Acylphosphatase interferes with SERCA2a-PLN association.
We previously reported that acylphosphatase, a cytosolic enzyme present in skeletal and heart muscle, actively hydrolyzes the phosphoenzyme (EP) of cardiac sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a), inducing an increased activity of this pump. We hypothesized that acylphosphatase-induced stimulation of SERCA2a, in addition to enhanced EP hydrolysis, may be due to a displacement of phospholamban (PLN), removing its inhibitory effect. To verify this hypothesis co-immunoprecipitation experiments were performed by adding recombinant muscle acylphosphatase to solubilized heart SR vesicles, used as a source of SERCA2a and PLN. With anti-acylphosphatase antibodies only SERCA2a was co-immunoprecipitated in an amount which increased in parallel to the concentrations of our enzyme. Conversely, using anti-SERCA2a antibody, both PLN and acylphosphatase were co-immunoprecipitated with SERCA2a, and the PLN amount in the precipitate decreased with increasing acylphosphatase concentrations. SERCA2a and PLN were co-immunoprecipitated by anti-phospholamban antibodies, but while the amount of precipitated phospholamban increased in the presence of acylphosphatase, the level of SERCA2a decreased. These preliminary results strengthen the supposed displacement of phospholamban by acylphosphatase.
Nediani
Chiara
C
Dipartimento di Scienze Biochimiche, Università di Firenze, viale Morgagni 50, 50134, Firenze, Italy.
Celli
Alessandra
A
Fiorillo
Claudia
C
Ponziani
Vanessa
V
Giannini
Lara
L
Nassi
Paolo
P
D017766:Acid Anhydride Hydrolases / Q000378:metabolism*; D000818:Animals; D000911:Antibodies, Monoclonal; D001667:Binding, Competitive; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D066298:In Vitro Techniques; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D011233:Precipitin Tests; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000097024:Acylphosphatase; D000099211:Phospholamban
D017766:Acid Anhydride Hydrolases; D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000097024:Acylphosphatase; D000099211:Phospholamban