Forebrain commissure formation in zebrafish embryo requires the binding of KLC1 to CRMP2.

Formation of the corpus callosum (CC), anterior commissure (AC), and postoptic commissure (POC), connecting the left and right cerebral hemispheres, is crucial for cerebral functioning. Collapsin response mediator protein 2 (CRMP2) has been suggested to be associated with the mechanisms governing this formation, based on knockout studies in mice and knockdown/knockout studies in zebrafish. Previously, we reported two cases of non-synonymous CRMP2 variants with S14R and R565C substitutions. Among the, the R565C substitution (p.R565C) was caused by the novel CRMP2 mutation c.1693C > T, and the patient presented with intellectual disability accompanied by CC hypoplasia. In this study, we demonstrate that crmp2 mRNA could rescue AC and POC formation in crmp2-knockdown zebrafish, whereas the mRNA with the R566C mutation could not. Zebrafish CRMP2 R566C corresponds to human CRMP2 R565C. Further experiments with transfected cultured cells indicated that CRMP2 with the R566C mutation could not bind to kinesin light chain 1 (KLC1). Knockdown of klc1a in zebrafish resulted in defective AC and POC formation, revealing a genetic interaction with crmp2. These findings suggest that the CRMP2 R566C mutant fails to bind to KLC1, preventing axonal elongation and leading to defective AC and POC formation in zebrafish and CC formation defects in humans. Our study highlights the importance of the interaction between CRMP2 and KLC1 in the formation of the forebrain commissures, revealing a novel mechanism associated with CRMP2 mutations underlying human neurodevelopmental abnormalities.

Zinc Deficiency Decreases Neurite Extension via CRMP2 Signal Pathway.

Previous reports indicated that zinc deficiency could increase the risk of infectious diseases and developmental retardation in children. In experimental study, it has been reported that zinc deficiency during the embryonic period inhibited fetal growth, and disturbed neural differentiation and higher brain function later in adulthood. Although it has been suggested that zinc deficiency during development can have significant effects on neuronal differentiation and maturation, the molecular mechanisms of the effects of low zinc on neuronal differentiation during development have not been elucidated in detail. This study was performed to determine the effects of low zinc status on neurite outgrowth and collapsin response mediator protein 2 (CRMP2) signal pathway. Low zinc suppressed neurite outgrowth, and caused increase levels of phosphorylated CRMP2 (pCRMP2) relative to CRMP2, and decrease levels of phosphorylated glycogen synthase kinase 3ß (pGSK3ß) relative to GSK3ß in human neuroblastoma cell line (SH-SY5Y) cells on days 1, 2, and 3 of neuronal differentiation induction. Neurite outgrowth inhibited by low zinc was restored by treatment with the GSK3ß inhibitor CHIR99021. These results suggested that low zinc causes neurite outgrowth inhibition via phosphorylation of CRMP2 by GSK3ß. In conclusion, this study is the first to demonstrate that CRMP signaling is involved in the suppression of neurite outgrowth by low zinc.

Axonal growth inhibitors and their receptors in spinal cord injury: from biology to clinical translation.

Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelin-associated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19 (that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the RhoA/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.

Inhibition of glycogen synthase kinase 3 by lithium, a mechanism in search of specificity.

Inhibition of Glycogen synthase kinase 3 (GSK3) is a popular explanation for the effects of lithium ions on mood regulation in bipolar disorder and other mental illnesses, including major depression, cyclothymia, and schizophrenia. Contribution of GSK3 is supported by evidence obtained from animal and patient derived model systems. However, the two GSK3 enzymes, GSK3α and GSK3ß, have more than 100 validated substrates. They are thus central hubs for major biological functions, such as dopamine-glutamate neurotransmission, synaptic plasticity (Hebbian and homeostatic), inflammation, circadian regulation, protein synthesis, metabolism, inflammation, and mitochondrial functions. The intricate contributions of GSK3 to several biological processes make it difficult to identify specific mechanisms of mood stabilization for therapeutic development. Identification of GSK3 substrates involved in lithium therapeutic action is thus critical. We provide an overview of GSK3 biological functions and substrates for which there is evidence for a contribution to lithium effects. A particular focus is given to four of these: the transcription factor cAMP response element-binding protein (CREB), the RNA-binding protein FXR1, kinesin subunits, and the cytoskeletal regulator CRMP2. An overview of how co-regulation of these substrates may result in shared outcomes is also presented. Better understanding of how inhibition of GSK3 contributes to the therapeutic effects of lithium should allow for identification of more specific targets for future drug development. It may also provide a framework for the understanding of how lithium effects overlap with those of other drugs such as ketamine and antipsychotics, which also inhibit brain GSK3.

