Chih Hsin Lin

The CAG repeat in SCA12 functions as a cis element to up-regulate PPP2R2B expression

PPP2R2B, a protein widely expressed in neurons, regulates the protein phosphatase 2A (PP2A) activity for dephosphorylation of tau and other substrates. CAG repeat expansion at the 5′-end of the PPP2R2B gene causes autosomal dominant spinocerebellar ataxia type 12. In the present study, we investigated the roles of CAG repeats and flanking cis elements and the associated proteins in controlling PPP2R2B expression. Deletion/site-directed mutagenesis, in silico searches and cDNA overexpression revealed that CREB1 and SP1 bind to the conserved sequence upstream the CAG repeats to up-regulate PPP2R2B expression, whereas TFAP4 binds to the conserved sequence downstream the CAG repeats to down-regulate PPP2R2B expression. The binding of CREB1, SP1, and TFAP4 to the PPP2R2B promoter was further confirmed by DNA pull-down and ChIP-PCR assays. CAG repeats itself also function as a cis element to up-regulate PPP2R2B expression as AT repeat length has no effect on PPP2R2B expression. Together, our data provide evidence that CREB1, SP1, and TFAP4 play roles in modulating PPP2R2B expression, thus offering a mechanism of regulating PP2A activity as the treatment of neurodegenerative diseases associated with abnormal PP2A activity.

PPP2R2B CAG repeat length in the Han Chinese in Taiwan: Association analyses in neurological and psychiatric disorders and potential functional implications.

PPP2R2B, a protein widely expressed in neurons throughout the brain, regulates the protein phosphatase 2A (PP2A) activity for the microtubule‐associated protein tau and other substrates. Altered PP2A activity has been implicated in spinocerebellar ataxia 12, Alzheimers disease (AD), and other tauopathies. Through a case‐control study and a reporter assay, we investigated the association of PPP2R2B CAG repeat polymorphism with Taiwanese AD, essential tremor (ET), Parkinsons disease (PD), and schizophrenia and clarified the functional implication of this polymorphism. The distribution of the alleles was not significantly different between patients and controls, with 68.6–76.1% alleles at lengths of 10, 13, and 16 triplets. No expanded alleles were detected in either group. However, the frequency of the individuals carrying the short 5‐, 6‐, and 7‐triplet alleles was notably higher in patients with AD (5/180 [2.8%], Fishers exact test, P = 0.003; including 2 homozygotes) and ET (4/132 [3.0%], Fishers exact test, P < 0.001) than in the controls (1/625 [0.2%]). The PPP2R2B transcriptional activity was significantly lower in the luciferase reporter constructs containing the (CAG)5–7 allele than in those containing the common 10‐, 13‐, and 16‐triplet alleles in both neuroblastoma and embryonic kidney cells. Therefore, our preliminary results suggest that the PPP2R2B gene CAG repeat polymorphism may be functional and may, in part, play a role in conferring susceptibility to AD and ET in Taiwan.

Aqueous Extract of Paeonia lactiflora and Paeoniflorin as Aggregation Reducers Targeting Chaperones in Cell Models of Spinocerebellar Ataxia 3

Spinocerebellar ataxia (SCA) types 1, 2, 3, 6, 7, and 17 as well as Huntingtons disease are a group of neurodegenerative disorders caused by expanded CAG repeats encoding a long polyglutamine (polyQ) tract in the respective proteins. Evidence has shown that the accumulation of intranuclear and cytoplasmic misfolded polyQ proteins leads to apoptosis and cell death. Thus suppression of aggregate formation is expected to inhibit a wide range of downstream pathogenic events in polyQ diseases. In this study, we established a high-throughput aggregation screening system using 293 ATXN3/Q75-GFP cells and applied this system to test the aqueous extract of Paeonia lactiflora (P. lactiflora) and its constituents. We found that the aggregation can be significantly prohibited by P. lactiflora and its active compound paeoniflorin. Meanwhile, P. lactiflora and paeoniflorin upregulated HSF1 and HSP70 chaperones in the same cell models. Both of them further reduced the aggregation in neuronal differentiated SH-SY5Y ATXN3/Q75-GFP cells. Our results demonstrate how P. lactiflora and paeoniflorin are likely to work on polyQ-aggregation reduction and provide insight into the possible working mechanism of P. lactiflora in SCA3. We anticipate our paper to be a starting point for screening more potential herbs for the treatment of SCA3 and other polyQ diseases.

