Ezrin mediates neuritogenesis via down-regulation of RhoA activity in cultured cortical neurons

Collaborative Roles for RAC1, ERM Proteins and PTEN During Adult Sensory Axon Regeneration

The role of local of growth cone (GC) manipulation in adult regenerative systems is largely unexplored despite substantial translational importance. Here we investigated collaboration among Rac1 GTPase, its partnering ERM proteins and PTEN in adult sensory neurons and adult nerve regeneration. We confirmed expression of both Rac1 and ERM in adults and noted substantial impacts on neurite outgrowth in naïve and pre-injured adult sensory neurons. PTEN inhibition added to this outgrowth. Rac1 activation acted directly on adult GCs facilitating both attractive turning and advancement. In vivo regeneration indices including electrophysiological recovery, return of sensation, walking, repopulation of myelinated axons and reinnervation of the target epidermis indicated benefits of local Rac1 activation. These indices suggested maximal GC activation whereas local PTEN inhibition offered only limited added improvement. Our findings provide support for the concept of manipulating adult GCs, by emphasizing local Rac1 activation in directing therapy for nerve repair.

Novel insight into the role of A-kinase anchoring proteins (AKAPs) in ischemic stroke and therapeutic potentials

Ischemic stroke, a devastating disease associated with high mortality and disability worldwide, has emerged as an urgent public health issue. A-kinase anchoring proteins (AKAPs) are a group of signal-organizing molecules that compartmentalize and anchor a wide range of receptors and effector proteins and have a major role in stabilizing mitochondrial function and promoting neurodevelopmental development in the central nervous system (CNS). Growing evidence suggests that dysregulation of AKAPs expression and activity is closely associated with oxidative stress, ion disorder, mitochondrial dysfunction, and blood-brain barrier (BBB) impairment in ischemic stroke. However, the underlying mechanisms remain inadequately understood. This review provides a comprehensive overview of the composition and structure of A-kinase anchoring protein (AKAP) family members, emphasizing their physiological functions in the CNS. We explored in depth the molecular and cellular mechanisms of AKAP complexes in the pathological progression and risk factors of ischemic stroke, including hypertension, hyperglycemia, lipid metabolism disorders, and atrial fibrillation. Herein, we highlight the potential of AKAP complexes as a pharmacological target against ischemic stroke in the hope of inspiring translational research and innovative clinical approaches.

Pip5k1γ regulates axon formation by limiting Rap1 activity

During their differentiation, neurons establish a highly polarized morphology by forming axons and dendrites. Cortical and hippocampal neurons initially extend several short neurites that all have the potential to become an axon. One of these neurites is then selected as the axon by a combination of positive and negative feedback signals that promote axon formation and prevent the remaining neurites from developing into axons. Here, we show that Pip5k1γ is required for the formation of a single axon as a negative feedback signal that regulates C3G and Rap1 through the generation of phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Impairing the function of Pip5k1γ results in a hyper-activation of the Fyn/C3G/Rap1 pathway, which induces the formation of supernumerary axons. Application of a hyper-osmotic shock to modulate membrane tension has a similar effect, increasing Rap1 activity and inducing the formation of supernumerary axons. In both cases, the induction of supernumerary axons can be reverted by expressing constitutively active Pip5k. Our results show that PI(4,5)P2-dependent membrane properties limit the activity of C3G and Rap1 to ensure the extension of a single axon.

Ezrin deficiency triggers glial fibrillary acidic protein upregulation and a distinct reactive astrocyte phenotype

Astrocytes are increasingly being recognized as contributors to physiological brain function and behavior. Astrocytes engage in glia-synaptic interactions through peripheral astrocyte processes, thus modulating synaptic signaling, for example, by handling glutamate removal from the synaptic cleft and (re)provision to axonal terminals. Peripheral astrocyte processes are ultrafine membrane protrusions rich in the membrane-to-actin cytoskeleton linker Ezrin, an essential component of in vitro filopodia formation and in vivo peripheral astrocyte process motility. Consequently, it has been postulated that Ezrin significantly contributes to neurodevelopment as well as astrocyte functions within the adult brain. However, while Ezrin has been studied in vitro within cultured primary astrocytes, in vivo studies on the role of Ezrin in astrocytes remain to be conducted and consequences of its depletion to be studied. Here, we investigated consequences of Ezrin deletion in the mouse brain starting from early neuronal specification. While Ezrin knockout did not impact prenatal cerebral cortex development, behavioral phenotyping depicted reduced exploratory behavior. Starting with postnatal appearance of glia cells, Ezrin was verified to remain predominantly expressed in astrocytes. Proteome analysis of Ezrin deficient astrocytes revealed alterations in glutamate and ion homeostasis, metabolism and cell morphology - important processes for synaptic signal transmission. Notably, Ezrin deletion in astrocytes provoked (GFAP) glial fibrillary acidic protein upregulation - a marker of astrocyte activation and reactive astrogliosis. However, this spontaneous, reactive astrogliosis exhibited proteome changes distinct from ischemic-induced reactive astrogliosis. Moreover, in experimental ischemic stroke, Ezrin knockout mice displayed reduced infarct volume, indicating a protective effect of the Ezrin deletion-induced changes and astrogliosis.

