Steven P. Braithwaite

Kainate receptors: subunits, synaptic localization and function.

Although it is well established that kainate receptors constitute an entirely separate group of proteins from AMPA receptors, their physiological functions remain unclear. The molecular cloning of subunits that form kainate receptors and the ability to study recombinant receptors is leading to an increased understanding of their functional properties. Furthermore, the development of kainate receptor-selective agonists and antagonists over the past few years is now allowing the physiological roles of these receptors and, in some cases, specific subunits to be investigated. As a consequence, the synaptic activation of postsynaptic kainate receptors and the presence of presynaptic kainate receptors that serve to regulate excitatory and inhibitory synaptic transmission have been described, and will be discussed in this article by Ramesh Chittajallu, Steven Braithwaite, Vernon Clarke and Jeremy Henley.

Rapid and differential regulation of AMPA and kainate receptors at hippocampal mossy fibre synapses by PICK1 and GRIP.

We identified four PDZ domain-containing proteins, syntenin, PICK1, GRIP, and PSD95, as interactors with the kainate receptor (KAR) subunits GluR5(2b,) GluR5(2c), and GluR6. Of these, we show that both GRIP and PICK1 interactions are required to maintain KAR-mediated synaptic function at mossy fiber-CA3 synapses. In addition, PKC alpha can phosphorylate ct-GluR5(2b) at residues S880 and S886, and PKC activity is required to maintain KAR-mediated synaptic responses. We propose that PICK1 targets PKC alpha to phosphorylate KARs, causing their stabilization at the synapse by an interaction with GRIP. Importantly, this mechanism is not involved in the constitutive recycling of AMPA receptors since blockade of PDZ interactions can simultaneously increase AMPAR- and decrease KAR-mediated synaptic transmission at the same population of synapses.

Enhanced Phosphatase Activity Attenuates α-Synucleinopathy in a Mouse Model

α-Synuclein (α-Syn) is a key protein that accumulates as hyperphosphorylated aggregates in pathologic hallmark features of Parkinsons disease (PD) and other neurodegenerative disorders. Phosphorylation of this protein at serine 129 is believed to promote its aggregation and neurotoxicity, suggesting that this post-translational modification could be a therapeutic target. Here, we demonstrate that phosphoprotein phosphatase 2A (PP2A) dephosphorylates α-Syn at serine 129 and that this activity is greatly enhanced by carboxyl methylation of the catalytic C subunit of PP2A. α-Syn-transgenic mice raised on a diet supplemented with eicosanoyl-5-hydroxytryptamide, an agent that enhances PP2A methylation, dramatically reduced both α-Syn phosphorylation at Serine 129 and α-Syn aggregation in the brain. These biochemical changes were associated with enhanced neuronal activity, increased dendritic arborizations, and reduced astroglial and microglial activation, as well as improved motor performance. These findings support the notion that serine 129 phosphorylation of α-Syn is of pathogenetic significance and that promoting PP2A activity is a viable disease-modifying therapeutic strategy for α-synucleinopathies such as PD.

Interactions between AMPA receptors and intracellular proteins.

alpha-Amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) receptors mediate most fast excitatory synaptic transmission in the mammalian CNS. They play a central role in synapse stabilisation and plasticity and their prolonged activation is potently neurotoxic. Developmental and activity-dependent changes in the functional synaptic expression of these receptors are subject to tight cellular regulation. The molecular and cellular mechanisms which control the postsynaptic insertion and arrangement of individual AMPA receptor variants are therefore the subject of intense investigation and in the last two years there has been significant progress towards elucidating some of the processes involved. Much of the new information has come from the application of the yeast two-hybrid assay, which has led to the discovery of a hitherto unexpected complexity of proteins which selectively interact with individual AMPA receptor subunits. These proteins have been implicated in the regulation of AMPA receptor post-translational modification, targeting and trafficking, surface expression and anchoring. The aim of this article is to present an overview of the major interacting proteins described so far and to place these in the context of how they may participate in the well ordered series of events controlling the cell biology of AMPA receptors.

α-Synuclein phosphorylation as a therapeutic target in Parkinson’s disease

Abstract Phosphorylation is a key post-translational modification necessary for normal cellular signaling and, therefore, lies at the heart of cellular function. In neurodegenerative disorders, abnormal hyperphosphorylation of pathogenic proteins is a common phenomenon that contributes in important ways to the disease process. A prototypical protein that is hyperphosphorylated in the brain is α-synuclein (α-syn) – found in Lewy bodies and Lewy neurites – the pathological hallmarks of Parkinson’s disease (PD) and other α-synucleinopathies. The genetic linkage of α-syn to PD as well as its pathological association in both genetic and sporadic cases have made it the primary protein of interest. In understanding how α-syn dysfunction occurs, increasing focus is being placed on its abnormal aggregation and the contribution of phosphorylation to this process. Studies of both the kinases and phosphatases that regulate α-syn phosphorylation are beginning to reveal the roles of this post-translational modification in disease pathogenesis. Modulation of α-syn phosphorylation may ultimately prove to be a viable strategy for disease-modifying therapeutic interventions. In this review, we explore mechanisms related to α-syn phosphorylation, its biophysical and functional consequences, and its role in neurodegeneration.