The potential of synthetic indolylquinoline derivatives for Aβ aggregation reduction by chemical chaperone activity.

Alzheimers disease (AD) is the most prevalent form of dementia associated with progressive cognitive decline and memory loss. Extracellular β-amyloid (Aβ) is a major constituent of senile plaques, one of the pathological hallmarks of AD. Aβ deposition causes neuronal death via a number of possible mechanisms such as increasing oxidative stress. Therefore therapeutic approaches to identify novel Aβ aggregate reducers could be effective for AD treatment. Using a Trx-His-Aβ biochemical assay, we screened 11 synthetic indolylquinoline compounds, and found NC009-1, -2, -6 and -7 displaying potential to reduce Aβ aggregation. Treating Tet-On Aβ-GFP 293 cells with these compounds reduced Aβ aggregation and reactive oxygen species. These compounds also promoted neurite outgrowth in Tet-On Aβ-GFP SH-SY5Y cells. Furthermore, treatment with above compounds improved neuronal cell viability, neurite outgrowth, and synaptophysin expression level in mouse hippocampal primary culture under oligomeric Aβ-induced cytotoxicity. Moreover, the tested NC009-1 significantly ameliorated Aβ-induced inhibition of hippocampal long-term potentiation in mouse hippocampal slices. Our results demonstrate how synthetic indolylquinoline compounds are likely to work as chemical chaperones in Aβ-aggregation reduction and neuroprotection, providing insight into the possible applications of indolylquinoline compounds in AD treatment.

The potential of indole and a synthetic derivative for polyQ aggregation reduction by enhancement of the chaperone and autophagy systems.

In polyglutamine (polyQ)-mediated disorders, the expansion of translated CAG repeats in the disease genes result in long polyQ tracts in their respective proteins, leading to intracellular accumulation of aggregated polyQ proteins, production of reactive oxygen species, and cell death. The molecular chaperones act in preventing protein misfolding and aggregation, thus inhibiting a wide range of harmful downstream events. In the circumstance of accumulation of aggregated polyQ proteins, the autophagic pathway is induced to degrade the misfolded or aggregated proteins. In this study, we used Flp-In 293/SH-SY5Y cells with inducible SCA3 ATXN3/Q75-GFP expression to test the effect of indole and synthetic derivatives for neuroprotection. We found that ATXN3/Q75 aggregation can be significantly prohibited in Flp-In 293 cells by indole and derivative NC001-8. Meanwhile, indole and NC001-8 up-regulated chaperones and autophagy in the same cell models. Both of them further promote neurite outgrowth in neuronal differentiated SH-SY5Y ATXN3/Q75-GFP cells. Our results demonstrate how indole and derivative NC001-8 are likely to work in reduction of polyQ-aggregation and provide insight into the possible effectual mechanism of indole compounds in polyQ spinocerebellar ataxia (SCA) patients. These findings may have therapeutic applications in a broad range of clinical situations.

The Potential of Indole/Indolylquinoline Compounds in Tau Misfolding Reduction by Enhancement of HSPB1.

Neurofibrillary tangles formed from tau misfolding have long been considered one of the pathological hallmarks of Alzheimers disease (AD). The misfolding of tau in AD correlates with the clinical progression of AD and inhibition or reversal of tau misfolding may protect the affected neurons.

Identifying GSK-3β kinase inhibitors of Alzheimer's disease: Virtual screening, enzyme, and cell assays

Glycogen synthase kinase 3β (GSK-3β) is widely known as a critical target protein for treating Alzheimers disease (AD). We utilized virtual screening to search databases for compounds with the potential to be used in drugs targeting GSK-3β kinase, and kinase as well as cell assays to investigate top-scored, selected compounds. Virtual screening of >1.1 million compounds in the ZINC and in-house databases was conducted using an optimized computational protocol in the docking program GOLD. Of the top-ranked compounds, 16 underwent a luminescent kinase assay and a cell assay using HEK293 cells expressing DsRed-tagged ΔK280 in the repeat domain of tau (tauRD). The compounds VB-003 (a potent GSK-3β inhibitor) and VB-008 (AM404, an anandamide transport inhibitor), with determined IC50 values of 0.25 and 5.4μM, respectively, were identified as reducing tau aggregation. Both compounds increased expression of phospho-GSK-3β (Ser9) and reduced endogenous tau phosphorylation at the sites of Ser202, Thr231, and Ser396. In the ∆K280 tauRD-DsRed SH-SY5Y cells, VB-008, but not VB-003, enhanced HSPB1 and GRP78 expression, increased ∆K280 tauRD-DsRed solubility, and promoted neurite outgrowth. Thus VB-008 performed best to the end of the present study. The identified compound VB-008 may guide the identification and synthesis of potential inhibitors analogous to this compound.