Ezrin interacts with the tumor suppressor CHL1 and promotes neuronal differentiation of human neuroblastoma

In a previous study, we demonstrated that CHL1, the neuronal cell adhesion molecule close homolog of L1, acts as a tumor suppressor in human neuroblastoma (NB), a still highly lethal childhood malignancy, influencing its differentiation and proliferation degree. Here we found that ezrin, one of the ERM (ezrin, radixin, moesin) proteins involved in cytoskeleton organization, strongly interacts with CHL1. The low expression of EZRIN, as well as the low expression of CHL1 and of the neuronal differentiation marker MAP2, correlates with poor outcome in NB patients. Knock-down of ezrin in HTLA-230 cell line induces neurite retraction, enhances cell proliferation and migration, and triggers anchorage-independent growth, with effects very similar to those already obtained by CHL1 silencing. Furthermore, lack of ezrin inhibits the expression of MAP2 and of the oncosuppressor molecule p53, whereas it enhances MAPK activation, all typical features of tumor aggressiveness. As already described, CHL1 overexpression in IMR-32 cell line provokes an opposite trend, but the co-silencing of ezrin reduces these effects, confirming the hypothesis that CHL1 acts in close connection with ezrin. Overall, our data show that ezrin reinforces the differentiating and oncosuppressive functions of CHL1, identifying this ERM protein as a new targetable molecule for NB therapy.

Actin-Membrane Release Initiates Cell Protrusions

Despite the well-established role of actin polymerization as a driving mechanism for cell protrusion, upregulated actin polymerization alone does not initiate protrusions. Using a combination of theoretical modeling and quantitative live-cell imaging experiments, we show that local depletion of actin-membrane links is needed for protrusion initiation. Specifically, we show that the actin-membrane linker ezrin is depleted prior to protrusion onset and that perturbation of ezrin's affinity for actin modulates protrusion frequency and efficiency. We also show how actin-membrane release works in concert with actin polymerization, leading to a comprehensive model for actin-driven shape changes. Actin-membrane release plays a similar role in protrusions driven by intracellular pressure. Thus, our findings suggest that protrusion initiation might be governed by a universal regulatory mechanism, whereas the mechanism of force generation determines the shape and expansion properties of the protrusion.

Podoplanin Gene Disruption in Mice Promotes in vivo Neural Progenitor Cells Proliferation, Selectively Impairs Dentate Gyrus Synaptic Depression and Induces Anxiety-Like Behaviors

Podoplanin (Pdpn), a brain-tumor-related glycoprotein identified in humans and animals, is endogenously expressed in several organs critical for life support such as kidney, lung, heart and brain. In the brain, Pdpn has been identified in proliferative nestin-positive adult neural progenitor cells and in neurons of the neurogenic hippocampal dentate gyrus (DG), a structure associated to anxiety, critical for learning and memory functions and severely damaged in people with Alzheimer's Disease (AD). The in vivo role of Pdpn in adult neurogenesis and anxiety-like behavior remained however unexplored. Using mice with disrupted Pdpn gene as a model organism and applying combined behavioral, molecular biological and electrophysiological assays, we here show that the absence of Pdpn selectively impairs long-term synaptic depression in the neurogenic DG without affecting the CA3-Schaffer's collateral-CA1 synapses. Pdpn deletion also enhanced the proliferative capacity of DG neural progenitor cells and diminished survival of differentiated neuronal cells in vitro. In addition, mice with podoplanin gene disruption showed increased anxiety-like behaviors in experimentally validated behavioral tests as compared to wild type littermate controls. Together, these findings broaden our knowledge on the molecular mechanisms influencing hippocampal synaptic plasticity and neurogenesis in vivo and reveal Pdpn as a novel molecular target for future studies addressing general anxiety disorder and synaptic depression-related memory dysfunctions.

