Alzheimer's disease (AD) is the most common dementia, and no disease-modifying therapeutic agents are currently available. BDNF/TrkB signaling is impaired in AD and is associated with prominent delta-secretase (δ-secretase, also known as asparaginyl endopeptidase or legumain) activation, which simultaneously cleaves both APP and Tau and promotes Aβ production and neurofibrillary tangles (NFT) pathologies. Here we show that the optimized δ-secretase inhibitor (#11a) or TrkB receptor agonist (CF3CN) robustly blocks δ-secretase activity separately, and their combination synergistically blunts δ-secretase, exhibiting promising therapeutic efficacy in 3xTg AD mouse model. The optimal δ-secretase inhibitor reveals demonstrable brain exposure and oral bioavailability, suppressing APP N585 and Tau N368 cleavage by δ-secretase. Strikingly, CF3CN treatment evidently escalates BDNF levels. Both #11a and CF3CN display strong in vivo PK/PD properties and ability to suppress δ-secretase activity in the brain. Orally administrated CF3CN strongly activates TrkB that triggers active Akt to phosphorylate δ-secretase T322, preventing its proteolytic activation and mitigating AD pathologies. #11a or CF3CN significantly diminishes AD pathogenesis and improves cognitive functions with the combination exhibiting the maximal effect. Thus, our data support that these derivatives are strong pharmaceutical candidates for the treatment of AD.

Introduction Cerebrospinal fluid (CSF) tau biomarkers are reliable diagnostic markers for Alzheimer’s disease (AD). However, their strong association with amyloid pathology may limit their reliability as specific markers of tau neurofibrillary tangles. A recent study showed evidence that a ratio of CSF C-terminally truncated tau (tau368, a tangle-enriched tau species), especially in ratio with total tau (t-tau), correlates strongly with tau PET tracer uptake. In this study, we set to evaluate the performance of the tau368/t-tau ratio in capturing tangle pathology, as indexed by a high-affinity tau PET tracer, as well as its association with severity of clinical symptoms. Methods In total, 125 participants were evaluated cross-sectionally from the Translational Biomarkers of Aging and Dementia (TRIAD) cohort (21 young, 60 cognitively unimpaired [CU] elderly [15 Aβ+], 10 Aβ+ with mild cognitive impairment [MCI], 14 AD dementia patients, and 20 Aβ− individuals with non-AD cognitive disorders). All participants underwent amyloid and tau PET scanning, with [18F]-AZD4694 and [18F]-MK6240, respectively, and had CSF measurements of p-tau181, p-tau217, and t-tau. CSF concentrations of tau368 were quantified in all individuals with an in-house single molecule array assay. Results CSF tau368 concentration was not significantly different across the diagnostic groups, although a modest increase was observed in all groups as compared with healthy young individuals (all P < 0.01). In contrast, the CSF tau368/t-tau ratio was the lowest in AD dementia, being significantly lower than in CU individuals (Aβ−, P < 0.001; Aβ+, P < 0.01), as well as compared to those with non-AD cognitive disorders (P < 0.001). Notably, in individuals with symptomatic AD, tau368/t-tau correlated more strongly with [18F]-MK6240 PET SUVR as compared to the other CSF tau biomarkers, with increasing associations being seen in brain regions associated with more advanced disease (isocortical regions > limbic regions > transentorhinal regions). Importantly, linear regression models indicated that these associations were not confounded by Aβ PET SUVr. CSF tau368/t-tau also tended to continue to become more abnormal with higher tau burden, whereas the other biomarkers plateaued after the limbic stage. Finally, the tau368/t-tau ratio correlated more strongly with cognitive performance in individuals with symptomatic AD as compared to t-tau, p-tau217 and p-tau181. Conclusion The tau368/t-tau ratio captures novel aspects of AD pathophysiology and disease severity in comparison to established CSF tau biomarkers, as it is more closely related to tau PET SUVR and cognitive performance in the symptomatic phase of the disease.

