Two new diarylheptanoids, alpinin A (1) and alpinin B (2), together with 18 known diarylheptanoids (3–20), were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by comprehensive spectroscopic analysis, including high-resolution mass spectrometry, infrared spectroscopy, and one- and two-dimensional nuclear magnetic resonance spectroscopy. Structurally, alpinin A is a new member of the small family of oxa-bridged diarylheptanoids and contains the characteristic 2,6-cis-configured tetrahydropyran motif (C1–C5 oxa bridge). The absolute configuration of alpinin A was confirmed by asymmetric total synthesis of the enantiomer (ent-1), corroborating the assignment of the molecular structure. The absolute configuration of alpinin B was determined on the basis of the analysis of the circular dichroism exciton chirality spectrum. We evaluated the inhibitory activity of all isolated diarylheptanoids against α-synuclein aggregation at 10 μM. Alpinins A and B significantly inhibited α-synuclein aggregation by 66 and 67%, respectively.Keywords: Alpinia officinarum; alpinin A; alpinin B; diarylheptanoids; inhibit α-synuclein aggregation;

The experience-dependent modulation of brain circuitry depends on dynamic changes in synaptic connections that are guided by neuronal activity. In particular, postsynaptic maturation requires changes in dendritic spine morphology, the targeting of postsynaptic proteins, and the insertion of synaptic neurotransmitter receptors. Thus, it is critical to understand how neuronal activity controls postsynaptic maturation. Here we report that the scaffold protein liprinα1 and its phosphorylation by cyclin-dependent kinase 5 (Cdk5) are critical for the maturation of excitatory synapses through regulation of the synaptic localization of the major postsynaptic organizer postsynaptic density (PSD)-95. Whereas Cdk5 phosphorylates liprinα1 at Thr701, this phosphorylation decreases in neurons in response to neuronal activity. Blockade of liprinα1 phosphorylation enhances the structural and functional maturation of excitatory synapses. Nanoscale superresolution imaging reveals that inhibition of liprinα1 phosphorylation increases the colocalization of liprinα1 with PSD-95. Furthermore, disruption of liprinα1 phosphorylation by a small interfering peptide, siLIP, promotes the synaptic localization of PSD-95 and enhances synaptic strength in vivo. Our findings collectively demonstrate that the Cdk5-dependent phosphorylation of liprinα1 is important for the postsynaptic organization during activity-dependent synapse development.

•Initial spine growth is critical for formation of structural and functional synapses.•BDNF/TrkB regulates structural synaptic plasticity via coordinated Rho GTPases.•Ephs coordinate multiple GEFs and GAPs to regulate dendritic spine morphology.•Modulating Eph expression/activity provides a new strategy for Alzheimer’s disease.•Neuromodulation via GPCR MC4R alleviates impaired synaptic plasticity in Alzheimer’s.Morphological changes of dendritic spines are strongly associated with synaptic development and synaptic plasticity, which underlies learning and memory. These changes are driven by alterations of F-actin dynamics under the control of Rho GTPases or by synaptic trafficking and insertion of glutamate receptors. Understanding the molecular events that occur during the formation and stabilization of dendritic spines, and the signaling pathways regulating these processes, provides insights into the mechanisms of learning and memory. In this review, we discuss the recent advances on these postsynaptic signaling pathways, in particular, we discuss the specific signaling events that couple the cell-surface receptors to intracellular targets. In addition, we discuss the deregulation of these signaling pathways and their subsequent impact on synaptic dysfunction in Alzheimer’s disease.

Neurite outgrowth is crucial during neuronal development and regeneration, and strategies that aim at promoting neuritogenesis are beneficial for reconstructing synaptic connections after neuronal degeneration and injury. Using a bivalent analogue strategy as a successful approach, the current study identifies a series of novel dimeric securinine analogues as potent neurite outgrowth enhancers. Compounds 13, 14, 17–19, and 21–23, with different lengths of carbon chain of N,N-dialkyl substituting diacid amide linker between two securinine molecules at C-15 position, exhibited notable positive effects on both neuronal differentiation and neurite extension of neuronal cells. Compound 14, one of the most active compounds, was used as a representative compound for mechanistic studies. Its action on neurite outgrowth was through phosphorylation/activation of multiple signaling molecules including Ca2+/calmodulin-dependent protein kinase II (CaMKII), extracellular signal-regulated kinase (ERK) and Akt. These findings collectively identify a new group of beneficial compounds for neuritogenesis, and may provide insights on drug discovery of neural repair and regeneration.Keywords: Bivalent analogue strategy; neurite; neuronal differentiation; securinine

