Induction of neuronal differentiation by a peptide corresponding to the homophilic binding site of the second Ig module of the neural cell adhesion molecule

NCAM mimetic peptide P2 synergizes with bone marrow mesenchymal stem cells in promoting functional recovery after stroke

The neural cell adhesion molecule (NCAM) promotes neural development and regeneration. Whether NCAM mimetic peptides could synergize with bone marrow mesenchymal stem cells (BMSCs) in stroke treatment deserves investigation. We found that the NCAM mimetic peptide P2 promoted BMSC proliferation, migration, and neurotrophic factor expression, protected neurons from oxygen-glucose deprivation through ERK and PI3K/AKT activation and anti-apoptotic mechanisms in vitro. Following middle cerebral artery occlusion (MCAO) in rats, P2 alone or in combination with BMSCs inhibited neuronal apoptosis and induced the phosphorylation of ERK and AKT. P2 combined with BMSCs enhanced neurotrophic factor expression and BMSC proliferation in the ischemic boundary zone. Moreover, combined P2 and BMSC therapy induced translocation of nuclear factor erythroid 2-related factor, upregulated heme oxygenase-1 expression, reduced infarct volume, and increased functional recovery as compared to monotreatments. Treatment with LY294002 (PI3K inhibitor) and PD98059 (ERK inhibitor) decreased the neuroprotective effects of combined P2 and BMSC therapy in MCAO rats. Collectively, P2 is neuroprotective while P2 and BMSCs work synergistically to improve functional outcomes after ischemic stroke, which may be attributed to mechanisms involving enhanced BMSC proliferation and neurotrophic factor release, anti-apoptosis, and PI3K/AKT and ERK pathways activation.

The dynamic TRPV2 ion channel proximity proteome reveals functional links of calcium flux with cellular adhesion factors NCAM and L1CAM in neurite outgrowth

TRPV2 voltage-insensitive, calcium-permeable ion channels play important roles in cancer progression, immune response, and neuronal development. Despite TRPV2's physiological impact, underlying endogenous proteins mediating TRPV2 responses and affected signaling pathways remain elusive. Using quantitative peroxidase-catalyzed (APEX2) proximity proteomics we uncover dynamic changes in the TRPV2-proximal proteome and identify calcium signaling and cell adhesion factors recruited to the molecular channel neighborhood in response to activation. Quantitative TRPV2 proximity proteomics further revealed activation-induced enrichment of protein clusters with biological functions in neural and cellular projection. We demonstrate a functional connection between TRPV2 and the neural immunoglobulin cell adhesion molecules NCAM and L1CAM. NCAM and L1CAM stimulation robustly induces TRPV2 [Ca2+]I flux in neuronal PC12 cells and this TRPV2-specific [Ca2+]I flux requires activation of the protein kinase PKCα. TRPV2 expression directly impacts neurite lengths that are modulated by NCAM or L1CAM stimulation. Hence, TRPV2's calcium signaling plays a previously undescribed, yet vital role in cell adhesion, and TRPV2 calcium flux and neurite development are intricately linked via NCAM and L1CAM cell adhesion proteins.

Revolutionizing Alzheimer's treatment: Harnessing human serum albumin for targeted drug delivery and therapy advancements

Alzheimer's disease (AD) is a neurodegenerative disorder initiated by amyloid-beta (Aβ) accumulation, leading to impaired cognitive function. Several delivery approaches have been improved for AD management. Among them, human serum albumin (HSA) is broadly employed for drug delivery and targeting the Aβ in AD owing to its biocompatibility, Aβ inhibitory effect, and nanoform, which showed blood-brain barrier (BBB) crossing ability via glycoprotein 60 (gp60) receptor and secreted protein acidic and rich in cysteine (SPARC) protein to transfer the drug molecules in the brain. Thus far, there is no previous review focusing on HSA and its drug delivery system in AD. Hence, the reviewed article aimed to critically compile the HSA therapeutic as well as drug delivery role in AD management. It also delivers information on how HSA-incorporated nanoparticles with surfaced embedded ligands such as TAT, GM1, and so on, not only improve BBB permeability but also increase neuron cell targetability in AD brain. Additionally, Aβ and tau pathology, including various metabolic markers likely BACE1 and BACE2, etc., are discussed. Besides, the molecular interaction of HSA with Aβ and its distinctive forms are critically reviewed that HSA can segregate Zn(II) and Cu(II) metal ions from Aβ owing to high affinity. Furthermore, the BBB drug delivery challenges in AD are addressed. Finally, the clinical formulation of HSA for the management of AD is critically discussed on how the HSA inhibits Aβ oligomer and fibril, while glycated HSA participates in amyloid plaque formation, i.e., β-structure sheet formation. This review report provides theoretical background on HSA-based AD drug delivery and makes suggestions for future prospect-related work.

