CHENGDU, Sichuan, CHINA, 16 December 2025 — A groundbreaking review published today in Genomic Psychiatry by Dr. Peng Lei and his team offers a comprehensive synthesis of tau protein research, reshaping our understanding of this complex molecule. The review reveals tau as a versatile protein involved in processes from iron export to insulin secretion, while also playing a pivotal role in neurological and psychiatric disorders.
Discovered in the 1970s, tau was initially identified as a microtubule stabilizer. However, its role expanded significantly in the 1980s when researchers linked tau to neurofibrillary tangles in Alzheimer’s disease. This new review highlights tau’s essential functions in neurons beyond its structural role, emphasizing its involvement in axonal transport and synaptic plasticity, which are crucial for learning and memory.
The Protein That Defied Simple Classification
Tau’s journey from obscurity to prominence began with its discovery as a copurifying partner of tubulin. Its identification as a core component of neurofibrillary tangles in Alzheimer’s disease brains brought it into the spotlight. Yet, this pathological association overshadowed its vital physiological roles.
The review traces the evolution of scientific understanding, from viewing tau as a passive structural element to recognizing it as an active participant in neuronal physiology. “Tau, predominantly expressed in neurons, plays a crucial role in the assembly of microtubules and the maintenance of the microtubule network,” the authors write. However, this represents merely the beginning of its responsibilities.
Iron, Insulin, and Unexpected Connections
One of the most striking insights from the review is tau’s involvement in iron metabolism, synaptic plasticity, and insulin metabolism. Dr. Lei’s previous research demonstrated tau’s role in stabilizing iron transporters and facilitating iron export from neurons. When tau function fails, iron accumulates, leading to cognitive and motor decline.
“Twelve-month-old mice lacking tau exhibited iron deposition in neurons, loss of dopaminergic cells in the substantia nigra, and severe cognitive and motor decline.”
The review also highlights tau’s unexpected connection to insulin. Tau deficiency enhances insulin secretion in pancreatic cells, normalizing glucose levels in diabetic mouse models. This finding has significant implications, given that type 2 diabetes is a major risk factor for dementia.
The Architecture of Dysfunction
The review delves into how tau transforms from a neuronal function essential to an agent of destruction. A comprehensive taxonomy of tau’s posttranslational modifications is provided, detailing 95 modifications at 88 amino acid residues. Phosphorylation, in particular, dominates the pathological landscape.
“Healthy brains maintain tau phosphorylation at approximately 2-3 moles of phosphate per mole of protein. In Alzheimer’s disease, this ratio climbs to 5-9 moles.”
Not all phosphorylation promotes pathology; some sites inhibit aggregation while others accelerate it. This complexity suggests that therapeutic strategies must target phosphorylation with precision.
The Psychiatric Dimension
The review explores tau’s emerging connections to psychiatric disorders. In early-onset schizophrenia, plasma total tau levels are significantly lower than in controls. Adult-onset patients show decreased serum levels of both total and phosphorylated tau. Delirium presents another intriguing connection, with preoperative plasma phosphorylated tau correlating with postoperative delirium risk.
“Anesthesia and surgery acutely elevate blood p-tau217, which may cross the blood-brain barrier and induce delirium-like behaviors.”
The neuropsychiatric symptoms of Alzheimer’s disease, such as apathy, depression, and anxiety, correlate with tau pathology patterns. Tau PET imaging reveals stronger signals in patients experiencing delusions or hallucinations.
Biomarkers Emerging From Complexity
The review highlights tau as a disease biomarker, tracing its development from cerebrospinal fluid assays to contemporary blood-based tests. Plasma p-tau217 can distinguish Alzheimer’s disease from frontotemporal dementia with high accuracy.
“Different phosphorylated species appear at different disease stages, offering possibilities for staging disease progression and timing interventions.”
The microtubule-binding region of tau has emerged as another biomarker source, correlating strongly with tau PET results and outperforming other plasma tau biomarkers for detecting tangle burden.
Therapeutic Frontiers and Frustrations
Despite progress in understanding tau biology, no tau-targeting drug has shown significant clinical efficacy. The antisense oligonucleotide BIIB080 reduced tau levels in phase I trials for mild Alzheimer’s disease, but challenges remain. Kinase inhibitors and immunotherapy approaches have produced mixed results, highlighting the complexity of targeting tau pathology.
The Synthesis as Roadmap
The review identifies critical gaps demanding attention, such as the origins of blood-based phosphorylated tau species and the mechanisms by which tau pathology spreads. The synthesis suggests tau as a convergence point where multiple pathological processes intersect, requiring combination approaches for effective treatment.
This invited review in Genomic Psychiatry offers a comprehensive framework for understanding tau biology and pathology, providing researchers, clinicians, and policymakers with actionable insights. By integrating findings from over 300 studies, the authors offer a roadmap for future investigations, highlighting promising avenues for advancing the field.
The full review, titled “Tau protein: Physiological functions and multifaceted roles in neurodegenerative and psychiatric disorders,” is available via Open Access in Genomic Psychiatry from 16 December 2025. For more information, visit the Genomic Press Virtual Library.
