PPP6R2

PPP6R2 is a regulatory subunit of the protein phosphatase 6 (PP6) holoenzyme that controls RIPK1-dependent programmed cell death (PMID:38807188). Acting redundantly with its paralogous subunits PPP6R1 and PPP6R3, PPP6R2-containing PP6 promotes PANoptosis downstream of TAK1 inhibition, and only combined depletion of all three regulatory subunits blocks TAK1 inhibitor-induced death (PMID:38807188). Mechanistically, the complex tips RIPK1 toward a pro-death state by supporting auto-phosphorylation at S166 while reducing the pro-survival S321 phosphorylation (PMID:38807188). Beyond this role in cell-death signaling, the broader cellular functions of PPP6R2 have not been characterized in the available corpus.

1. 2013 Low

   Before any signaling role was known, a screen asked whether PPP6R2 influences cancer cell adhesion, establishing it as a functional modifier of hepatic microvascular retention.

   Evidence Random homozygous gene perturbation screen in HT-29 colorectal cancer cells with liver sinusoidal endothelial cell adhesion assay

   PMID:23629598

   Open questions at the time

   • No molecular mechanism or pathway placement established for the anti-adhesive phenotype
   • Effect of PP6 catalytic activity on adhesion not tested
   • Not connected to any defined phosphorylation substrate
2. 2024 Medium

   It was unknown how PP6 regulatory subunits gate RIPK1-driven death; this work showed PPP6R2 acts redundantly within PP6 to promote pro-death RIPK1 S166 auto-phosphorylation and suppress pro-survival S321 phosphorylation downstream of TAK1 inhibition.

   Evidence Cell death-based CRISPR screen with individual and combined loss-of-function of PP6 subunits and RIPK1 phospho-site analysis

   PMID:38807188

   Open questions at the time

   • Redundancy of PPP6R1/R2/R3 leaves the unique contribution of PPP6R2 undefined
   • Direct dephosphorylation of RIPK1 S321 by PP6 not demonstrated biochemically
   • Structural basis for substrate targeting not resolved
3. 2025 Low

   Whether PPP6R2 operates outside immune/death signaling was open; an interactome placed it within a postsynaptic CC2D1A-associated complex in neurons.

   Evidence Co-immunoprecipitation/mass spectrometry of CC2D1A in mouse hippocampus with Cc2d1a hypomorph controls (preprint)

   PMID:40667103

   Open questions at the time

   • Single Co-IP/MS without reciprocal validation or functional consequence
   • Direct versus indirect nature of the CC2D1A association unresolved
   • No demonstration of PP6 phosphatase activity at the synapse

• How PPP6R2 confers substrate specificity to PP6 and whether its adhesion, death-signaling, and neuronal interactions reflect one shared biochemical activity remains unresolved.
• No PPP6R2-specific (non-redundant) substrate identified
• No structural model of the PPP6R2-containing holoenzyme
• Mechanism linking PP6 activity to adhesion and synaptic biology unknown