Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The rate of response to thyroid hormone on cardiac growth, heart rate, and the relative changes in messenger RNA (mRNA) coding for alpha- and beta-myosin heavy chain (MHC), slow sarcoplasmic reticulum calcium-adenosine triphosphatase, and thyroid hormone receptors in ventricular tissue of hypothyroid rats was investigated. Hypothyroid rats had significantly smaller hearts, with slower heart rates and expressed no alpha-MHC mRNA as analyzed by an S1 nuclease protection assay when compared to euthyroid animals that expressed 79% alpha-MHC. Twelve hours after treating hypothyroid rats with 20 micrograms of L-T4, detectable levels of alpha-MHC mRNA were present and the shift to alpha-MHC mRNA was complete by 72 h of treatment. Northern blot analysis showed that hypothyroidism resulted in a 60% decrease in the level of sarcoplasmic reticulum calcium-adenosine triphosphatase mRNA which increased after 12 h of T4 administration and was 2.5-fold (P less than 0.05) greater than euthyroid levels after 72 h. In contrast, thyroid hormone receptor mRNA levels measured in poly(A)+ RNA were elevated in hypothyroid rats and decreased to euthyroid levels within 24 h after thyroid hormone treatment. These changes in cardiac gene expression occurred simultaneously with changes in both cardiac size and heart rate. The current studies characterize the coordinated changes and the time course for gene expression that occur in the hypothyroid heart after acute T4 administration.
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PMID:Time course of the in vivo effects of thyroid hormone on cardiac gene expression. 131 35

We investigated the expression of myosin subunits (myosin heavy chains) as well as light chains and the in vivo phosphorylation of the phosphorylatable myosin light chain in the heart ventricle of the adult male European hamster (Cricetus cricetus L.). Two myosin heavy chain isoenzymes could be detected under native and denaturing electrophoretic conditions having high (alpha-myosin heavy chain) and low (beta-myosin heavy chain) enzymatic activity. Enzymatic activity of alpha- and beta-myosin heavy chain revealed a different temperature dependency. When temperature increased ATPase activity of the alpha-myosin heavy chain isoenzyme increased relatively more than ATPase activity of the beta-myosin heavy chain isoenzyme. Summer animals expressed predominantly the beta-myosin heavy chain (79% of total myosin) while during hibernation the alpha-myosin heavy chain expression increased to 53% of total myosin. Winter-active hamsters kept at 22 degrees C and 12 h day/night rhythm showed the same myosin heavy chain isoenzyme pattern as summer-active animals. Two myosin light chain forms were expressed in the ventricle of all animal groups. The in vivo phosphorylation level of the phosphorylatable myosin light chain decreased from 45% in summer-active hamster to 23% during hibernation.
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PMID:Expression of myosin heavy and light chains and phosphorylation of the phosphorylatable myosin light chain in the heart ventricle of the European hamster during hibernation and in summer. 131 40

The role of subcellular alterations in the process of heart failure remains ill-defined. Because contractile performance of failing heart muscle is depressed, possible alterations in the myosin molecule could be of particular relevance. There is increasing evidence that myofibrillar ATPase activity is reduced in congestive heart failure, whereas the findings on myosin ATPase are still controversial. The molecular causes of the reduced activity are currently not known. Because alpha-MHC is present only in small amounts in normal ventricles, a shift in favor of beta-MHC is of minor importance. Also immunohistochemical data on subspecies of beta-MHC seem not to provide an explanation. A new type of myosin heterogeneity was found by optimizing native polyacrylamide gel electrophoresis in the presence of pyrophosphate. Two bands (VA and VB) were observed in ventricles of patients with valvular disease. Because the two bands were detected also in normal hearts of large mammals, the existence of VA/VB cannot be diagnostic of diseased heart. However, the VA/VB ratio was influenced by the hemodynamic load, whereby the fast migrating band (VA) increased with the diastolic and systolic load. Because a relationship with the hemodynamic load was observed only in surgical muscle specimens, it appears that this heterogeneity is prone to post mortem modification. Further work is required to identify the molecular nature of this heterogeneity and to examine the therapeutic potential of a pharmacological modification of the VA/VB ratio.
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PMID:Structural and functional diversity of human ventricular myosin. 138 32

