Role of phosphorylation of Thr(17) residue of phospholamban in mechanical recovery during hypercapnic acidosis.
OBJECTIVE
To assess the time course of phosphorylation of phospholamban residues, the underlying mechanisms determining these phosphorylations, and their functional impact on the mechanical recovery during acidosis.


METHODS
Langendorff perfused rat hearts were submitted to 30 min of hypercapnic acidosis. Contractility, relaxation, and phosphorylation of phospholamban residues, immunodetected by specific antibodies, were determined.


RESULTS
Acidosis produced a mechanical impairment followed by a spontaneous recovery, most of which occurred within the first 3 min of acidosis (early recovery). During this period, contractility and relaxation recovered by 67+/-9% and 77+/-11%, respectively, from its maximal depression, together with an increase in the Ca(2+)-calmodulin-dependent protein kinase II (CaMKII)-dependent phosphorylation of Thr(17). The CaMKII inhibitor KN-93, at 1, 5 and 10 microM, decreased Thr(17) phosphorylation to basal levels and produced a similar impairment of the early relaxation recovery (50%). However, only 5 and 10 microM KN-93 inhibited the early contractile recovery and completely blunted the late mechanical recovery. Inhibition of the reverse mode of the Na(+)/Ca(2+) exchanger by KB-R7943 decreased Thr(17) phosphorylation but accelerated the early contractile recovery.


CONCLUSIONS
CaMKII-dependent Thr(17) phosphorylation significantly increased at the beginning of acidosis, is responsible for 50% of the early relaxation recovery, and is linked to the activation of the reverse Na(+)/Ca(2+) mode. The early contractile recovery and the late mechanical recovery are dependent on CaMKII but independent of the phosphorylation of the Thr(17) residue of phospholamban. The reverse Na(+)/Ca(2+) mode has an additional negative effect that opposes the early mechanical recovery.
Mundiña-Weilenmann
Cecilia
C
Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, 60 y 120, (1900) La Plata, Argentina.
Ferrero
Paola
P
Said
Matilde
M
Vittone
Leticia
L
Kranias
Evangelia G
EG
Mattiazzi
Alicia
A
D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D003864:Depression, Chemical; D004591:Electrophoresis, Polyacrylamide Gel; D006935:Hypercapnia / Q000378:metabolism*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010477:Perfusion; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D013449:Sulfonamides / Q000494:pharmacology; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D013912:Threonine / Q000378:metabolism*; D013997:Time Factors; D000099211:Phospholamban; D000096926:Benzenesulfonamides
D001596:Benzylamines; D002135:Calcium-Binding Proteins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D047428:Protein Kinase Inhibitors; D019831:Sodium-Calcium Exchanger; D013449:Sulfonamides; D013890:Thiourea; D013912:Threonine; D000099211:Phospholamban; C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; C072105:KN 93; D000096926:Benzenesulfonamides