Implication of Adipogenesis-Coupled CRMP2 Functional Profile in Metabolic Homeostasis and Imbalance.

Our previous studies demonstrated that collapsin response mediator protein 2 (CRMP2) is associated with obesity and, in addition, that hyperglycemia-suppressed CRMP2 augments malignant traits of colorectal cancer and is associated with advanced tumor stage. Regulation of CRMP2 profile was further explored in this study using 3T3-L1 pre-adipocyte adipogenesis as a study model for illustrating the roles of CRMP2 in metabolic homeostasis. Hyperglycemia inhibited expression of CRMP2, adipogenic machinery and adipocyte markers. CRMP2 displayed f-CRMP2 (62~66 kDa) and s-CMRP2 (58 kDa) isoforms at the growth arrest phase. Expression of s-CRMP2 was coupled with the mitotic clonal expansion (MCE) phase to direct cell proliferation and rapidly down-regulated in post-mitotic cells. In the late differentiation phase, f-CRMP2 was co-localized with tubulin in the cortical area. Insulin-enhanced CRMP2-glucose transporter 4 (GLUT4) co-localization and CRMP2 puncta on lipid droplets (LDs) suggested participation of CRMP2 in GLUT4 translocation and LD fusion. Collectively, the CRMP2 functional profile must be finely controlled to adjust cytoskeletal stability for meeting dynamic cellular needs. Manipulating the s-CRMP2/f-CRMP2 ratio and thus the cytoskeleton dynamics is anticipated to improve glucose uptake and insulin sensitivity. In summary, our data provide molecular evidence explaining the functions of CRMP2 in physiological, pathological and disease progression in metabolic homeostasis and disorders related to metabolic abnormalities, including cancer.

Riluzole Promotes Neurite Growth in Rats after Spinal Cord Injury through the GSK-3ß/CRMP-2 Pathway.

Spinal cord injury (SCI) is a disastrous event that often leads to permanent neurological deficits involving motor, sensory, and autonomic dysfunctions in patients. Accumulating research has demonstrated that riluzole may play crucial roles in the process of spinal tissue repair, but the underlying mechanisms remain elusive. This study verified the effectiveness of riluzole and speculated that a riluzole-afforded protection mechanism may be associated with the glycogen synthase kinase-3 beta (GSK-3ß)/collapsin response mediator protein-2 (CRMP-2) pathway in rats after spinal cord injury. Here, a modified Allen's weight dropping model was generated and riluzole at 4 mg/kg was injected intraperitoneally after surgery and twice a day for 7 consecutive days. At 6 weeks after SCI, we found that riluzole treatment reduced the central cavity size of the spinal cord and improved neurological functions. Meanwhile, riluzole-treated rats exhibited shorter latency and larger amplitude in motor evoked potentials and somatosensory evoked potentials, compared with vehicle-treated rats. Furthermore, Western blotting and immunofluorescence data revealed that the expression levels of GSK-3ß and phosphorylated-GSK-3ß were lower in riluzole-treated SCI rats compared with vehicle-treated rats. We next detected the expression CRMP-2 and phosphorylated CRMP-2 and found that the expression of CRMP-2 showed no difference between the riluzole-treated and vehicle-treated groups; however, administration of riluzole downregulated phosphorylated CRMP-2 expression. The current findings suggest that after SCI, administration of riluzole promotes neurological functional restoration, which may be associated, in part, with its activation of the GSK-3ß/CRMP-2 signaling pathway.

Small molecule targeting NaV1.7 via inhibition of the CRMP2-Ubc9 interaction reduces and prevents pain chronification in a mouse model of oxaliplatin-induced neuropathic pain.