The noradrenergic locus ceruleus (LC) is the first site of detectable tau pathology in Alzheimer’s disease (AD), but the mechanisms underlying the selective vulnerability of the LC in AD have not been completely identified. In the present study, we show that DOPEGAL, a monoamine oxidase A (MAO-A) metabolite of norepinephrine (NE), reacts directly with the primary amine on the Lys353 residue of tau to stimulate its aggregation and facilitate its propagation. Inhibition of MAO-A or mutation of the Lys353 residue to arginine (Lys353Arg) decreases tau Lys353–DOPEGAL levels and diminishes tau pathology spreading. Wild-type tau preformed fibrils (PFFs) trigger Lys353–DOPEGAL formation, tau pathology propagation and cognitive impairment in MAPT transgenic mice, all of which are attenuated with PFFs made from the Lys353Arg mutant. Thus, the selective vulnerability of LC neurons in AD may be explained, in part, by NE oxidation via MAO-A into DOPEGAL, which covalently modifies tau and accelerates its aggregation, toxicity and propagation.

There is increasing evidence that anterior pituitary hormones, traditionally thought to have unitary functions in regulating single endocrine targets, act on multiple somatic tissues, such as bone, fat, and liver. There is also emerging evidence for anterior pituitary hormone action on brain receptors in mediating central neural and peripheral somatic functions. Here, we have created the most comprehensive neuroanatomical atlas on the expression of TSHR, LHCGR, and FSHR. We have used RNAscope, a technology that allows the detection of mRNA at single-transcript level, together with protein level validation, to document Tshr expression in 173 and Fshr expression in 353 brain regions, nuclei and subnuclei identified using the Atlas for the Mouse Brain in Stereotaxic Coordinates. We also identified Lhcgr transcripts in 401 brain regions, nuclei and subnuclei. Complementarily, we used ViewRNA, another single-transcript detection technology, to establish the expression of FSHR in human brain samples, where transcripts were co-localized in MALAT1-positive neurons. In addition, we show high expression for all three receptors in the ventricular region—with yet unknown functions. Intriguingly, Tshr and Fshr expression in the ependymal layer of the third ventricle was similar to that of the thyroid follicular cells and testicular Sertoli cells, respectively. In contrast, Fshr was localized to NeuN-positive neurons in the granular layer of the dentate gyrus in murine and human brain—both are Alzheimer’s disease-vulnerable regions. Our atlas thus provides a vital resource for scientists to explore the link between the stimulation or inactivation of brain glyco-protein hormone receptors on somatic function. New actionable pathways for human disease may be unmasked through further studies.

Asparagine endopeptidase (AEP), a newly identified delta-secretase, simultaneously cleaves both APP and Tau, promoting Alzheimer's disease (AD) pathologies. However, its pathological role in AD remains incompletely understood. Here we show that delta-secretase cleaves BACE1, a rate-limiting protease in amyloid-β (Aβ) generation, escalating its enzymatic activity and enhancing senile plaques deposit in AD. Delta-secretase binds BACE1 and cuts it at N294 residue in an age-dependent manner and elevates its protease activity. The cleaved N-terminal motif is active even under neutral pH and associates with senile plaques in human AD brains. Subcellular fractionation reveals that delta-secretase and BACE1 reside in the endo-lysosomes. Interestingly, truncated BACE1 enzymatic domain (1-294) augments delta-secretase enzymatic activity and accelerates Aβ production, facilitating AD pathologies and cognitive impairments in APP/PS1 AD mouse model. Uncleavable BACE1 (N294A) inhibits delta-secretase activity and Aβ production and decreases AD pathologies in 5XFAD mice, ameliorating cognitive dysfunctions. Hence, delta- and beta- secretases’ crosstalk aggravates each other's roles in AD pathogenesis.

It remains unclear how cancer cells coordinate glycolysis and biosynthesis to support rapidly growing tumors. We found that glycolytic enzyme phosphoglycerate mutase 1 (PGAM1), commonly upregulated in human cancers due to loss of TP53, contributes to biosynthesis regulation in part by controlling intracellular levels of its substrate 3-phosphoglycerate (3-PG) and product 2-phosphoglycerate (2-PG). 3-PG binds to and inhibits 6-phosphogluconate dehydrogenase in the oxidative pentose phosphate pathway (PPP), while 2-PG activates 3-phosphoglycerate dehydrogenase to provide feedback control of 3-PG levels. Inhibition of PGAM1 by shRNA or a small molecule inhibitor PGMI-004A results in increased 3-PG and decreased 2-PG levels in cancer cells, leading to significantly decreased glycolysis, PPP flux and biosynthesis, as well as attenuated cell proliferation and tumor growth.

