Arrestin regulates almost all G protein-coupled receptor (GPCR)-mediated signaling and trafficking. We report that the multidomain protein, spinophilin, antagonizes these multiple arrestin functions. Through blocking G protein receptor kinase 2 (GRK2) association with receptor-Gbetagamma complexes, spinophilin reduces arrestin-stabilized receptor phosphorylation, receptor endocytosis, and the acceleration of mitogen-activated protein kinase (MAPK) activity following endocytosis. Spinophilin knockout mice were more sensitive than wild-type mice to sedation elicited by stimulation of alpha2 adrenergic receptors, whereas arrestin 3 knockout mice were more resistant, indicating that the signal-promoting, rather than the signal-terminating, roles of arrestin are more important for certain response pathways. The reciprocal interactions of GPCRs with spinophilin and arrestin represent a regulatory mechanism for fine-tuning complex receptor-orchestrated cell signaling and responses.

G protein-coupled receptors (GPCRs) modulate diverse physiological and behavioral signaling pathways by virtue of changes in receptor activation and inactivation states. Functional changes in receptor properties include dynamic interactions with regulatory molecules and trafficking to various cellular compartments at various stages of the life cycle of a GPCR. This review focuses on trafficking of GPCRs to the cell surface, stabilization there, and agonist-regulated turnover. GPCR interactions with a variety of newly revealed partners also are reviewed with the intention of provoking further analysis of the relevance of these interactions in GPCR trafficking, signaling, or both. The disease consequences of mislocalization of GPCRs also are described.

Neuronal hyperexcitability occurs early in the pathogenesis of Alzheimer's disease (AD) and contributes to network dysfunction in AD patients. In other disorders with neuronal hyperexcitability, dysfunction in the dendrites often contributes, but dendritic excitability has not been directly examined in AD models. We used dendritic patch-clamp recordings to measure dendritic excitability in the CA1 region of the hippocampus. We found that dendrites, more so than somata, of hippocampal neurons were hyperexcitable in mice overexpressing A␤. This dendritic hyperexcitability was associated with depletion of Kv4.2, a dendritic potassium channel important for regulating dendritic excitability and synaptic plasticity. The antiepileptic drug, levetiracetam, blocked Kv4.2 depletion. Tau was required, as crossing with tau knock-out mice also prevented both Kv4.2 depletion and dendritic hyperexcitability. Dendritic hyperexcitability induced by Kv4.2 deficiency exacerbated behavioral deficits and increased epileptiform activity in hAPP mice. We conclude that increased dendritic excitability, associated with changes in dendritic ion channels including Kv4.2, may contribute to neuronal dysfunction in early stages AD.

Brassica vegetables are known to contain relatively high concentrations of bioactive compounds associated with human health. A comprehensive profiling of polyphenols from five Brassica species microgreens was conducted using ultra high-performance liquid chromatography photo diode array high-resolution multi-stage mass spectrometry (UHPLC-PDA-ESI/HRMSn). A total of 164 polyphenols including 30 anthocyanins, 105 flavonol glycosides, and 29 hydroxycinnamic acid and hydroxybenzoic acid derivatives were putatively identified.The putative identifications were based on UHPLC-HRMSn analysis using retention times, elution orders, UV/Vis spectra and high resolution mass spectra, in-house polyphenol database, and as well as literature comparisons. This study showed that these five Brassica species microgreens could be considered as good sources of food polyphenols.

No abstract

The brain noradrenergic system supplies the neurotransmitter norepinephrine throughout the brain via widespread efferent projections, and plays a pivotal role in modulating cognitive activities in the cortex. Profound noradrenergic degeneration in Alzheimer's disease (AD) patients has been observed for decades, with recent research suggesting that the locus coeruleus (where noradrenergic neurons are mainly located) is a predominant site where AD-related pathology begins. Mounting evidence indicates that the loss of noradrenergic innervation greatly exacerbates AD pathogenesis and progression, although the precise roles of noradrenergic components in AD pathogenesis remain unclear. The aim of this review is to summarize current findings on noradrenergic dysfunction in AD, as well as to point out deficiencies in our knowledge where more research is needed.