Treatment with anti-neoplastic agents can lead to the development of chemotherapy induced peripheral neuropathy (CIPN), which is long lasting and often refractory to treatment. This neuropathic pain develops along dermatomes innervated by peripheral nerves with cell bodies located in the dorsal root ganglia (DRG). The voltage-gated sodium channel NaV1.7 is expressed at high levels in peripheral nerve tissues and has been implicated in the development of CIPN. Efforts to develop novel analgesics directly inhibiting NaV1.7 have been unsuccessful, and our group has pioneered an alternative approach based on indirect modulation of channel trafficking by the accessory protein collapsin response mediator protein 2 (CRMP2). We have recently reported a small molecule, compound 194, that inhibits CRMP2 SUMOylation by the E2 SUMO-conjugating enzyme Ubc9 (Cai et al. , Sci. Transl. Med. 2021 13(6 1 9):eabh1314). Compound 194 is a potent and selective inhibitor of NaV1.7 currents in DRG neurons and reverses mechanical allodynia in models of surgical, inflammatory, and neuropathic pain, including spared nerve injury and paclitaxelinduced peripheral neuropathy. Here we report that, in addition to its reported effects in rats, 194 also reduces mechanical allodynia in male CD-1 mice treated with platinumcomplex agent oxaliplatin. Importantly, treatment with 194 prevented the development of mechanical allodynia when co-administered with oxaliplatin. No effects were observed on the body weight of animals treated with oxaliplatin or 194 throughout the study period. These findings support the notion that 194 is a robust inhibitor of CIPN that reduces established neuropathic pain and prevents the emergence of neuropathic pain during treatment with multiple anti-neoplastic agents in both mice and rats.

Clinical evidence that a dysregulated master neural network modulator may aid in diagnosing schizophrenia.

There are no validated biomarkers for schizophrenia (SCZ), a disorder linked to neural network dysfunction. We demonstrate that collapsin response mediator protein-2 (CRMP2), a master regulator of cytoskeleton and, hence, neural circuitry, may form the basis for a biomarker because its activity is uniquely imbalanced in SCZ patients. CRMP2's activity depends upon its phosphorylation state. While an equilibrium between inactive (phosphorylated) and active (nonphosphorylated) CRMP2 is present in unaffected individuals, we show that SCZ patients are characterized by excess active CRMP2. We examined CRMP2 levels first in postmortem brains (correlated with neuronal morphometrics) and then, because CRMP2 is expressed in lymphocytes as well, in the peripheral blood of SCZ patients versus age-matched unaffected controls. In the brains and, more starkly, in the lymphocytes of SCZ patients <40 y old, we observed that nonphosphorylated CRMP2 was higher than in controls, while phosphorylated CRMP2 remained unchanged from control. In the brain, these changes were associated with dendritic structural abnormalities. The abundance of active CRMP2 with insufficient opposing inactive p-CRMP2 yielded a unique lowering of the p-CRMP2:CRMP2 ratio in SCZ patients, implying a disruption in the normal equilibrium between active and inactive CRMP2. These clinical data suggest that measuring CRMP2 and p-CRMP2 in peripheral blood might reflect intracerebral processes and suggest a rapid, minimally invasive, sensitive, and specific adjunctive diagnostic aid for early SCZ: increased CRMP2 or a decreased p-CRMP2:CRMP2 ratio may help cinch the diagnosis in a newly presenting young patient suspected of SCZ (versus such mimics as mania in bipolar disorder, where the ratio is high).

Somatostatin Ameliorates ß-Amyloid-Induced Cytotoxicity via the Regulation of CRMP2 Phosphorylation and Calcium Homeostasis in SH-SY5Y Cells.