SRPK, a family of cell cycle regulated protein kinases, phosphorylate Serine/Arginine (SR) domain-containing proteins in nuclear speckles and mediate the pre-mRNA splicing. However, the physiological roles of this event in cell cycle are incompletely understood. Here we show that SRPK2 binds and phosphorylates acinus, an SR protein essential for RNA splicing, and redistributes it from the nuclear speckles to the nucleoplasm, resulting in cyclin A1 but not A2 upregulation. Acinus S422D, an SRPK2 phosphorylation mimetic, enhances cyclin A1 transcription, whereas acinus S422A, an unphosphorylatable mutant, blocks the stimulatory effect of SRPK2. Ablation of acinus or SRPK2 abrogates cyclin A1 expression in leukemia cells and arrest cells at G1 phase. Overexpression of acinus or SRPK2 increases leukemia cell proliferation. Further, both SRPK2 and acinus are overexpressed in some of human AML patients and correlate with elevated cyclin A1 expression levels, fitting with the oncogenic activity of cyclin A1 in leukemia. Thus, our findings establish a molecular mechanism by which SR splicing machinery regulates cell cycle and contributes to leukemia tumorigenesis.

Cyclin A1 is essential for leukemia progression, and its expression is tightly regulated by acinus, a nuclear speckle protein. However, the molecular mechanism of how acinus mediates cyclin A1 expression remains elusive. Here we show that transcription corepressor CtBP2 directly binds acinus, which is regulated by NGF, inhibiting its stimulatory effect on cyclin A1 but not cyclin A2 expression in leukemia. NGF, a cognate ligand for the neurotrophic receptor TrkA, promotes the interaction between CtBP2 and acinus through triggering acinus phosphorylation by Akt. Overexpression of CtBP2 diminishes cyclin A1 transcription, whereas depletion of CtBP2 abolishes NGF’s suppressive effect on cyclin A1 expression. Strikingly, gambogic amide, a newly identified TrkA agonist, potently represses cyclin A1 expression, thus blocking K562 cell proliferation. Moreover, gambogic amide ameliorates the leukemia progression in K562 cells inoculated nude mice. Hence, NGF down-regulates cyclin A1 expression through escalating CtBP2/acinus complex formation, and gambogic amide might be useful for human leukemia treatment.

Diabetes is a risk factor for Alzheimer’s disease (AD), which is also called type 3 diabetes with insulin reduction and insulin resistance in AD patient brains. However, the molecular mechanism coupling diabetes to AD onset remains incompletely understood. Here we show that inflammation, associated with obesity and diabetes elicited by high-fat diet (HFD), activates neuronal C/EBPβ/AEP signaling that drives AD pathologies and cognitive disorders. HFD stimulates diabetes and insulin resistance in neuronal Thy1-C/EBPβ transgenic (Tg) mice, accompanied with prominent mouse Aβ accumulation and hyperphosphorylated Tau aggregation in the brain, triggering cognitive deficits. These effects are profoundly diminished when AEP is deleted from C/EBPβ Tg mice. Chronic treatment with inflammatory lipopolysaccharide (LPS) facilitates AD pathologies and cognitive disorders in C/EBPβ Tg but not in wild-type mice, and these deleterious effects were substantially alleviated in C/EBPβ Tg/AEP −/− mice. Remarkably, the anti-inflammatory drug aspirin strongly attenuates HFD-induced diabetes and AD pathologies in neuronal C/EBPβ Tg mice. Therefore, our findings demonstrate that inflammation-activated neuronal C/EBPβ/AEP signaling couples diabetes to AD.

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders. However, its cellular and molecular mechanisms still wrap in the mist. This is partially caused by the absence of appropriate animal models mimicking sporadic PD that constitutes the majority of cases. Previously, we reported that a cysteine protease, asparagine endopeptidase (AEP), is activated in an age-dependent manner, and cleaves α-synuclein in the brain of sporadic PD patients. The AEP-derived α-synuclein 1-103 fragment is required for the pathogenesis of PD. Thus, we designed and characterized a novel transgenic mouse line expressing α-synuclein 1-103 (designated N103 mice). This model shows an abundant accumulation of pathological α-synuclein in the central nervous system, loss of dopaminergic neurons in the substantia nigra, and progressive striatal synaptic degeneration. The N103 mice also manifest age-dependent PD-like behavioral impairments. Notably, the mice show weight loss and constipation, which are the common non-motor symptoms in PD. The RNA-sequencing analysis found that the transcriptomics pattern was extensively altered in N103 mice. In conclusion, the N103 mouse line, as a brand-new tool, might provide new insights into PD research.