Perspectives for Ezrin and Radixin in Astrocytes: Kinases, Functions and Pathology

Astrocytes are increasingly perceived as active partners in physiological brain function and behaviour. The structural correlations of the glia–synaptic interaction are the peripheral astrocyte processes (PAPs), where ezrin and radixin, the two astrocytic members of the ezrin-radixin-moesin (ERM) family of proteins are preferentially localised. While the molecular mechanisms of ERM (in)activation appear universal, at least in mammalian cells, and have been studied in great detail, the actual ezrin and radixin kinases, phosphatases and binding partners appear cell type specific and may be multiplexed within a cell. In astrocytes, ezrin is involved in process motility, which can be stimulated by the neurotransmitter glutamate, through activation of the glial metabotropic glutamate receptors (mGluRs) 3 or 5. However, it has remained open how this mGluR stimulus is transduced to ezrin activation. Knowing upstream signals of ezrin activation, ezrin kinase(s), and membrane-bound binding partners of ezrin in astrocytes might open new approaches to the glial role in brain function. Ezrin has also been implicated in invasive behaviour of astrocytomas, and glial activation. Here, we review data pertaining to potential molecular interaction partners of ezrin in astrocytes, with a focus on PKC and GRK2, and in gliomas and other diseases, to stimulate further research on their potential roles in glia-synaptic physiology and pathology.

Ezrin Promotes Stem Cell Properties in Pancreatic Ductal Adenocarcinoma

Self-renewal maintains the long-term clonogenic growth that is required for cancer relapse and progression, but the cellular processes regulating this property are not fully understood. In many diseases, self-renewal is enhanced in cancer stem cells (CSC), and in pancreatic ductal adenocarcinoma (PDAC), CSCs are characterized by the surface expression of CD44. In addition to cell adhesion, CD44 impacts cell shape and morphology by modulating the actin cytoskeleton via Ezrin, a member of the Ezrin/Radixin/Moesin (ERM) family of linker proteins. We examined the expression of Ezrin in PDAC cells and found higher levels of both total and activated Ezrin in CSCs compared with bulk tumor cells. We also found that the knockdown of Ezrin in PDAC cells decreased clonogenic growth, self-renewal, cell migration, and CSC frequency in vitro as well as tumor initiation in vivo. These effects were associated with cytoskeletal changes that are similar to those occurring during the differentiation of normal stem cells, and the inhibition of actin remodeling reversed the impact of Ezrin loss. Finally, targeting Ezrin using a small-molecule inhibitor limited the self-renewal of clinically derived low-passage PDAC xenografts. Our findings demonstrate that Ezrin modulates CSCs properties and may represent a novel target for the treatment of PDAC. IMPLICATIONS: Our findings demonstrate that Ezrin modulates CSCs' properties and may represent a novel target for the treatment of PDAC.

Activation of RHO-1 in cholinergic motor neurons competes with dopamine signalling to control locomotion

The small GTPase RhoA plays a crucial role in the regulation of neuronal signalling to generate behaviour. In the developing nervous system RhoA is known to regulate the actin cytoskeleton, however the effectors of RhoA-signalling in adult neurons remain largely unidentified. We have previously shown that activation of the RhoA ortholog (RHO-1) in C. elegans cholinergic motor neurons triggers hyperactivity of these neurons and loopy locomotion with exaggerated body bends. This is achieved in part through increased diacylglycerol (DAG) levels and the recruitment of the synaptic vesicle protein UNC-13 to synaptic release sites, however other pathways remain to be identified. Dopamine, which is negatively regulated by the dopamine re-uptake transporter (DAT), has a central role in modulating locomotion in both humans and C. elegans. In this study we identify a new pathway in which RHO-1 regulates locomotory behaviour by repressing dopamine signalling, via DAT-1, linking these two pathways together. We observed an upregulation of dat-1 expression when RHO-1 is activated and show that loss of DAT-1 inhibits the loopy locomotion phenotype caused by RHO-1 activation. Reducing dopamine signalling in dat-1 mutants through mutations in genes involved in dopamine synthesis or in the dopamine receptor DOP-1 restores the ability of RHO-1 to trigger loopy locomotion in dat-1 mutants. Taken together, we show that negative regulation of dopamine signalling via DAT-1 is necessary for the neuronal RHO-1 pathway to regulate locomotion.

