The PP1 interactome plays a central role in HF pathogenesis and is dysregulated at the level of the R-subunits in the failing heart, resulting in differential phosphorylation status of proteins across different subcellular compartments.With the combination if immunoaffinity purification and mass spectrometry we were able to map the PP1 interactome in a mouse model with dilated cardiomyopaty, which is the most common form of primary cardiomyopaty leading to HF.