Somatostatin is involved in the regulation of multiple signaling pathways and affords neuroprotection in response to neurotoxins. In the present study, we investigated the role of Somatostatin-14 (SST) in cell viability and the regulation of phosphorylation of Collapsin Response Mediator Protein 2 (CRMP2) (Ser522) via the blockade of Ca2+ accumulation, along with the inhibition of cyclin-dependent kinase 5 (CDK5) and Calpain activation in differentiated SH-SY5Y cells. Cell Viability and Caspase 3/7 assays suggest that the presence of SST ameliorates mitochondrial stability and cell survival pathways while augmenting pro-apoptotic pathways activated by Aß. SST inhibits the phosphorylation of CRMP2 at Ser522 site, which is primarily activated by CDK5. Furthermore, SST effectively regulates Ca2+ influx in the presence of Aß, directly affecting the activity of calpain in differentiated SH-SY5Y cells. We also demonstrated that SSTR2 mediates the protective effects of SST. In conclusion, our results highlight the regulatory role of SST in intracellular Ca2+ homeostasis. The neuroprotective role of SST via axonal regeneration and synaptic integrity is corroborated by regulating changes in CRMP2; however, SST-mediated changes in the blockade of Ca2+ influx, calpain expression, and toxicity did not correlate with CDK5 expression and p35/25 accumulation. To summarize, our findings suggest two independent mechanisms by which SST mediates neuroprotection and confirms the therapeutic implications of SST in AD as well as in other neurodegenerative diseases where the effective regulation of calcium homeostasis is required for a better prognosis.

Schizophrenia risk-gene Crmp2 deficiency causes precocious critical period plasticity and deteriorated binocular vision.

Brain-specific loss of a microtubule-binding protein collapsin response mediator protein-2 (CRMP2) in the mouse recapitulates many schizophrenia-like behaviors of human patients, possibly resulting from associated developmental deficits in neuronal differentiation, path-finding, and synapse formation. However, it is still unclear how the Crmp2 loss affects neuronal circuit function and plasticity. By conducting in vivo and ex vivo electrophysiological recording in the mouse primary visual cortex (V1), we reveal that CRMP2 exerts a key regulation on the timing of postnatal critical period (CP) for experience-dependent circuit plasticity of sensory cortex. In the developing V1, the Crmp2 deficiency induces not only a delayed maturation of visual tuning functions but also a precocious CP for visual input-induced ocular dominance plasticity and its induction activity - coincident binocular inputs right after eye-opening. Mechanistically, the Crmp2 deficiency accelerates the maturation process of cortical inhibitory transmission and subsequently promotes an early emergence of balanced excitatory-inhibitory cortical circuits during the postnatal development. Moreover, the precocious CP plasticity results in deteriorated binocular depth perception in adulthood. Thus, these findings suggest that the Crmp2 deficiency dysregulates the timing of CP for experience-dependent refinement of circuit connections and further leads to impaired sensory perception in later life.

Effect of aluminum-maltolate on primary hippocampal neuron neurite damage by regulating CRMP2 through GSK-3β in mice / 环境与职业医学

