Polyamines are ubiquitous aliphatic polycations, meaning they carry multiple positive charges that allow them to bind avidly to negatively charged molecules throughout the cell. This electrochemical versatility explains their astonishing range of functions. Polyamines regulate how nucleic acids fold and interact, modulate the activity of ion channels in neuronal membranes, govern autophagy, the cellular recycling system, maintain redox balance, support proteostasis, and shape immune signaling pathways. In healthy tissue, the concentrations of putrescine, spermidine, and spermine are controlled with exquisite precision by an interconnected network of biosynthetic enzymes such as ornithine decarboxylase, spermidine synthase, and spermine synthase, catabolic enzymes including spermine oxidase and polyamine oxidase, the acetylation enzyme spermidine/spermine-N1-acetyltransferase 1, and a dedicated polyamine transport system that shuttles these molecules across cellular compartments.

The review details how disruption of each node in this network has been linked to neurological disease. In Alzheimer’s disease, altered polyamine flux intersects directly with the two hallmark protein pathologies. Recent work has shown that aberrant activity of antizyme inhibitor 2 and the resulting polyamine imbalance can precipitate tau neuropathology, while separate studies found that reducing spermine synthase activity enhances autophagy and thereby suppresses tau accumulation. Targeted metabolomic and transcriptomic analyses of Alzheimer’s patients have revealed dysregulation across multiple metabolic networks involving brain transmethylation and polyamine pathways, and single-cell metabolomics of ageing and Alzheimer’s brains has now mapped distinctive polyamine signatures in microglia, astrocytes, and neurons. The picture that emerges is one of a metabolic system pushed off balance, with excess spermine and its oxidation products contributing to oxidative stress and impaired autophagic clearance of toxic protein aggregates.

Parkinson’s disease tells a complementary story centered on transport and interconversion. The lysosomal transporter ATP13A2, mutations in which cause the inherited Kufor-Rakeb syndrome, a form of early-onset parkinsonism, has been shown to export polyamines from lysosomes. When this transporter fails, polyamines accumulate inside lysosomes, contributing to lysosomal dysfunction, mitochondrial oxidative stress, and heightened vulnerability of dopaminergic neurons to alpha-synuclein toxicity. Structural studies of human ATP13A2 have revealed the molecular basis of its polyamine transport activity, and experiments in fruit flies have demonstrated that manipulating polyamine interconversion enzymes such as SAT1 can directly alter alpha-synuclein levels and toxicity. Metabolomic studies in Parkinson’s patients have independently identified polyamine-related signatures associated with diagnosis and clinical severity, strengthening the case that these pathways are not merely bystanders but active participants in the disease process.

Beyond the two most common neurodegenerative disorders, the review catalogues polyamine involvement across a striking breadth of conditions. In amyotrophic lateral sclerosis, dysregulated polyamine metabolism contributes to muscle fiber vulnerability, and alterations in ornithine decarboxylase activity have been documented in mouse models of motor neuron degeneration. Interestingly, spermidine supplementation has shown beneficial transcriptomic effects in ALS mouse models, and modulation of histone methylation by spermidine has improved motor neuron survival, highlighting the dual character of these molecules. In Snyder-Robinson syndrome, a rare X-linked disorder caused by spermine synthase deficiency, the loss of spermine production leads to lysosomal dysfunction and oxidative stress, producing intellectual disability, muscle and bone abnormalities, and movement problems. Bachmann-Bupp syndrome, caused by mutations in the ornithine decarboxylase gene, has even yielded to targeted therapy, with the polyamine synthesis inhibitor eflornithine used to restore metabolic balance in affected children.