Infrared nanoimaging of neuronal ultrastructure and nanoparticle interaction with cells

Here we introduce scattering-type scanning near-field optical microscopy (s-SNOM) as a novel tool for nanoscale chemical-imaging of sub-cellular organelles, nanomaterials and of the interactions between them. Our setup uses a tuneable mid-infrared laser and a sharp scanning probe to image at a resolution substantially surpassing the diffraction limit. The laser can be tuned to excite vibrational modes of functional groups in biomolecules, (e.g. amide moieties), in a way that enables direct chemical mapping without the need for labelling. We, for the first time, chemically image neuronal ultrastructure, identify neuronal organelles and sub-organelle structures as small as 10 nm and validate our findings using transmission electron microscopy (TEM). We produce chemical and morphological maps of neurons treated with gold nanospheres and characterize nanoparticle size and intracellular location, and their interaction with the plasma membrane. Our results show that the label-free nature of s-SNOM means it has a 'true' chemical resolution of up to 20 nm which can be further improved. We argue that it offers significant potential in nanomedicine for nanoscale chemical imaging of cell ultrastructure and the subcellular distribution of nanomaterials within tissues.

Nanostars Carrying Multifunctional Neurotrophic Dendrimers Protect Neurons in Preclinical In Vitro Models of Neurodegenerative Disorders

A challenge in neurology is the lack of efficient brain-penetrable neuroprotectants targeting multiple disease mechanisms. Plasmonic gold nanostars are promising candidates to deliver standard-of-care drugs inside the brain but have not been trialed as carriers for neuroprotectants. Here, we conjugated custom-made peptide dendrimers (termed H3/H6), encompassing motifs of the neurotrophic S100A4-protein, onto star-shaped and spherical gold nanostructures (H3/H6-AuNS/AuNP) and evaluated their potential as neuroprotectants and interaction with neurons. The H3/H6 nanostructures crossed a model blood-brain barrier, bound to plasma membranes, and induced neuritogenesis with the AuNS, showing higher potency/efficacy than the AuNP. The H3-AuNS/NP protected neurons against oxidative stress, the H3-AuNS being more potent, and against Parkinson's or Alzheimer's disease (PD/AD)-related cytotoxicity. Unconjugated S100A4 motifs also decreased amyloid beta-induced neurodegeneration, introducing S100A4 as a player in AD. Using custom-made dendrimers coupled to star-shaped nanoparticles is a promising route to activate multiple neuroprotective pathways and increase drug potency to treat neurodegenerative disorders.

Precise gene delivery systems with detachable albumin shell remodeling dysfunctional microglia by TREM2 for treatment of Alzheimer's disease

Intervention of the over-activated microglia-aggravated neuroinflammation represents a promising therapeutic strategy for Alzheimer's disease (AD). Upregulation of triggering receptor expressed on myeloid cells-2 (TREM2) attenuates the neuroinflammatory processes and normalizes the dysfunctional microglia. However, Trem2-gene therapy for AD by the effective non-invasive delivery systems is unexploited. Herein, we report the microglia-targeted gene delivery systems (PHSA@PF/pTREM2) composed of a core of fluorinated polyethylenimine condensing the TREM2-encoding plasmid (PF/pTREM2) and a shell of human serum albumin conjugated with both cis-aconitic anhydride and neural cell adhesion molecule-mimetic peptide P2 (PHSA). Thanks to the shedding effect of the albumin coated, PHSA@PF/pTREM2 exhibit prolonged blood circulation and low cytotoxicity. PHSA@PF/pTREM2 achieve brain accumulation as high as 2.17% injected dose per gram of brain and the microglial-targeting effect (targeting specificity of 41.9%) via the systemic administration. The nanocomplexes can be detached PHSA-shell in the acidic endo-lysosomes via the cleavage of cis-aconitic amide bond, resulting in PF/pTREM2 exposure for efficient endo-lysosomal escape and gene transfection. PHSA@PF/pTREM2 upregulate the TREM2 level and regulate microglial polarization toward M2-phenotype for remodeling the inflammatory microenvironment and enhanced Aβ clearance, leading to an improvement of cognitive performance in APP/PS1 mice. This work provides a promising gene delivery platform to reverse dysfunctional microglia for AD therapy.