Background Aluminum can induce irreversible structural and synaptic functional damage, and the associated mechanism may be related to the neurite damage regulated by glycogen synthase kinase-3β (GSK-3β)/collapsin response mediator protein 2 (CRMP2). Objective This experiment is conducted to investigate the effect of aluminum-maltolate [Al(mal)3] on primary hippocampal neuron neurites in mice, and reveal the role of GSK-3β-CRMP2 in this process. Methods The hippocampus of newborn ICR mice (≤ 24 h old) was used for primary neuronal cultures. On the 5th day in vitro (DIV5), neuron purity detection were performed by confocal laser scanning microscopy. On DIV7, the neurons were transfected with lentiviral vector-mediated mNeonGreen. On DIV10, the neurons with mNeonGreen fluorescence in good growth state were treated with Al(mal)3. The stage I experimental groups were blank control group, maltol group, 10 µmol·L−1 Al group, 20 µmol·L−1 Al group, and 40 µmol·L−1 Al group. Then 20 µmol·L−1 Al was used to establish a model of neurite injury and for the intervention. The stage II experimental groups were blank control group, dimethyl sulfoxide (DMSO) group, Al (20 µmol·L−1) group, SB (GSK-3β inhibitor, 1 µmol·L−1), and SB (1 µmol·L−1)+Al (20 µmol·L−1) group. CCK-8 method was used to detect the viability of neurons. The primary hippocampal neurons of mice were scanned with high content analysis system at 0 h and 48 h after Al or SB treatment, and the density and length of neurites were analyzed. Western blotting was used to detect the expression and phosphorylation levels of CRMP2 and GSK-3β in primary hippocampal neurons of mice. Results The immunofluorescence results showed that the purity of primary neurons was more than 90%. Compared with the blank control group in stage I, the cell viability rates of the 10, 20, and 40 µmol·L−1 Al groups were decreased after 48h of Al(mal)3 treatment (P<0.05), while the cell viability rate of the maltol group had no significant change. There was no significant difference in cell viability rate among the DMSO group, the SB group, and the control group after 48h of SB treatment, and the viability rate of neurons in the SB+Al group was higher than that in the Al group (P<0.05) in stage II. The 48 h/0 h ratios of average number and length of neurites in the control group were 90.13%±11.70% and 113.24%±8.34%, respectively. The 48 h/0 h ratios in the Al group were 56.47%±16.36% and 62.06%±6.75%, respectively, which were lower than those in the control group (P<0.05). The 48 h/0 h ratios of average number of neurites in the SB group (99.03%±21.83%) was not significantly different from that in the control group, but the 48 h/0 h ratio of average length of neurites in the SB group (128.72%±15.39%) was higher than that in the control group (P<0.05). The 48 h/0 h ratios of average number (72.59%±10.89%) and length of neurites (93.84%±14.65%) in the SB+Al group were significantly increased compared with those in the Al group (P<0.05). Western blotting results showed that: There was no significant difference in GSK-3β protein level among all groups; compared with the control group (1.00±0.18), the protein level of p-GSK-3β in the Al group (0.45±0.05) was significantly decreased, and that in the SB group (1.32±0.23) was significantly increased; the protein level of p-GSK-3β in the SB+Al group (0.80±0.05) was significantly higher than that in the Al group (P<0.05). Compared with the control group (1.00±0.07), the CRMP2 protein level in the Al group (0.66±0.11) was significantly decreased (P<0.05), while that in the SB group (1.01±0.02) was not significantly changed. Compared with the control group (1.00±0.13), the p-CRMP2 protein level in the Al group (1.50±2.18) was significantly increased, and that in the SB group (0.62±0.09) was significantly decreased (P<0.05); the protein level of p-CRMP2 in the SB+Al group (1.28±0.24) was lower than that in the Al group (P<0.05). Conclusion Aluminum may activate GSK-3β, increase CRMP2 phosphorylation level, and damage neurite growth.

Amphetamine causing damage of dopamine cells via inhibiting of protein kinase B / glycogen synthase kinase-3β/ collapsin response mediator protein-2 signal pathway / 解剖学报

Objective To explore the damage mechanism of dopamine cells induced by amphetamine (AMPH). Methods The damage model of dopaminergic cells in mice was established by intraperitoneal injection of AMPH. The mice were randomly grouped into control, saline, amphetamine treatment for 1 day, 7 days, 14 days and 28 days. Each group contained 10 mice. The model of cell injury was established by use of AMPH in PC12 cells. The dopaminergic fibers of corpus striatum and PC12 cells were observed by the immunohistochemistry and immunofluorescence method, and changes of proteins in the protein kinase B (Akt) / glycogen synthase kinase 3β(GSK-3β) / collapsin response mediator protein 2 (CRMP-2) signal pathway were detected by Western blotting. Results AMPH caused the damage of dopaminergic fibers in the mouse corpus striatum and PC12 cells. Meanwhile, AMPH inhibited Akt and GSK-3β phosphorylation levels, and increased phosphorylated CRMP-2 level. Nerve growth factor(NGF), an agonist of Akt, or SB216763, an inhibitor of GSK-3β protected PC12 cells against AMPH-induced toxicity through upregulation of Aat and GSK-3β phosphorylation and downregulated of phosphorylation CRMP-2. Conclusion AMPH causes damage of dopamine cells via inhibition of Akt/ GSK-3β/ CRMP-2 signal pathway.

PKCγ-Mediated Phosphorylation of CRMP2 Regulates Dendritic Outgrowth in Cerebellar Purkinje Cells.