Urokinase-type plasminogen activator (uPA) promotes ezrin-mediated reorganization of the synaptic cytoskeleton in the ischemic brain

Synaptic repair in the ischemic brain is a complex process that requires reorganization of the actin cytoskeleton. Ezrin, radixin, and moesin (ERM) are a group of evolutionarily conserved proteins that link the plasma membrane to the actin cytoskeleton and act as scaffolds for signaling transduction. Urokinase-type plasminogen activator (uPA) is a serine proteinase that upon binding to the urokinase-type plasminogen activator receptor (uPAR) catalyzes the conversion of plasminogen into plasmin on the cell surface and activates intracellular signaling pathways. Early studies indicate that uPA and uPAR expression increase during the recovery phase from an ischemic stroke and that uPA binding to uPAR promotes neurorepair in the ischemic brain. The in vitro and in vivo studies presented here show that either the release of neuronal uPA or treatment with recombinant uPA induces the local synthesis of ezrin in the synapse and the recruitment of β3-integrin to the postsynaptic density (PSD) of cerebral cortical neurons by a plasminogen-independent mechanism. We found that β3-integrin has a double effect on ezrin, inducing its recruitment to the PSD via the intercellular adhesion molecule-5 (ICAM-5) and its subsequent activation by phosphorylation at Thr-567. Finally, our data indicate that by triggering the reorganization of the actin cytoskeleton in the postsynaptic terminal, active ezrin induces the recovery of dendritic spines and synapses that have been damaged by an acute ischemic stroke. In summary, our data show that uPA-uPAR binding promotes synaptic repair in the ischemic brain via ezrin-mediated reorganization of the actin cytoskeleton in the postsynaptic terminal.

CPI-17 drives oncogenic Ras signaling in human melanomas via Ezrin-Radixin-Moesin family proteins

Hyperactive Ras signaling has strong oncogenic effects causing several different forms of cancer. Hyperactivity is frequently induced by mutations within Ras itself, which account for up to 30% of all human cancers. In addition, hyperactive Ras signaling can also be triggered independent of Ras by either mutation or by misexpression of various upstream regulators and immediate downstream effectors. We have previously reported that C-kinase potentiated protein phosphatase-1 inhibitor of 17 kDa (CPI-17) can drive Ras activity and promote tumorigenic transformation by inhibition of the tumor suppressor Merlin. We now describe an additional element of this oncogenic mechanism in the form of the ezrin-radixin-moesin (ERM) protein family, which exhibits opposing roles in Ras activity control. Thus, CPI-17 drives Ras activity and tumorigenesis in a two-fold way; inactivation of the tumor suppressor merlin and activation of the growth promoting ERM family. The in vivo significance of this oncogenic switch is highlighted by demonstrating CPI-17's involvement in human melanoma pathogenesis.

Regulation of RhoA by STAT3 coordinates glial scar formation

The transcription factor STAT3 is known to control glial scar formation, but the underlying mechanism is unknown. Renault-Mihara et al. show that inhibition of the small GTPase RhoA by STAT3 coordinates reactive astrocyte dynamics during glial scar formation.

Understanding how the transcription factor signal transducer and activator of transcription–3 (STAT3) controls glial scar formation may have important clinical implications. We show that astrocytic STAT3 is associated with greater amounts of secreted MMP2, a crucial protease in scar formation. Moreover, we report that STAT3 inhibits the small GTPase RhoA and thereby controls actomyosin tonus, adhesion turnover, and migration of reactive astrocytes, as well as corralling of leukocytes in vitro. The inhibition of RhoA by STAT3 involves ezrin, the phosphorylation of which is reduced in STAT3-CKO astrocytes. Reduction of phosphatase and tensin homologue (PTEN) levels in STAT3-CKO rescues reactive astrocytes dynamics in vitro. By specific targeting of lesion-proximal, reactive astrocytes in Nestin-Cre mice, we show that reduction of PTEN rescues glial scar formation in Nestin-Stat3^+/− mice. These findings reveal novel intracellular signaling mechanisms underlying the contribution of reactive astrocyte dynamics to glial scar formation.

