Collapsin response mediator proteins (CRMPs): involvement in nervous system development and adult neurodegenerative disorders

Inhibition of ERK1/2 or CRMP2 Disrupts Alcohol Memory Reconsolidation and Prevents Relapse in Rats

Relapse to alcohol abuse, often caused by cue-induced alcohol craving, is a major challenge in alcohol addiction treatment. Therefore, disrupting the cue-alcohol memories can suppress relapse. Upon retrieval, memories transiently destabilize before they reconsolidate in a process that requires protein synthesis. Evidence suggests that the mammalian target of rapamycin complex 1 (mTORC1), governing the translation of a subset of dendritic proteins, is crucial for memory reconsolidation. Here, we explored the involvement of two regulatory pathways of mTORC1, phosphoinositide 3-kinase (PI3K)-AKT and extracellular regulated kinase 1/2 (ERK1/2), in the reconsolidation process in a rat (Wistar) model of alcohol self-administration. We found that retrieval of alcohol memories using an odor-taste cue increased ERK1/2 activation in the amygdala, while the PI3K-AKT pathway remained unaffected. Importantly, ERK1/2 inhibition after alcohol memory retrieval impaired alcohol-memory reconsolidation and led to long-lasting relapse suppression. Attenuation of relapse was also induced by post-retrieval administration of lacosamide, an inhibitor of collapsin response mediator protein-2 (CRMP2)-a translational product of mTORC1. Together, our findings indicate the crucial role of ERK1/2 and CRMP2 in the reconsolidation of alcohol memories, with their inhibition as potential treatment targets for relapse prevention.

Mechanism, and treatment of anti-CV2/CRMP5 autoimmune pain

Paraneoplastic neurological syndromes arise from autoimmune reactions against nervous system antigens due to a maladaptive immune response to a peripheral cancer. Patients with small cell lung carcinoma or malignant thymoma can develop an autoimmune response against the CV2/collapsin response mediator protein 5 (CRMP5) antigen. For reasons that are not understood, approximately 80% of patients experience painful neuropathies. Here, we investigated the mechanisms underlying anti-CV2/CRMP5 autoantibodies (CV2/CRMP5-Abs)-related pain. We found that patient-derived CV2/CRMP5-Abs can bind to their target in rodent dorsal root ganglia (DRG) and superficial laminae of the spinal cord. CV2/CRMP5-Abs induced DRG neuron hyperexcitability and mechanical hypersensitivity in rats that were abolished by preventing binding to their cognate autoantigen CRMP5. The effect of CV2/CRMP5-Abs on sensory neuron hyperexcitability and mechanical hypersensitivity observed in patients was recapitulated in rats using genetic immunization providing an approach to rapidly identify possible therapeutic choices for treating autoantibody-induced pain including the repurposing of a monoclonal anti-CD20 antibody that selectively deplete B-lymphocytes. These data reveal a previously unknown neuronal mechanism of neuropathic pain in patients with paraneoplastic neurological syndromes resulting directly from CV2/CRMP5-Abs-induced nociceptor excitability. CV2/CRMP5-Abs directly sensitize pain responses by increasing sensory neuron excitability and strategies aiming at either blocking or reducing CV2/CRMP5-Abs can treat pain as a comorbidity in patients with paraneoplastic neurological syndromes.

Quercetin attenuated ischemic stroke induced neurodegeneration by modulating glutamatergic and synaptic signaling pathways

Ischemic strokes originate whenever the circulation to the brain is interrupted, either temporarily or permanently, resulting in a lack of oxygen and other nutrients. This deprivation primarily impacts the cerebral cortex and striatum, resulting in neurodegeneration. Several experimental stroke models have demonstrated that the potent antioxidant quercetin offers protection against stroke-related damage. Multiple pathways have been associated with quercetin's ability to safeguard the brain from ischemic injury. This study examines whether the administration of quercetin alters glutamate NMDA and GluR1 receptor signaling in the cortex and striatum 72 h after transient middle cerebral artery occlusion. The administration of 10 mg/kg of quercetin shielded cortical and striatal neurons from cell death induced by ischemia in adult SD rats. Quercetin reversed the ischemia-induced reduction of NR2a/PSD95, consequently promoting the pro-survival AKT pathway and reducing CRMP2 phosphorylation. Additionally, quercetin decreased the levels of reactive oxygen species and inflammatory pathways while increasing the expression of the postsynaptic protein PSD95. Our results suggest that quercetin may be a promising neuroprotective drug for ischemic stroke therapy as it recovers neuronal damage via multiple pathways.

Nicotine Exposure in a Phencyclidine-Induced Mice Model of Schizophrenia: Sex-Selective Medial Prefrontal Cortex Protein Markers of the Combined Insults in Adolescent Mice

Tobacco misuse as a comorbidity of schizophrenia is frequently established during adolescence. However, comorbidity markers are still missing. Here, the method of label-free proteomics was used to identify deregulated proteins in the medial prefrontal cortex (prelimbic and infralimbic) of male and female mice modelled to schizophrenia with a history of nicotine exposure during adolescence. Phencyclidine (PCP), used to model schizophrenia (SCHZ), was combined with an established model of nicotine minipump infusions (NIC). The combined insults led to worse outcomes than each insult separately when considering the absolute number of deregulated proteins and that of exclusively deregulated ones. Partially shared Reactome pathways between sexes and between PCP, NIC and PCPNIC groups indicate functional overlaps. Distinctively, proteins differentially expressed exclusively in PCPNIC mice reveal unique effects associated with the comorbidity model. Interactome maps of these proteins identified sex-selective subnetworks, within which some proteins stood out: for females, peptidyl-prolyl cis-trans isomerase (Fkbp1a) and heat shock 70 kDa protein 1B (Hspa1b), both components of the oxidative stress subnetwork, and gamma-enolase (Eno2), a component of the energy metabolism subnetwork; and for males, amphiphysin (Amph), a component of the synaptic transmission subnetwork. These are proposed to be further investigated and validated as markers of the combined insult during adolescence.

Collapsin response mediator protein 5-associated optic neuropathy: clinical characteristics, radiologic clues, and outcomes

Objective

Collapsin response mediator protein 5-associated optic neuropathy (CRMP5-ON) is a rare entity of autoimmune optic neuropathy. This study aimed to review the neuro-ophthalmic findings and outcomes in a series of patients with CRMP5-ON to further characterize its clinical phenotype, radiologic clues, and outcomes.

Methods

This was a retrospective case series and a single-center medical chart review of all patients with CRPM5-seropositive ON at the Department of Neurology, Beijing Tongren Hospital, from December 1, 2020, to March 31, 2023. The main outcome measures were neuro-ophthalmic manifestations, radiologic characteristics, and clinical outcomes of CRMP5-ON; coexisting neural autoantibody, paraneoplastic associations, and the impact of immunosuppressant therapy.

Results

Five patients were identified. Four (80%) were female, and the average age at onset was 59.4 years (range 53-69 years), with an average follow-up of 15.3 months (range 1.4-28.7 months). The average best-corrected visual acuity (BCVA) at nadir was 20/120 (range 20/20 to count fingers). Seven of ten affected eyes (70%) showed diffuse defects of the central field. Painless bilateral involvement and optic disk edema occurred in 100% of patients, combined with vitritis, uveitis, or retinitis in four (80%). Four patients (80%) had MRI abnormalities along the optic nerve (one patient with optic nerve enhancement and three patients had optic nerve sheath enhancement or peribulbar fat enhancement). Three patients (60%) had optic neuropathy with other neurologic symptoms. Four patients (80%) had confirmed cancer (two were small-cell lung carcinoma, one was papillary thyroid carcinoma and another was thymoma and invasive pulmonary adenocarcinoma). All cancers were identified after the presentation of the optic neuropathy. The intervention included IVIG, IVMP, surgery and chemotherapy. The average BCVA at the last follow-up was 20/50 (range 20/20 to count fingers). Three patients had surgery during the initial hospitalization, and were stable during the follow-up. Among two patients who received IVMP, both had improvement after treatment, although one patient had worsening non-ocular neurologic symptoms during the steroid taper.

