH dependence of Ca-ATPase activity, and that of the absorption spectrum of 2,4,6-trinitrophenyl groups attached to myosin.

For both cardiac and skeletal myosin, the Ca-ATPase activity of myosin at acidic pH was shown to be different from that at alkaline pH, in the susceptibility to heat-inactivation, the effects of organic solvents, and the effect of trinitrophenylation of the myosin. It is therefore suggested that there are two different types of Ca-ATPase of both cardiac and skeletal myosin. Differences in the Ca-ATPase activity were also found between cardiac and skeletal myosins. (a) The Ca-ATPase activity of cardiac myosin was more susceptible to heat-inactivation at alkaline pH than at acidic pH. In contrast, the activity of skeletal myosin was more susceptible to heat-inactivation at acidic pH than at alkaline pH. (b) Dioxane weakly stimulated the activity of cardiac myosin at acidic pH, but strongly activated that of skeletal myosin at acidic pH. Acetone very strongly inhibited the activity of cardiac myosin at alkaline pH, but not so strongly that of skeletal myosin at alkaline pH. (c) Trinitrophenylation of the myosin resulted in loss of the activity optimum at acidic pH with skeletal myosin but not with cardiac myosin. As reported by Srivastava et al. (J. Biochem. 86, 725-731, 1979), 1 mol of lysine residue per mol of cardiac myosin quickly reacted with 2,4,6-trinitrobenzene sulfonate (TNBS) either in the absence or presence of inorganic pyrophosphate (PPi). However, trinitrophenyl (TNP) groups bound to cardiac myosin in the presence of PPi were significantly different, in the pH dependence of the absorption spectrum, from those bound (to cardiac myosin) in the absence of PPi.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