Quantification of blood-brain barrier transport and neuronal toxicity of unlabelled multiwalled carbon nanotubes as a function of surface charge

Nanoparticles capable of penetrating the blood-brain barrier (BBB) will greatly advance the delivery of therapies against brain disorders. Carbon nanotubes hold great potential as delivery vehicles due to their high aspect-ratio and cell-penetrating ability. Studies have shown multiwalled carbon nanotubes (MWCNT) cross the BBB, however they have largely relied on labelling methods to track and quantify transport, or on individual electron microscopy images to qualitatively assess transcytosis. Therefore, new direct and quantitative methods, using well-defined and unlabelled MWCNT, are needed to compare BBB translocation of different MWCNT types. Using highly controlled anionic (-), cationic (+) and non-ionic (0) functionalized MWCNT (fMWCNT), we correlate UV-visible spectroscopy with quantitative transmission electron microscopy, quantified from c. 270 endothelial cells, to examine cellular uptake, BBB transport and neurotoxicity of unlabelled fMWCNT. Our results demonstrate that: (i) a large fraction of cationic and non-ionic, but not anionic fMWCNT become trapped at the luminal brain endothelial cell membrane; (ii) despite high cell association, fMWCNT uptake by brain endothelial cells is low (<1.5% ID) and does not correlate with BBB translocation, (iii) anionic fMWCNT have highest transport levels across an in vitro model of the human BBB compared to non-ionic or cationic nanotubes; and (iv) fMWCNT are not toxic to hippocampal neurons at relevant abluminal concentrations; however, fMWCNT charge has an effect on carbon nanotube neurotoxicity at higher fMWCNT concentrations. This quantitative combination of microscopy and spectroscopy, with cellular assays, provides a crucial strategy to predict brain penetration efficiency and neurotoxicity of unlabelled MWCNT and other nanoparticle technologies relevant to human health.

Microscopic Viscosity of Neuronal Plasma Membranes Measured Using Fluorescent Molecular Rotors: Effects of Oxidative Stress and Neuroprotection

Molecular mobility in neuronal plasma membranes is a crucial factor in brain function. Microscopic viscosity is an important parameter that determines molecular mobility. This study presents the first direct measurement of the microviscosity of plasma membranes of live neurons. Microviscosity maps were obtained using fluorescence lifetime imaging of environment-sensing dyes termed "molecular rotors". Neurons were investigated both in the basal state and following common neurodegenerative stimuli, excitotoxicity, or oxidative stress. Both types of neurotoxic challenges induced microviscosity decrease in cultured neurons, and oxidant-induced membrane fluidification was counteracted by the wide-spectrum neuroprotectant, the H3 peptide. These results provide new insights into molecular mobility in neuronal membranes, paramount for basic brain function, and suggest that preservation of membrane stability may be an important aspect of neuroprotection in brain insults and neurodegenerative disorders.

Artemin and an Artemin-Derived Peptide, Artefin, Induce Neuronal Survival, and Differentiation Through Ret and NCAM

Artemin (ARTN) is a neurotrophic factor from the GDNF family ligands (GFLs) that is involved in development of the nervous system and neuronal differentiation and survival. ARTN signals through a complex receptor system consisting of the RET receptor tyrosine kinase and a glycosylphosphatidylinositol-anchored co-receptor GFL receptor α, GFRα3. We found that ARTN binds directly to neural cell adhesion molecule (NCAM) and that ARTN-induced neuritogenesis requires NCAM expression and activation of NCAM-associated signaling partners, thus corroborating that NCAM is an alternative receptor for ARTN. We designed a small peptide, artefin, that could interact with GFRα3 and demonstrated that this peptide agonist induces RET phosphorylation and mimics the biological functions of ARTN – neuroprotection and neurite outgrowth. Moreover, artefin mimicked the binding of ARTN to NCAM and required NCAM expression and activation for its neurite elongation effect, thereby suggesting that artefin represents a binding site for NCAM within ARTN. We showed that biological effects of ARTN and artefin can be inhibited by abrogation of both NCAM and RET, suggesting a more complex signaling mechanism that previously thought. As NCAM plays a significant role in neurodevelopment, regeneration, and synaptic plasticity we suggest that ARTN and its mimetics are promising candidates for treatment of neurological disorders and warrant further investigations.

The S100A4 Protein Signals through the ErbB4 Receptor to Promote Neuronal Survival

Understanding the mechanisms of neurodegeneration is crucial for development of therapies to treat neurological disorders. S100 proteins are extensively expressed in the injured brain but S100's role and signalling in neural cells remain elusive. We recently demonstrated that the S100A4 protein protects neurons in brain injury and designed S100A4-derived peptides mimicking its beneficial effects. Here we show that neuroprotection by S100A4 involves the growth factor family receptor ErbB4 and its ligand Neuregulin 1 (NRG), key regulators of neuronal plasticity and implicated in multiple brain pathologies. The neuroprotective effect of S100A4 depends on ErbB4 expression and the ErbB4 signalling partners ErbB2/Akt, and is reduced by functional blockade of NRG/ErbB4 in cell models of neurodegeneration. We also detect binding of S100A4 with ErbB1 (EGFR) and ErbB3. S100A4-derived peptides interact with, and signal through ErbB, are neuroprotective in primary and immortalized dopaminergic neurons, and do not affect cell proliferation/motility - features which make them promising as potential neuroprotectants. Our data suggest that the S100-ErbB axis may be an important mechanism regulating neuronal survival and plasticity.