The signalling protein PKCγ is a major regulator of Purkinje cell development and synaptic function. We have shown previously that increased PKCγ activity impairs dendritic development of cerebellar Purkinje cells. Mutations in the protein kinase Cγ gene (PRKCG) cause spinocerebellar ataxia type 14 (SCA14). In a transgenic mouse model of SCA14 expressing the human S361G mutation, Purkinje cell dendritic development is impaired in cerebellar slice cultures similar to pharmacological activation of PKC. The mechanisms of PKCγ-driven inhibition of dendritic growth are still unclear. Using immunoprecipitation-coupled mass spectrometry analysis, we have identified collapsin response mediator protein 2 (CRMP2) as a protein interacting with constitutive active PKCγ(S361G) and confirmed the interaction with the Duolink™ proximity ligation assay. We show that in cerebellar slice cultures from PKCγ(S361G)-mice, phosphorylation of CRMP2 at the known PKC target site Thr555 is increased in Purkinje cells confirming phosphorylation of CRMP2 by PKCγ. miRNA-mediated CRMP2 knockdown decreased Purkinje cell dendritic outgrowth in dissociated cerebellar cultures as did the transfection of CRMP2 mutants with a modified Thr555 site. In contrast, dendritic development was normal after wild-type CRMP2 overexpression. In a novel knock-in mouse expressing only the phospho-defective T555A-mutant CRMP2, Purkinje cell dendritic development was reduced in dissociated cultures. This reduction could be rescued by transfecting wild-type CRMP2 but only partially by the phospho-mimetic T555D-mutant. Our findings establish CRMP2 as an important target of PKCγ phosphorylation in Purkinje cells mediating its control of dendritic development. Dynamic regulation of CRMP2 phosphorylation via PKCγ is required for its correct function.

Coordinating Synaptic Signaling with CRMP2.

Synaptic transmission is a complex process, dysregulation of which underlies several neurological conditions. Collapsin response mediator protein 2 (CRMP2) is a microtubule associated protein expressed ubiquitously in the central nervous system. Identified initially in the context of Semaphorin 3A (Collapsin) induced growth cone collapse, more recent findings revealed the involvement of CRMP2 in ion channel trafficking, kinesin-dependent axonal transport and maintenance of intracellular calcium homeostasis. CRMP2 is a synaptic protein, expressed at pre- and post-synaptic sites. Interactions with proteins such as N-methyl-D-aspartate receptors, syntaxin1A as well as voltage-gated calcium and sodium channels, suggest that CRMP2 may control both the electrical and chemical components of synaptic transmission. This short review will outline the known synaptic interactions of CRMP2 and illustrate its role in synaptic transmission, thereby introducing CRMP2 as a prospective target for the pathophysiological modulation of aberrant synaptic activity.

Regulation of Adipogenesis and Lipid Deposits by Collapsin Response Mediator Protein 2.

As emerging evidence suggesting neurodegenerative diseases and metabolic diseases have common pathogenesis, we hypothesized that the neurite outgrowth-controlling collapsin response mediator protein 2 (CRMP2) was involved in energy homeostasis. Therefore, putative roles of CRMP2 in adipocyte differentiation (adipogenesis) and lipid metabolism were explored and addressed in this study. CRMP2 expression profiles were in vitro and in vivo characterized during adipogenic process of 3T3-L1 pre-adipocytes and diet-induced obese (DIO) mice, respectively. Effects of CRMP2 on lipid metabolism and deposits were also analyzed. Our data revealed that CRMP2 expression pattern was coupled with adipogenic stages. CRMP2 overexpression inhibited cell proliferation at MCE phase, and significantly reduced lipid contents by down-regulating adipogenesis-driving transcription factors and lipid-synthesizing enzymes. Interestingly, GLUT4 translocation and the lipid droplets fusion were disturbed in CRMP2-silencing cells by affecting actin polymerization. Moreover, adipose CRMP2 was significantly increased in DIO mice, indicating CRMP2 is associated with obesity. Accordingly, CRMP2 exerts multiple functions in adipogenesis and lipid deposits through mediating cell proliferation, glucose/lipid metabolism and cytoskeleton dynamics. The present study identifies novel roles of CRMP2 in mediating adipogenesis and possible implication in metabolic disorders, as well as provides molecular evidence supporting the link of pathogenesis between neurodegenerative diseases and metabolic abnormalities.

Tau-tubulin kinase 1 and amyloid-ß peptide induce phosphorylation of collapsin response mediator protein-2 and enhance neurite degeneration in Alzheimer disease mouse models.

