Heterotrimeric kinesin-2, together with kinesin-1, steers vesicular acetylcholinesterase movements toward the synapse

Tricaprylin, a medium-chain triglyceride, aggravates high-fat diet-induced fat deposition but improves intestinal health

Medium-chain triglycerides (MCTs) are absorbed and metabolized more rapidly than long-chain triglycerides (LCTs) and therefore are considered to have obesity-prevention potential in foods. The effect of adding tricaprylin, an MCT, to food on fat deposition and intestinal health is uncharted. In this study, mice were randomly divided into four groups and fed a normal diet (ND), ND with tricaprylin, a high-fat diet (HFD), or HFD with tricaprylin. Supplementation of 2% tricaprylin in HFD significantly increased the body weight, fat mass, liver weight, adipocyte size in adipose tissue and liver, and upregulated genes related to fat deposition. Metabolomic analysis of serum and adipose tissue revealed that tricaprylin significantly increased the contents of metabolites related to lipid metabolism, triglyceride storage, and fat deposition related signaling pathways. In vitro experiments and molecular docking analysis suggest that octanoic acid, a primary decomposition product of tricaprylin, may promote adipogenic differentiation of preadipocytes by acting as a PPARγ ligand to activate the expression of lipogenesis-related genes. Although supplementation with 2% tricaprylin in HFD cannot reduce fat deposition, it has a beneficial effect on intestinal health. Tricaprylin improved intestinal morphology, digestive enzyme activity, short-chain fatty acid concentration, and intestinal barrier function-related protein expression, while reducing inflammatory factor levels and the abundance of harmful intestinal microorganisms.

Phosphoregulation of Kinesins Involved in Long-Range Intracellular Transport

Kinesins, the microtubule-dependent mechanochemical enzymes, power a variety of intracellular movements. Regulation of Kinesin activity and Kinesin-Cargo interactions determine the direction, timing and flux of various intracellular transports. This review examines how phosphorylation of Kinesin subunits and adaptors influence the traffic driven by Kinesin-1, -2, and -3 family motors. Each family of Kinesins are phosphorylated by a partially overlapping set of serine/threonine kinases, and each event produces a unique outcome. For example, phosphorylation of the motor domain inhibits motility, and that of the stalk and tail domains induces cargo loading and unloading effects according to the residue and context. Also, the association of accessory subunits with cargo and adaptor proteins with the motor, respectively, is disrupted by phosphorylation. In some instances, phosphorylation by the same kinase on different Kinesins elicited opposite outcomes. We discuss how this diverse range of effects could manage the logistics of Kinesin-dependent, long-range intracellular transport.

Chemical Constituents and their Antioxidant, Anti-Inflammatory and Anti-Acetylcholinesterase Activities from Pholidota cantonensis

Alzheimer's disease (AD) has the third highest health expenditures after heart disease and cancer. It has emerged as a serious global health issue. The discovery of new drugs to prevent and treat AD is of utmost importance. Pholidota cantonensis is an edible medicinal plant consumed in China. It is widely used in traditional Chinese medicine to treat various diseases. P. cantonensis has been reported to have antioxidant, anti-inflammatory, antitumor and antibacterial activities. Among these properties, its potent antioxidant activity has attracted our attention, since oxidative stress is one of the important pathological mechanisms involved in AD. This study aimed to isolate the compounds from the active extract and evaluate their bioactivities. Fifteen compounds, including one new compound, were obtained. The isolates were tested for 2,2'-diphenyl-1-picrylhydrazyl (DPPH)/2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities, anti-acetylcholinesterase (anti-AChE) activities and inhibitory effects on nitrogen monoxide (NO) release in the BV-2 cells. Compounds 1, 2, 4, 6, 8, and 13-15 exhibited two kinds of AD-associated bioactivities. More importantly, compound 13 showed more potent NO inhibitory activity (IC₅₀ = 0.72 ± 0.08 μM) than the positive control quercetin (IC₅₀ = 12.94 ± 0.08 μM). Compound 13 also had a higher inhibitory rate (99.59 ± 0.43%) on AChE than that of the positive control galantamine (78.32 ± 1.16%) at the concentrate of 50 μg/mL. Our studies provide new insights into this plant in terms of its potential in the development of new multi-target anti-Alzheimer's disease (anti-AD) drugs.

Randomized Clinical Trial Examining the Impact of Lactobacillus rhamnosus GG Probiotic Supplementation on Cognitive Functioning in Middle-aged and Older Adults

PURPOSE

The gut microbiome has been linked to cognitive function and appears to worsen with aging. Probiotic supplementation has been found to improve the health of the gut microbiome. As such, it is possible that probiotic supplementation may protect the aging brain. The current study examined the cognitive benefits of probiotic supplementation (Lactobacillus rhamnosus GG) in healthy middle-aged and older adults.