•Extract of Adelostemma gracillimum is neuroprotective against excitotoxicity.•Four novel and two known lignans, and five known acetophenones were isolated.•Two novel and one known lignans are active in neuroprotection.•These molecules hold potential for treating diseases marked with neuronal death.Adelostemma gracillimum is an herb used as nourishing and roborant drugs and in the treatment of convulsions in children. To date, a few molecular constituents have been isolated from the root of this herb and chemically characterized, but their biological activities have never been reported. Here, we demonstrate that the crude extract of A. gracillimum (AGE) can protect primary cortical neurons against N-methyl-d-aspartate (NMDA)-induced cytotoxicity. Further fractionations of AGE led to the isolation of four novel lignans (1–4), two known lignans (5, 11), and five known acetophenones (6–10); their structures were elucidated by comparison with related literature, extensive analyses of NMR spectroscopy and high-resolution mass spectrometry. Of the eleven isolates, lignans 2, 3 and 5 exhibit significant neuroprotection against NMDA-induced cell death. This is the first report of isolating lignans with neuroprotective activity from A. gracillimum.

Alzheimer’s disease (AD) is a devastating condition with no known effective treatment. AD is characterized by memory loss as well as impaired locomotor ability, reasoning, and judgment. Emerging evidence suggests that the innate immune response plays a major role in the pathogenesis of AD. In AD, the accumulation of β-amyloid (Aβ) in the brain perturbs physiological functions of the brain, including synaptic and neuronal dysfunction, microglial activation, and neuronal loss. Serum levels of soluble ST2 (sST2), a decoy receptor for interleukin (IL)-33, increase in patients with mild cognitive impairment, suggesting that impaired IL-33/ST2 signaling may contribute to the pathogenesis of AD. Therefore, we investigated the potential therapeutic role of IL-33 in AD, using transgenic mouse models. Here we report that IL-33 administration reverses synaptic plasticity impairment and memory deficits in APP/PS1 mice. IL-33 administration reduces soluble Aβ levels and amyloid plaque deposition by promoting the recruitment and Aβ phagocytic activity of microglia; this is mediated by ST2/p38 signaling activation. Furthermore, IL-33 injection modulates the innate immune response by polarizing microglia/macrophages toward an antiinflammatory phenotype and reducing the expression of proinflammatory genes, including IL-1β, IL-6, and NLRP3, in the cortices of APP/PS1 mice. Collectively, our results demonstrate a potential therapeutic role for IL-33 in AD.

Three novel zwitterionic alkaloids—ningpoensine A (1) and a pair of epimers, ningpoensines B/C (2a/2b)—with unprecedented molecular skeletons were isolated from the root of Scrophularia ningpoensis. Their structures were established by extensive spectroscopic analyses, and the absolute configuration of ningpoensine A was determined by quantum chemical calculations. A biosynthetic pathway leading to ningpoensines A–C from harpagide and natural amino acids is proposed. Ningpoensines B/C tended to promote wound closure in human embryonic keratinocytes.

Alzheimer’s disease (AD), characterized by cognitive decline, has emerged as a disease of synaptic failure. The present study reveals an unanticipated role of erythropoietin-producing hepatocellular A4 (EphA4) in mediating hippocampal synaptic dysfunctions in AD and demonstrates that blockade of the ligand-binding domain of EphA4 reverses synaptic impairment in AD mouse models. Enhanced EphA4 signaling was observed in the hippocampus of amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mouse model of AD, whereas soluble amyloid-β oligomers (Aβ), which contribute to synaptic loss in AD, induced EphA4 activation in rat hippocampal slices. EphA4 depletion in the CA1 region or interference with EphA4 function reversed the suppression of hippocampal long-term potentiation in APP/PS1 transgenic mice, suggesting that the postsynaptic EphA4 is responsible for mediating synaptic plasticity impairment in AD. Importantly, we identified a small-molecule rhynchophylline as a novel EphA4 inhibitor based on molecular docking studies. Rhynchophylline effectively blocked the EphA4-dependent signaling in hippocampal neurons, and oral administration of rhynchophylline reduced the EphA4 activity effectively in the hippocampus of APP/PS1 transgenic mice. More importantly, rhynchophylline administration restored the impaired long-term potentiation in transgenic mouse models of AD. These findings reveal a previously unidentified role of EphA4 in mediating AD-associated synaptic dysfunctions, suggesting that it is a new therapeutic target for this disease.

