Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have identified and highly purified a "low Km" cAMP phosphodiesterase from bovine cardiac muscle. This phosphodiesterase was inhibited by low concentrations of cGMP and has, therefore, been temporarily designated as cGMP-inhibited phosphodiesterase. After a 16,000-fold increase in specific activity, the highly purified enzyme had a specific activity of 6 mumol/min-mg and contained three major polypeptides. Initial data indicated that all of these polypeptides were derived from a single common precursor by proteolysis. We used this enzyme preparation to generate polyclonal antisera and monoclonal antibodies directed against the "low Km" phosphodiesterase. Immunoadsorption and immunoblot analysis allowed us to identify and isolate several molecular weight species of phosphodiesterase, including a larger form than previously reported for any purified low Km phosphodiesterase. This large form of the enzyme had a subunit molecular weight of approximately 110,000 and was the only one seen in fresh extracts of cardiac muscle. Full catalytic activity was recovered in the phosphodiesterase-antibody complex and enzyme prepared by immunoprecipitation exhibited Michaelis-Menten kinetics for cAMP hydrolysis and for inhibition by cGMP. The Km for cAMP hydrolysis was 0.15 microM and the Ki for cGMP inhibition of cAMP hydrolysis was 0.06 microM. This immunoprecipitation approach also allowed us to determine that the enzyme was phosphorylated on serine residues by cAMP-dependent protein kinase, and that the low Km, cGMP-inhibited phosphodiesterase was selectively inhibited by several new cardiotonic agents. Milrinone, amrinone, and fenoximone were highly selective inhibitors of this isozyme, and the relative affinities of these inhibitors were consistent with their order of potency as positive inotropic agents. These studies suggest that the cGMP-inhibited phosphodiesterase is a receptor for several new cardiotonic drugs.
Mol Pharmacol 1986 May
PMID:Isolation and characterization of bovine cardiac muscle cGMP-inhibited phosphodiesterase: a receptor for new cardiotonic drugs. 301 79

Our previous data suggested that, in cardiac muscle sarcoplasmic reticulum fragments, GTP hydrolysis occurs by an alternative enzyme cycle of the Ca2+ ATPase which is insensitive to (Ca2+) and does not involve an acyl phosphate intermediate. Despite this, GTP induces the incorporation of calcium into a membrane pool that is not translocated to the vesicular lumen. The present study suggests that this GTP-induced intermediate calcium pool is identical to a modulable component of the calcium translocation process in that: it has an identical pH sensitivity; the initial incorporation of calcium in response to GTP eliminates the initial rapid burst and lag component of the typical ATP-induced calcium uptake curve when ATP is added during GTP-induced calcium accumulation. Instead, the addition of ATP during GTP-induced calcium accumulation results in the prompt onset of the linear phase of calcium translocation; GTP-induced calcium accumulation directly affects the pH sensitivity of subsequent ATP-induced calcium accumulation. We suggest that the intermediate calcium pool is in series with calcium translocation and is the site of the pH sensitivity observed in calcium flux.
J Mol Cell Cardiol 1986 Aug
PMID:Roussel award for cardiology. The mechanism of nucleotide induced calcium translocation across sarcoplasmic reticulum membranes: evidence for a non-translocated intermediate pool of calcium. 301 65

