Phospholamban expressed in slow-twitch and chronically stimulated fast- twitch muscles minimally affects calcium affinity of sarcoplasmic reticulum Ca2+-ATPase

F. N. Briggs, K. F. Lee, A. W. Wechsler, L. R. Jones

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Abstract

Chronic excitation, at 2 Hz for 6-7 weeks, of the predominantly fast-twitch canine latissimus dorsi muscle promoted the expression of phospholamban, a protein found in sarcoplasmic reticulum (SR) from slowtwitch and cardiac muscle but not in fast-twitch muscle. At the same time that phospholamban was expressed, there was a switch from the fast-twitch (SERCA1) to the slow-twitch (SERCA2a) Ca2+-ATPase isoform. Antibodies against Ca2+-ATPase (SERCA2a) and phospholamban were used to assess the relative amounts of the slow-twitch/cardiac isoform of the Ca2+-ATPase and phospholamban, which were found to be virtually the same in SR vesicles from the slowtwitch muscle, vastus intermedius; cardiac muscle; and the chronically stimulated fast-twitch muscle, latissimus dorsi. The phospholamban monoclonal antibody 2D12 was added to SR vesicles to evaluate the regulatory effect of phospholamban on calcium uptake. The antibody produced a strong stimulation of calcium uptake into cardiac SR vesicles, by increasing the apparent affinity of the Ca2+ pump for calcium by 2.8-fold. In the SR from the conditioned latissimus dorsi, however, the phospholamban antibody produced only a marginal effect on Ca2+ pump calcium affinity. These different effects of phospholamban on calcium uptake suggest that phospholamban is not tightly coupled to the Ca2+-ATPase in SR vesicles from slow-twitch muscles and that phospholamban may have some other function in slow-twitch and chronically stimulated fast-twitch muscle.

Original languageEnglish (US)
Pages (from-to)26056-26061
Number of pages6
JournalJournal of Biological Chemistry
Volume267
Issue number36
StatePublished - Dec 1 1992

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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