The Neural Cell Adhesion Molecule (NCAM) Promotes Clustering and Activation of EphA3 Receptors in GABAergic Interneurons to Induce Ras Homolog Gene Family, Member A (RhoA)/Rho-associated protein kinase (ROCK)-mediated Growth Cone Collapse

Establishment of a proper balance of excitatory and inhibitory connectivity is achieved during development of cortical networks and adjusted through synaptic plasticity. The neural cell adhesion molecule (NCAM) and the receptor tyrosine kinase EphA3 regulate the perisomatic synapse density of inhibitory GABAergic interneurons in the mouse frontal cortex through ephrin-A5-induced growth cone collapse. In this study, it was demonstrated that binding of NCAM and EphA3 occurred between the NCAM Ig2 domain and EphA3 cysteine-rich domain (CRD). The binding interface was further refined through molecular modeling and mutagenesis and shown to be comprised of complementary charged residues in the NCAM Ig2 domain (Arg-156 and Lys-162) and the EphA3 CRD (Glu-248 and Glu-264). Ephrin-A5 induced co-clustering of surface-bound NCAM and EphA3 in GABAergic cortical interneurons in culture. Receptor clustering was impaired by a charge reversal mutation that disrupted NCAM/EphA3 association, emphasizing the importance of the NCAM/EphA3 binding interface for cluster formation. NCAM enhanced ephrin-A5-induced EphA3 autophosphorylation and activation of RhoA GTPase, indicating a role for NCAM in activating EphA3 signaling through clustering. NCAM-mediated clustering of EphA3 was essential for ephrin-A5-induced growth cone collapse in cortical GABAergic interneurons, and RhoA and a principal effector, Rho-associated protein kinase, mediated the collapse response. This study delineates a mechanism in which NCAM promotes ephrin-A5-dependent clustering of EphA3 through interaction of the NCAM Ig2 domain and the EphA3 CRD, stimulating EphA3 autophosphorylation and RhoA signaling necessary for growth cone repulsion in GABAergic interneurons in vitro, which may extend to remodeling of axonal terminals of interneurons in vivo.

Neural tissue engineering: Bioresponsive nanoscaffolds using engineered self-assembling peptides

Rescuing or repairing neural tissues is of utmost importance to the patient's quality of life after an injury. To remedy this, many novel biomaterials are being developed that are, ideally, non-invasive and directly facilitate neural wound healing. As such, this review surveys the recent approaches and applications of self-assembling peptides and peptide amphiphiles, for building multi-faceted nanoscaffolds for direct application to neural injury. Specifically, methods enabling cellular interactions with the nanoscaffold and controlling the release of bioactive molecules from the nanoscaffold for the express purpose of directing endogenous cells in damaged or diseased neural tissues is presented. An extensive overview of recently derived self-assembling peptide-based materials and their use as neural nanoscaffolds is presented. In addition, an overview of potential bioactive peptides and ligands that could be used to direct behaviour of endogenous cells are categorized with their biological effects. Finally, a number of neurotrophic and anti-inflammatory drugs are described and discussed. Smaller therapeutic molecules are emphasized, as they are thought to be able to have less potential effect on the overall peptide self-assembly mechanism. Options for potential nanoscaffolds and drug delivery systems are suggested.

STATEMENT OF SIGNIFICANCE

Self-assembling nanoscaffolds have many inherent properties making them amenable to tissue engineering applications: ease of synthesis, ease of customization with bioactive moieties, and amenable for in situ nanoscaffold formation. The combination of the existing knowledge on bioactive motifs for neural engineering and the self-assembling propensity of peptides is discussed in specific reference to neural tissue engineering.

Cell Adhesion Molecules and Ubiquitination-Functions and Significance

Cell adhesion molecules of the immunoglobulin (Ig) superfamily represent the biggest group of cell adhesion molecules. They have been analyzed since approximately 40 years ago and most of them have been shown to play a role in tumor progression and in the nervous system. All members of the Ig superfamily are intensively posttranslationally modified. However, many aspects of their cellular functions are not yet known. Since a few years ago it is known that some of the Ig superfamily members are modified by ubiquitin. Ubiquitination has classically been described as a proteasomal degradation signal but during the last years it became obvious that it can regulate many other processes including internalization of cell surface molecules and lysosomal sorting. The purpose of this review is to summarize the current knowledge about the ubiquitination of cell adhesion molecules of the Ig superfamily and to discuss its potential physiological roles in tumorigenesis and in the nervous system.