A chimeric plasmid containing about 2/3 of the rat skeletal muscle actin gene plus 730 base pairs of its 5' flanking sequences fused to the 3' end of a human embryonic globin gene (D. Melloul, B. Aloni, J. Calvo, D. Yaffe, and U. Nudel, EMBO J. 3:983-990, 1984) was inserted into mice by microinjection into fertilized eggs. Eleven transgenic mice carrying the chimeric gene with or without plasmid pBR322 DNA sequences were identified. The majority of these mice transmitted the injected DNA to about 50% of their progeny. However, in transgenic mouse CV1, transmission to progeny was associated with amplification or deletion of the injected DNA sequences, while in transgenic mouse CV4 transmission was distorted, probably as a result of insertional mutagenesis. Tissue-specific expression was dependent on the removal of the vector DNA sequences from the chimeric gene sequences prior to microinjection. None of the transgenic mice carrying the chimeric gene together with plasmid pBR322 sequences expressed the introduced gene in striated muscles. In contrast, the six transgenic mice carrying the chimeric gene sequences alone expressed the inserted gene specifically in skeletal and cardiac muscles. Moreover, expression of the chimeric gene was not only tissue specific, but also developmentally regulated. Similar to the endogenous skeletal muscle actin gene, the chimeric gene was expressed at a relatively high level in cardiac muscle of neonatal mice and at a significantly lower level in adult cardiac muscle. These results indicate that the injected DNA included sufficient cis-acting control elements for its tissue-specific and developmentally regulated expression in transgenic mice.
Mol Cell Biol 1986 Jul
PMID:Tissue-specific and developmentally regulated expression of a chimeric actin-globin gene in transgenic mice. 302 42

Intracellular acidosis is capable of stimulating a rapid amiloride-sensitive Na/H exchange mechanism in the cell membrane of cultured chick heart cells. The sequence of changes of intracellular sodium and potassium contents during recovery from an acid load in heart cells was determined by atomic absorption spectrophotometry and correlated with electrophysiological measurements. Induction of an intracellular acid load by removal of NH4Cl from the bathing solution caused a rapid rise in sodium content that was amiloride-sensitive. Following a peak, sodium content declined concomitant with a rise in potassium content; these changes were ouabain-sensitive and corresponded with a ouabain-sensitive membrane hyperpolarization beyond the calculated potassium equilibrium potential. These observations indicate that pHi regulation in cardiac muscle, following an intracellular acid load involves extrusion of H+ by electroneutral Na/H exchange with the consequent rise in Nai stimulating the electrogenic Na/K pump to return Nai to control level. In the presence of amiloride (10(-4) M), the hyperpolarization was slower although still present: this suggests the existence of another sodium uptake mechanism which contributes to stimulation of electrogenic transport.
J Mol Cell Cardiol 1986 Nov
PMID:Na/H exchange in cultured chick heart cells: secondary stimulation of electrogenic transport during recovery from intracellular acidosis. 302 58

Although muscle and nerve are reasonably well protected against active oxygen and related free radicals, environmental or inherited malfunctions can overpower their defences. Active oxygen is involved in many neuropathies and myopathies. In every case the damage is caused by agents which exert effects disproportionately greater than the quantities encountered, through a variety of amplification mechanisms. We can categorize these amplification mechanisms as follows: (a) non-replacement of targets (e.g. loss of genetic information, ataxia telangectasia being an hereditary ataxia in which an oxygen mediated chromosomal instability is apparent), (b) non-removal of unwanted materials (e.g. lipofuscin accumulation in brain and heart), (c) redox cycling, usually involving catalysis by trace-metal ions (e.g. some forms of Parkinsonism), (d) non-redox catalysis (e.g. toxicity in cardiac muscle or brain due to vanadium or aluminium respectively), (e) modification of ion transport (e.g. calcium ionophore or acrylamide induce histopathological changes in muscle, similar in some respects to those seen in Duchenne muscular dystrophy), (f) compromised defences (e.g. muscle and nerve become particularly susceptible to free radical damage after loss of the protective actions of vitamin E), and (g) amplification by inflammatory and immune responses (e.g. multiple sclerosis, reperfusion injury to brain and heart, and traumatic injury to nervous tissue). Unfortunately, a variety of therapeutic agents which might be expected to protect against almost every conceivable form of oxygen mediated damage have proved clinically ineffective in most of these disorders. The reasons for this will be explored with an emphasis on common features, differences, mechanisms, and potential therapeutic approaches.
Mol Cell Biochem 1988 Dec
PMID:Active oxygen in neuromuscular disorders. 306 22

