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A novel interaction mechanism accounting for different acylphosphatase effects on cardiac and fast twitch skeletal muscle sarcoplasmic reticulum calcium pumps
Author(s) -
Nediani Chiara,
Fiorillo Claudia,
Rigacci Stefania,
Magherini Francesca,
Francalanci Michela,
Liguri Gianfranco,
Pacini Alessandra,
Nassi Paolo
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)01717-7
Subject(s) - phospholamban , chemistry , endoplasmic reticulum , atp hydrolysis , skeletal muscle , stimulation , cardiac muscle , serca , atpase , calcium , calcium atpase , biochemistry , biophysics , medicine , enzyme , endocrinology , biology , organic chemistry
In cardiac and skeletal muscle Ca 2+ translocation from cytoplasm into sarcoplasmic reticulum (SR) is accomplished by different Ca 2+ ‐ATPases whose functioning involves the formation and decomposition of an acylphosphorylated phosphoenzyme intermediate (EP). In this study we found that acylphosphatase, an enzyme well represented in muscular tissues and which actively hydrolyzes EP, had different effects on heart (SERCA2a) and fast twitch skeletal muscle SR Ca 2+ ‐ATPase (SERCA1). With physiological acylphosphatase concentrations SERCA2a exhibited a parallel increase in the rates of both ATP hydrolysis and Ca 2+ transport; in contrast, SERCA1 appeared to be uncoupled since the stimulation of ATP hydrolysis matched an inhibition of Ca 2+ pump. These different effects probably depend on phospholamban, which is associated with SERCA2a but not SERCA1. Consistent with this view, the present study suggests that acylphosphatase‐induced stimulation of SERCA2a, in addition to an enhanced EP hydrolysis, may be due to a displacement of phospholamban, thus to a removal of its inhibitory effect.