Isolation of sarcolemmal membrane, membrane orientation, and lipid asymmetry

Kj, Kako

doi:10.1002/med.2610070407

Cited by 3 publications

(1 citation statement)

References 194 publications

(26 reference statements)

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“…It is noteworthy that such hydrolysis occurs with a minimal effect, if any, on release of creatine kinase from the C2C12 myotubes, indicating that sarcolemmal integrity was largely preserved at these time intervals, and therefore that phospholipid hydrolysis precedes overt plasma membrane disruption. These results may be interpreted in light of the finding that the majority of PE and all PS are present on the internal leaflet of the sarcolemma and on intracellular membranes, but there is little PA on the surface, where the predominant phospholipid is PC . On this basis, the results obtained here clearly indicate that B. asper Mt‐I only exerts its hydrolytic activity on the external leaflet of the plasma membrane, creating a high concentration of lysoPC and lysoPE, with consequences on membrane permeability that are discussed below.…”

Section: Resultssupporting

confidence: 56%

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins – distinct mechanisms of action

et al. 2013

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Bothrops snakes are the major cause of ophidian envenomings in Latin America. Their venom contains myotoxins that cause prominent muscle damage, which may lead to permanent disability. These toxins include myotoxins Mt-I and Mt-II, which share the phospholipase A 2 (PLA 2 ) fold, but Mt-II lacks enzymatic activity because the essential active site Asp49 is replaced by Lys. Both myotoxins cause sarcolemma alterations, with Ca 2+ entry and loss of ATP and K + from muscle cells, but the molecular lesions at the basis of their cellular action are not known, particularly the role of phospholipid hydrolysis. Here we tested their PLA 2 activity in vivo, and evaluated the hypothesis that Ca 2+ -activated endogenous PLA 2 s may be involved in the action of Mt-II. The time course of phospholipid hydrolysis by Mt-I and Mt-II in myotubes in culture and in tibialis anterior mouse muscles was determined. Mt-I rapidly hydrolyzed phosphatidylcholine and phosphatidylethanolamine but not phosphatidylserine, but no phospholipids were hydrolyzed in the presence of Mt-II. Whole Bothrops asper venom induced a higher extent of phospholipid hydrolysis than Mt-I alone. These results demonstrate in vivo PLA 2 activity of Mt-I for the first time, and indicate that it acts only on the external monolayer of the sarcolemma. They also exclude activation of endogenous PLA 2 s in the action of Mt-II, implying that plasma membrane disruption by this toxin does not depend on phospholipid hydrolysis. Therefore, both Bothrops myotoxins induce Ca 2+ entry and release of ATP and cause myonecrosis, but through different biochemical mechanisms.

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Section: Resultssupporting

confidence: 56%

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins – distinct mechanisms of action

et al. 2013

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Na+/Ca2+ exchange of isolated sarcolemmal membrane: effects of insulin, oxidants and insulin deficiency

Kato

Kako

1988

Mol Cell Biochem

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In this study we prepared sarcolemmal fractions from bovine and rat hearts; their Na+K+ ATPase activities, measured in the presence of saponin to unmask latent Na+K+ ATPase, were 59.4 and 48.8 mu mol Pi/mg protein.h, respectively. The rate of Na+ dependent Ca2+ uptake was linear for the first 10 s and a plateau was reached in 3 min. Oxidation by free radical generation either with H2O2, FeSO4 plus DTT or xanthine oxidase plus hypoxanthine stimulated Na+/Ca2+ exchange in a time-dependent manner. The stimulation was abolished by deferoxamine or o-phenanthroline. By contrast, oxidation by HOCl inhibited Na+/Ca2+ exchange in proportion to its concentration, and this inhibition was antagonized by DTT. DTT alone had no effect on the exchange. Insulin stimulated Na+/Ca2+ exchange, its maximal effect was attained after 30 min incubation with 100 mu units/ml. N-ethylmaleimide inhibited the exchange both in the presence and in the absence of insulin. Sarcolemmal fractions prepared from hearts of alloxan-treated, acutely diabetic rats showed a significant decrease in Na+/Ca2+ exchange. Addition of insulin in vitro significantly stimulated Na+/Ca2+ exchange of both diabetic and control groups. The results indicate that sarcolemmal Na+/Ca2+ exchange function is modulated by oxidation-reduction states and by the presence of insulin.

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Oxidative Myocardial Injury and Cardiac-Derived Experimental Systems

Janero¹

1990

Biological Oxidation Systems

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Isolation of sarcolemmal membrane, membrane orientation, and lipid asymmetry

Cited by 3 publications

References 194 publications

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins – distinct mechanisms of action

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins – distinct mechanisms of action

Na+/Ca2+ exchange of isolated sarcolemmal membrane: effects of insulin, oxidants and insulin deficiency

Oxidative Myocardial Injury and Cardiac-Derived Experimental Systems

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Isolation of sarcolemmal membrane, membrane orientation, and lipid asymmetry

Cited by 3 publications

References 194 publications

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A2 myotoxins – distinct mechanisms of action

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A2 myotoxins – distinct mechanisms of action

Na+/Ca2+ exchange of isolated sarcolemmal membrane: effects of insulin, oxidants and insulin deficiency

Oxidative Myocardial Injury and Cardiac-Derived Experimental Systems

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Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins – distinct mechanisms of action

Muscle phospholipid hydrolysis by Bothrops asper Asp49 and Lys49 phospholipase A₂ myotoxins – distinct mechanisms of action