The review also emphasizes roles for polyamine catabolism in epilepsy, cerebral ischemia, and diabetic retinopathy. Transgenic mice overexpressing spermine oxidase in cortical neurons show astrocyte dysfunction and increased susceptibility to epileptic seizures, and neuroinflammation has been shown to promote spermine degradation in temporal lobe epilepsy, contributing to drug resistance. In cerebral ischemia, the spermine oxidation product 3-aminopropanal acts as a potent neurotoxin, and neutralizing it in animal models provides marked neuroprotection. In diabetic retinopathy, spermine oxidase activity drives retinal neurodegeneration, and pharmacological inhibition of this enzyme has preserved visual acuity and retinal function in diabetic mice. These findings collectively suggest that the specific catabolic products of polyamine breakdown, rather than polyamines themselves, may be the critical toxic agents in several contexts.

To organize this sprawling evidence, the authors frame four interconnected mechanistic themes through which polyamine dysregulation damages the nervous system: autophagy, oxidative stress, proteostasis, and neuroinflammation. Spermidine has emerged as a bona fide autophagy inducer, essential even for fasting-mediated autophagy and longevity benefits, and its epigenetic effects on histone modifications appear to underlie some of its neuroprotective actions. Yet the same molecules can generate reactive oxygen species when oxidized by spermine oxidase and polyamine oxidase, producing hydrogen peroxide and reactive aldehydes. Polyamine stress responses triggered by tauopathy and other protein aggregation states further complicate the balance, and polyamine metabolism in immune cells has been shown to promote Th17 polarization and inflammatory disease progression, linking this ancient metabolic pathway to neuroinflammation.

Therapeutically, the review outlines three broad strategies now under investigation. The first is direct spermidine administration, which has reduced neuroinflammation and soluble amyloid-beta in Alzheimer’s mouse models and improved cognitive measures in studies of ageing, though it carries an unresolved risk that autophagy induction could, in some settings, tip toward apoptosis. The second is pharmacological modulation of polyamine-metabolic enzymes and transporters, exemplified by difluoromethylornithine, an inhibitor of ornithine decarboxylase with an established history in oncology and now demonstrated benefit in Bachmann-Bupp syndrome, as well as SMOX inhibition in diabetic retinopathy and phenylbutyrate-mediated modulation of polyamine acetylation in Snyder-Robinson syndrome models. The third involves combination strategies that pair polyamine interventions with autophagy modulation, anti-inflammatory agents, or delivery technologies designed to cross the formidable barrier of the blood-brain barrier.

The authors are careful to stress that polyamines exert both protective and toxic effects depending on concentration, cellular compartment, and disease context, a duality that makes simplistic supplementation or depletion strategies risky. A dose of spermidine that enhances autophagic clearance of alpha-synuclein in one model could, in another cellular compartment or disease stage, fuel the biomolecular condensation processes implicated in the aggregation of tau and alpha-synuclein. Successful translation, the review concludes, will require CNS-relevant biomarkers to track polyamine flux in living patients, careful optimization of dose and route of administration, and explicit attention to blood-brain barrier constraints that determine whether orally or peripherally administered agents can ever reach their neuronal targets. As the global burden of dementia and other neurodegenerative diseases continues to climb, the humble polyamines, once a footnote of cell biology, are now positioned as one of the most mechanistically rich and therapeutically tantalizing frontiers in neuroscience.

Subject of Research: Dysregulated polyamine metabolism in neurological disorders

Article Title: Dysregulated polyamine metabolism in neurological disorders: molecular mechanisms and therapeutic opportunities

Article References: Li, K., Si, Q., Zhang, C., Zhang, C., Wang, M., Liu, J., Zhao, J., Xing, H., & Liu, J. (2026). Dysregulated polyamine metabolism in neurological disorders: molecular mechanisms and therapeutic opportunities. Molecular Biology Reports, 53(1), Article 1602. https://doi.org/10.1007/s11033-026-12774-y

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12774-y

Keywords: polyamine metabolism, spermidine, neurodegeneration, Alzheimer's disease, Parkinson's disease, autophagy, oxidative stress, tauopathy, ATP13A2, spermine oxidase, therapeutic targets, neurological disorders