Peptide mimetic of the S100A4 protein modulates peripheral nerve regeneration and attenuates the progression of neuropathy in myelin protein P0 null mice

We recently found that S100A4, a member of the multifunctional S100 protein family, protects neurons in the injured brain and identified two sequence motifs in S100A4 mediating its neurotrophic effect. Synthetic peptides encompassing these motifs stimulated neuritogenesis and survival in vitro and mimicked the S100A4-induced neuroprotection in brain trauma. Here, we investigated a possible function of S100A4 and its mimetics in the pathologies of the peripheral nervous system (PNS). We found that S100A4 was expressed in the injured PNS and that its peptide mimetic (H3) affected the regeneration and survival of myelinated axons. H3 accelerated electrophysiological, behavioral and morphological recovery after sciatic nerve crush while transiently delaying regeneration after sciatic nerve transection and repair. On the basis of the finding that both S100A4 and H3 increased neurite branching in vitro, these effects were attributed to the modulatory effect of H3 on initial axonal sprouting. In contrast to the modest effect of H3 on the time course of regeneration, H3 had a long-term neuroprotective effect in the myelin protein P0 null mice, a model of dysmyelinating neuropathy (Charcot-Marie-Tooth type 1 disease), where the peptide attenuated the deterioration of nerve conduction, demyelination and axonal loss. From these results, S100A4 mimetics emerge as a possible means to enhance axonal sprouting and survival, especially in the context of demyelinating neuropathies with secondary axonal loss, such as Charcot-Marie-Tooth type 1 disease. Moreover, our data suggest that S100A4 is a neuroprotectant in PNS and that other S100 proteins, sharing high homology in the H3 motif, may have important functions in PNS pathologies.

The metastasis-promoting S100A4 protein confers neuroprotection in brain injury

Identification of novel pro-survival factors in the brain is paramount for developing neuroprotective therapies. The multifunctional S100 family proteins have important roles in many human diseases and are also upregulated by brain injury. However, S100 functions in the nervous system remain unclear. Here we show that the S100A4 protein, mostly studied in cancer, is overexpressed in the damaged human and rodent brain and released from stressed astrocytes. Genetic deletion of S100A4 exacerbates neuronal loss after brain trauma or excitotoxicity, increasing oxidative cell damage and downregulating the neuroprotective protein metallothionein I+II. We identify two neurotrophic motifs in S100A4 and show that these motifs are neuroprotective in animal models of brain trauma. Finally, we find that S100A4 rescues neurons via the Janus kinase/STAT pathway and, partially, the interleukin-10 receptor. Our data introduce S100A4 as a therapeutic target in neurodegeneration, and raise the entire S100 family as a potentially important factor in central nervous system injury.

NCAM function in the adult brain: lessons from mimetic peptides and therapeutic potential

Neural cell adhesion molecules (NCAMs) are complexes of transmembranal proteins critical for cell-cell interactions. Initially recognized as key players in the orchestration of developmental processes involving cell migration, cell survival, axon guidance, and synaptic targeting, they have been shown to retain these functions in the mature adult brain, in relation to plastic processes and cognitive abilities. NCAMs are able to interact among themselves (homophilic binding) as well as with other molecules (heterophilic binding). Furthermore, they are the sole molecule of the central nervous system undergoing polysialylation. Most interestingly polysialylated and non-polysialylated NCAMs display opposite properties. The precise contributions each of these characteristics brings in the regulations of synaptic and cellular plasticity in relation to cognitive processes in the adult brain are not yet fully understood. With the aim of deciphering the specific involvement of each interaction, recent developments led to the generation of NCAM mimetic peptides that recapitulate identified binding properties of NCAM. The present review focuses on the information such advances have provided in the understanding of NCAM contribution to cognitive function.

Neural cell adhesion molecules in brain plasticity and disease

Neural cell adhesion molecule (NCAM) has been studied extensively. But it is only in recent times that interest in this molecule has shifted to conditions such as Alzheimer's disease, Multiple Sclerosis and Schizophrenia, focusing on its role in neurodegeneration and abnormal neurodevelopment. NCAM is important in neurite outgrowth, long-term potentiation in the hippocampus and synaptic plasticity. Reduced as well as increased levels in NCAM have been linked to pathology in the brain suggesting that a shift in the equilibrium may be the key. Hence, increasing our understanding of the role of NCAM in health and disease should clear some of the ambiguity surrounding the molecule and even lead to newer potential therapeutic targets. This review consolidates our current understanding of NCAM, focusing on the consequences of dysregulation, its role in neurodegenerative and neurodevelopmental disorders, and the future of NCAM plus potential options for therapy.

A peptide derived from the CD loop-D helix region of ciliary neurotrophic factor (CNTF) induces neuronal differentiation and survival by binding to the leukemia inhibitory factor (LIF) receptor and common cytokine receptor chain gp130