Conclusion

CRMP5-ON presented with optic disc edema, often bilateral involved and combined with vitreitis, retinitis, or uveitis. CRMP5-ON can present with MRI optic nerve or perineural optic nerve enhancement, especially in the optic nerve sheath. CRMP5-ON is closely related to paraneoplastic neurologic syndrome. Cancer screening and intervention are crucial to prognosis.

CRMP2 Participates in Regulating Mitochondrial Morphology and Motility in Alzheimer's Disease

Mitochondrial bioenergetics and dynamics (alterations in morphology and motility of mitochondria) play critical roles in neuronal reactions to varying energy requirements in health and disease. In Alzheimer's disease (AD), mitochondria undergo excessive fission and become less motile. The mechanisms leading to these alterations are not completely clear. Here, we show that collapsin response mediator protein 2 (CRMP2) is hyperphosphorylated in AD and that is accompanied by a decreased interaction of CRMP2 with Drp1, Miro 2, and Mitofusin 2, which are proteins involved in regulating mitochondrial morphology and motility. CRMP2 was hyperphosphorylated in postmortem brain tissues of AD patients, in brain lysates, and in cultured cortical neurons from the double transgenic APP/PS1 mice, an AD mouse model. CRMP2 hyperphosphorylation and dissociation from its binding partners correlated with increased Drp1 recruitment to mitochondria, augmented mitochondrial fragmentation, and reduced mitochondrial motility. (S)-lacosamide ((S)-LCM), a small molecule that binds to CRMP2, decreased its phosphorylation at Ser 522 and Thr 509/514, and restored CRMP2's interaction with Miro 2, Drp1, and Mitofusin 2. This was paralleled by decreased Drp1 recruitment to mitochondria, diminished mitochondrial fragmentation, and improved motility of the organelles. Additionally, (S)-LCM-protected cultured cortical AD neurons from cell death. Thus, our data suggest that CRMP2, in a phosphorylation-dependent manner, participates in the regulation of mitochondrial morphology and motility, and modulates neuronal survival in AD.

Elevated Hippocampal CRMP5 Mediates Chronic Stress-Induced Cognitive Deficits by Disrupting Synaptic Plasticity, Hindering AMPAR Trafficking, and Triggering Cytokine Release

Chronic stress is a critical risk factor for developing depression, which can impair cognitive function. However, the underlying mechanisms involved in chronic stress-induced cognitive deficits remain unclear. Emerging evidence suggests that collapsin response mediator proteins (CRMPs) are implicated in the pathogenesis of psychiatric-related disorders. Thus, the study aims to examine whether CRMPs modulate chronic stress-induced cognitive impairment. We used the chronic unpredictable stress (CUS) paradigm to mimic stressful life situations in C57BL/6 mice. In this study, we found that CUS-treated mice exhibited cognitive decline and increased hippocampal CRMP2 and CRMP5 expression. In contrast to CRMP2, CRMP5 levels strongly correlated with the severity of cognitive impairment. Decreasing hippocampal CRMP5 levels through shRNA injection rescued CUS-induced cognitive impairment, whereas increasing CRMP5 levels in control mice exacerbated memory decline after subthreshold stress treatment. Mechanistically, hippocampal CRMP5 suppression by regulating glucocorticoid receptor phosphorylation alleviates chronic stress-induced synaptic atrophy, disruption of AMPA receptor trafficking, and cytokine storms. Our findings show that hippocampal CRMP5 accumulation through GR activation disrupts synaptic plasticity, impedes AMPAR trafficking, and triggers cytokine release, thus playing a critical role in chronic stress-induced cognitive deficits.

Contribution of the dihydropyrimidinase-like proteins family in synaptic physiology and in neurodevelopmental disorders

The dihydropyrimidinase-like (DPYSL) proteins, also designated as the collapsin response mediators (CRMP) proteins, constitute a family of five cytosolic phosphoproteins abundantly expressed in the developing nervous system but down-regulated in the adult mouse brain. The DPYSL proteins were initially identified as effectors of semaphorin 3A (Sema3A) signaling and consequently involved in regulation of growth cone collapse in young developing neurons. To date, it has been established that DPYSL proteins mediate signals for numerous intracellular/extracellular pathways and play major roles in variety of cellular process including cell migration, neurite extension, axonal guidance, dendritic spine development and synaptic plasticity through their phosphorylation status. The roles of DPYSL proteins at early stages of brain development have been described in the past years, particularly for DPYSL2 and DPYSL5 proteins. The recent characterization of pathogenic genetic variants in DPYSL2 and in DPYSL5 human genes associated with intellectual disability and brain malformations, such as agenesis of the corpus callosum and cerebellar dysplasia, highlighted the pivotal role of these actors in the fundamental processes of brain formation and organization. In this review, we sought to establish a detailed update on the knowledge regarding the functions of DPYSL genes and proteins in brain and to highlight their involvement in synaptic processing in later stages of neurodevelopment, as well as their particular contribution in human neurodevelopmental disorders (NDDs), such as autism spectrum disorders (ASD) and intellectual disability (ID).

Proteomic characterization of spontaneously regrowing spinal cord following injury in the teleost fish Apteronotus leptorhynchus, a regeneration-competent vertebrate

In adult mammals, spontaneous repair after spinal cord injury (SCI) is severely limited. By contrast, teleost fish successfully regenerate injured axons and produce new neurons from adult neural stem cells after SCI. The molecular mechanisms underlying this high regenerative capacity are largely unknown. The present study addresses this gap by examining the temporal dynamics of proteome changes in response to SCI in the brown ghost knifefish (Apteronotus leptorhynchus). Two-dimensional difference gel electrophoresis (2D DIGE) was combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and tandem mass spectrometry (MS/MS) to collect data during early (1 day), mid (10 days), and late (30 days) phases of regeneration following caudal amputation SCI. Forty-two unique proteins with significant differences in abundance between injured and intact control samples were identified. Correlation analysis uncovered six clusters of spots with similar expression patterns over time and strong conditional dependences, typically within functional families or between isoforms. Significantly regulated proteins were associated with axon development and regeneration; proliferation and morphogenesis; neuronal differentiation and re-establishment of neural connections; promotion of neuroprotection, redox homeostasis, and membrane repair; and metabolism or energy supply. Notably, at all three time points examined, significant regulation of proteins involved in inflammatory responses was absent.

Phosphorylated CRMP1, axon guidance protein, is a component of spheroids and is involved in axonal pathology in amyotrophic lateral sclerosis

In amyotrophic lateral sclerosis (ALS), neurodegeneration is characterized by distal axonopathy that begins at the distal axons, including the neuromuscular junctions, and progresses proximally in a “dying back” manner prior to the degeneration of cell bodies. However, the molecular mechanism for distal axonopathy in ALS has not been fully addressed. Semaphorin 3A (Sema3A), a repulsive axon guidance molecule that phosphorylates collapsin response mediator proteins (CRMPs), is known to be highly expressed in Schwann cells near distal axons in a mouse model of ALS. To clarify the involvement of Sema3A–CRMP signaling in the axonal pathogenesis of ALS, we investigated the expression of phosphorylated CRMP1 (pCRMP1) in the spinal cords of 35 patients with sporadic ALS and seven disease controls. In ALS patients, we found that pCRMP1 accumulated in the proximal axons and co-localized with phosphorylated neurofilaments (pNFs), which are a major protein constituent of spheroids. Interestingly, the pCRMP1:pNF ratio of the fluorescence signal in spheroid immunostaining was inversely correlated with disease duration in 18 evaluable ALS patients, indicating that the accumulation of pCRMP1 may precede that of pNFs in spheroids or promote ALS progression. In addition, overexpression of a phospho-mimicking CRMP1 mutant inhibited axonal outgrowth in Neuro2A cells. Taken together, these results indicate that pCRMP1 may be involved in the pathogenesis of axonopathy in ALS, leading to spheroid formation through the proximal progression of axonopathy.

