This study demonstrates that phospholamban directly interacts with and lowers the Ca2+ affinity of SERCA2, explaining its inhibitory role in cardiac muscle sarcoplasmic reticulum.
Confirms direct phospholamban inhibition of SERCA2; extends mechanistic insights but leaves open clinical translation.
Full length cDNAs encoding both slow-twitch/cardiac (SERCA2) and fast-twitch skeletal muscle (SERCA1) Ca2(+)-ATPases were expressed by transient transfection of COS-1 cells. Studies of the Ca2(+)-dependency of Ca2(+)-transport in microsomes isolated from these cells showed that both isoforms had an affinity for Ca2+ of about 0.2 microM. The Ca2(+)-affinity of SERCA2 was lowered when phospholamban was co-expressed with it, demonstrating that the two proteins interact in this expression system. These studies support the view that phospholamban inhibition accounts for the low Ca2(+)-affinity and low activity of SERCA2 in cardiac muscle sarcoplasmic reticulum.
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Fujii et al. (1990) studied this question.
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