Four series of novel heterodimers comprised of donepezil and huperzine A (HupA) fragments were designed, synthesized, and evaluated in search of potent acetylcholinesterase (AChE) inhibitors as potential therapeutic treatment for Alzheimer’s disease. Heterodimers comprised of dimethoxyindanone (from donepezil), hupyridone (from HupA), and connected with a multimethylene linker, were identified as potent and selective inhibitors of AChE. Diastereomeric heterodimers (RS,S)-17b (with a tetramethylene linker) exhibited the highest potency of inhibition towards AChE with an IC50 value of 9 nM and no detectable inhibitory effect on butyrylcholinesterase at 1 mM.Heterodimers of donepezil and huperzine A fragments tethered with a tetramethylene linker exhibited high potency and selectivity towards acetylcholinesterase inhibition.

Dammarane-type saponins (1–7), together with five known compounds, were isolated from the aerial parts of Gynostemma pentaphyllum. Compounds 1–4, 6 and 7 induced the phosphorylation of ERK protein in primary rat cortical neurons, which indicates their potential neuroactivity. On the other hand, no induction of ERK phosphorylation was observed for HEK293 cells following treatment with saponins 1, 3, 4 and 7.Dammarane-type saponins (1–7) were isolated from the aerial parts of Gynostemma pentaphyllum. Compounds 1–4, 6 and 7 induced the phosphorylation of ERK protein in primary rat cortical neurons, indicative of their potential neuroactivities.

Parkinson's disease (PD) is the most common neurodegenerative movement disorder that affects about 1% of the population worldwide. Despite significant advances in the identification of genetic mutations and signaling pathways that are associated with the disease, the precise mechanisms implicated in the pathophysiology of the disease are not well understood. More importantly, treatments that are effective in reversing the progression of the disease is essentially lacking. Further investigation into the pathogenic mechanisms of PD thus presents a pressing concern for neuroscientists. Recently, deregulation of the autophagic pathway is observed in the brains of PD patients and in models of PD. In this review we summarize current literature on the emerging involvement of autophagy in PD, and the implication for future development of treatment against the disorder.

EphA4-dependent growth cone collapse requires reorganization of actin cytoskeleton through coordinated activation of Rho family GTPases. Whereas various guanine exchange factors have recently been identified to be involved in EphA4-mediated regulation of Rho GTPases and growth cone collapse, the functional roles of GTPase-activating proteins in the process are largely unknown. Here we report that EphA4 interacts with α2-chimaerin through its Src homology 2 domain. Activated EphA4 induces a rapid increase of tyrosine phosphorylation of α2-chimaerin and enhances its GTPase-activating protein activity toward Rac1. More importantly, α2-chimaerin regulates the action of EphA4 in growth cone collapse through modulation of Rac1 activity. Our findings have therefore identified a new α2-chimaerin-dependent signaling mechanism through which EphA4 transduces its signals to the actin cytoskeleton and modulates growth cone morphology.

Cyclin-dependent kinase (Cdk)5 is a key regulator of neural development. We have previously demonstrated that Cdk5/p35 are localized to the postsynaptic muscle and are implicated in the regulation of neuregulin/ErbB signaling in myotube culture. To further elucidate whether Cdk5 activity contributes to neuromuscular junction (NMJ) development in vivo, the NMJ of Cdk5-/- mice was examined. Consistent with our previous demonstration that Cdk5 phosphorylates ErbB2/3 to regulate its tyrosine phosphorylation, we report here that the phosphorylation of ErbB2 and ErbB3 and the ErbB2 kinase activity are reduced in Cdk5-deficient muscle. In addition, Cdk5-/- mice also display morphological abnormalities at the NMJ pre- and postsynaptically. Whereas the outgrowth of the main nerve trunk is grossly normal, the intramuscular nerve projections exhibit profuse and anomalous branching patterns in the Cdk5-/- embryos. The central band of acetylcholine receptor (AChR) clusters is also wider in Cdk5-/- diaphragms, together with the absence of S100 immunoreactivity along the phrenic nerve during late embryonic stages. Moreover, we unexpectedly discovered that the agrin-induced formation of large AChR clusters is significantly increased in primary muscle cultures prepared from Cdk5-null mice and in C2C12 myotubes when Cdk5 activity was suppressed. These abnormalities are accompanied by elevated frequency of miniature endplate potentials in Cdk5-null diaphragm. Taken together, our findings reveal the essential role of Cdk5 in regulating the development of motor axons and neuromuscular synapses in vivo.

