Target-Based Discovery of an Inhibitor of the Regulatory Phosphatase PPP1R15B

  • Cell. 2018 Aug 23;174(5):1216-1228.e19. doi: 10.1016/j.cell.2018.06.030.
Agnieszka Krzyzosiak  1 ,  Anna Sigurdardottir  1 ,  Laura Luh  1 ,  Marta Carrara  1 ,  Indrajit Das  1 ,  Kim Schneider  1 ,  Anne Bertolotti  2
Affiliations
  • 1. Neurobiology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
  • 2. Neurobiology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK. Electronic address: [email protected].
PMID: 30057111 DOI: 10.1016/j.cell.2018.06.030
Abstract

Protein phosphorylation is a prevalent and ubiquitous mechanism of regulation. Kinases are popular drug targets, but identifying selective Phosphatase inhibitors has been challenging. Here, we used surface plasmon resonance to design a method to enable target-based discovery of selective serine/threonine Phosphatase inhibitors. The method targeted a regulatory subunit of protein Phosphatase 1, PPP1R15B (R15B), a negative regulator of proteostasis. This yielded Raphin1, a selective inhibitor of R15B. In cells, Raphin1 caused a rapid and transient accumulation of its phosphorylated substrate, resulting in a transient attenuation of protein synthesis. In vitro, Raphin1 inhibits the recombinant R15B-PP1c holoenzyme, but not the closely related R15A-PP1c, by interfering with substrate recruitment. Raphin1 was orally bioavailable, crossed the blood-brain barrier, and demonstrated efficacy in a mouse model of Huntington's disease. This identifies R15B as a druggable target and provides a platform for target-based discovery of inhibitors of serine/threonine phosphatases.

Keywords
Huntington’s disease; PPP1R15B; drug discovery; eukaryotic initiation factor-2; neurodegenerative diseases; protein misfolding; protein phosphatase 1; protein quality control; proteostasis; stress response.
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