Research Article Age-Dependent Protein Expression of Serine/Threonine PhosphatasesandTheirInhibitorsintheHumanCardiacAtrium Ulrich Gergs , 1 Theresa Trapp, 1 Hasan Bushnaq, 2 Andreas Simm, 2 Rolf-Edgar Silber, 2 and Joachim Neumann 1 1 Institut f¨ ur Pharmakologie und Toxikologie, Medizinische Fakult¨ at, Martin-Luther-Universit¨ at Halle-Wittenberg, 06112 Halle (Saale), Germany 2 Klinik f¨ ur Herz- und oraxchirurgie, Medizinische Fakult¨ at, Martin-Luther-Universit¨ at Halle-Wittenberg, 06097 Halle, Germany Correspondence should be addressed to Joachim Neumann; joachim.neumann@medizin.uni-halle.de Received 21 February 2018; Revised 22 November 2018; Accepted 29 November 2018; Published 2 January 2019 Academic Editor: Gaja Sherbet Copyright © 2019 Ulrich Gergs et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Heart failure and aging of the heart show many similarities regarding hemodynamic and biochemical parameters. ere is evidence that heart failure in experimental animals and humans is accompanied and possibly exacerbated by increased activity of protein phosphatase (PP) 1 and/or 2A. Here, we wanted to study the age-dependent protein expression of major members of the protein phosphatase family in human hearts. Right atrial samples were obtained during bypass surgery. Patients (n � 60) were suffering from chronic coronary artery disease (CCS 2-3; New York Heart Association (NYHA) stage 1–3). Age ranged from 48 to 84 years (median 69). All patients included in the study were given β-adrenoceptor blockers. Other medications included angiotensin-converting enzyme (ACE) or angiotensin-receptor-1 (AT 1 ) inhibitors, statins, nitrates, and acetylsalicylic acid (ASS). 100 µg of right atrial homogenates was used for western blotting. Antibodies against catalytic subunits (and their major regulatory proteins) of all presently known cardiac serine/threonine phosphatases were used for antigen detection. In detail, we studied the expression of the catalytic subunit of PP1 (PP1c); I 1 PP1 and I 2 PP1 , proteins that can inhibit the activity of PP1c; the catalytic subunit of PP2A (PP2Ac); regulatory A-subunit of PP2A (PP2A A ); regulatory B56α-subunit of PP2A (PP2A B ); I 1 PP2A and I 2 PP2A , inhibitory subunits of PP2A; catalytic and regulatory subunits of calcineurin: PP2B A and PP2B B ; PP2C; PP5; and PP6. All data were obtained within the linear range of the assay. ere was a significant decline in PP2Ac and I 2 PP2A expression in older patients, whereas all other parameters remained unchanged with age. It remains to be elucidated whether the decrease in the protein expression of I 2 PP2A might elevate cardiac PP2A activity in a detrimental way or is overcome by a reduced protein expression and thus a reduced activity of PP2Ac. 1.Introduction In the myocardium, Ca 2+ -induced Ca 2+ release from the sarcoplasmic reticulum (SR) via activation of ryanodine re- ceptors is the main mechanism of cardiac excitation- contraction coupling [1]. e ensuing increase in in- tracellular Ca 2+ concentration is responsible for muscle contraction [1]. For relaxation, Ca 2+ is mainly removed from the cytosol by the action of SR Ca 2+ -ATPase (SERCA) into the SR. e affinity of SERCA for Ca 2+ is regulated by phos- pholamban (PLB) located in the SR. Phospholamban itself can be dephosphorylated by two serine/threonine phosphatases, namely, PP1 and PP2A in animal hearts and the human heart [2–5]. e catalytic subunit of PP1 can be inhibited by, amongst others, two endogenous proteins (for review, see [4], http://www.phosphatome.net, and http://www.depod.org) with peculiar physicochemical properties (preserved action after boiling of samples). ese heat stable proteins have been named inhibitor 1 of PP1 (I 1 PP1 [6]) and inhibitor 2 of PP1 (I 2 PP1 [6]). Long-term cardiac specific overexpression of I 1 leads upon aging in mouse hearts to decreased systolic contractility, suggesting that low PP1 activity is also detri- mental for cardiac function in the long run [7]. On the other hand, increased PP1 overexpression in the mouse heart can lead to cardiac hypertrophy and death [8]. In contrast to PP1, another related phosphatase, namely, PP2A, probably mainly Hindawi Advances in Medicine Volume 2019, Article ID 2675972, 9 pages https://doi.org/10.1155/2019/2675972