Diagnosis and classification of optic neuritis

There is no consensus regarding the classification of optic neuritis, and precise diagnostic criteria are not available. This reality means that the diagnosis of disorders that have optic neuritis as the first manifestation can be challenging. Accurate diagnosis of optic neuritis at presentation can facilitate the timely treatment of individuals with multiple sclerosis, neuromyelitis optica spectrum disorder, or myelin oligodendrocyte glycoprotein antibody-associated disease. Epidemiological data show that, cumulatively, optic neuritis is most frequently caused by many conditions other than multiple sclerosis. Worldwide, the cause and management of optic neuritis varies with geographical location, treatment availability, and ethnic background. We have developed diagnostic criteria for optic neuritis and a classification of optic neuritis subgroups. Our diagnostic criteria are based on clinical features that permit a diagnosis of possible optic neuritis; further paraclinical tests, utilising brain, orbital, and retinal imaging, together with antibody and other protein biomarker data, can lead to a diagnosis of definite optic neuritis. Paraclinical tests can also be applied retrospectively on stored samples and historical brain or retinal scans, which will be useful for future validation studies. Our criteria have the potential to reduce the risk of misdiagnosis, provide information on optic neuritis disease course that can guide future treatment trial design, and enable physicians to judge the likelihood of a need for long-term pharmacological management, which might differ according to optic neuritis subgroups.

CRMP2 and CRMP4 are required for the formation of commissural tracts in the developing zebrafish forebrain

Axonal connections between the two sides of the brain are essential for processing sensorimotor functions, especially in animals with bilateral symmetry. The anterior commissure and post-optic commissure are two crucial axonal projections that develop early in the zebrafish central nervous system. In this study, we characterized the function of collapsin response mediator protein 2 (CRMP2) and CRMP4 in patterning the development of the anterior and post-optic commissures by analyzing morpholino-knockdown zebrafish morphants and CRISPR/Cas9-edited gene-knockout mutants. We observed a loss of commissural structures or a significant reduction in axon bundles connecting the two hemispheres, but the defects could be largely recovered by co-injecting CRMP2 or CRMP4 mRNA. Loss of both CRMP2 and CRMP4 function resulted in a synergistic increase in the number of commissural defects. To elucidate the mechanism by which CRMP2 and CRMP4 provide guidance cues for the development of the anterior and post-optic commissures, we included neuropilin 1a (Nrp1a) morphants and double morphants (CRMP2/Nrp1a and CRMP4/Nrp1a) for analysis. Our experimental results indicated that CRMP2 and CRMP4 might mediate their activities through the common semaphorin 3/Nrp1a signaling pathway. This article is protected by copyright. All rights reserved.

Genetic inhibition of collapsin response mediator protein-2 phosphorylation ameliorates retinal ganglion cell death in normal-tension glaucoma models

Glaucoma is a neurodegenerative disorder caused by the death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is a cause of glaucoma. However, glaucoma often develops with normal IOP and is known as normal-tension glaucoma (NTG). Glutamate neurotoxicity is considered as one of the significant causes of NTG, resulting in excessive stimulation of retinal neurons via the N-methyl-D-aspartate (NMDA) receptors. The present study examined the phosphorylation of collapsin response mediator protein-2 (CRMP2), a protein that is abundantly expressed in neurons and involved in their development. In two mouse models, NMDA-injection and glutamate/aspartate transporter (GLAST) mutant, CRMP2 phosphorylation at the cyclin-dependent kinase-5 (Cdk5) site was elevated in RGCs. We confirmed that the decrease in the number of RGCs and thickness of the inner retinal layer (IRL) could be suppressed after NMDA administration in CRMP2KI/KI mice with genetically inhibited CRMP2 phosphorylation. Next, we investigated GLAST heterozygotes (GLAST+/-) with CRMP2KI/KI (GLAST+/-;CRMP2KI/KI) and GLAST knockout (GLAST-/-) mice with CRMP2KI/KI (GLAST-/-;CRMP2KI/KI) mice and compared them with GLAST+/- and GLAST-/- mice. pCRMP2 (S522) inhibition significantly reduced RGC loss and IRL thinning. These results suggest that the inhibition of CRMP2 phosphorylation could be a novel strategy for treating NTG.

Proteomic Analysis of Retinal Conditioned Medium: The Effect on Early Differentiation of Embyonic Stem Cells into Retina

Stem cell replacement therapy has emerged as one of the most promising treatment options for retinal degenerative diseases, which are the main causes of irreversible vision loss. Three-dimensional (3D) retinal organoid culture is a cutting-edge technology for differentiating embryonic stem cells into retinal cells by forming a laminated retinal structure. However, 3D culture systems have strict requirements with respect to the experimental environment and culture technologies. Our study aimed to investigate the effect of retinal conditioned medium (RCM) at different developmental stages on the early differentiation of embryonic stem cells into retina in a 3D culture system. Here, we added RCM to the 3D culture system and found it could promote the differentiation of mouse embryonic stem cells (mESCs) into neuroretina. We further explored the possible mechanisms of RCM that regulate differentiation through proteomic analysis. RCM at different time points disclosed different protein profiles. Proteins which improved energy metabolism of mESCs might help improve the viability of embryonic bodies (EBs). We then screened out Snap25, Cntn1, Negr1, Dpysl2, Dpysl3, and Crmp1 as candidate proteins that might play roles in the differentiation and neurogenesis processes of mESCs, hoping to provide a basis for optimizing a retinal differentiation protocol from embryonic stem cells.

CV2/CRMP5-antibody-related Paraneoplastic Neurologic Syndrome Associated with Gastrointestinal Stromal Tumor

Paraneoplastic neurological syndrome (PNS) is a heterogeneous group of neurological disorders caused by immune-mediated inflammatory mechanisms. We herein report a 77-year-old man with CV2/CRMP5-antibody-related PNS associated with a gastrointestinal stromal tumor (GIST). He was admitted for forgetfulness and delusional behavior. His neurological symptoms were subacute, and a whole-body examination revealed a gastric GIST. Serology showed CV2/collapsin response mediator protein (CRMP)-5 antibodies. Partial gastrectomy was performed for the GIST, and the neurological symptoms and serum CV2/CRMP5 antibodies disappeared. No relapse has occurred since the surgery. PNS should be considered in patients with subacute neurological disorders.

The GADD45G/p38 MAPK/CDC25B signaling pathway enhances neurite outgrowth by promoting microtubule polymerization

GADD45G, one of the genes containing the human-specific conserved deletion enhancer-sequence (hCONDEL), has contributed to the evolution of the human cerebrum, but its function in human neurons has not been established. Here, we show that the GADD45G/p38 MAPK/CDC25B signaling pathway promotes neurite outgrowth in human neurons by facilitating microtubule polymerization. This pathway ultimately promotes dephosphorylation of phosphorylated CRMP2 which in turn promotes microtubule assembly. We also found that GADD45G was highly expressed in developing human cerebral specimens. In addition, RK-682, which is the inhibitor of a phosphatase of p38 MAPK and was found in Streptomyces sp., was shown to promote microtubule polymerization and neurite outgrowth by enhancing p38 MAPK/CDC25B signaling. These in vitro and in vivo results indicate that GADD45G/p38 MAPK/CDC25B enhances neurite outgrowth in human neurons.

Research Progress of Collapse Response Mediator Proteins in Neurodegenerative Diseases

Collapse response mediator proteins (CRMPs) are a family of cytoplasmic phosphorylated proteins, and the mechanism of action has always been the research focus of neurological diseases. Previous studies on the CRMPs family have revealed that CRMPs mediate the growth and development of neuronal cytoskeleton through different signaling pathways in the body. It plays an important role in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and spinocerebellar ataxia, which has attracted the attention of researchers. This article reviews the recent literature on the biological characteristics and mechanisms of CRMPs in different neurodegenerative diseases.

CRMP4-mediated fornix development involves Semaphorin-3E signaling pathway

Neurodevelopmental axonal pathfinding plays a central role in correct brain wiring and subsequent cognitive abilities. Within the growth cone, various intracellular effectors transduce axonal guidance signals by remodeling the cytoskeleton. Semaphorin-3E (Sema3E) is a guidance cue implicated in development of the fornix, a neuronal tract connecting the hippocampus to the hypothalamus. Microtubule-associated protein 6 (MAP6) has been shown to be involved in the Sema3E growth-promoting signaling pathway. In this study, we identified the collapsin response mediator protein 4 (CRMP4) as a MAP6 partner and a crucial effector in Sema3E growth-promoting activity. CRMP4-KO mice displayed abnormal fornix development reminiscent of that observed in Sema3E-KO mice. CRMP4 was shown to interact with the Sema3E tripartite receptor complex within detergent-resistant membrane (DRM) domains, and DRM domain integrity was required to transduce Sema3E signaling through the Akt/GSK3 pathway. Finally, we showed that the cytoskeleton-binding domain of CRMP4 is required for Sema3E's growth-promoting activity, suggesting that CRMP4 plays a role at the interface between Sema3E receptors, located in DRM domains, and the cytoskeleton network. As the fornix is affected in many psychiatric diseases, such as schizophrenia, our results provide new insights to better understand the neurodevelopmental components of these diseases.

