TogoPhosTAC as a delivery-ready platform for targeted protein dephosphorylation

Abstract

Phosphorylation-targeting chimeras (PhosTACs) enable targeted protein dephosphorylation by recruiting phosphatases through induced proximity. However, the direct recruitment of phosphatase subunits or holoenzymes with small molecules remains challenging, as suitable ligands are scarce and often compromise enzymatic activity or cellular function. Here, we present togoPhosTAC, a hybrid modality that integrates a small-molecule PhosTAC, an engineered FKBP12F36V-phosphatase, and a lipid nanoparticle delivery system. This strategy allows delivery of preassembled PhosTAC–FKBP12F36V-phosphatase complexes or PhosTAC–phosphatase mRNA, enabling rapid and efficient intracellular dephosphorylation. We demonstrate that togoPhosTAC can selectively dephosphorylate EGFR, α-synuclein, and tau in biological contexts, providing a versatile strategy that circumvents the need for genetically engineered phosphatases. We also find togoPhosTAC further enhances tau dephosphorylation as well as its disaggregation in cellulo. Importantly, intrahippocampal or intranasal delivery of togoPhosTAC in PS19 tau transgenic male mice leads to a marked reduction in pathological tau phosphorylation across multiple sites (Ser202, Thr205, Thr231, Ser396, and Ser404), decreases pathological tau burden in related brain regions, and improves Alzheimer’s disease–related behavioral deficits. Together, these findings establish a versatile and generalizable approach for precise protein dephosphorylation in disease-relevant systems, overcoming key limitations in phosphatase-recruiting drug discovery. This study presents togoPhosTAC, a biologic platform that directs engineered phosphatases to target proteins for phosphate removal, reducing pathological tau phosphorylation and alleviating behavioral deficits in male PS19 tauopathy mice.