Dual κ‐agonist/μ‐antagonist opioid receptor modulation reduces levodopa‐induced dyskinesia and corrects dysregulated striatal changes in the nonhuman primate model of Parkinson disease

Effective medical management of levodopa‐induced dyskinesia (LID) remains an unmet need for patients with Parkinson disease (PD). Changes in opioid transmission in the basal ganglia associated with LID suggest a therapeutic opportunity. Here we determined the impact of modulating both mu and kappa opioid receptor signaling using the mixed agonist/antagonist analgesic nalbuphine in reducing LID and its molecular markers in the nonhuman primate model.

Targeting phosphatases as the next generation of disease modifying therapeutics for Parkinson’s disease

Phosphorylation is a key post-translational modification for cellular signaling, and abnormalities in this process are observed in several neurodegenerative disorders. Among these disorders, Parkinsons disease (PD) is particularly intriguing as there are both genetic causes of disease that involve phosphorylation, and pathological hallmarks of disease composed of a hyperphosphorylated protein. Two of the major genes linked to PD are themselves kinases - leucine rich repeat kinase 2 (LRRK2) and phosphatase and tensin induced homolog kinase 1 (PINK1). Mutations in LRRK2 lead to its increased kinase activity and dominantly inherited PD, while mutations in PINK1 lead to loss of function and recessive PD. A third genetic linkage to disease is α-synuclein, a protein that is heavily phosphorylated in Lewy bodies and Lewy neurites, the pathological hallmarks of PD. The phosphorylation of α-synuclein at various residues influences its aggregation, either positively or negatively, thereby impacting its central role in disease pathogenesis. Given these associations of phosphorylation with PD, modulation of this modification is an attractive therapeutic strategy. The kinases that act in these disease relevant pathways have been the primary target for such approaches. But, the development of kinase inhibitors has been complicated by the necessary specificity to retain safety, the redundancy of kinases leading to lack of efficacy, and the difficulties in overcoming the blood-brain barrier. The field of modulating phosphatases has the potential to overcome some of these issues and provide the next generation of therapeutic targets for PD. In this review, we address the phosphorylation pathways involved in PD, the kinases and issues related to their inhibition, and the evolving field of the phosphatases relevant in PD and how they may be targeted pharmacologically.

BENEFICAL PROPERTIES OF A HUMAN PLASMA FRACTION FOR AGE-RELATED COGNITIVE DISORDERS

directly targeting CRH using a high affinity antibody.Methods:Using molecular cloning, vaccination, and hybridoma technology we have successfully generated and purified a monoclonal Anti CRH antibody for use as a potential therapeutic. This antibody is currently being tested as a therapeutic in both mutant APP and tau transgenic mice. Results:A one time intraperitoneal injection of 25 mg/kg of Anti-CRH antibody in mice is able to provide >80% suppression of the corticosterone response to acute restraint stress and is able to reverse the cushingoid phenotype seen in mice that overexpress CRHwithin the brain. This suppression of corticosterone from one dose remains present even four days past injection and possibly much longer. Conclusions:We have generated a high affinity (Kd<1.0E-12) monoclonal CRH antibody that is able to reduce the glucocorticoid response to acute restraint stress by greater than 80%while also maintaining basal glucocorticoid levels in mice. These studies have broad implication for stress-related disorders in addition to AD, and may herald a new class of central nervous system therapies that target neuropeptides using high affinity antibodies.

TARGETING THE EOTAXIN/CCR3 PATHWAY IN AGING-ASSOCIATED COGNITIVE DECLINE

after treatment. Student t-test was used to compare the different groups of animals. Animals were visually and histologically inspected for tumor formation. Results: Treatment of eSCs and mSCs by a less-invasive intravenous route in the MPTP PD rodent model provided augmentation in motor abilities at early (10 days post-treatment) and later (3 months post-treatment) time points. Also, this treatment was deemed to be safe from teratomas. Conclusions: Motor impairment observed in MPTP-induced PD mice ameliorates after the treatment with NPs, and this is more evident several days after the therapy. Therefore, peripheral administration of NPs could be a promising therapy to treat motor impairment associated to PD.