To investigate the relationship between the mechanical and biochemical properties of cardiac myosin, the sliding velocity of isolated cardiac myosin obtained from both euthyroid and hyperthyroid rabbits on actin cables was measured with an in vitro motility assay system. Ten rabbits (T) were treated with L-thyroxine to induce hyperthyroidism, and eight nontreated animals (N) were used as controls. Myosin was purified from the left ventricles of anesthetized animals. Myosin isozyme content was analyzed by the pyrophosphate gel electrophoresis method, and myosin adenosinetriphosphatase (ATPase) activity was determined on the same sample. Long well-organized actin cables of green algae, Nitellopsis, were used in the in vitro motility assay. Small latex beads were coated with purified cardiac myosin and introduced onto the Nitellopsis actin cables. Active unidirectional movement of the beads on the actin cables was observed under a photomicroscope, and the velocity was measured. The velocity was dependent on ATP concentrations, and the optimal pH for bead movement was approximately 7.0-7.5. The mean velocity was higher in T than in N (0.66 +/- 0.12 vs. 0.32 +/- 0.09 micron/s, P less than 0.01). Both Ca(2+)-activated ATPase activity and the percentage of alpha-myosin heavy chain were also higher in T than in N (0.691 +/- 0.072 vs. 0.335 +/- 0.072 microM Pi.mg-1.min-1, P less than 0.01, and 79 +/- 12 vs. 26 +/- 7%, P less than 0.01, respectively). The velocity of myosin closely correlated with both Ca(+2)-activated myosin ATPase activity (r = 0.87, P less than 0.01) and the percentage of alpha-myosin heavy chain (r = 0.87, P less than 0.01).
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PMID:Sliding velocity of isolated rabbit cardiac myosin correlates with isozyme distribution. 138 92

Prior studies have demonstrated the importance of hemodynamic loading in mediating thyroxine (T4)-induced cardiac hypertrophy. Direct cellular effects of thyroid hormone have been implicated in modulating the expression of the myosin heavy chain (MHC) genes and the slow sarcoplasmic reticulum calcium adenosine triphosphatase (SR Ca(2+)-ATPase) gene. In the present report, administration of T4 for 72 h did not stimulate growth of the hemodynamically unloaded heterotopic isograft. The synthetic rates of total cardiac proteins and MHC in the isograft remained significantly lower at 64 and 53% of the respective rates measured simultaneously in the in situ working heart. Although total left ventricle RNA content in the isograft was unchanged by T4, alpha-MHC and SR Ca(2+)-ATPase mRNA concentrations were increased 181 and 208%, respectively, and the previously observed beta-MHC expression was completely prevented. These data indicate that, although T4 requires an increased hemodynamic load to stimulate cardiac protein synthesis, it is capable of directly altering the expression of at least two myocyte-specific genes. Therefore some of the phenotypic alterations observed with thyroid hormone treatment are the result of direct effects of the hormones on specific cardiac genes and independent of changes in cardiac growth.
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PMID:Thyroid hormone effects on cardiac gene expression independent of cardiac growth and protein synthesis. 141 33

Cardiac adaptation to hemodynamic stress involves both quantitative (hypertrophy) and qualitative (pattern of gene expression) changes. Our previous studies have shown that advancing age in the rat is associated with diminished capacity to develop left ventricular hypertrophy in response to either ascending aortic constriction (AoC). In this study, we examined whether the expression of protooncogenes and contractile protein genes in response to AoC differs between adult (9-mo-old) and old (18-mo-old) rats. RNA was isolated from the left ventricles of AoC animals of both age groups subjected to a similar hemodynamic stress. Immediately after AoC, the levels of the ventricular expression of c-fos and c-jun protooncogenes were markedly lower in the old rats than in the adult animals. 5 d after the operation, the ratio of beta- to alpha-myosin heavy chain mRNAs increased significantly after AoC in both age groups. In contrast, AoC was associated with a marked reduction in the levels of mRNAs encoding sarcoplasmic reticulum Ca(2+)-ATPase (by 69%) and cardiac calsequestrin (by 49%) in the old rats but not in the adults. The mRNAs encoding atrial natriuretic factor and skeletal alpha-actin increased in response to AoC only in the adult rats. There were no significant differences in expression of the cardiac alpha-actin mRNA among the experimental groups. These data suggest that (a) the expression of protooncogenes in response to acute pressure overload is significantly reduced in the aged rats and (b) the pattern of expression of the contractile protein gene in response to AoC in the old rats differs qualitatively as well as quantitatively from that in younger animals. These age-related differences may play a role in the higher frequency of heart failure in the aged during hemodynamic stress.
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PMID:Age-related differences in the expression of proto-oncogene and contractile protein genes in response to pressure overload in the rat myocardium. 153 37

