Final Report Summary - PP1TOOLS (Development of chemical biology tools for the elucidation of protein phosphatase-1 substrates and druggability)
Within intracellular signaling networks, protein phosphatases, which remove phosphate groups from amino acids such as serine (Ser) and threonine (Thr) are counter players of protein kinases and play crucial roles in health and disease. Protein serine/threonine-specific phosphatases (PSTPs) are considered as not useful drug targets although they are involved in the most prominent post-translational modifications. This was thought to be mainly due to an apparent lack of substrate specificity. One important PSTP is protein phosphatase-1 (PP1), a ubiquitous PSTP that is predicted to catalyze a majority of Ser and Thr dephosphorylations in eukaryotic cells, counteracting more than hundred kinases. PP1 activity is restrained in vivo by numerous PP1-interacting proteins functioning for example as substrate-targeting proteins and forming so-called holoenzymes with PP1. PP1 holoenzymes play a role in many different diseases such as cancer, diabetes, and cardiomyopathies. Currently, there are few chemical modulators available that target PP1 selectively. We previously developed the PP1-disrupting peptides (PDPs) that selectively activate PP1 in intact cells, leading to rapid dephosphorylation of nearby PP1 substrates. The activator does not act on the most closely related protein phosphatase-2A, nor on the family member PP2B.
This project aimed to generate and apply tools for the investigation of PP1, in part based on our previously developed activator. The tools included selective, photo-releasable chemical activators, semisynthetic proteins and non-hydrolyzable phosphonoSer-analogs, and they were applied to study PP1–substrate interactions. This revealed that PP1 is redox-regulated, and identified new PP1 substrates as well as distinct features between PP1 and PP2A regarding the recognition of their substrates. Furthermore, activating PP1 with PDPs in heart failure patient samples showed a beneficial response reverting the phenotype to an earlier disease stage, suggesting PP1 as promising drug target.
The research provided selective chemical tools to study PP1 by applying new concepts of activator design using peptide and small molecule chemistry to an enzyme class that is difficult to be targeted chemically. This research program contributed to a more detailed understanding of PP1 biology, and opened doors to investigate PP1 as drug target.
This project aimed to generate and apply tools for the investigation of PP1, in part based on our previously developed activator. The tools included selective, photo-releasable chemical activators, semisynthetic proteins and non-hydrolyzable phosphonoSer-analogs, and they were applied to study PP1–substrate interactions. This revealed that PP1 is redox-regulated, and identified new PP1 substrates as well as distinct features between PP1 and PP2A regarding the recognition of their substrates. Furthermore, activating PP1 with PDPs in heart failure patient samples showed a beneficial response reverting the phenotype to an earlier disease stage, suggesting PP1 as promising drug target.
The research provided selective chemical tools to study PP1 by applying new concepts of activator design using peptide and small molecule chemistry to an enzyme class that is difficult to be targeted chemically. This research program contributed to a more detailed understanding of PP1 biology, and opened doors to investigate PP1 as drug target.