Ciliary neurotrophic factor (CNTF) induces neuronal differentiation and promotes the survival of various neuronal cell types by binding to a receptor complex formed by CNTF receptor α (CNTFRα), gp130, and the leukemia inhibitory factor (LIF) receptor (LIFR). The CD loop-D helix region of CNTF has been suggested to be important for the cytokine interaction with LIFR. We designed a peptide, termed cintrofin, that encompasses this region. Surface plasmon resonance analysis demonstrated that cintrofin bound to LIFR and gp130, but not to CNTFRα, with apparent KD values of 35 nM and 1.1 nM, respectively. Cintrofin promoted the survival of cerebellar granule neurons (CGNs), in which cell death was induced either by potassium withdrawal or H2O2 treatment. Cintrofin induced neurite outgrowth from CGNs, and this effect was inhibited by specific antibodies against both gp130 and LIFR, indicating that these receptors are involved in the effects of cintrofin. The C-terminal part of the peptide, corresponding to the D helix region of CNTF, was shown to be essential for the neuritogenic action of the peptide. CNTF and LIF induced neurite outgrowth in CGNs plated on laminin-coated slides. On uncoated slides, CNTF and LIF had no neuritogenic effect but were able to inhibit cintrofin-induced neuronal differentiation, indicating that cintrofin and cytokines compete for the same receptors. In addition, cintrofin induced the phosphorylation of STAT3, Akt, and ERK, indicating that it exerts cell signaling properties similar to those induced by CNTF and may be a valuable survival agent with possible therapeutic potential.

A screen for peptide agonists of the G-CSF receptor

BACKGROUND

Granulocyte-colony stimulating factor (G-CSF) is one of the most important pharmacologically used proteins. Potential uses beyond the stimulation of neutrophilic granulocytes are the treatment of CNS disorders. Disadvantages of the G-CSF protein as a drug are its moderate plasma half-life time and considerable production costs. We therefore conducted a screen for peptide agonists derived from the sequence of human G-CSF.

FINDINGS

Despite of the high sensitivity of our screening system we could not detect any positive hits in a single peptide approach. In a multiplex approach using a permutation of any combination of 10 different peptides we could also not detect a positive block.

CONCLUSIONS

We conclude that larger coherent parts of the protein or dimerising peptides may be needed to achieve activation of the receptor.

A metallothionein mimetic peptide protects neurons against kainic acid-induced excitotoxicity

Metallothioneins I and II (MTI/II) are metal-binding proteins overexpressed in response to brain injury. Recently, we have designed a peptide, termed EmtinB, which is modeled after the beta-domain of MT-II and mimics the biological effects of MTI/II in vitro. Here, we demonstrate the neuroprotective effect of EmtinB in the in vitro and in vivo models of kainic acid (KA)-induced neurotoxicity. We show that EmtinB passes the blood-brain barrier and is detectable in plasma for up to 24 hr. Treatment with EmtinB significantly attenuates seizures in C57BL/6J mice exposed to moderate (20 mg/kg) and high (30 mg/kg) KA doses and tends to decrease mortality induced by the high KA dose. Histopathological evaluation of hippocampal (CA3 and CA1) and cortical areas of mice treated with 20 mg/kg KA shows that EmtinB treatment reduces KA-induced neurodegeneration in the CA1 region. These findings establish EmtinB as a promising target for therapeutic development.

Neural cell adhesion molecule is a cardioprotective factor up-regulated by metabolic stress

Screening for cell surface proteins up-regulated under stress conditions may lead to the identification of new therapeutic targets. To search for genes whose expression was enhanced by treatment with oligomycin, a mitochondrial-F(0)F(1) ATP synthase inhibitor, signal sequence trapping was performed in H9C2 rat cardiac myoblasts. One of the genes identified was that for neural cell adhesion molecule (NCAM, CD56), a major regulator of development, cell survival, migration, and neurite outgrowth in the nervous system. Immunohistochemical analyses in a mouse myocardial infarction model revealed that NCAM was strongly expressed in residual cardiac myocytes in the infarcted region. Increased expression of NCAM was also found during the remodeling period in a rat model of hypertension-induced heart failure. Lentivirus-mediated knockdown of NCAM decreased the cell growth and survival following oligomycin treatment in H9C2 cells. In primary rat neonatal cardiac myocytes, NCAM was also found to be up-regulated and played a protective role following oligomycin treatment. Analyses of downstream signaling revealed that knockdown of NCAM significantly decreased the basal AKT phosphorylation level. In contrast, NCAM mimetic peptide P2d activated AKT and significantly reduced oligomycin-induced cardiomyocyte death, which was abolished by treatment with the PI3K inhibitor LY-294002 as well as overexpression of the dominant-negative AKT mutant. These findings demonstrate that NCAM is a cardioprotective factor up-regulated under metabolic stress in cardiomyocytes and augmentation of this signal improved survival.

