The Pin1-cis P-tau Axis: A Key Common Early Pathogenic Driver, Biomarker and Therapeutic Target Across...

Tauopathies comprise a heterogeneous group of neurological and systemic disorders characterized by pathological tau dysregulation, traditionally including Alzheimer's disease (AD), traumatic brain injury (TBI), and chronic traumatic encephalopathy (CTE). Emerging evidence suggests that tauopathy may also occur in selected vascular and systemic disease contexts, including ischemic stroke, vascular dementia (VaD), and preeclampsia (PE), although the strength and clinical significance of this evidence vary among these conditions. Compelling evidence suggests that the Pin1-cis phosphorylated tau (cis P-tau) axis may represent a convergent molecular mechanism linking these conditions. Pin1 is a phosphorylation-specific peptidyl-prolyl cis-trans isomerase that protects against tauopathy and cognitive impairment by catalyzing conversion of pathological cis P-tau to the physiological trans conformation at phosphorylated Thr231-Pro motifs. Under stress conditions such as oxidative stress, hypoxia, inflammation, mechanical injury, or aging, Pin1 activity becomes impaired through oxidation, phosphorylation, sequestration, or transcriptional downregulation, resulting in the accumulation of neurotoxic cis P-tau. cis P-tau is proposed to initiate a pathogenic cascade termed cistauosis in neurons, characterized by axonal microtubule collapse and transport failure, mitochondrial dysfunction, synaptic degeneration, neuroinflammation, neuronal death, and prion-like spread. Importantly, cis P-tau appears rapidly after insults long before overt neurofibrillary tangle (NFT) formation in several experimental and clinical contexts, supporting its role as an upstream pathogenic driver and early biomarker. Crucially, conformation-specific monoclonal antibodies targeting cis P-tau selectively eliminate pathological cis P-tau while sparing physiological trans P-tau, demonstrating promising therapeutic effects in preclinical models of TBI, vascular injury, AD-related tauopathy, and PE. This review summarizes the molecular basis of the Pin1-cis P-tau axis, examines its role across conventional and unconventional tauopathies, evaluates its biomarker potential, and highlights cis-specific immunotherapy as a potentially broad therapeutic strategy for neurodegenerative, traumatic, and vascular cognitive disorders.