A combined enzyme-histochemical (ATPase reactivity) and immunohistochemical study has been performed on sections of rabbit masseter muscle. The majority of the fibres previously designated as type IIC and/or type I according to their ATPase activity were found to contain 'cardiac' alpha-myosin heavy chain in addition to other myosin heavy chains. All alpha-myosin heavy chain-containing fibres reveal ATPase activity after pre-incubation at pH 4.2-4.6 similar to that of the classical type I fibres, while, in that pH range, limb type IIC fibres show intermediate ATPase activity. One group of these fibres reveal ATPase activity after pre-incubation at pH 10.1-10.3 as well, but not at pH 10.4-10.5. These fibres contain exclusively either alpha- or alpha- and I-myosin heavy chains but do not contain the IIA-myosin heavy chain. The second part of the fibres reveals ATPase activity after treatment within the whole alkaline pre-incubation range (pH 10.1-10.5) and these fibres contain alpha-myosin and IIA-myosin but no I-myosin heavy chain. It is concluded that the classical IIC fibre type is not present in the rabbit masseter muscle. Furthermore, ATPase reactivity does not allow us to distinguish fibres on their myosin heavy chain content in rabbit masseter muscle.
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PMID:Presence of cardiac alpha-myosin correlates with histochemical myosin Ca2+ ATPase activity in rabbit masseter muscle. 153 66

Skinned fibers from the normal human heart with the beta-myosin heavy chain (ventricular fibers) revealed both a higher force generation per cross section and a higher Ca2+ sensitivity than skinned fibers with the alpha-myosin heavy chain (atrial fibers). The relation between isometric ATPase activity and isometric tension of atrial fibers was higher than that of ventricular fibers. Since the ATPase-tension relation equals the rate constant for the transition from force-generating into non-force-generating crossbridge states (g(app)), myosin heavy chain isoenzymes seem to have different crossbridge turnover kinetics. Modulation of g(app) by myosin heavy chain isoenzymes could explain the different contractile behavior of atrial and ventricular fibers. g(app) was independent of Ca2+.
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PMID:Modulation of crossbridge kinetics by myosin isoenzymes in skinned human heart fibers. 182 36

The mRNA encoding the sarcoplasmic reticulum (SR) Ca2+ ATPase is highly influenced by thyroid hormone (T3) in the hearts of intact animals. We show here that this effect of T3 can be mimicked in primary neonatal rat cardiocytes, both in serum-containing and in serum-free media; the expression of SR Ca2+ ATPase mRNA is myocyte-specific and is also modulated by retinoic acid (RA). RA also induces myosin heavy chain (MHC) alpha-mRNA in this system. The induction of Ca2+ ATPase mRNA is sensitive to T3 (EC50 approximately 30 pM) and less sensitive to RA (EC50 approximately 2 nM). Transient transfection experiments utilizing various segments of the Ca2+ATPase promoter fused to the reporter gene chloramphenicol acetyltransferase (CAT) indicate a minimal thyroid hormone response element (TRE) between nucleotides -262 and -322, while sequences between -322 and -559 are required for maximal trans-activation. RA is not able to regulate these constructs. Likewise, a clear effect of T3 but no effect of RA was observed when the CAT gene was driven by a TRE derived from the rat alpha-MHC gene. In contrast, CAT expression was induced by either hormone when placed under the control of a synthetic palindromic TRE. Taken together, these results indicate that T3 and RA induce gene expression in primary cardiac myocytes, but through distinct response elements and/or mechanisms.
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PMID:Influence of thyroid hormone and retinoic acid on slow sarcoplasmic reticulum Ca2+ ATPase and myosin heavy chain alpha gene expression in cardiac myocytes. Delineation of cis-active DNA elements that confer responsiveness to thyroid hormone but not to retinoic acid. 182 23

The mechanisms by which the aged heart adapts to a superimposed pressure load such as hypertension have not been described. We therefore investigated biochemical and molecular genetic adaptations in the 24-month-old rat heart subjected to renovascular hypertension. Compared with 4-month-old rats, aging was associated with a 68% increase in left ventricular mass without any change in heart weight-to-body weight ratio, a 33% reduction in calcium-activated myosin ATPase activity, and a shift from a V1 to a V3 predominant myosin heavy chain (MHC) isoform distribution. A 46% reduction in alpha-MHC mRNA and a reciprocal increase in beta-MHC mRNA was seen. When hypertension was superimposed, there was a further 75% increase in ventricular mass, a 63% increase in heart weight-to-body weight ratio, and a 19% reduction in myosin ATPase. Myosin isozyme distribution was further shifted to V3, and the ratio of alpha-MHC to beta-MHC mRNA was reduced. In addition, with hypertension a significant (greater than 50%) reduction in the mRNA level of the cardiac sarcoplasmic reticular calcium-activated ATPase was seen. These data demonstrate that the aged myocardium is able to respond to a superimposed pressure load with a molecular genetic and protein synthetic pattern of hypertrophy analogous to that seen in younger animals.
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PMID:Effect of aging and hypertension on myosin biochemistry and gene expression in the rat heart. 183 8


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