Design and adsorption of modular engineered proteins to prepare customized, neuron-compatible coatings

Neural prosthetic implants are currently being developed for the treatment and study of both peripheral and central nervous system disorders. Effective integration of these devices upon implantation is a critical hurdle to achieving function. As a result, much attention has been directed towards the development of biocompatible coatings that prolong their in vivo lifespan. In this work, we present a novel approach to fabricate such coatings, which specifically involves the use of surface-adsorbed, nanoscale-designed protein polymers to prepare reproducible, customized surfaces. A nanoscale modular design strategy was employed to synthesize six engineered, recombinant proteins intended to mimic aspects of the extracellular matrix proteins fibronectin, laminin, and elastin as well as the cell-cell adhesive protein neural cell adhesion molecule. Physical adsorption isotherms were experimentally determined for these engineered proteins, allowing for direct calculation of the available ligand density present on coated surfaces. As confirmation that ligand density in these engineered systems impacts neuronal cell behavior, we demonstrate that increasing the density of fibronectin-derived RGD ligands on coated surfaces while maintaining uniform protein surface coverage results in enhanced neurite extension of PC-12 cells. Therefore, this engineered protein adsorption approach allows for the facile preparation of tunable, quantifiable, and reproducible surfaces for in vitro studies of cell-ligand interactions and for potential application as coatings on neural implants.

Pharmacology of cell adhesion molecules of the nervous system

Cell adhesion molecules (CAMs) play a pivotal role in the development and maintenance of the nervous system under normal conditions. They also are involved in numerous pathological processes such as inflammation, degenerative disorders, and cancer, making them attractive targets for drug development. The majority of CAMs are signal transducing receptors. CAM-induced intracellular signalling is triggered via homophilic (CAM-CAM) and heterophilic (CAM - other counter-receptors) interactions, which both can be targeted pharmacologically. We here describe the progress in the CAM pharmacology focusing on cadherins and CAMs of the immunoglobulin (Ig) superfamily, such as NCAM and L1. Structural basis of CAM-mediated cell adhesion and CAM-induced signalling are outlined. Different pharmacological approaches to study functions of CAMs are presented including the use of specific antibodies, recombinant proteins, and synthetic peptides. We also discuss how unravelling of the 3D structure of CAMs provides novel pharmacological tools for dissection of CAM-induced signalling pathways and offers therapeutic opportunities for a range of neurological disorders.

Neural cell adhesion molecule-180-mediated homophilic binding induces epidermal growth factor receptor (EGFR) down-regulation and uncouples the inhibitory function of EGFR in neurite outgrowth

The neural cell adhesion molecule (NCAM) plays important roles in neuronal development, regeneration, and synaptic plasticity. NCAM homophilic binding mediates cell adhesion and induces intracellular signals, in which the fibroblast growth factor receptor plays a prominent role. Recent studies on axon guidance in Drosophila suggest that NCAM also regulates the epidermal growth factor receptor (EGFR) (Molecular and Cellular Neuroscience, 28, 2005, 141). A possible interaction between NCAM and EGFR in mammalian cells has not been investigated. The present study demonstrates for the first time a functional interaction between NCAM and EGFR in mammalian cells and investigates the molecular mechanisms underlying this interaction. First, NCAM and EGFR are shown to play opposite roles in neurite outgrowth regulation in cerebellar granular neurons. The data presented indicate that negative regulation of EGFR is one of the mechanisms underlying the neuritogenic effect of NCAM. Second, it is demonstrated that expression of the NCAM-180 isoform induces EGFR down-regulation in transfected cells and promotes EGFR down-regulation induced by EGF stimulation. It is demonstrated that the mechanism underlying this NCAM-180-induced EGFR down-regulation involves increased EGFR ubiquitination and lysosomal EGFR degradation. Furthermore, NCAM-180-mediated EGFR down-regulation requires NCAM homophilic binding and interactions of the cytoplasmic domain of NCAM-180 with intracellular interaction partners, but does not require NCAM-mediated fibroblast growth factor receptor activation.

Metallothionein and a peptide modeled after metallothionein, EmtinB, induce neuronal differentiation and survival through binding to receptors of the low-density lipoprotein receptor family

Accumulating evidence suggests that metallothionein (MT)-I and -II promote neuronal survival and regeneration in vivo. The present study investigated the molecular mechanisms underlying the differentiation and survival-promoting effects of MT and a peptide modeled after MT, EmtinB. Both MT and EmtinB directly stimulated neurite outgrowth and promoted survival in vitro using primary cultures of cerebellar granule neurons. In addition, expression and surface localization of megalin, a known MT receptor, and the related lipoprotein receptor-related protein-1 (LRP) are demonstrated in cerebellar granule neurons. By means of surface plasmon resonance MT and EmtinB were found to bind to both megalin and LRP. The bindings were abrogated in the presence of receptor-associated protein-1, an antagonist of the low-density lipoprotein receptor family, which also inhibited MT- and EmtinB-induced neurite outgrowth and survival. MT-mediated neurite outgrowth was furthermore inhibited by an anti-megalin serum. EmtinB-mediated inhibition of apoptosis occurred without a reduction of caspase-3 activity, but was associated with reduced expression of the pro-apoptotic B-cell leukemia/lymphoma-2 interacting member of cell death (Bim(S)). Finally, evidence is provided that MT and EmtinB activate extracellular signal-regulated kinase, protein kinase B, and cAMP response element binding protein. Altogether, these results strongly suggest that MT and EmtinB induce their neuronal effects through direct binding to surface receptors belonging to the low-density lipoprotein receptor family, such as megalin and LRP, thereby activating signal transduction pathways resulting in neurite outgrowth and survival.