Involvement of CRMP2 in Regulation of Mitochondrial Morphology and Motility in Huntington's Disease

Mitochondrial morphology and motility (mitochondrial dynamics) play a major role in the proper functioning of distant synapses. In Huntington’s disease (HD), mitochondria become fragmented and less motile, but the mechanisms leading to these changes are not clear. Here, we found that collapsin response mediator protein 2 (CRMP2) interacted with Drp1 and Miro 2, proteins involved in regulating mitochondrial dynamics. CRMP2 interaction with these proteins inversely correlated with CRMP2 phosphorylation. CRMP2 was hyperphosphorylated in postmortem brain tissues of HD patients, in human neurons derived from induced pluripotent stem cells from HD patients, and in cultured striatal neurons from HD mouse model YAC128. At the same time, CRMP2 interaction with Drp1 and Miro 2 was diminished in HD neurons. The CRMP2 hyperphosphorylation and dissociation from Drp1 and Miro 2 correlated with increased fission and suppressed motility. (S)-lacosamide ((S)-LCM), a small molecule that binds to CRMP2, decreased its phosphorylation at Thr 509/514 and Ser 522 and rescued CRMP2’s interaction with Drp1 and Miro 2. This was accompanied by reduced mitochondrial fission and enhanced mitochondrial motility. Additionally, (S)-LCM exerted a neuroprotective effect in YAC128 cultured neurons. Thus, our data suggest that CRMP2 may regulate mitochondrial dynamics in a phosphorylation-dependent manner and modulate neuronal survival in HD.

Phosphorylation of CRMP2 by Cdk5 Negatively Regulates the Surface Delivery and Synaptic Function of AMPA Receptors

AMPA receptor mediate most fast excitatory synaptic transmission and play a key role in synaptic plasticity in the central nervous system (CNS) by trafficking and targeting of its subunits to individual postsynaptic membrane. Collapsing response mediator protein 2 (CRMP2), an intracellular phospho-protein, has been reported to promote the maturation of the dendritic spine and transfer AMPA receptors to the membrane. However, our knowledge about the molecular mechanisms of CRMP2 regulating AMPA receptors trafficking is limited. Here, we reported that CRMP2 promoted the surface expression of AMPA receptor GluA1 subunit in cultured hippocampal neurons and in HEK293T cells expressing GluA1 subunits. Furthermore, we found that CRMP2 interacted with GluA1, and their interaction was inhibited by CRMP2 phosphorylation at ser522. Moreover, our results showed that phosphorylation of CRMP2 at ser522 by cyclin-dependent kinase 5 (Cdk5) decreased the fluorescence intensity of surface GluA1 and the amplitude and frequency of miniature excitatory synaptic currents (mEPSCs) in cultured hippocampal neurons, indicating a reduction levels and synaptic function of AMPA receptors. Taken together, our data demonstrated that phosphorylation of CRMP2 by Cdk5 is important for AMPA receptor surface delivery in hippocampal neurons.

CRMP2 Is Involved in Regulation of Mitochondrial Morphology and Motility in Neurons

Regulation of mitochondrial morphology and motility is critical for neurons, but the exact mechanisms are unclear. Here, we demonstrate that these mechanisms may involve collapsin response mediator protein 2 (CRMP2). CRMP2 is attached to neuronal mitochondria and binds to dynamin-related protein 1 (Drp1), Miro 2, and Kinesin 1 light chain (KLC1). Treating neurons with okadaic acid (OA), an inhibitor of phosphatases PP1 and PP2A, resulted in increased CRMP2 phosphorylation at Thr509/514, Ser522, and Thr555, and augmented Drp1 phosphorylation at Ser616. The CRMP2-binding small molecule (S)-lacosamide ((S)-LCM) prevented an OA-induced increase in CRMP2 phosphorylation at Thr509/514 and Ser522 but not at Thr555, and also failed to alleviate Drp1 phosphorylation. The increased CRMP2 phosphorylation correlated with decreased CRMP2 binding to Drp1, Miro 2, and KLC1. (S)-LCM rescued CRMP2 binding to Drp1 and Miro 2 but not to KLC1. In parallel with CRMP2 hyperphosphorylation, OA increased mitochondrial fission and suppressed mitochondrial traffic. (S)-LCM prevented OA-induced alterations in mitochondrial morphology and motility. Deletion of CRMP2 with a small interfering RNA (siRNA) resulted in increased mitochondrial fission and diminished mitochondrial traffic. Overall, our data suggest that the CRMP2 expression level and phosphorylation state are involved in regulating mitochondrial morphology and motility in neurons.

CRMP5 regulates cell proliferation and development of colorectal cancer via MAPK-dependent signaling

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Collapsin response mediator protein 5 (CRMP5) belongs to a family of five cytosolic proteins that serve a major role in neural development. CRMP5 has been identified as a biomarker of numerous cancer types, including lung cancer and glioblastoma. However, the role of CRMP5 in CRC remains unclear. In the present study, CRMP5 was characterized as a novel biomarker of poor survival in CRC. CRMP5-overexpression in CRC cells promoted cell proliferation and migration while CPMP5-knockdown decreased cell growth and migration. A novel mechanism was uncovered, by which CRMP5 regulates MAPK signaling to drive CRC cell proliferation and development. Furthermore, CRMP5-overexpression induced chemotherapy resistance and tumor recurrence in CRC. Taken together, these results demonstrated the important role of CRMP5 in the development and proliferation of CRC cells and suggested that CRMP5 may be a novel therapeutic target for CRC.

Inflammation and Mitochondrial Dysfunction in Autism Spectrum Disorder

Autism Spectrum Disorders (ASD) is a severe childhood psychiatric condition with an array of cognitive, language and social impairments that can significantly impact family life. ASD is classically characterized by reduced communication skills and social interactions, with limitations imposed by repetitive patterns of behavior, interests, and activities. The pathophysiology of ASD is thought to arise from complex interactions between environmental and genetic factors within the context of individual development. A growing body of research has raised the possibility of identifying the aetiological causes of the disorder. This review highlights the roles of immune-inflammatory pathways, nitro-oxidative stress and mitochondrial dysfunctions in ASD pathogenesis and symptom severity. The role of NK-cells, T helper, T regulatory and B-cells, coupled with increased inflammatory cytokines, lowered levels of immune-regulatory cytokines, and increased autoantibodies and microglial activation is elucidated. It is proposed that alterations in mitochondrial activity and nitrooxidative stress are intimately associated with activated immune-inflammatory pathways. Future research should determine as to whether the mitochondria, immune-inflammatory activity and nitrooxidative stress changes in ASD affect the development of amygdala-frontal cortex interactions. A number of treatment implications may arise, including prevention-orientated prenatal interventions, treatment of pregnant women with vitamin D, and sodium butyrate. Treatments of ASD children and adults with probiotics, sodium butyrate and butyrate-inducing diets, antipurinergic therapy with suramin, melatonin, oxytocin and taurine are also discussed.

A CRMP4-dependent retrograde axon-to-soma death signal in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal non-cell-autonomous neurodegenerative disease characterized by the loss of motor neurons (MNs). Mutations in CRMP4 are associated with ALS in patients, and elevated levels of CRMP4 are suggested to affect MN health in the SOD1G93A -ALS mouse model. However, the mechanism by which CRMP4 mediates toxicity in ALS MNs is poorly understood. Here, by using tissue from human patients with sporadic ALS, MNs derived from C9orf72-mutant patients, and the SOD1G93A -ALS mouse model, we demonstrate that subcellular changes in CRMP4 levels promote MN loss in ALS. First, we show that while expression of CRMP4 protein is increased in cell bodies of ALS-affected MN, CRMP4 levels are decreased in the distal axons. Cellular mislocalization of CRMP4 is caused by increased interaction with the retrograde motor protein, dynein, which mediates CRMP4 transport from distal axons to the soma and thereby promotes MN loss. Blocking the CRMP4-dynein interaction reduces MN loss in human-derived MNs (C9orf72) and in ALS model mice. Thus, we demonstrate a novel CRMP4-dependent retrograde death signal that underlies MN loss in ALS.