MATERIALS AND METHODS

The study was a double-blind, placebo-controlled, randomized clinical trial. Two hundred community-dwelling adults aged 52-75 were enrolled (mean age=64.3, SD=5.52). A three-month intervention involved daily consumption of probiotic or placebo. Independent sample t-tests, chi-squared tests, and repeated measure ANOVAs compared groups and examined changes over time. Primary outcome was change in NIH Toolbox Total Cognition Score from baseline to follow-up.

RESULTS

A total of 145 participants were examined in primary analyses (probiotic=77, placebo=68) and excluded persons due to discontinuation, low adherence, missing data, or outlier values. Established criteria (ie ≥1 subtest t-scores ≤35; n=19, n=23) were used to operationally define cognitive impairment. Repeated measures ANOVAs revealed that persons with cognitive impairment who consumed probiotics exhibited a greater total cognition score improvement than persons with cognitive impairment in the placebo group and cognitively intact persons in probiotic or placebo groups.

CONCLUSION

Lactobacillus rhamnosus GG probiotic supplementation was associated with improved cognitive performance in middle-aged and older adults with cognitive impairment. Probiotic supplementation may be a novel method for protecting cognitive health in aging.

Microtubule motor transport in the delivery of melanosomes to the actin-rich apical domain of the retinal pigment epithelium

Melanosomes are motile, light-absorbing organelles that are present in pigment cells of the skin and eye. It has been proposed that melanosome localization, in both skin melanocytes and the retinal pigment epithelium (RPE), involves melanosome capture from microtubule motors by an unconventional myosin, which dynamically tethers the melanosomes to actin filaments. Recent studies with melanocytes have questioned this cooperative capture model. Here, we test the model in RPE cells by imaging melanosomes associated with labeled actin filaments and microtubules, and by investigating the roles of different motor proteins. We found that a deficiency in cytoplasmic dynein phenocopies the lack of myosin-7a, in that melanosomes undergo fewer of the slow myosin-7a-dependent movements and are absent from the RPE apical domain. These results indicate that microtubule-based motility is required for the delivery of melanosomes to the actin-rich apical domain and support a capture mechanism that involves both microtubule and actin motors.

Aerial parts of maca (Lepidium meyenii Walp.) as functional vegetables with gastrointestinal prokinetic efficacy in vivo

Lepidium meyenii Walp. (maca) has been utilized in the Andean region because of its edibleness and medicinal value. The aerial parts of maca (APM) were analyzed for protein, total sugar, vitamins, amino acids, and minerals and its characteristic active ingredients at five different growth stages. The results showed the high protein, total sugar, vitamin C, niacin, potassium, and calcium contents of APM. All 17 amino acids and the characteristic active ingredients, namely, macamide, glucosinolates, adenosine, and total saponins, were detected. We examined the effects of maca plant powders on gastric emptying and intestinal propulsion and the levels of serum motilin and gastrin in atropine-treated mice. Benzyl isothiocyanate (BITC) was investigated to identify the potential active material in APM. The results revealed that both maca plant powders and BITC can promote the gastrointestinal prokinetic efficacy. Thus, APM feature potential as new functional vegetable sources.

Cholinergic activity is essential for maintaining the anterograde transport of Choline Acetyltransferase in Drosophila

Cholinergic activity is essential for cognitive functions and neuronal homeostasis. Choline Acetyltransferase (ChAT), a soluble protein that synthesizes acetylcholine at the presynaptic compartment, is transported in bulk in the axons by the heterotrimeric Kinesin-2 motor. Axonal transport of soluble proteins is described as a constitutive process assisted by occasional, non-specific interactions with moving vesicles and motor proteins. Here, we report that an increase in the influx of Kinesin-2 motor and association between ChAT and the motor during a specific developmental period enhances the axonal entry, as well as the anterograde flow of the protein, in the sensory neurons of intact Drosophila nervous system. Loss of cholinergic activity due to  Hemicholinium and Bungarotoxin treatments, respectively, disrupts the interaction between ChAT and Kinesin-2 in the axon, and the episodic enhancement of axonal influx of the protein. Altogether, these observations highlight a phenomenon of synaptic activity-dependent, feedback regulation of a soluble protein transport in vivo, which could potentially define the quantum of its pre-synaptic influx.

A method for estimating relative changes in the synaptic density in Drosophila central nervous system

Background

Synapse density is an essential indicator of development and functioning of the central nervous system. It is estimated indirectly through the accumulation of pre and postsynaptic proteins in tissue sections. 3D reconstruction of the electron microscopic images in serial sections is one of the most definitive means of estimating the formation of active synapses in the brain. It is tedious and highly skill-dependent. Confocal imaging of whole mounts or thick sections of the brain provides a natural alternative for rapid gross estimation of the synapse density in large areas. The optical resolution and other deep-tissue imaging aberrations limit the quantitative scope of this technique.