The activity of cyclin-dependent kinase 5 (Cdk5) depends on the association with one of its activators, p35 and p39, which are prominently expressed in the nervous system. Studies on the repertoire of protein substrates for Cdk5 have implicated the involvement of Cdk5 in neuronal migration and synaptic plasticity. Our recent analysis of the sequence of signal transducer and activator of transcription (STAT)3, a key transcription factor, reveals the presence of potential Cdk5 phosphorylation site. We report here that the Cdk5/p35 complex associates with STAT3 and phosphorylates STAT3 on the Ser-727 residue in vitro and in vivo. Intriguingly, whereas the Ser phosphorylation of STAT3 can be detected in embryonic and postnatal brain and muscle of wild-type mice, it is essentially absent from those of Cdk5-deficient embryos. In addition, treatment of cultured myotubes with neuregulin enhances the Ser phosphorylation of STAT3 and transcription of STAT3 target genes, such as c-fos and junB, in a Cdk5-dependent manner. Both the DNA-binding activity of STAT3 and the transcription of specific target genes, such as fibronectin, are reduced in Cdk5-deficient muscle. Taken together, these results reveal a physiological role of Cdk5 in regulating STAT3 phosphorylation and modulating its transcriptional activity.

Here we describe an important involvement of Cdk5/p35 in regulating the gene expression of acetylcholine receptor (AChR) at the neuromuscular synapse. Cdk5 and p35 were prominently expressed in embryonic muscle, and concentrated at the neuromuscular junction in adulthood. Neuregulin increased the p35-associated Cdk5 kinase activity in the membrane fraction of cultured C2C12 myotubes. Co-immunoprecipitation studies revealed the association between Cdk5, p35 and ErbB receptors in muscle and cultured myotubes. Inhibition of Cdk5 activity not only blocked the NRG-induced AChR transcription, but also attenuated ErbB activation in cultured myotubes. In light of our finding that overexpression of p35 alone led to an increase in AChR promoter activity in muscle, Cdk5 activation is sufficient to mediate the up-regulation of AChR gene expression. Taken together, these results reveal the unexpected involvement of Cdk5/p35 in neuregulin signaling at the neuromuscular synapse.

Precise regulation of synapse formation, maintenance and plasticity is crucial for normal cognitive function, and synaptic failure has been suggested as one of the hallmarks of neurodegenerative diseases. In this review, we describe the recent progress in our understanding of how the receptor tyrosine kinase Ephs and their ligands ephrins regulate dendritic spine morphogenesis, synapse formation and maturation, as well as synaptic plasticity. In particular, we discuss the emerging evidence implicating that deregulation of Eph/ephrin signaling contributes to the aberrant synaptic functions associated with cognitive impairment in Alzheimer's disease. Understanding how Eph/ephrin regulates synaptic function may therefore provide new insights into the development of therapeutic agents against neurodegenerative diseases.Highlights► Eph/ephrin signaling regulates spine and synapse development. ► Eph/ephrin signaling plays vital roles in synaptic plasticity. ► Dysfunction of Ephs and ephrins is implicated in neurodegenerative diseases.

Since the identification of cyclin-dependent kinase-5 (Cdk5) as a tau kinase and member of the Cdk family almost 20 years ago, deregulation of Cdk5 activity has been linked to an array of neurodegenerative diseases. As knowledge on the etiopathological mechanisms of these diseases evolved through the years, Cdk5 has also been implicated in additional cellular events that are affected under these pathological conditions. From the role of Cdk5 in the regulation of synaptic functions to its involvement in autophagy deregulation, significant insights have been obtained regarding the role of Cdk5 as a key regulator of neurodegeneration. Here, we summarize recent findings on the involvement of Cdk5 in the pathophysiological mechanisms underlying various neurodegenerative diseases.