Depletion of the Fragile X Mental Retardation Protein in Embryonic Stem Cells Alters the Kinetics of Neurogenesis

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and a leading cause of autism. FXS is due to the silencing of the Fragile X Mental Retardation Protein (FMRP), an RNA binding protein mainly involved in translational control, dendritic spine morphology and synaptic plasticity. Despite extensive studies, there is currently no cure for FXS. With the purpose to decipher the initial molecular events leading to this pathology, we developed a stem-cell-based disease model by knocking-down the expression of Fmr1 in mouse embryonic stem cells (ESCs). Repressing FMRP in ESCs increased the expression of amyloid precursor protein (APP) and Ascl1. When inducing neuronal differentiation, βIII-tubulin, p27^kip1 , NeuN, and NeuroD1 were upregulated, leading to an accelerated neuronal differentiation that was partially compensated at later stages. Interestingly, we observed that neurogenesis is also accelerated in the embryonic brain of Fmr1-knockout mice, indicating that our cellular model recapitulates the molecular alterations present in vivo. Importantly, we rescued the main phenotype of the Fmr1 knockdown cell line, not only by reintroducing FMRP but also by pharmacologically targeting APP processing, showing the role of this protein in the pathophysiology of FXS during the earliest steps of neurogenesis. Our work allows to define an early therapeutic window but also to identify more effective molecules for treating this disorder. Stem Cells 2017;35:374-385.

Ginsenoside Rg1 Protects against Oxidative Stress-induced Neuronal Apoptosis through Myosin IIA-actin Related Cytoskeletal Reorganization

Oxidative stress-induced cytoskeletal dysfunction of neurons has been implicated as a crucial cause of cell apoptosis or death in the central nervous system (CNS) diseases, such as neurodegenerative and psychiatric diseases. The application of neuroprotectants rescuing the neurons from cytoskeletal damage and apoptosis can be a potential treatment for these CNS diseases. Ginsenoside Rg1 (Rg1), one of the major active components of ginseng, has been reported possessing notable neuroprotective activities. However, there is rare report about its effect on cytoskeleton and its undergoing mechanism. The current study is to reveal the regulatory effects of Rg1 on cytoskeletal and morphological lesion in oxidative stress-induced neuronal apoptosis. The results demonstrated that pre-treatment with Rg1 (0.1-10 μM) attenuated hydrogen peroxide (H₂O₂)-induced neuronal apoptosis and oxidative stress through reducing the intracellular reactive oxygen species (ROS) production and methane dicarboxylic aldehyde (MDA) level. The Rg1 treatment also abolished H₂O₂-induced morphological changes, including cell rounding, membrane blebbing, neurite retraction and nuclei condensation, which were generated by myosin IIA-actin interaction. These effects were mediated via the down-regulation of caspase-3, ROCK1 (Rho-associated kinase1) activation and myosin light chain (MLC, Ser-19) phosphorylation. Furthermore, inhibiting myosin II activity with blebbistatin partly blocked the neuroprotective effects of Rg1. The computer-aided homology modelling revealed that Rg1 preferentially positioned in the actin binding cleft of myosin IIA and might block the binding of myosin IIA to actin filaments. Accordingly, the neuroprotective mechanism of Rg1 is related to the activity that inhibits myosin IIA-actin interaction and the caspase-3/ROCK1/MLC signaling pathway. These findings put some insights into the unique neuroprotective properties of Rg1 associated with the regulation of myosin IIA-actin cytoskeletal structure under oxidative stress and provide experimental evidence for Rg1 in CNS diseases.

Impact of the Autism-Associated Long Noncoding RNA MSNP1AS on Neuronal Architecture and Gene Expression in Human Neural Progenitor Cells

We previously identified the long noncoding RNA (lncRNA) MSNP1AS (moesin pseudogene 1, antisense) as a functional element revealed by genome wide significant association with autism spectrum disorder (ASD). MSNP1AS expression was increased in the postmortem cerebral cortex of individuals with ASD and particularly in individuals with the ASD-associated genetic markers on chromosome 5p14.1. Here, we mimicked the overexpression of MSNP1AS observed in postmortem ASD cerebral cortex in human neural progenitor cell lines to determine the impact on neurite complexity and gene expression. ReNcell CX and SK-N-SH were transfected with an overexpression vector containing full-length MSNP1AS. Neuronal complexity was determined by the number and length of neuronal processes. Gene expression was determined by strand-specific RNA sequencing. MSNP1AS overexpression decreased neurite number and neurite length in both human neural progenitor cell lines. RNA sequencing revealed changes in gene expression in proteins involved in two biological processes: protein synthesis and chromatin remodeling. These data indicate that overexpression of the ASD-associated lncRNA MSNP1AS alters the number and length of neuronal processes. The mechanisms by which MSNP1AS overexpression impacts neuronal differentiation may involve protein synthesis and chromatin structure. These same biological processes are also implicated by rare mutations associated with ASD, suggesting convergent mechanisms.