Requirement of CRMP2 Phosphorylation in Neuronal Migration of Developing Mouse Cerebral Cortex and Hippocampus and Redundant Roles of CRMP1 and CRMP4

The mammalian cerebral cortex is characterized by a 6-layer structure, and proper neuronal migration is critical for its formation. Cyclin-dependent kinase 5 (Cdk5) has been shown to be a critical kinase for neuronal migration. Several Cdk5 substrates have been suggested to be involved in ordered neuronal migration. However, in vivo loss-of-function studies on the function of Cdk5 phosphorylation substrates in neuronal migration in the developing cerebral cortex have not been reported. In this study, we demonstrated that Cdk5-mediated phosphorylation of collapsing mediator protein (CRMP) 2 is critical for neuronal migration in the developing cerebral cortex with redundant functions of CRMP1 and CRMP4. The cerebral cortices of triple-mutant CRMP1 knock-out (KO); CRMP2 knock-in (KI)/KI; and CRMP4 KO mice showed disturbed positioning of layers II-V neurons in the cerebral cortex. Further experiments using bromodeoxyuridine birthdate-labeling and in utero electroporation implicated radial migration defects in cortical neurons. Ectopic neurons were detected around the CA1 region and dentate gyrus in CRMP1 KO; CRMP2 KI/KI; and CRMP4 KO mice. These results suggest the importance of CRMP2 phosphorylation by Cdk5 and redundancy of CRMP1 and CRMP4 in proper neuronal migration in the developing cerebral cortex and hippocampus.

One Raft to Guide Them All, and in Axon Regeneration Inhibit Them

Central nervous system damage caused by traumatic injuries, iatrogenicity due to surgical interventions, stroke and neurodegenerative diseases is one of the most prevalent reasons for physical disability worldwide. During development, axons must elongate from the neuronal cell body to contact their precise target cell and establish functional connections. However, the capacity of the adult nervous system to restore its functionality after injury is limited. Given the inefficacy of the nervous system to heal and regenerate after damage, new therapies are under investigation to enhance axonal regeneration. Axon guidance cues and receptors, as well as the molecular machinery activated after nervous system damage, are organized into lipid raft microdomains, a term typically used to describe nanoscale membrane domains enriched in cholesterol and glycosphingolipids that act as signaling platforms for certain transmembrane proteins. Here, we systematically review the most recent findings that link the stability of lipid rafts and their composition with the capacity of axons to regenerate and rebuild functional neural circuits after damage.

Missense variants in DPYSL5 cause a neurodevelopmental disorder with corpus callosum agenesis and cerebellar abnormalities

The collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and βIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and βIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders.

Cytoskeletal proteins as glioblastoma biomarkers and targets for therapy: A systematic review

Glioblastoma, the most common primary brain malignancy, is an exceptionally fatal cancer. Lack of suitable biomarkers and efficient treatment largely contribute to the therapy failure. Cytoskeletal proteins are crucial proteins in glioblastoma pathogenesis and can potentially serve as biomarkers and therapeutic targets. Among them, GFAP, has gained most attention as potential diagnostic biomarker, while vimentin and microtubules are considered as prospective therapeutic targets. Microtubules represent one of the best anti-cancer targets due to their critical role in cell proliferation. Despite testing in clinical trials, the efficiency of taxanes, epothilones, vinca-domain binding drugs, colchicine-domain binding drugs and γ-tubulin binding drugs remains to be confirmed. Moreover, tumor treating field that disrupts microtubules draw attention because of its high efficiency and is called "the fourth cancer treatment modality". Thereby, because of the involvement of cytoskeleton in key physiological and pathological processes, its therapeutic potential in glioblastoma is currently extensively investigated.

Inhibition of RhoA Activity Does Not Rescue Synaptic Development Abnormalities and Long-Term Cognitive Impairment After Sevoflurane Exposure

General anesthetics interfere with dendritic development and synaptogenesis, resulting in cognitive impairment in the developing animals. RhoA signal pathway plays important roles in dendritic development by regulating cytoskeleton protein such as tubulin and actin. However, it's not clear whether RhoA pathway is involved in inhaled general anesthetics sevoflurane-induced synaptic development abnormalities and long-term cognitive dysfunction. Rats at postnatal day 7 (PND7) were injected intraperitoneally with RhoA pathway inhibitor Y27632 or saline 20 min before exposed to 2.8% sevoflurane for 4 h. The apoptosis-related proteins and RhoA/CRMP2 pathway proteins in the hippocampus were measured 6 h after sevoflurane exposure. Cognitive functions were evaluated by the open field test on PND25 rats and contextual fear conditioning test on PND32-33 rats. The dendritic morphology and density of dendritic spines in the pyramidal neurons of hippocampus were determined by Golgi staining and the synaptic plasticity-related proteins were also measured on PND33 rats. Long term potentiation (LTP) from hippocampal slices was recorded on PND34-37 rats. Sevoflurane induced caspase-3 activation, decreased the ratio of Bcl-2/Bax and increased TUNEL-positive neurons in hippocampus of PND7 rats, which were attenuated by inhibition of RhoA. However, sevoflurane had no significant effects on activity of RhoA/CRMP2 pathway. Sevoflurane disturbed dendritic morphogenesis, reduced the number of dendritic spines, decreased proteins expression of PSD-95, drebrin and synaptophysin, inhibited LTP in hippocampal slices and impaired memory ability in the adolescent rats, while inhibition of RhoA activity did not rescue the changes above induced by sevoflurane. RhoA signal pathway did not participate in sevoflurane-induced dendritic and synaptic development abnormalities and cognitive dysfunction in developing rats.

Mechanisms and Therapeutic Implications of GSK-3 in Treating Neurodegeneration

Neurodegenerative disorders are spreading worldwide and are one of the greatest threats to public health. There is currently no adequate therapy for these disorders, and therefore there is an urgent need to accelerate the discovery and development of effective treatments. Although neurodegenerative disorders are broad ranging and highly complex, they may share overlapping mechanisms, and thus potentially manifest common targets for therapeutic interventions. Glycogen synthase kinase-3 (GSK-3) is now acknowledged to be a central player in regulating mood behavior, cognitive functions, and neuron viability. Indeed, many targets controlled by GSK-3 are critically involved in progressing neuron deterioration and disease pathogenesis. In this review, we focus on three pathways that represent prominent mechanisms linking GSK-3 with neurodegenerative disorders: cytoskeleton organization, the mammalian target of rapamycin (mTOR)/autophagy axis, and mitochondria. We also consider the challenges and opportunities in the development of GSK-3 inhibitors for treating neurodegeneration.

An altered secretome is an early marker of the pathogenesis of CLN6 Batten disease

Neuronal ceroid lipofuscinoses (NCLs) are a group of inherited childhood neurodegenerative disorders. In addition to the accumulation of auto-fluorescent storage material in lysosomes, NCLs are largely characterised by region-specific neuroinflammation that can predict neuron loss. These phenotypes suggest alterations in the extracellular environment-making the secretome an area of significant interest. This study investigated the secretome in the CLN6 (ceroid-lipofuscinosis neuronal protein 6) variant of NCL. To investigate the CLN6 secretome, we co-cultured neurons and glia isolated from Cln6^nclf or Cln6^± mice, and utilised mass spectrometry to compare protein constituents of conditioned media. The significant changes noted in cathepsin enzymes, were investigated further via western blotting and enzyme activity assays. Viral-mediated gene therapy was used to try and rescue the wild-type phenotype and restore the secretome-both in vitro in co-cultures and in vivo in mouse plasma. In Cln6^nclf cells, proteomics revealed a marked increase in catabolic and cytoskeletal-associated proteins-revealing new similarities between the pathogenic signatures of NCLs with other neurodegenerative disorders. These changes were, in part, corrected by gene therapy intervention, suggesting these proteins as candidate in vitro biomarkers. Importantly, these in vitro changes show promise for in vivo translation, with Cathepsin L (CTSL) activity reduced in both co-cultures and Cln6^nclf plasma samples post gene-therapy. This work suggests the secretome plays a role in CLN6 pathogenesis and highlights its potential use as an in vitro model. Proteomic changes present a list of candidate biomarkers for monitoring disease and assessing potential therapeutics in future studies.