Results

Here we demonstrate a simple sample preparation method that could enhance the clarity of the confocal images of the neuropil regions of the ventral nerve cord of Drosophila larvae, providing a clear view of synapse distributions. We estimated the gross volume occupied by the synaptic junctions using 3D object counter plug-in of Fiji/ImageJ^®. It gave us a proportional estimate of the number of synaptic junctions in the neuropil region. The method is corroborated by correlated super-resolution imaging analysis and through genetic perturbation of synaptogenesis in the larval brain.

Conclusions

The method provides a significant improvement in the relative estimate of region-specific synapse density in the central nervous system. Also, it reduced artifacts in the super-resolution images obtained using the stimulated emission depletion microscopy technique.

Electronic supplementary material

The online version of this article (10.1186/s12868-018-0430-3) contains supplementary material, which is available to authorized users.

Autoinhibition of kinesin-1 is essential to the dendrite-specific localization of Golgi outposts

Neuronal polarity relies on the axon- or dendrite-specific localization of cargo by molecular motors such as kinesin-1. This study shows how autoinhibition regulates both kinesin-1 activity and localization to keep dendritic Golgi outposts from entering axons.

Neuronal polarity relies on the selective localization of cargo to axons or dendrites. The molecular motor kinesin-1 moves cargo into axons but is also active in dendrites. This raises the question of how kinesin-1 activity is regulated to maintain the compartment-specific localization of cargo. Our in vivo structure–function analysis of endogenous Drosophila melanogaster kinesin-1 reveals a novel role for autoinhibition in enabling the dendrite-specific localization of Golgi outposts. Mutations that disrupt kinesin-1 autoinhibition result in the axonal mislocalization of Golgi outposts. Autoinhibition also regulates kinesin-1 localization. Uninhibited kinesin-1 accumulates in axons and is depleted from dendrites, correlating with the change in outpost distribution and dendrite growth defects. Genetic interaction tests show that a balance of kinesin-1 inhibition and dynein activity is necessary to localize Golgi outposts to dendrites and keep them from entering axons. Our data indicate that kinesin-1 activity is precisely regulated by autoinhibition to achieve the selective localization of dendritic cargo.

Anterograde Transport of Rab4-Associated Vesicles Regulates Synapse Organization in Drosophila

Local endosomal recycling at synapses is essential to maintain neurotransmission. Rab4GTPase, found on sorting endosomes, is proposed to balance the flow of vesicles among endocytic, recycling, and degradative pathways in the presynaptic compartment. Here, we report that Rab4-associated vesicles move bidirectionally in Drosophila axons but with an anterograde bias, resulting in their moderate enrichment at the synaptic region of the larval ventral ganglion. Results from FK506 binding protein (FKBP) and FKBP-Rapamycin binding domain (FRB) conjugation assays in rat embryonic fibroblasts together with genetic analyses in Drosophila indicate that an association with Kinesin-2 (mediated by the tail domain of Kinesin-2α/KIF3A/KLP64D subunit) moves Rab4-associated vesicles toward the synapse. Reduction in the anterograde traffic of Rab4 causes an expansion of the volume of the synapse-bearing region in the ventral ganglion and increases the motility of Drosophila larvae. These results suggest that Rab4-dependent vesicular traffic toward the synapse plays a vital role in maintaining synaptic balance in this neuronal network.

Two kinesins drive anterograde neuropeptide transport

Motor-dependent anterograde transport, a process that moves cytoplasmic components from sites of biosynthesis to sites of use within cells, is crucial in neurons with long axons. Evidence has emerged that multiple anterograde kinesins can contribute to some transport processes. To test the multi-kinesin possibility for a single vesicle type, we studied the functional relationships of axonal kinesins to dense core vesicles (DCVs) that were filled with a GFP-tagged neuropeptide in the Drosophila nervous system. Past work showed that Unc-104 (a kinesin-3) is a key anterograde DCV motor. Here we show that anterograde DCV transport requires the well-known mitochondrial motor Khc (kinesin-1). Our results indicate that this influence is direct. Khc mutations had specific effects on anterograde run parameters, neuron-specific inhibition of mitochondrial transport by Milton RNA interference had no influence on anterograde DCV runs, and detailed colocalization analysis by superresolution microscopy revealed that Unc-104 and Khc coassociate with individual DCVs. DCV distribution analysis in peptidergic neurons suggest the two kinesins have compartment specific influences. We suggest a mechanism in which Unc-104 is particularly important for moving DCVs from cell bodies into axons, and then Unc-104 and kinesin-1 function together to support fast, highly processive runs toward axon terminals.