The potential of lactulose and melibiose, two novel trehalase-indigestible and autophagy-inducing disaccharides, for polyQ-mediated neurodegenerative disease treatment.

The unique property of trehalose encourages its pharmaceutical application in aggregation-mediated neurodegenerative disorders, including Alzheimers, Parkinsons, and many polyglutamine (polyQ)-mediated diseases. However, trehalose is digested into glucose by trehalase and which reduced its efficacy in the disease target tissues. Therefore, searching trehalase-indigestible analogs of trehalose is a potential strategy to enhance therapeutic effect. In this study, two trehalase-indigestible trehalose analogs, lactulose and melibiose, were selected through compound topology and functional group analyses. Hydrogen-bonding network analyses suggest that the elimination of the hydrogen bond between the linker ether and aspartate 321 (D321) of human trehalase is the key for lactulose and melibiose to avoid the hydrolyzation. Using polyQ-mediated spinocerebellar ataxia type 17 (SCA17) cell and slice cultures, we found the aggregation was significantly prohibited by trehalose, lactulose, and melibiose, which may through up-regulating of autophagy. These findings suggest the therapeutic applications of trehalase-indigestible trehalose analogs in aggregation-associated neurodegenerative diseases.

FBXO7 Y52C polymorphism as a potential protective factor in Parkinson's disease

Mutations in the F-box only protein 7 gene (FBXO7), the substrate-specifying subunit of SCF E3 ubiquitin ligase complex, cause Parkinsons disease (PD)-15 (PARK15). To identify new variants, we sequenced FBXO7 cDNA in 80 Taiwanese early onset PD patients (age at onset ≤50) and only two known variants, Y52C (c.155A>G) and M115I (c.345G>A), were found. To assess the association of Y52C and M115I with the risk of PD, we conducted a case–control study in a cohort of PD and ethnically matched controls. There was a nominal difference in the Y52C G allele frequency between PD and controls (p = 0.045). After combining data from China [1], significant difference in the Y52C G allele frequency between PD and controls (p = 0.012) and significant association of G allele with decreased PD risk (p = 0.017) can be demonstrated. Upon expressing EGFP-tagged Cys52 FBXO7 in cells, a significantly reduced rate of FBXO7 protein decay was observed when compared with cells expressing Tyr52 FBXO7. In silico modeling of Cys52 exhibited a more stable feature than Tyr52. In cells expressing Cys52 FBXO7, the level of TNF receptor-associated factor 2 (TRAF2) was significantly reduced. Moreover, Cys52 FBXO7 showed stronger interaction with TRAF2 and promoted TRAF2 ubiquitination, which may be responsible for the reduced TRAF2 expression in Cys52 cells. After induced differentiation, SH-SY5Y cells expressing Cys52 FBXO7 displayed increased neuronal outgrowth. We therefore hypothesize that Cys52 variant of FBXO7 may contribute to reduced PD susceptibility in Chinese.

Genetic and functional characters of GRN p.T487I mutation in Taiwanese patients with atypical parkinsonian disorders

BACKGROUND Mutations in the GRN (granulin precursor) are a frequent cause of frontotemporal dementia (FTD) and other atypical parkinsonian disorders. However, the frequency of GRN mutations in Asian patients with atypical parkinsonian disorders is still uncertain. METHODS We screened GRN mutations by sequencing cDNA from 98 patients with FTD or atypical parkinsonian disorders. The functional properties of the identified mutation were evaluated by overexpression in human embryonic kidney (HEK)-293 cells. RESULTS We identified a new missense (GRN p.T487I) mutation in a female patient with undefined atypical parkinsonism. The overexpression experiment further demonstrated that p.T487I mutation reduced the progranulin protein level and stability in HEK-293 cells. CONCLUSION GRN p.T487I mutation, which decreases the stability of progranulin protein, could be a new causative mutation in patients with atypical parkinsonian disorders.