Loss of Collapsin Response Mediator Protein 4 Attenuates 6-Hydroxydopamine-Induced Impairments in a Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by impaired motor symptoms induced by the degeneration of dopaminergic neurons of the substantia nigra pars compacta (SNc). Many factors are speculated to operate in the mechanism of PD, including oxidative stress, mitochondrial dysfunction, abnormal protein handling, and PD induced apoptosis. Besides, researchers have recently shown that inflammatory secretions may engage neighboring cells such as astrocytes, which then induce autocrine and paracrine responses that amplify the inflammation, leading to neurodegeneration. In the present study, we analyzed the neuroprotective and anti-inflammatory effects of collapsin response mediator protein 4 (CRMP4) deletion in 6-hydroxydopamine (6-OHDA)-injected male mice, as well as its effects on motor impairments. Our findings indicated that the deletion of CRMP4 could maintain the TH-positive fibers in the striatum and the TH-positive cells in SNc, attenuate the inflammatory responses, and improve motor coordination and rotational behavior. Furthermore, based on our findings at the early time points, we hypothesized that primary differences between the Crmp4+/+ and Crmp4-/- mice may occur in microglia instead of neurons. Although further work should be carried out to clarify the specific role of CRMP4 in the pathogenesis of PD, our findings suggest that it could be a possible target for the treatment of PD.

Ultrasound with microbubbles improves memory, ameliorates pathology and modulates hippocampal proteomic changes in a triple transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease manifested by cognitive impairment. As a unique approach to open the blood-brain barrier (BBB) noninvasively and temporarily, a growing number of studies showed that low-intensity focused ultrasound in combination with microbubbles (FUS/MB), in the absence of therapeutic agents, is capable of ameliorating amyloid or tau pathology, concurrent with improving memory deficits of AD animal models. However, the effects of FUS/MB on both the two pathologies simultaneously, as well as the memory behaviors, have not been reported so far.

Methods: In this study, female triple transgenic AD (3×Tg-AD) mice at eight months of age with both amyloid-β (Aβ) deposits and tau phosphorylation were treated by repeated FUS/MB in the unilateral hippocampus twice per week for six weeks. The memory behaviors were investigated by the Y maze, the Morris water maze and the step-down passive avoidance test following repeated FUS/MB treatments. Afterwards, the involvement of Aβ and tau pathology were assessed by immunohistochemical analysis. Neuronal health and phagocytosis of Aβ deposits by microglia in the hippocampus were examined by confocal microscopy. Further, hippocampal proteomic alterations were analyzed by employing two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) combined with mass spectrometry.

Results: The three independent memory tasks were indicative of evident learning and memory impairments in eight-month-old 3×Tg-AD mice, which developed intraneuronal Aβ, extracellular diffuse Aβ deposits and phosphorylated tau in the hippocampus and amygdala. Following repeated FUS/MB treatments, significant improvement in learning and memory ability of the 3×Tg-AD mice was achieved. Amelioration in both Aβ deposits and phosphorylated tau in the sonicated hemisphere was induced in FUS/MB-treated 3×Tg-AD mice. Albeit without increase in neuron density, enhancement in axonal neurofilaments emerged from the FUS/MB treatment. Confocal microscopy revealed activated microglia engulfing Aβ deposits in the FUS/MB-treated hippocampus. Further, proteomic analysis revealed 20 differentially expressed proteins, associated with glycolysis, neuron projection, mitochondrial pathways, metabolic process and ubiquitin binding etc., in the hippocampus between FUS/MB-treated and sham-treated 3×Tg-AD mice.

Conclusions: Our findings reinforce the positive therapeutic effects on AD models with both Aβ and tau pathology induced by FUS/MB-mediated BBB opening, further supporting the potential of this treatment regime for clinical applications.

Druggability of CRMP2 for Neurodegenerative Diseases

Collapsin response mediator proteins (CRMPs) are ubiquitously expressed phosphoproteins that coordinate cytoskeletal formation and regulate cellular division, migration, polarity, and synaptic connection. CRMP2, the most studied of the five family members, is best known for its affinity for tubulin heterodimers and function in regulating the microtubule network. Accumulating evidence has also demonstrated a key role for CRMP2 in trafficking of voltage- and ligand-gated ion channels. These functions are tightly regulated by post-translational modifications including phosphorylation and SUMOylation (addition of a small ubiquitin like modifier). Over the past decade, it has become increasingly clear that dysregulated post-translational modifications of CRMP2 contribute to the pathomechanisms of diverse diseases, including cancer, neurodegenerative diseases, chronic pain, and bipolar disorder. Here, we review the discovery, functions, and current putative preclinical and clinical therapeutics targeting CRMP2. These potential therapeutics include CRMP2-based peptides that inhibit protein-protein interactions and small-molecule compounds. Capitalizing on the availability of structural information, we identify druggable pockets on CRMP2 and predict binding modes for five known CRMP2-targeting compounds, setting the stage for optimization and de novo drug discovery targeting this multifunctional protein.

Collapsin Response Mediator Protein 2 and Endophilin2 Coordinate Regulation of AMPA Receptor GluA1 Subunit Recycling

The dynamic trafficking of AMPA receptors (AMPARs), which enables the endocytosis, recycling, and exocytosis of AMPARs, is crucial for synaptic plasticity. Endophilin2, which directly interacts with the GluA1 subunit of AMPARs, plays an important role in AMPAR endocytosis. Collapsin response mediator protein 2 (CRMP2) promotes the maturation of the dendritic spine and can transfer AMPARs to the membrane. Although the mechanisms of AMPAR endocytosis and exocytosis are well known, the exact molecular mechanisms underlying AMPAR recycling remain unclear. Here, we report a unique interaction between CRMP2 and endophilin2. Our results showed that overexpression of CRMP2 and endophilin2 increased the amplitude and frequency of miniature excitatory synaptic currents (mEPSCs) and modestly enhanced AMPAR levels in hippocampal neurons. Furthermore, the CRMP2 and endophilin2 overexpression phenotype failed to occur when the interaction between these two proteins was inhibited. Further analysis revealed that this interaction was regulated by CRMP2 phosphorylation. The phosphorylation of CRMP2 inhibited its interaction with endophilin2; this was mainly affected by the phosphorylation of Thr514 and Ser518 by glycogen synthase kinase (GSK) 3β. CRMP2 phosphorylation increased degradation and inhibited the surface expression of AMPAR GluA1 subunits in cultured hippocampal neurons. However, the dephosphorylation of CRMP2 inhibited degradation and promoted the surface expression of AMPAR GluA1 subunits in cultured hippocampal neurons. Taken together, our data demonstrated that the interaction between CRMP2 and endophilin2 was conductive to the recycling of AMPA receptor GluA1 subunits in hippocampal neurons.

Dihydropyrimidinase-related protein 5 controls glioblastoma stem cell characteristics as a biomarker of proneural-subtype glioblastoma stem cells

Glioblastoma (GBM) is the most aggressive and malignant brain tumor, resulting in a poor prognosis. The current therapy for GBM consists in concurrent radiation and chemotherapy following removal of the tumor. Although the therapy prolongs patient survival, recurrence often occurs. The major cause of tumor recurrence is thought to be GBM stem cells (GSCs), which aid the development of chemo-radiotherapy resistance, and can self-renew and aberrantly differentiate. Therefore, GSCs should be targeted to eradicate the tumor and prevent recurrence. Transcriptomic analysis has categorized GBM into proneural (PN), mesenchymal and classical subtypes, and the outcome of recurrence and prognosis markedly depends on subtype. To identify specific GSC markers, the present study analyzed public microarray and RNA-seq data and identified dihydropyrimidinase-related protein 5 (DRP5) as a candidate GSC marker. DRP5 is known to mediate semaphorin 3A signaling and is involved in the regulation of neurite outgrowth and axon guidance during neuronal development. In the present study, DRP5 was specifically upregulated in the PN-subtype GSCs and served crucial roles in maintaining GSC properties, including tumor sphere formation, stem cell marker expression and xenograft tumor growth. Furthermore, bioinformatics analysis revealed that DRP5 expression was positively correlated with signatures of stemness, including Notch, Hedgehog and Wnt/β-catenin expression, which are also known to be positively correlated with PN-subtype gene signatures. Conversely, DRP5 expression was negatively correlated with NF-κB and signal transducer and activator of transcription 3 stemness signatures, which are negatively correlated with PN-subtype gene signatures. Taken together, these findings suggested that DRP5 was specifically expressed in PN-subtype GSCs and may be used as a functional marker of PN-subtype GSCs.