The accumulation of phosphorylated tau protein (pTau) in the entorhinal cortex (EC) is the earliest tau pathology in Alzheimer's disease (AD). Tau tubulin kinase-1 (TTBK1) is a neuron-specific tau kinase and expressed in the EC and hippocampal regions in both human and mouse brains. Here we report that collapsin response mediator protein-2 (CRMP2), a critical mediator of growth cone collapse, is a new downstream target of TTBK1 and is accumulated in the EC region of early stage AD brains. TTBK1 transgenic mice show severe axonal degeneration in the perforant path, which is exacerbated by crossing with Tg2576 mice expressing Swedish familial AD mutant of amyloid precursor protein (APP). TTBK1 mice show accumulation of phosphorylated CRMP2 (pCRMP2), in the EC at 10 months of age, whereas age-matched APP/TTBK1 bigenic mice show pCRMP2 accumulation in both the EC and hippocampal regions. Amyloid-ß peptide (Aß) and TTBK1 suppress the kinetics of microtubule polymerization and TTBK1 reduces the neurite length of primary cultured neurons in Rho kinase-dependent manner in vitro. Silencing of TTBK1 or expression of dominant-negative Rho kinase demonstrates that Aß induces CRMP2 phosphorylation at threonine 514 in a TTBK1-dependent manner, and TTBK1 enhances Aß-induced CRMP2 phosphorylation in Rho kinase-dependent manner in vitro. Furthermore, TTBK1 expression induces pCRMP2 complex formation with pTau in vitro, which is enhanced upon Aß stimulation in vitro. Finally, pCRMP2 forms a complex with pTau in the EC tissue of TTBK1 mice in vivo, which is exacerbated in both the EC and hippocampal tissues in APP/TTBK1 mice. These results suggest that TTBK1 and Aß induce phosphorylation of CRMP2, which may be causative for the neurite degeneration and somal accumulation of pTau in the EC neurons, indicating critical involvement of TTBK1 and pCRMP2 in the early AD pathology.

CRMP2 mediates Sema3F-dependent axon pruning and dendritic spine remodeling.

Regulation of axon guidance and pruning of inappropriate synapses by class 3 semaphorins are key to the development of neural circuits. Collapsin response mediator protein 2 (CRMP2) has been shown to regulate axon guidance by mediating semaphorin 3A (Sema3A) signaling; however, nothing is known about its role in synapse pruning. Here, using newly generated crmp2-/- mice we demonstrate that CRMP2 has a moderate effect on Sema3A-dependent axon guidance in vivo, and its deficiency leads to a mild defect in axon guidance in peripheral nerves and the corpus callosum. Surprisingly, crmp2-/- mice display prominent defects in stereotyped axon pruning in hippocampus and visual cortex and altered dendritic spine remodeling, which is consistent with impaired Sema3F signaling and with models of autism spectrum disorder (ASD). We demonstrate that CRMP2 mediates Sema3F signaling in primary neurons and that crmp2-/- mice display ASD-related social behavior changes in the early postnatal period as well as in adults. Together, we demonstrate that CRMP2 mediates Sema3F-dependent synapse pruning and its dysfunction shares histological and behavioral features of ASD.

Intravitreal application of AAV-BDNF or mutant AAV-CRMP2 protects retinal ganglion cells and stabilizes axons and myelin after partial optic nerve injury.