A new study published in the Journal of Advanced Research offers a strikingly different approach to attacking tau at its upstream source. Rather than blocking the activity of one of tau’s key dysregulating kinases, the research team designed a small molecule that eliminates the kinase protein itself. The target is death-associated protein kinase 1, or DAPK1, an enzyme that has accumulated an impressive pathogenic dossier in Alzheimer’s research. DAPK1 activates MARK1/2 to trigger abnormal tau phosphorylation, directly phosphorylates tau at disease-relevant residues, and through phosphorylation of SENP1 promotes tau SUMOylation, exacerbating tau pathology and cognitive dysfunction. Genetic knockdown and pharmacological inhibition of DAPK1 have both been shown to reduce tau phosphorylation and mitigate neurodegeneration in cell and animal models. Yet traditional small-molecule kinase inhibitors suffer from well-known drawbacks: short-lived efficacy, compensatory signaling from parallel pathways, and substantial off-target liability.

To overcome these limitations, the team turned to targeted protein degradation, a next-generation pharmacological strategy that hijacks the cell’s own proteostasis machinery. Their specific platform is hydrophobic tagging, or HyT, in which a bifunctional molecule couples a ligand that binds the protein of interest to a bulky hydrophobic moiety, typically adamantane, that mimics the exposed greasy surfaces of misfolded proteins. The cell’s quality-control machinery is fooled into ubiquitinating the tagged protein and destroying it via the ubiquitin-proteasome system. Adamantane-based hydrophobic tags carry distinct advantages over the better-known PROTAC degraders: simpler molecular design, lower molecular weight, favorable ADME characteristics, and high degradation efficiency. The approach has already been used to degrade tau, TDP-43, and mutant huntingtin, but it had never been applied to DAPK1.

From a library of candidate degraders built by conjugating a previously characterized DAPK1-binding ligand to adamantane- or fluorene-based hydrophobic tags through alkylamine linkers of varying length, one compound emerged as the clear leader. Named CJ1, the molecule reduced DAPK1 protein levels in mouse primary cortical neurons to roughly half of control levels at a screening concentration of 1 micromolar, outperforming all other compounds in the series. Molecular docking suggested that CJ1’s DAPK1-binding moiety occupies a distinct hydrophobic pocket on the kinase surface, with favorable electrostatic complementarity at the binding interface. Critically, cytotoxicity testing showed that CJ1 did not compromise the viability of primary neurons even at concentrations up to 20 micromolar, providing a wide margin between functional activity and cellular harm.

The mechanistic characterization of CJ1 was rigorous. In primary cortical neurons, the compound degraded DAPK1 in a dose-dependent fashion, with a half-maximal degradation concentration of approximately 0.18 micromolar, and a time course showing detectable degradation beginning four hours after treatment and sustained suppression lasting up to 48 hours. Quantitative PCR confirmed that DAPK1 mRNA levels were unchanged, indicating a posttranslational mechanism. When cells were pretreated with the proteasome inhibitor MG-132, CJ1-induced degradation was abolished, and ubiquitination assays demonstrated markedly increased polyubiquitinated DAPK1 in the presence of the compound. Together, these experiments established that CJ1 marks DAPK1 for ubiquitin-dependent proteasomal destruction, precisely the event-driven behavior expected of a hydrophobic tagging degrader.

With the mechanism confirmed, the investigators asked whether eliminating DAPK1 would tame tau. In primary cortical neurons, SH-SY5Y neuroblastoma cells, and SH-SY5Y cells expressing the P301L mutant human tau, CJ1 treatment reduced levels of tau phosphorylated at threonine 231, serine 262, and serine 396, along with total tau. These phosphorylation sites are deeply meaningful in Alzheimer’s biology: phosphorylation at Ser262 within the microtubule-binding repeat domain critically weakens tau’s grip on microtubules, Thr231 primes tau for further phosphorylation by GSK3beta and contributes to microtubule destabilization, and the Ser396/404 epitope marks advanced pathological tau. Several control experiments reinforced the specificity of the effect. CJ1 did not alter the levels of the major tau kinases GSK3beta and CDK5, the phosphatase PP2A, or the related kinase DAPK3. In DAPK1 knockout neurons, CJ1 lost its ability to reduce tau or phospho-tau, and a control compound lacking the DAPK1-binding moiety was inert. Overexpressing DAPK1 in cells also rescued the phenotype, strongly arguing that CJ1 acts specifically through DAPK1 degradation rather than through incidental off-target effects.