The three ␣ 2 -adrenergic receptor (␣ 2 AR) 1 subtypes are members of the type II, biogenic amine-binding, G protein-coupled receptor family. These receptor subtypes all couple via the G i /G o family of GTP-binding proteins to the inhibition of adenylyl cyclase, inhibition of voltage-dependent calcium channels, potentiation of potassium currents via G protein-coupled, inwardly rectifying potassium channels, activation of phospholipase D, and activation of MAP kinase in native cells (1-4). In heterologous cell systems, these receptors also couple to the activation of a variety of signaling molecules, including Ras (5-7), p70 S6 kinase (8), MAP kinase (9, 10), and phospholipase D (11).Although all three ␣ 2 ARs appear to activate similar signaling pathways, differences in the cellular trafficking of these subtypes have been reported, both in naive cells and following agonist activation. Subtype-selective differences in agonistelicited ␣ 2 AR redistribution have been noted in several experimental systems (12-18). The ␣ 2B AR subtype is readily internalized following agonist activation, whereas the ␣ 2A AR subtype typically is not (14, 18). The ␣ 2C AR subtype has not been explored in as much detail with regard to agonist-elicited redistribution because of its considerable accumulation intracellularly (14). The ␣ 2 AR subtypes also manifest different trafficking itineraries in polarized Madin-Darby canine kidney II (MDCKII) cells, even in the absence of agonist treatment. The ␣ 2A AR subtype is targeted directly to the basolateral surface (19), whereas the ␣ 2B AR subtype is delivered randomly to both the apical and basolateral surfaces but is selectively retained on the basolateral surface (t1 ⁄2 ϭ 10 -12 h) in contrast to its rapid loss from the apical surface (t1 ⁄2 ϭ 5-15 min) (20). These findings suggest that there is a molecular mechanism responsible for the selective retention of the ␣ 2B AR on the basolateral sub-domain of MDCK cells, probably a retention mechanism shared by the basolaterally targeted ␣ 2A -and ␣ 2C AR subtypes (20). Although ␣ 2C ARs, like ␣ 2A ARs, are directly targeted to and retained on the basolateral subdomain, a significant proportion of these receptors is identifiable in an intracellular pool at steady state (14,18,20); the functional relevance of this intracellular ␣ 2C AR pool has yet to be clarified.Receptor retention on the lateral subdomain of MDCKII cells likely involves the third intracellular loop of the ␣ 2 AR subtypes. For example, deletion of this loop in the ␣ 2A AR subtype (⌬3i ␣ 2A AR) results in accelerated basolateral receptor turnover (t1 ⁄2 Х 4.5 h) when compared with that for the wild-type receptor or with ␣ 2A AR structures that have been mutated in the N terminus or the C-terminal tail (all possessing a t1 ⁄2 of 10 -12 h) (21). Similarly, the ⌬3i ␣ 2B AR is not enriched at the basolateral surface of MDCKII cells at steady state (22).Based on our findings that the ␣ 2B AR is rapidly removed from the apical surface following random delivery and that removal of the...

We examined the extent to which three Fraxinus cultivars and a wild population that vary in their resistance to Emerald Ash Borer (EAB) could be differentiated on the basis of a suite of constitutive chemical defense traits in phloem extracts. The EAB-resistant Manchurian ash (F. mandshurica, cv. Mancana) was characterized by having a rapid rate of wound browning, a high soluble protein concentration, low trypsin inhibitor activities, and intermediate levels of peroxidase activity and total soluble phenolic concentration. The EAB-susceptible white ash (F. americana, cv. Autumn Purple) was characterized by a slow wound browning rate and low levels of peroxidase activity and total soluble phenolic concentrations. An EAB-susceptible green ash cultivar (F. pennsylvanica, cv. Patmore) and a wild accession were similar to each other on the basis of several chemical defense traits, and were characterized by high activities of peroxidase and trypsin inhibitor, a high total soluble phenolic concentration, and an intermediate rate of wound browning. Lignin concentration and polyphenol oxidase activities did not differentiate resistant and susceptible species. Of 33 phenolic compounds separated by HPLC and meeting a minimum criterion for analysis, nine were unique to Manchurian ash, five were shared among all species, and four were found in North American ashes and not in the Manchurian ash. Principal components analysis revealed clear separations between Manchurian, white, and green ashes on the basis of all phenolics, as well as clear separations on the basis of quantities of phenolics that all species shared. Variation in some of these constitutive chemical defense traits may contribute to variation in resistance to EAB in these species.