Secondary degeneration following an initial injury to the central nervous system (CNS) results in increased tissue loss and is associated with increasing functional impairment. Unilateral partial dorsal transection of the adult rat optic nerve (ON) has proved to be a useful experimental model in which to study factors that contribute to secondary degenerative events. Using this injury model, we here quantified the protective effects of intravitreally administered bi-cistronic adeno-associated viral (AAV2) vectors encoding either brain derived neurotrophic factor (BDNF) or a mutant, phospho-resistant, version of collapsin response mediator protein 2 (CRMP2T555A) on retinal ganglion cells (RGCs), their axons, and associated myelin. To test for potential synergistic interactions, some animals received combined injections of both vectors. Three months post-injury, all treatments maintained RGC numbers in central retina, but only AAV2-BDNF significantly protected ventrally located RGCs exclusively vulnerable to secondary degeneration. Behaviourally, treatments that involved AAV2-BDNF significantly restored the number of smooth-pursuit phases of optokinetic nystagmus. While all therapeutic regimens preserved axonal density and proportions of typical complexes, including heminodes and single nodes, BDNF treatments were generally more effective in maintaining the length of the node of Ranvier in myelin surrounding ventral ON axons after injury. Both AAV2-BDNF and AAV2-CRMP2T555A prevented injury-induced changes in G-ratio and overall myelin thickness, but only AAV2-BDNF administration protected against large-scale myelin decompaction in ventral ON. In summary, in a model of secondary CNS degeneration, both BDNF and CRMP2T555A vectors were neuroprotective, however different efficacies were observed for these overexpressed proteins in the retina and ON, suggesting disparate cellular and molecular targets driving responses for neural repair. The potential use of these vectors to treat other CNS injuries and pathologies is discussed.

Dynamic CRMP2 Regulation of CaV2.2 in the Prefrontal Cortex Contributes to the Reinstatement of Cocaine Seeking.

Cocaine addiction remains a major health concern with limited effective treatment options. A better understanding of mechanisms underlying relapse may help inform the development of new pharmacotherapies. Emerging evidence suggests that collapsin response mediator protein 2 (CRMP2) regulates presynaptic excitatory neurotransmission and contributes to pathological changes during diseases, such as neuropathic pain and substance use disorders. We examined the role of CRMP2 and its interactions with a known binding partner, CaV2.2, in cocaine-seeking behavior. We employed the rodent self-administration model of relapse to drug seeking and focused on the prefrontal cortex (PFC) for its well-established role in reinstatement behaviors. Our results indicated that repeated cocaine self-administration resulted in a dynamic and persistent alteration in the PFC expression of CRMP2 and its binding partner, the CaV2.2 (N-type) voltage-gated calcium channel. Following cocaine self-administration and extinction training, the expression of both CRMP2 and CaV2.2 was reduced relative to yoked saline controls. By contrast, cued reinstatement potentiated CRMP2 expression and increased CaV2.2 expression above extinction levels. Lastly, we utilized the recently developed peptide myr-TAT-CBD3 to disrupt the interaction between CRMP2 and CaV2.2 in vivo. We assessed the reinstatement behavior after infusing this peptide directly into the medial PFC and found that it decreased cue-induced reinstatement of cocaine seeking. Taken together, these data suggest that neuroadaptations in the CRMP2/CaV2.2 signaling cascade in the PFC can facilitate drug-seeking behavior. Targeting such interactions has implications for the treatment of cocaine relapse behavior.

aFGF Promotes Neurite Growth by Regulating GSK3ß-CRMP2 Signaling Pathway in Cortical Neurons Damaged by Amyloid-ß.

Glycogen synthase kinase 3ß (GSK3ß) is a key component of pathogenesis in Alzheimer's disease, and its inhibitors can restore cognitive function as therapeutic interventions in neurodegenerative diseases. The previous studies showed that acidic fibroblast growth factor (aFGF) could increase the phosphorylation of GSK3ß through the PI3K/Akt signaling pathway. We found that aFGF14-154 markedly increased the average length of neurites in neurons damaged by amyloid-ß (Aß), and this promoting effect was blocked by GSK3ß inhibitor. It is still unknown which downstream substrates of GSK3ß are related to the neurite growth facilitated by aFGF14-154. The downstream substrates interacting with GSK3ß were screened by co-immunoprecipitation and LTQ-Orbitrap proteomics technology in our study. Collapsin response mediator protein 2 (CRMP2) has been identified as a protein interacting with GSK3ß, which is involved in the axon formation and neuron regeneration by regulating microtubule reorganization. aFGF14-154 increased the phosphorylation of GSK3ß (Ser9) to inhibit its activity, then was followed by a low phosphorylation level of CRMP2 (Thr514), which led to the neurite growth. The knockdown of CRMP2 blocked the rescue of aFGF14-154 with broken neurites and shrunken cell bodies in neurons with Aß injury. These results highlight the important role of CRMP2 and its phosphorylation through GSK3ß in the effect that aFGF14-154 promoted the growth of neurite damaged by Aß.