A Novel Small-Molecule Protac Selectively Promotes Tau Clearance To Improve Cognitive Functions In Alzheimer-Like Models

BackgroundIntracellular accumulation of tau is a hallmark pathology in Alzheimer disease(AD)and the related tauopathies,thus targeting tau could be promising for drug development.Proteolysis Targeting Chimeras(PROTACs)is a novel drug discovery strategy for selective protein degradation from within cells.MethodsA novel small-molecule PROTAC,named as C004019 with a molecular mass of 1,035.29 dalton,was designed to simultaneously recruite tau and E3-ligase(Vhl)and thus to selectively enhance ubiquitination and proteolysis of tau proteins.In the present study,cell viability was determined by CCK8 and pharmacokinetic determination by liquid chromatography-mass spectrometry.Western blotting,immunofluoresence and immunohistochemical staining were employed to verify the effects of C004019 in cell models(HEK293 and SH-SY5Y)and mouse models(hTau-transgenic and 3xTg-AD),respectively.The cognitive capacity of the mice was assessed by a suite of behavior experiments.Electrophysiology and Golgi staining were used to evaluate the synaptic plasticity.Results1.C004019 induced a robust tau clearance via promoting its ubiquitinationproteasome-dependent proteolysis in HEK293 cells with stable(HEK293-hTau cells)or transient overexpression of human tau(hTau)(HEK293-3xFlag-hTau and HEK293-EGFP-hTau cells),and in SH-SY5 Y that constitutively overexpress hTau.2.Intracerebral ventricular infusion of C004019 induced a robust tau clearance in vivo.3.Most importantly,single-dose subcutaneous administration of C004019 in the brains of wild-type remarkably decreased tau levels and this effect lasted for at least eight days.4.Multiple-doses(once per 6 days for a total 5 times)subcutaneous administration of C004019 promotes tau clearance in hTau transgenic mice with improvement of synaptic and cognitive functions.5.Multiple-doses(once per 6 days for a total 5 times)subcutaneous administration of C004019 promotes tau clearance in 3xTg-AD transgenic mice with improvement of synaptic and cognitive functions.ConclusionsThe PROTAC(C004019)created in the current study can selectively and efficiently promote tau clearance both in vitro and in vivo,which provides a promising drug candidate for AD and the related tauopathies.