Bosca, L. | bioRxiv Science

bioRxiv2026

A Toxic Tau-PFKFB3 Circuit Reduces F2,6BP Levels and Drives Neurodegeneration

Alzheimers disease (AD) and related dementias are progressive neurodegenerative disorders manifested by aggregation of Tau and Amyloid beta (A{beta}). Emerging evidence suggests that metabolic dysregulation contributes to AD pathogenesis, yet how metabolic alterations interface with neuronal integrity remains unclear. Here, we identify dysfunction in PFKFB3-F2,6BP (fructose-2,6-bisphosphate) metabolic axis as a key feature of AD. We show that pathological Tau aggregates aberrantly sequester PFKFB3, limiting its activity and resulting in F2,6BP depletion. F2,6BP exerts protective effects through multiple convergent mechanisms: (i) direct activation of polynucleotide kinase 3-phosphatase (PNKP) to facilitate DNA strand break repair; (ii) transcriptional upregulation of the protein phosphatase 2A catalytic subunit (PP2CA) to limit Tau phosphorylation; (iii) stabilization of PFKFB3 to diminish its sequestration into aggregates; and (iv) direct inhibition of Tau aggregation. These findings establish F2,6BP as a central node linking metabolic regulation to both genomic stability and proteostasis in AD. Importantly, exogenous F2,6BP supplementation rescues multiple pathological features across diverse model systems, including induced neuronal cell lines (iN), primary neurons, organotypic hippocampal slice cultures, and in a Drosophila model of AD. These findings redefine F2,6BP as a metabolite that directly coordinates genome maintenance and proteostasis in neurons. Overall, this study identifies the PFKFB3-F2,6BP axis as a central driver of AD pathogenesis and a promising therapeutic target. HighlightsO_LITau aggregates sequester PFKFB3 depletes neuronal F2,6BP C_LIO_LIF2,6BP links metabolism to DNA repair and Tau proteostasis C_LIO_LIF2,6BP activates PNKP and upregulates PP2A to counter Tau pathology C_LIO_LIF2,6BP supplementation rescues AD phenotypes across models C_LI

neuroscience↗

bioRxiv2023

A glycolytic metabolite restores DNA repair activity of polynucleotide kinase 3-phosphatase in polyglutamine (PolyQ) diseases

Huntingtons disease (HD) and spinocerebellar ataxia type 3 (SCA3) are the two most prevalent polyglutamine (polyQ) neurodegenerative diseases, caused by CAG (encoding glutamine) repeat expansion in the coding region of the huntingtin (HTT) and ataxin-3 (ATXN3) proteins, respectively. We have earlier reported that the activity, but not the protein level, of an essential DNA repair enzyme, polynucleotide kinase 3-phosphatase (PNKP), is severely abrogated in both HD and SCA3 resulting in accumulation of double-strand breaks in patients brain genome. While investigating the mechanistic basis for the loss of PNKP activity and accumulation of DNA double-strand breaks leading to neuronal death, we observed that PNKP interacts with the nuclear isoform of 6-phosphofructo-2-kinase fructose-2,6-bisphosphatase 3 (PFKFB3). Depletion of PFKFB3 markedly abrogates PNKP activity without changing its protein level. Notably, the levels of both PFKFB3 and its product fructose-2,6 bisphosphate (F2,6BP), an allosteric modulator of glycolysis, are significantly lower in the nuclear extracts of post-mortem brain tissues of HD and SCA3 patients. Supplementation of F2,6BP restored PNKP activity in the nuclear extracts of patients brain. Moreover, intracellular delivery of F2,6BP restored both the activity of PNKP and the integrity of transcribed genome in neuronal cells derived from striatum of HD mouse. Importantly, supplementing F2,6BP rescued the HD phenotype in Drosophila, suggesting F2,6BP to serve in vivo as a cofactor for the proper functionality of PNKP and thereby, of brain health. Our results thus provide a compelling rationale for exploring the therapeutic use of F2,6BP and structurally related compounds for treating polyQ diseases. SignificanceTo unravel the biological basis for the loss of PNKP activity in HD and SCA3, the two most prevalent polyglutamine neurodegenerative disorders, we analyzed PNKP interactome and found that the nuclear isoform of a glycolytic enzyme PFKFB3 associated with PNKP and other repair proteins forming a multiprotein complex. Surprisingly, we found that PFKFB3 and its biosynthetic product, F2,6BP are significantly low in the affected region of patients brain. Exogenous addition of F2,6BP restored PNKP activity in patients brain nuclear extract. Moreover, supplementing F2,6BP in HD cells and fruit flies restored genome integrity and rescued the disease symptoms. While there is no curative therapy for HD/SCA3, except symptom management, our discovery suggests that F2,6BP supplementation would be a promising therapeutic option.

biochemistry↗