We have determined the sequences of three recombinant cDNAs complementary to different mouse actin mRNAs that contain more than 90% of the coding sequences and complete or partial 3' untranslated regions (3'UTRs): pAM 91, complementary to the actin mRNA expressed in adult skeletal muscle (alpha sk actin); pAF 81, complementary to an actin mRNA that is accumulated in fetal skeletal muscle and is the major transcript in adult cardiac muscle (alpha c actin); and pAL 41, identified as complementary to a beta nonmuscle actin mRNA on the basis of its 3'UTR sequence. As in other species, the protein sequences of these isoforms are highly (greater than 93%) conserved, but the three mRNAs show significant divergence (13.8-16.5%) at silent nucleotide positions in their coding regions. A nucleotide region located toward the 5' end shows significantly less divergence (5.6-8.7%) among the three mouse actin mRNAs; a second region, near the 3' end, also shows less divergence (6.9%), in this case between the mouse beta and alpha sk actin mRNAs. We propose that recombinational events between actin sequences may have homogenized these regions. Such events distort the calculated evolutionary distances between sequences within a species. Codon usage in the three actin mRNAs is clearly different, and indicates that there is no strict relation between the tissue type, and hence the tRNA precursor pool, and codon usage in these and other muscle mRNAs examined. Analysis of codon usage in these coding sequences in different vertebrate species indicates two tendencies: increases in bias toward the use of G and C in the third codon position in paralogous comparisons (in the order alpha c less than beta less than alpha sk), and in orthologous comparisons (in the order chicken less than rodent less than man). Comparison of actin-coding sequences between species was carried out using the Perler method of analysis. As one moves backward in time, changes at silent sites first accumulate rapidly, then begin to saturate after -(30-40) million years (MY), and actually decrease between -400 and -500 MY. Replacements or silent substitutions therefore cannot be used as evolutionary clocks for these sequences over long periods. Other phenomena, such as gene conversion or isochore compartmentalization, probably distort the estimated divergence time.
J Mol Evol 1986
PMID:Comparison of three actin-coding sequences in the mouse; evolutionary relationships between the actin genes of warm-blooded vertebrates. 308 97

Isolated sheep cardiac Purkinje fibers were pulled through a latex membrane and both segments were independently superfused with modified Tyrode solutions. Transmembrane potentials and intracellular pH (pHi) were continuously measured in one segment (test compartment, TC), using double-barreled pH sensitive glass microelectrodes, while the internal H+ activity was altered in the adjacent part of the fiber (experimental compartment, EC). In the latter local pHi changes were produced by removal of CO2/HCO3-, by superfusing acidic (pH 6.8) solution, and by addition and subsequent withdrawal of NH4Cl. Withdrawal of CO2/HCO3- in EC was found to have no influence on pHi in TC at 0.35 to 1.0 mm distance. The action potential first shortened and later on prolonged above control duration after switching to HCO3- -free medium. Perfusing EC with an acidic solution had virtually no effect on pHi in TC while action potential duration (APD) increased. Addition and withdrawal of NH4+ in EC decreased, respectively increased, APD. In TC no change in pHi was observed at 0.8 to 1.0 mm distance. At shorter distance a slow acidification was seen, associated with the presence of NH4+ in EC. The presence of amiloride, a blocker of the pHi regulating mechanism, could not unmask a larger pHi change. It is concluded that, in cardiac muscle, large gradients of pHi are possible over a relatively short distance, while electrotonic interaction can produce changes in the time course of the action potential in neighbouring cells having a normal intracellular pH.
J Mol Cell Cardiol 1988 Mar
PMID:Influence of local intracellular pH changes on pH and action potentials in adjacent parts of cardiac Purkinje fibers. 313 14

