Carbonylation Contributes to Serca2 Activity Loss During Diabetes

Abstract

The present study was undertaken to determine if carbonylation of SERCA2 contributes to the prolongation of active cardiac relaxation time during diabetes. Type 1 diabetes was induced in male Sprague‐Dawley rats using streptozotocin (STZ). After seven weeks, serum reactive carbonyl species (RCS) increased 300%. Cardiac transmitral valve flow pattern (E:A ratio) and myocyte relaxation rate were decreased by 25% and 22%. Myocyte evoked Ca2+‐transient decay time increased 3.8‐fold. Ca2+ uptake and SERCA2 Ca2+ATPase activity were reduced by 57% and 60%. SERCA2 expression decreased by 10% but phospholamban levels remained unchanged. Trypsin digestion followed by mass spectroscopic analysis revealed elevated levels of carbonyl adducts on select basic residues of SERCA2. Crosslinking pentosidine adducts were also found on SERCA2 using adduct‐specific antibodies. Incubating hSERCA2 with the methylglyoxal reduced its ability to transport Ca2+. Arg164(Y)E, Arg636(Y)E, Lys475(Y)E and Lys481(Y)E mutations to mimic adducts formed during diabetes reduced the ability of SERCA2 to transport Ca2+. Treating STZ‐diabetic rats with pyridoxamine for five weeks, starting two weeks after STZ injections reduced serum RCS levels and blunted SERCA2 activity loss without altering steady state levels of SERCA2 or phospholamban. Pyridoxamine treatment also attenuated carbonylation of SERCA2. These new data demonstrate that carbonylation of SERCA2 is functionally important and contributes to the prolongation of active cardiac relaxation time during diabetes (SUPPORTED BY ADA)