Morphological plasticity of astroglia: Understanding synaptic microenvironment

Memory formation in the brain is thought to rely on the remodeling of synaptic connections which eventually results in neural network rewiring. This remodeling is likely to involve ultrathin astroglial protrusions which often occur in the immediate vicinity of excitatory synapses. The phenomenology, cellular mechanisms, and causal relationships of such astroglial restructuring remain, however, poorly understood. This is in large part because monitoring and probing of the underpinning molecular machinery on the scale of nanoscopic astroglial compartments remains a challenge. Here we briefly summarize the current knowledge regarding the cellular organisation of astroglia in the synaptic microenvironment and discuss molecular mechanisms potentially involved in use-dependent astroglial morphogenesis. We also discuss recent observations concerning morphological astroglial plasticity, the respective monitoring methods, and some of the newly emerging techniques that might help with conceptual advances in the area.

Input-specific regulation of hippocampal circuit maturation by non-muscle myosin IIB

Myh9 and Myh10, which encode two major isoforms of non-muscle myosin II expressed in the brain, have emerged as risk factors for developmental brain disorders. Myosin II motors regulate neuronal cytoskeletal dynamics leading to optimization of synaptic plasticity and memory formation. However, the role of these motor complexes in brain development remains poorly understood. Here, we disrupted the in vivo expression of Myh9 and/or Myh10 in developing hippocampal neurons to determine how these motors contribute to circuit maturation in this brain area important for cognition. We found that Myh10 ablation in early postnatal, but not mature, CA1 pyramidal neurons reduced excitatory synaptic function in the Schaffer collateral pathway, whereas more distal inputs to CA1 neurons were relatively unaffected. Myh10 ablation in young neurons also selectively impaired the elongation of oblique dendrites that receive Schaffer collateral inputs, whereas the structure of distal dendrites was normal. We observed normal spine density and spontaneous excitatory currents in these neurons, indicating that Myh10 KO impaired proximal pathway synaptic maturation through disruptions to dendritic development rather than post-synaptic strength or spine morphogenesis. To address possible redundancy and/or compensation by other Myosin II motors expressed in neurons, we performed similar experiments in Myh9 null neurons. In contrast to findings in Myh10 mutants, evoked synaptic function in young Myh9 KO hippocampal neurons was normal. Data obtained from double Myh9/Myh10 KO neurons largely resembled the MyH10 KO synaptic phenotype. These data indicate that Myosin IIB is a key molecular factor that guides input-specific circuit maturation in the developing hippocampus. Non-muscle myosin II is an actin binding protein with three isoforms in the brain (IIA, IIB and IIC) encoded by the myh9, myh10, and myh14 genes in mice, respectively. We have studied the structure and the function of hippocampal CA1 neurons missing NMIIB and/or NMIIA proteins at different times during development. We have discovered that NMIIB is the major isoform regulating Schaffer collateral inputs, and that this regulation is restricted to early postnatal development.

Robust Neuritogenesis-Promoting Activity by Bis(heptyl)-Cognitin Through the Activation of alpha7-Nicotinic Acetylcholine Receptor/ERK Pathway

AIMS

Neurodegenerative disorders are caused by progressive neuronal loss in the brain, and hence, compounds that could promote neuritogenesis may have therapeutic values. In this study, the effects of bis(heptyl)-cognitin (B7C), a multifunctional dimer, on neurite outgrowth were investigated in both PC12 cells and primary cortical neurons.

METHODS

Immunocytochemical staining was used to evaluate the proneuritogenesis effects, and Western blot and short hairpin RNA assays were applied to explore the underlying mechanisms.

RESULTS

B7C (0.1-0.5 μM) induced robust neurite outgrowth in PC12 cells, as evidenced by the neurite-bearing morphology and upregulation of growth-associated protein-43 expression. In addition, B7C markedly promoted neurite outgrowth in primary cortical neurons as shown by the increase in the length of β-III-tubulin-positive neurites. Furthermore, B7C rapidly increased ERK phosphorylation. Specific inhibitors of alpha7-nicotinic acetylcholine receptor (α7-nAChR) and MEK, but not those of p38 or JNK, blocked the neurite outgrowth as well as ERK phosphorylation induced by B7C. Most importantly, genetic depletion of α7-nAChR significantly abolished B7C-induced neurite outgrowth in PC12 cells.

CONCLUSION

B7C promoted neurite outgrowth through the activation of α7-nAChR/ERK pathway, which offers novel insight into the potential application of B7C in the treatment of neurodegenerative disorders.