The regulatory and enzymatic functions of CRMPs in neuritogenesis, synaptic plasticity, and gene transcription

Collapsin response mediator proteins (CRMPs) are ubiquitously expressed in neurons from worms to humans. A cardinal feature of CRMPs is to mediate growth cone collapse in response to Semaphorin-3A signaling through interactions with cytoskeletal proteins. These are critical regulatory roles that CRMPs play during neuritogenesis and neural network formation. Through post-translational modifications, such as phosphorylation, O-GlcNAcylation, SUMOylation, and proteolytic cleavage, CRMPs participate in synaptic plasticity by modulating NMDA receptors, L- and N-type voltage-gated calcium channels (VGCCs), thus affecting neurotransmitter release. CRMPs also possess histone deacetylase (HDAC) activity, which deacetylates histone H4 during neuronal death. Calcium-dependent proteolytic cleavage of CRMPs results in the truncation of CRMPs, producing a large 54 kD fragment (p54). Translocation of the p54 fragment into the nucleus leads to deacetylation of nuclear histone H4 and de-repression of transcription factor E2F1 expression. Increased expression of E2F1 elevates the expression of genes in cell cycle and death. These new and exciting studies lead to the realization that CRMPs are multifunctional proteins with both regulatory and enzymatic functions. Increasing numbers of studies associate these functions of CRMPs with the development of mental and neurological disorders, such as schizophrenia, Alzheimer's diseases, brain trauma, and stroke. This review focuses on new evidence showing the regulatory and enzymatic functions of CRMPs and highlights recent understandings of CRMPs' roles in neurological diseases.

Lacosamide intake during pregnancy increases the incidence of foetal malformations and symptoms associated with schizophrenia in the offspring of mice

The use of first and second generation antiepileptic drugs during pregnancy doubles the risk of major congenital malformations and other teratogenic defects. Lacosamide (LCM) is a third-generation antiepileptic drug that interacts with collapsing response mediator protein 2, a protein that has been associated with neurodevelopmental diseases like schizophrenia. The aim of this study was to test the potential teratogenic effects of LCM on developing embryos and its effects on behavioural/histological alterations in adult mice. We administered LCM to pregnant mice, assessing its presence, and that of related compounds, in the mothers’ serum and in embryonic tissues using liquid chromatography coupled to quadrupole/time of flight mass spectrometry detection. Embryo morphology was evaluated, and immunohistochemistry was performed on adult offspring. Behavioural studies were carried out during the first two postnatal weeks and on adult mice. We found a high incidence of embryonic lethality and malformations in mice exposed to LCM during embryonic development. Neonatal mice born to dams treated with LCM during gestation displayed clear psychomotor delay and behavioural and morphological alterations in the prefrontal cortex, hippocampus and amygdala that were associated with behaviours associated with schizophrenia spectrum disorders in adulthood. We conclude that LCM and its metabolites may have teratogenic effects on the developing embryos, reflected in embryonic lethality and malformations, as well as behavioural and histological alterations in adult mice that resemble those presented by patients with schizophrenia.

Proteomic analysis involved with synaptic plasticity improvement by GABAA receptor blockade in hippocampus of a mouse model of Alzheimer's disease

GABAergic system plays a part in synaptic plasticity in the hippocampus. We had reported a long-term potentiation (LTP)-like facilitation in vivo, known as synaptic plasticity, through GABA_A receptor blockade by bicuculline and the expression of proteins involved with this synaptic plasticity in mouse hippocampus. In the present study, we aimed to show improvement of impaired synaptic plasticity through GABA_A receptor blockade and to clarify the molecular mechanisms involved with this improvement in the hippocampus of mice overexpressing human amyloid precursor protein with the E693Δ mutation (APP_OSK-Tg) as an Alzheimer's disease model showing impaired synaptic plasticity. Electrophysiological study showed that the LTP-like facilitation expressed with application of bicuculline in vivo was significantly greater than impaired tetanic LTP in APP_OSK-Tg mice, which was improved by bicuculline. Proteomic analysis showed that the expression of 11 proteins in the hippocampus was significantly changed 8 h after bicuculline application to APP_OSK-Tg mice. The identified proteins could be functionally classified as chaperone, cytoskeletal protein, energy metabolism, metabolism, neuronal development, and synaptic component. Additionally, western blotting validated the changes in four proteins. We therefore propose that the improvement of impaired synaptic plasticity through GABA_A receptor blockade could be mediated by the changed expression of these proteins.

miR-214-5p inhibits human prostate cancer proliferation and migration through regulating CRMP5

OBJECTIVES

In men, human prostate cancer (PCa) has become the second most common cancer. miRNAs are short non-coding RNAs that can inhibit target gene mRNAs. Studies have showed that the alternation of miRNAs expression in cancer is relevant to pathogenesis of tumor. In present study, we aimed to investigate functions of miR-214-5p in PCa.

MATERIALS AND METHODS

10 paired human prostate tumor tissues and homologous para-tumor tissues were recruited, and the levels of miR-214-5p and CRMP5 were respectively determined by qRT-PCR assay. Luciferase activity analysis was performed to explore the regulation of CRMP5 mRNA 3'UTR by miR-214-5p. Then, cell experiments, including cell proliferation, apoptosis, cell cycle, migration and colony formation ability, were performed after proper plasmids or RNAs transfection.

RESULTS

In PCa tissues and cell lines, expression of miR-214-5p was decreased compared with para-tumor tissues or normal prostate epithelial cell lines. Luciferase activity assay showed a direct combination of miR-214-5p and CRMP5 mRNA 3'UTR, and indicated that the absence of miR-214-5p in PCa cells may contributes to a high level of CRMP5. Cell experiments showed that miR-214-5p can induce inhibition of tumor cell growth, migration and colony forming efficiency, promotion of apoptosis and G1-phase arrest, on the other hand, co-expression of CRMP5 somewhat counteracted these phenotype induced by miR-214-5p.

CONCLUSION

Taken together, miR-214-5p shows tumor suppression effects in PCa cells. Loss expression of miR-214-5p in PCa increase levels of CRMP5 through regulating CRMP5 3'UTR, which could be a potential therapy target for PCa.

Collapsin Response Mediator Proteins: Novel Targets for Alzheimer's Disease

Numerous experimental and postmortem studies have increasingly reported dystrophic axons and dendrites, and alterations of dendritic spine morphology and density in the hippocampus as prominent changes in the early stages of Alzheimer's disease (AD). Furthermore, these alterations tend to correlate well with the progressive cognitive decline observed in AD. For these reasons, and because these neurite structures have a capacity to re-grow, re-establish lost connections, and are critical for learning and memory, there is compelling evidence to suggest that therapeutic interventions aimed at preventing their degradation or promoting their regrowth may hold tremendous promise in preventing the progression of AD. In this regard, collapsin response mediator proteins (CRMPs), a family of phosphoproteins playing a major role in axon guidance and dendritic growth, are especially interesting. The roles these proteins play in neurons and immune cells are reviewed here.