Association of haplotypic variants in DRD2, ANKK1, TTC12 and NCAM1 to alcohol dependence in independent case–control and family samples

There have been many conflicting reports concerning the association of the DRD2 locus with alcohol dependence (AD). To investigate whether these findings could be reconciled by considering the genomic region of DRD2 in greater detail, we conducted two separate association studies of AD in 1220 European-American subjects using family-based (488 subjects) and case-control (318 cases and 414 controls) designs, and 43 single nucleotide polymorphisms mapped to the gene cluster of NCAM1, TTC12, ANKK1 and DRD2. We used a generalized linear model and haplotype score tests for the case-control sample, and the family-based association test for the family sample. Haplotype associations centered on TTC12 exon 3 [rs1893699-rs723077; optimal individual haplotype simulated P-value (P(oihs)) = 0.00021] in both independent samples (family and case-control). Additional AD-associated haplotypes centered around NCAM1 exon 12 in the family sample (P(oihs) = 0.0032), and at exons 2 and 5 of ANKK1 in the case-control sample (P(oihs) = 0.00058). LD contrasts between cases and controls support selection at TTC12 exon 3 and ANKK1 exon 2. The armadillo repeat domains encoded by TTC12 and dopamine interact in the Wnt pathway and may have effects on dopamine cell development in the ventral midbrain. We conclude that risk for AD is attributable in part to variants in four regions within this cluster: exon 3 of TTC12, exon 12/intron13 of NCAM1 and exons 2 and 5 of ANKK1. The complexity of these relationships, many of which replicate between our independent samples, may explain prior inconsistent results.

Separation and enrichment of neural stem cells using segregation in an expanded bed

An expanded bed system has been developed for a novel application in which the separation and enrichment of neural stem cells from a sample containing a mixture of stem and progenitor cells is achieved based on the difference in the sizes of the aggregates of these types of cells. Inert Sephadex beads and flocculated yeast cells were used as experimental controls and references. The characteristics of the separation of neural stem cell aggregates based on size are similar to those achieved with flocculated yeast where cell-to-cell aggregation controls the pattern of size separation different from those of inert Sephadex beads.

Tolerability, safety and pharmacokinetics of the FGLL peptide, a novel mimetic of neural cell adhesion molecule, following intranasal administration in healthy volunteers

BACKGROUND

The FG loop peptide (FGL(L)), a novel mimetic of the neural cell adhesion molecule (NCAM), is in clinical development for neurodegenerative disorders such as Alzheimer's disease. Preclinical studies in rats, dogs and monkeys have demonstrated exposure in plasma and cerebrospinal fluid after parenteral or intranasal administration of FGL(L), with no systemic toxicity. This article reports on the results of the first administration of FGL(L) in humans.

OBJECTIVE

To determine the tolerability, safety and pharmacokinetics of ascending, single intranasal doses of FGL(L) 25, 100 and 200mg in healthy subjects.

METHODS

In an 8-day, open-label, phase I study, 24 healthy male volunteers (mean age 42 [range 24-55] years) received single intranasal doses of FGL(L) (25, 100 and 200mg) in accordance with an ascending dose, sequential-cohort design.

RESULTS

All three intranasal doses of FGL(L) were well tolerated and there were no clinical notable abnormalities in ECG recordings, vital signs or laboratory tests. Three subjects (13%) reported five adverse events. A transient (<3 minutes) burning sensation in the nose was reported in two subjects at the 200mg dose level while runny eyes (<2 minutes) were experienced in one subject at 25mg. These events had an onset immediately following intranasal administration, and a relationship to FGL(L) was suspected. One of the latter subjects who had experienced a burning sensation in the nose also experienced dizziness, vomiting and headache with onset >2 days after single-dose administration of FGL(L); no relationship to the study drug was suspected. Quantifiable plasma concentrations of FGL(L) were observed up to 1 hour after intranasal administration of the 100mg dose and up to 4 hours after the 200mg dose (plasma FGL(L) concentrations were undetectable at all timepoints for the 25mg dose). Increasing doses of FGL(L) were associated with higher systemic exposures: mean C(max) 0.52 ng/mL and 1.38 ng/mL (100mg and 200mg, respectively); mean AUC(24) 1.27 ng x h/mL and 4.05 ng x h/mL (100mg and 200mg, respectively).

CONCLUSIONS

Intranasal administration of FGL(L) (25, 100 and 200mg) was well tolerated in healthy male volunteers, with no safety concerns and a pharmacokinetic profile that was generally dose related. Further studies are currently being planned to evaluate the effects of FGL(L) in patients with Alzheimer's disease.