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Activation of Ca2+-stimulated ATPase by phospholipid N-methylation in cardiac sarcoplasmic reticulum

P K Ganguly, V Panagia, K Okumura

    Biochemical and Biophysical Research Communications
    |July 16, 1985
    PubMed

    Insights

    Phospholipid N-methylation of cardiac sarcoplasmic reticulum (SR) enhances Ca2+-ATPase activity, suggesting a regulatory role in the SR Ca2+-pump mechanism. This finding impacts understanding of cardiac muscle function.

    Area of Science:

    • Biochemistry
    • Cellular Physiology
    • Molecular Biology

    Background:

    • Cardiac sarcoplasmic reticulum (SR) is crucial for regulating intracellular calcium levels in heart muscle.
    • The SR Ca2+-ATPase (SERCA) pump is vital for muscle relaxation by sequestering calcium.
    • Phospholipid methylation is a known cellular process, but its role in SR function is unclear.

    Purpose of the Study:

    • To investigate the effect of phospholipid N-methylation on the activity of cardiac SR.
    • To determine if N-methylation influences the Ca2+-stimulated ATPase activity of the SR Ca2+-pump.

    Main Methods:

    • Incubation of cardiac SR with S-adenosyl-L-methionine (a methyl donor).
    • Assay of Ca2+-stimulated ATPase activity.
    • Treatment with methyl acetimidate, an inhibitor of phospholipid N-methylation.

    Main Results:

    • S-adenosyl-L-methionine significantly increased Ca2+-stimulated ATPase activity in cardiac SR.
    • The observed increase in activity was independent of changes in Ca2+ affinity.
    • Methyl acetimidate blocked the enhancing effect of S-adenosyl-L-methionine, confirming the role of N-methylation.

    Conclusions:

    • Phospholipid N-methylation, specifically of phosphatidylethanolamine, can enhance cardiac SR Ca2+-ATPase activity.
    • This process may play a regulatory role in the SR Ca2+-pump mechanism.
    • Findings suggest a novel mechanism for modulating cardiac contractility and relaxation.

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