Differential Regulation of DNA Methylation at the CRMP2 Promoter Region Between the Hippocampus and Prefrontal Cortex in a CUMS Depression Model

Current evidence supports the idea that neural plasticity is a potential cause of depression. Abundant studies indicate that CRMP2 has important roles in neural plasticity. Moreover, CRMP2 may contribute to the etiology of depression. However, the regulatory mechanisms underlying the role of CRMP2 remain unclear. DNA methylation alteration is generally acknowledged to be involved in the development of depression. The aim of this study was to explore the relationship between the expression and DNA methylation of CRMP2 in the hippocampus and prefrontal cortex of a rat depression model. Chronic unpredictable mild stress (CUMS) was used to establish a rat depression model, and body weight and behavioral tests were used to evaluate the effects of stress. Real-time PCR and Western blotting were used to test CRMP2 mRNA and protein expression, respectively, in the hippocampus and prefrontal cortex of rats. DNA methylation levels of the CRMP2 promoter were analyzed by bisulfite sequencing PCR (BSP). CUMS caused depressive-like behavior in rats, as evidenced by: decreased body weight and sucrose preference rate; decreases in the total distance traveled, rearing frequency, velocity, and duration in the center in the open field test (OFT); and prolonged immobility in the forced swimming test (FST). CRMP2 mRNA and protein expression in the hippocampus and prefrontal cortex were significantly decreased in the CUMS group compared with the control group. The levels of CRMP2 promoter DNA methylation in the hippocampus of the CUMS group were significantly higher than those of the control group, while these changes were not observed in the prefrontal cortex of CUMS rats. Our data provide evidence that altered expression of CRMP2 in the hippocampus and prefrontal cortex is associated with the pathogenesis of depression. Moreover, the results also suggest regional differences in the regulation of DNA methylation in the CRMP2 promoter between the hippocampus and prefrontal cortex during the development of depression.

Alcohol drinking exacerbates neural and behavioral pathology in the 3xTg-AD mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that represents the most common cause of dementia in the United States. Although the link between alcohol use and AD has been studied, preclinical research has potential to elucidate neurobiological mechanisms that underlie this interaction. This study was designed to test the hypothesis that nondependent alcohol drinking exacerbates the onset and magnitude of AD-like neural and behavioral pathology. We first evaluated the impact of voluntary 24-h, two-bottle choice home-cage alcohol drinking on the prefrontal cortex and amygdala neuroproteome in C57BL/6J mice and found a striking association between alcohol drinking and AD-like pathology. Bioinformatics identified the AD-associated proteins MAPT (Tau), amyloid beta precursor protein (APP), and presenilin-1 (PSEN-1) as the main modulators of alcohol-sensitive protein networks that included AD-related proteins that regulate energy metabolism (ATP5D, HK1, AK1, PGAM1, CKB), cytoskeletal development (BASP1, CAP1, DPYSL2 [CRMP2], ALDOA, TUBA1A, CFL2, ACTG1), cellular/oxidative stress (HSPA5, HSPA8, ENO1, ENO2), and DNA regulation (PURA, YWHAZ). To address the impact of alcohol drinking on AD, studies were conducted using 3xTg-AD mice that express human MAPT, APP, and PSEN-1 transgenes and develop AD-like brain and behavioral pathology. 3xTg-AD and wild-type mice consumed alcohol or saccharin for 4 months. Behavioral tests were administered during a 1-month alcohol-free period. Alcohol intake induced AD-like behavioral pathologies in 3xTg-AD mice including impaired spatial memory in the Morris Water Maze, diminished sensorimotor gating as measured by prepulse inhibition, and exacerbated conditioned fear. Multiplex immunoassay conducted on brain lysates showed that alcohol drinking upregulated primary markers of AD pathology in 3xTg-AD mice: Aβ 42/40 ratio in the lateral entorhinal and prefrontal cortex and total Tau expression in the lateral entorhinal cortex, medial prefrontal cortex, and amygdala at 1-month post alcohol exposure. Immunocytochemistry showed that alcohol use upregulated expression of pTau (Ser199/Ser202) in the hippocampus, which is consistent with late-stage AD. According to the NIA-AA Research Framework, these results suggest that alcohol use is associated with Alzheimer's pathology. Results also showed that alcohol use was associated with a general reduction in Akt/mTOR signaling via several phosphoproteins (IR, IRS1, IGF1R, PTEN, ERK, mTOR, p70S6K, RPS6) in multiple brain regions including hippocampus and entorhinal cortex. Dysregulation of Akt/mTOR phosphoproteins suggests alcohol may target this pathway in AD progression. These results suggest that nondependent alcohol drinking increases the onset and magnitude of AD-like neural and behavioral pathology in 3xTg-AD mice.

Enhanced carbonyl stress induces irreversible multimerization of CRMP2 in schizophrenia pathogenesis

Enhanced carbonyl stress results in neurodevelopmental deficits by affecting microtubule function through the formation of irreversible dysfunctional multimer of carbonylated CRMP2.

Enhanced carbonyl stress underlies a subset of schizophrenia, but its causal effects remain elusive. Here, we elucidated the molecular mechanism underlying the effects of carbonyl stress in iPS cells in which the gene encoding zinc metalloenzyme glyoxalase I (GLO1), a crucial enzyme for the clearance of carbonyl stress, was disrupted. The iPS cells exhibited significant cellular and developmental deficits, and hyper-carbonylation of collapsing response mediator protein 2 (CRMP2). Structural and biochemical analyses revealed an array of multiple carbonylation sites in the functional motifs of CRMP2, particularly D-hook (for dimerization) and T-site (for tetramerization), which are critical for the activity of the CRMP2 tetramer. Interestingly, carbonylated CRMP2 was stacked in the multimer conformation by irreversible cross-linking, resulting in loss of its unique function to bundle microtubules. Thus, the present study revealed that the enhanced carbonyl stress stemmed from the genetic aberrations results in neurodevelopmental deficits through the formation of irreversible dysfunctional multimer of carbonylated CRMP2.

Dysregulation of CRMP2 Post-Translational Modifications Drive Its Pathological Functions

Collapsin response mediator proteins (CRMPs) are a family of ubiquitously expressed, homologous phosphoproteins best known for coordinating cytoskeletal formation and regulating cellular division, migration, polarity, and synaptic connection. CRMP2, the most studied of the five family members, is best known for its affinity for tubulin heterodimers and function in regulating the microtubule network. These functions are tightly regulated by post-translational modifications including phosphorylation, SUMOylation, oxidation, and O-GlcNAcylation. While CRMP2's physiological functions rely mostly on its non-phosphorylated state, dysregulation of CRMP2 phosphorylation and SUMOylation has been reported to be involved in the pathophysiology of multiple diseases including cancer, chronic pain, spinal cord injury, neurofibromatosis type 1, and others. Here, we provide a consolidated update on what is known about CRMP2 signaling and function, first focusing on axonal growth and neuronal polarity, then illustrating the link between dysregulated CRMP2 post-translational modifications and diseases. We additionally discuss the roles of CRMP2 in non-neuronal cells, both in the CNS and regions of the periphery. Finally, we offer thoughts on the therapeutic implications of modulating CRMP2 function in a variety of diseases.

Role of miRNAs in Alzheimer's Disease and Possible Fields of Application

miRNAs (or microRNAs) are a class of single-stranded RNA molecules, responsible for post-transcriptional gene silencing through binding to the coding region as well as 3' and 5' untranslated region of target genes. About 70% of experimentally detectable miRNAs are expressed in the brain and some studies suggest that miRNAs are intimately involved in synaptic function and in specific signals during memory formation. More and more evidence demonstrates the possible involvement of miRNAs in Alzheimer's disease (AD). AD is the most common form of senile dementia, a disease that affects memory and cognitive functions. It is a neurodegenerative disorder characterized by loss of synapses, extracellular amyloid plaques composed of the amyloid-β peptide (Aβ), and intracellular aggregates of hyperphosphorylated TAU protein. This review aims to provide an overview of the in vivo studies of the last 5 years in the literature describing the role of the different miRNAs involved in AD. miRNAs hold huge potential as diagnostic and prognostic biomarkers and, at the same time, their modulation could be a potential therapeutic strategy against AD.

Antigenic Targets of Patient and Maternal Autoantibodies in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder whose behavioral symptoms become apparent in early childhood. The underlying pathophysiological mechanisms are only partially understood and the clinical manifestations are heterogeneous in nature, which poses a major challenge for diagnosis, prognosis and intervention. In the last years, an important role of a dysregulated immune system in ASD has emerged, but the mechanisms connecting this to a disruption of brain development are still largely unknown. Although ASD is not considered as a typical autoimmune disease, self-reactive antibodies or autoantibodies against a wide variety of targets have been found in a subset of ASD patients. In addition, autoantibodies reactive to fetal brain proteins have also been described in the prenatal stage of neurodevelopment, where they can be transferred from the mother to the fetus by transplacental transport. In this review, we give an extensive overview of the antibodies described in ASD according to their target antigens, their different origins, and timing of exposure during neurodevelopment.