The in vivo results were the most consequential. A central hurdle for any Alzheimer’s therapeutic is crossing the blood-brain barrier, and liquid chromatography-mass spectrometry confirmed that intact CJ1 was detectable in mouse brain after systemic administration. In a tauopathy model created by injecting an adeno-associated virus carrying human P301L tau into the hippocampal CA3 region, DAPK1 was upregulated and CJ1 treatment lowered it in a dose-dependent manner, with 10 milligrams per kilogram nearly restoring baseline levels. CJ1 reduced human tau accumulation and phosphorylation at Thr231 and the AT8 epitope in the hippocampus. In aged hTau transgenic mice, which express all six human tau isoforms and develop genuine neurofibrillary tangles, five weeks of CJ1 treatment significantly reduced tangle burden in the cortex and lowered total tau and phospho-tau at multiple AD-relevant sites in both sarkosyl-soluble and, importantly, sarkosyl-insoluble fractions, the biochemical signature of aggregated, pathological tau.

Pathology translated into preserved brain structure and function. CJ1-treated tauopathy mice retained more NeuN-positive neurons, showed restored MAP2 immunoreactivity indicating healthier dendrites, and displayed dose-dependent recovery of dendritic spine density on Golgi-Cox staining. Neuroinflammation also receded: astrocytic activation marked by GFAP and microglial activation marked by Iba1 were both suppressed, pro-inflammatory iNOS decreased, and anti-inflammatory Arg-1 increased. Functionally, in the Morris water maze, CJ1-treated mice learned the platform location faster, spent more time in the target quadrant during the probe trial, and crossed the former platform location more often, with all groups swimming at comparable speeds, ruling out motor confounds. Notably, only the higher dose produced cognitive improvement, suggesting that partial biochemical correction of tau pathology is insufficient and that robust suppression is required for behavioral benefit.

Safety data were encouraging. CJ1 showed negligible hemolysis at concentrations up to 800 micrograms per milliliter, serum creatinine, ALT, and AST remained within normal ranges, and histological examination of the heart, liver, lung, and kidney revealed no treatment-related abnormalities. The authors are candid about limitations: the behavioral findings derive from an acute, region-specific model; the selectivity screen covered only a small panel of proteins; and the detailed brain distribution of CJ1 remains unmapped, as do potential differential effects on 3R versus 4R tau isoforms. Nonetheless, the study establishes CJ1 as a first-in-class DAPK1 degrader and provides a compelling proof of concept that hydrophobic tagging can eliminate an upstream driver of tau pathology inside cells, something neither conventional kinase inhibitors, which transiently block catalytic activity, nor tau immunotherapies, which target extracellular aggregates, can accomplish. By abolishing all of DAPK1’s functional domains and scaffolding roles in a catalytic, substoichiometric manner, this degrader strategy offers a mechanistically distinct and potentially more durable route to slowing the neurodegeneration that lies at the heart of Alzheimer’s disease.