The respective roles of exogenous polyunsaturated fatty acids on the lipid composition, physiological properties and enzyme release was investigated on isolated cardiac muscle cells in normoxia and hypoxia. Rat neonatal ventricular myocytes were grown for 5 days in conventional serum-supplemented medium. Cells were then incubated for 24 h in fully chemically-defined media featuring a balanced fatty acid composition containing either linoleic acid (18:2 n-6) or linolenic acid (18:3 n-3) as sole polyunsaturated fatty acid source. Transmembrane potentials were monitored with microelectrodes and contractions with a photoelectric device. The radio of n-6 to n-3 phospholipid fatty acids increased from 6.3 in control cells to 20.2 in cells exposed to n-6 fatty acids (SM6) and decreased to 1.4 in those exposed to n-3 fatty acids (SM3). These modifications had no influence on the electrical and mechanical activities and on automaticity in normoxic conditions. The action potential depression under hypoxia was less severe in SM6 cells, whereas there was a better electrophysiological recovery upon reoxygenation in SM3 cells. However, the loss of lactate dehydrogenase during sustained hypoxic treatment was not affected by changes in phospholipid fatty acid pattern. These results suggest that the effect of the polyunsaturated fatty acid balance depends on the cellular function under study and on the environmental conditions.
J Mol Cell Cardiol 1988 Oct
PMID:Modification of the n-6/n-3 fatty acid ratio in the phospholipids of rat ventricular myocytes in culture by the use of synthetic media: functional and biochemical consequences in normoxic and hypoxic conditions. 321 98

There is evidence that the steep ascending limb of the force-length curve in cardiac muscle (Frank-Starling relation) is based on a length-dependence of myofilament Ca2+ sensitivity. Previous work from this laboratory has indicated that in the sarcomere length range corresponding to the ascending limb of the cardiac force length curve (1.7 to 2.3 microns) the Ca2+-troponin C affinity is length-dependent. In this study Ca2+ binding to chemically skinned bovine cardiac muscle bundles was measured during ATP-induced force generation with fiber bundles having sarcomere lengths of 2.2 to 2.4 microns and 1.6 to 1.8 microns. A double isotope technique was used to make concurrent determinations of the force-pCa and bound Ca2+-pCa relationships. At the longer sarcomere lengths the fibers bound, at saturation, an amount of Ca2+ equivalent to approximately 3 mol Ca2+/mol troponin C. Force development appeared to be coupled to titration of the single, low-affinity Ca2+-specific site. In the pCa range 7.0 to 6.0 sarcomere length had no effect on Ca2+ binding. In the pCa range 6.0 to 5.0, in which force increased steeply, there was, in addition to a decreased relative force, a significant reduction in bound Ca2+ at the shorter sarcomere length. Thus sarcomere length appears to influence the Ca2+ binding properties of the regulatory site on troponin C. These data provide direct evidence that length-dependent modulation of Ca2+-troponin C affinity may make a major contribution to the force-length relationship in cardiac muscle.
J Mol Cell Cardiol 1988 Aug
PMID:Bound calcium and force development in skinned cardiac muscle bundles: effect of sarcomere length. 322 7

A chick embryonic myosin alkali light chain L23 gene that is expressed transiently at embryonic stages in chick skeletal, cardiac and smooth muscles and in brain continuously from embryo to adult stages, was isolated and characterized. Sequence analysis showed that the exonic sequence of this gene was identical with that of embryonic myosin light chain mRNA except for one base replacement. This gene is a single gene of 5200 bases, which is divided into seven exons by six introns, and the positions of inserts of all the introns are well-conserved as in the skeletal and cardiac muscle myosin alkali light chain genes. Therefore, this embryonic myosin light chain gene can be classified as a member of the myosin alkali light chain gene family, and these three genes may have originated from a common ancestral gene. Transcription of the embryonic light chain gene starts from the same initiation site 33 bases upstream from ATG in embryonic muscle tissues and brain. Comparison of the nucleotide sequence around the promotor region of the embryonic myosin light chain gene with the corresponding regions of the skeletal and cardiac myosin light chain genes showed that the 11-base consensus sequence (TCCTATTTATAG) is present about 100 bases upstream from the transcription initiation site in each gene.
J Mol Biol 1988 Dec 05
PMID:Isolation of the chick myosin alkali light chain gene expressed in embryonic gizzard muscle and transitional expression of the light chain gene family in vivo. 322 43


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