Protein phosphatase 5 regulates titin phosphorylation and function at a sarcomere-associated mechanosensor complex in cardiomyocytes

• Published in: Nature communications 2018-01, Vol.9 (1), p.262-14, Article 262
• Main Authors: Krysiak, Judith, Unger, Andreas, Beckendorf, Lisa, Hamdani, Nazha, von Frieling-Salewsky, Marion, Redfield, Margaret M., dos Remedios, Cris G., Sheikh, Farah, Gergs, Ulrich, Boknik, Peter, Linke, Wolfgang A.
• Format: Article
• Language: English
• Subjects: 13/1; 13/51; 13/95; 14/19; 14/28; 45/70; 631/57/343/1667; 631/80/458/1733; 64/110; 64/60; 692/4019/592/75/230; 82/111; 82/29; Animals; Binding; Cardiomyocytes; Cardiomyopathy, Dilated - metabolism; Cell culture; Connectin; Connectin - metabolism; Dogs; Enzymatic activity; Heart; Heart Failure, Diastolic - metabolism; Hsp90 protein; Humanities and Social Sciences; Humans; Kinases; MAP Kinase Signaling System; Mechanotransduction, Cellular; Mice; Mice, Transgenic; multidisciplinary; Myocytes, Cardiac - metabolism; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phosphatase; Phosphoprotein Phosphatases - genetics; Phosphoprotein Phosphatases - metabolism; Phosphorylation; Protein phosphatase; Proteins; Sarcomeres; Science; Science (multidisciplinary); Serine; Signaling; Threonine; Transgenic mice
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-017-02483-3

Serine/threonine protein phosphatase 5 (PP5) is ubiquitously expressed in eukaryotic cells; however, its function in cardiomyocytes is unknown. Under basal conditions, PP5 is autoinhibited, but enzymatic activity rises upon binding of specific factors, such as the chaperone Hsp90. Here we show that PP5 binds and dephosphorylates the elastic N2B-unique sequence (N2Bus) of titin in cardiomyocytes. Using various binding and phosphorylation tests, cell-culture manipulation, and transgenic mouse hearts, we demonstrate that PP5 associates with N2Bus in vitro and in sarcomeres and is antagonistic to several protein kinases, which phosphorylate N2Bus and lower titin-based passive tension. PP5 is pathologically elevated and likely contributes to hypo-phosphorylation of N2Bus in failing human hearts. Furthermore, Hsp90-activated PP5 interacts with components of a sarcomeric, N2Bus-associated, mechanosensor complex, and blocks mitogen-activated protein-kinase signaling in this complex. Our work establishes PP5 as a compartmentalized, well-controlled phosphatase in cardiomyocytes, which regulates titin properties and kinase signaling at the myofilaments. Protein phosphatase 5 (PP5) is expressed in many cell types but its role in cardiomyocytes is unknown. Here the authors show that PP5 binds and dephosphorylates elastic titin in cardiac sarcomeres, and that PP5 is increased in heart failure, reducing cardiomyocyte compliance.