Subject of Research: A hydrophobic tagging degrader that selectively eliminates DAPK1 to attenuate tau pathology in Alzheimer's disease

Article Title: Selective degradation of DAPK1 via a novel hydrophobic tagging attenuates tau pathology in Alzheimer’s disease

Article References: Li, R., Wu, X., Yao, J., Chen, J., Shui, X., Zheng, X., Tian, W., Wang, L., Zhou, Y., Zhang, T., Chen, D., Liu, Y., & Lee, T. H. (2026). Selective degradation of DAPK1 via a novel hydrophobic tagging attenuates tau pathology in Alzheimer’s disease. Journal of Advanced Research, 87, 1027-1043. https://doi.org/10.1016/j.jare.2025.12.037

Image Credits: AI Generated

DOI: 10.1016/j.jare.2025.12.037

Keywords: Alzheimer's disease, DAPK1, tau pathology, hydrophobic tagging, targeted protein degradation, neurofibrillary tangles, proteasome, tau phosphorylation, blood-brain barrier, neurodegeneration, drug discovery, tauopathy

Proteins are not static entities. After they are translated from messenger RNA, they undergo a dizzying array of chemical modifications: phosphate groups are added and removed, the protein backbone is clipped by proteases, small protein tags such as ubiquitin are attached, and amino acids can be chemically altered in dozens of other ways. Each unique combination of modifications and sequence variants constitutes a distinct proteoform. The trouble is that two proteoforms of the same protein can behave in radically different ways inside a cell, one folding into a harmless shape and another seeding the toxic aggregates that kill neurons. Standard proteomics methods, which typically chop proteins into small peptides before identifying them, lose the connectivity information that reveals which modifications coexisted on the same original molecule. As a result, the proteoform landscape of even a well-studied protein like tau has remained only partially charted.

Iterative Mapping of proteoforms tackles this problem by interrogating individual protein molecules directly, preserving the integrity of each proteoform throughout the measurement. The core idea is to perform repeated cycles of imaging-based readout on single immobilized molecules, building up a pattern of signals that serves as a molecular fingerprint. Because each molecule is observed on its own, the resulting data reflect genuine single-molecule heterogeneity rather than population averages. This matters enormously for tau, where rare proteoforms may be the biologically decisive species. A modification present on only one percent of tau molecules could be invisible to bulk measurements, yet a small pool of aberrantly modified molecules might be sufficient to nucleate the pathological aggregates that spread through the brain in Alzheimer’s disease.

The scale of the new approach is what sets it apart. Earlier single-molecule protein characterization methods, while conceptually elegant, were limited in throughput, making it impractical to survey the full diversity of proteoforms in complex biological samples. Iterative Mapping achieves large-scale measurement by combining highly parallel detection with an iterative readout strategy, allowing millions of individual molecules to be characterized in a single experiment. The researchers validated the technique using control samples of known composition, a critical step that established the method’s accuracy in quantifying predefined proteoform groups. Only after demonstrating that the technique could correctly identify and count proteoforms in mixtures of known makeup did the team apply it to more complex and clinically relevant material.

Tau is an unusually challenging target for such an analysis. In the human brain, the MAPT gene produces six major isoforms of tau through alternative splicing, differing in the number of microtubule-binding repeats and N-terminal inserts. On top of this isoform diversity, tau carries an enormous number of possible phosphorylation sites, with dozens of serine, threonine, and tyrosine residues that can be modified individually or in combination. The phosphorylation state of tau governs its normal function in stabilizing microtubules, the structural scaffolds of neurons, but hyperphosphorylation promotes tau’s detachment from microtubules, its misfolding, and ultimately its aggregation into the paired helical filaments that compose neurofibrillary tangles. Because the biological consequences of phosphorylation depend on which sites are modified together on the same molecule, knowing the total amount of tau phosphorylation in a sample is far less informative than knowing the actual distribution of proteoforms.

The demonstration in model systems used in tauopathy research provides a bridge between controlled validation experiments and human tissue. Cell and animal models of tauopathy are workhorses of the field, used to test hypotheses about how tau becomes pathological and to screen candidate therapies. Applying Iterative Mapping to these systems allows researchers to characterize how the tau proteoform landscape shifts as disease-like states develop, and to compare the proteoform signatures of different models against one another. Such comparisons could help resolve a persistent problem in the field: different model systems recapitulate different aspects of tau pathology, and it has been difficult to know which models most faithfully reflect the human disease. A quantitative, single-molecule proteoform census offers a new common currency for making those comparisons.