The receptor tyrosine kinase Eph and its membrane-bound ligand ephrin are emerging key players in synapse formation and plasticity in the central nervous system. Understanding how ephrin/Eph regulate synapse formation and functions is often complicated by the fact that both ligands and receptors are expressed in the pre-synaptic and post-synaptic neurons and upon their interaction, bi-directional signaling cascades can be triggered. By elucidating the respective downstream targets and generating signaling-deficient mutants, the specific roles of forward (Eph receptor) and reverse (ephrin) signaling are beginning to be unraveled. In this review, we summarize recent advances in our understanding of how ephrin and Eph differentially participate in specific aspects of synapse formation in developing neurons, and activity-dependent plasticity in the adult brain.

The vertebrate neuromuscular junction (NMJ), a peripheral synapse formed between motoneuron and skeletal muscle, is characterized by a protracted postnatal period of maturation and life-long maintenance. In neuromuscular disorders such as congenital myasthenic syndromes (CMSs), disruptions of NMJ maturation and/or maintenance are frequently observed. In particular, defective neuromuscular transmission associated with structural and molecular abnormalities at the pre- and postsynaptic membranes, as well as at the synaptic cleft, has been reported in these patients. Here, we review recent advances in the understanding of molecular and cellular events that mediate NMJ maturation and maintenance. The underlying regulatory mechanisms, including key molecular regulators at the presynaptic nerve terminal, synaptic cleft, and postsynaptic muscle membrane, are discussed.

The recent identification of Gαz expression in C2C12 myoblasts and its demonstrated interaction with the transcription factor Eya2 inferred an unanticipated role of Gαz in muscle development. In the present study, endogenous Gαz mRNA and protein expressions in C2C12 cells increased upon commencement of myogenesis and peaked at around 4–6 days after induction but were undetectable in adult skeletal muscle. Surprisingly, stable expression of recombinant Gαz in C2C12 myoblasts strongly suppressed myotube formation upon serum deprivation, and the constitutively active mutant GαzQL exerted more pronounced effects. Transcriptional activities of reporter genes responsive to early (MyoD, MEF2 and myogenin) and late (muscle creatine kinase and myosin heavy chain) myogenic markers were reduced by transiently expressed GαzQL. Membrane attachment of Gαz was apparently required for the suppressive effects because a fatty acylation-deficient Gαz mutant could not inhibit myogenin expression. Introduction of siRNA against Gαz enhanced myogenin-driven luciferase activity and increased myosin heavy chain expression. Immunostaining of C2C12 cells over-expressing Gαz showed delayed nuclear expression of myogenin and severe myotube deformation. Gαz expression was accompanied by reduced levels of Rock2, RhoA and RhoGAP, enhanced expression of Rnd3, and a reduction of serum-responsive factor-driven reporter activity. These results support a novel role of Gαz in restraining myogenic differentiation through the disruption of Rho signaling.

Previously, challenges faced by women scientists have made it difficult for them to realize their dreams. The remarkable growth of Asian bioscience over the past decade, however, has created opportunities for young women in their home countries. The time is ripe for women in Asia to pursue their scientific aspirations.

Tight regulation of gene transcription is critical in muscle development as well as during the formation and maintenance of the neuromuscular junction (NMJ). We previously demonstrated that the transcription of G protein β1 (Gβ1) is enhanced by treatment of cultured myotubes with neuregulin (NRG), a trophic factor that plays an important role in neural development. In the current study, we report that the transcript levels of Gβ1 and Gβ2 subunits in skeletal muscle are up-regulated following sciatic nerve injury or blockade of nerve activity. These observations prompted us to explore the possibility that G protein subunits regulate NRG-mediated signaling and gene transcription. We showed that overexpression of Gβ1 or Gβ2 in COS7 cells attenuates NRG-induced extracellular signal-regulated kinase (ERK) 1/2 activation, whereas suppression of Gβ2 expression in C2C12 myotubes enhances NRG-mediated ERK1/2 activation and c-fos transcription. These results suggest that expression of Gβ protein negatively regulates NRG-stimulated gene transcription in cultured myotubes. Taken together, our observations provide evidence that specific heterotrimeric G proteins regulate NRG-mediated signaling and gene transcription during rat muscle development.