The most striking application, however, is the analysis of human-derived brain tissue samples. Post-mortem brain tissue from individuals with Alzheimer’s disease and related tauopathies is a precious and technically difficult resource, often available in limited quantities and frequently affected by post-mortem delays and variable tissue quality. Demonstrating that Iterative Mapping can extract meaningful proteoform quantification from such material establishes the method’s readiness for real-world translational research. The ability to profile tau proteoform groups directly in human brain tissue means that hypotheses generated in models can now be tested against the actual molecular substrate of disease, and that proteoform patterns associated with specific diagnoses, disease stages, or clinical outcomes can be systematically searched for.

The implications for drug development could be substantial. A growing number of therapeutic strategies target tau directly, including antisense oligonucleotides designed to reduce tau production, immunotherapies intended to clear pathological tau species, and small molecules aimed at inhibiting the kinases that phosphorylate tau. Each of these approaches would benefit from a measurement technology that can report precisely which proteoforms are reduced or altered following treatment. Bulk phosphorylation assays can indicate that total tau phosphorylation has decreased, but they cannot reveal whether the specific proteoform groups thought to drive toxicity have been affected. Single-molecule proteoform quantification provides exactly that granularity, potentially enabling biomarker-guided clinical trials in which molecular responses are monitored at the level of individual protein species.

Beyond tau, the demonstration establishes a general template for large-scale single-molecule proteoform analysis that could be extended to other proteins of biomedical importance. Alpha-synuclein in Parkinson’s disease, huntingtin in Huntington’s disease, TDP-43 in amyotrophic lateral sclerosis, and amyloid precursor protein in Alzheimer’s disease all share the same basic challenge: their pathological behavior depends on proteoform-level details that bulk methods obscure. If Iterative Mapping can be adapted to these targets, the technology could catalyze a broader shift in proteomics toward intact-protein, single-molecule measurement, complementing the peptide-centric workflows that have dominated the field for decades. The convergence of single-molecule imaging, iterative biochemical readout, and computational analysis reflected in this work suggests that the long-sought goal of routinely reading complete proteoforms is moving from aspiration toward practice.

Challenges remain before such methods become routine in laboratories and clinics. Sample preparation for single-molecule analysis must preserve labile modifications, the computational pipelines for interpreting iterative readout patterns must be robust across diverse sample types, and the proteoform groups quantified today represent a subset of the full molecular diversity that likely exists in brain tissue. Nevertheless, the demonstration that large-scale, single-molecule proteoform measurement is achievable, validated against known controls, and applicable to human tissue marks a genuine advance. For a protein like tau, whose transformation from a neuronal workhorse into a killer aggregate has puzzled researchers for decades, the ability to count and classify its molecular forms one molecule at a time may finally provide the resolution needed to understand, and ultimately interrupt, the progression of tauopathy.

Subject of Research: Large-scale single-molecule measurement of intact tau proteoforms using Iterative Mapping

Article Title: Large-scale single-molecule analysis of tau proteoforms

Article References: Joly, J., Budamagunta, V., Zhang, Z., Nortman, B., Jouzi, M., Bhatnagar, R., Egertson, J. D., Flaster, M. E., Grothe, R., Guha, S., Kaneshige, K., McVey, K., Nelson, N., Perera, R. T., Tan, S. J., Trinh, T., Arnott, D., Lipka, J., Pandya, N. J., … Mallick, P. (2026). Large-scale single-molecule analysis of tau proteoforms. Nature Methods, 23(9), 1786-1797. https://doi.org/10.1038/s41592-026-03188-6

Image Credits: AI Generated

DOI: 10.1038/s41592-026-03188-6

Keywords: tau, proteoforms, single-molecule analysis, Iterative Mapping, tauopathy, Alzheimer's disease, phosphorylation, proteomics, neurodegeneration, brain tissue, biomarkers, drug development