Expression of collapsin response mediator proteins 1, 2 and 5 is differentially regulated in newly generated and mature neurons of the adult olfactory system

Proteomics-Guided Study on Buyang Huanwu Decoction for Its Neuroprotective and Neurogenic Mechanisms for Transient Ischemic Stroke: Involvements of EGFR/PI3K/Akt/Bad/14-3-3 and Jak2/Stat3/Cyclin D1 Signaling Cascades

Buyang Huanwu Decoction (BHD), a classic traditional Chinese medicine (TCM) formula, has been used for recovering neurological dysfunctions and treating post-stroke disability in China for 200 years. In the present study, we investigated the effects of BHD on inhibiting neuronal apoptosis, promoting proliferation and differentiation of neural stem cells (NSCs) and neurite formation and enhancing learning and memory functional recovery in an experimental rat ischemic stroke model. BHD significantly reduced infarct volume and decreased cell apoptosis in the ischemic brain. BHD enhanced neuronal cell viability in vitro. BHD dose-dependently promoted the proliferation of NSCs in ischemic rat brains in vivo. Moreover, BHD promoted neuronal and astrocyte differentiation in primary cultured NSCs in vitro. Water maze test revealed that BHD promoted the recovery of learning function but not memory functions in the transient ischemic rats. We then investigated the changes of the cellular signaling molecules by using two-dimension (2D) gel electrophoresis and focused on the PI3K/Akt/Bad and Jak2/Stat3/cyclin D1signaling pathway to uncover its underlying mechanisms for its neuroprotective and neurogenetic effects. BHD significantly upregulated the expression of p-PI3K, p-Akt, and p-Bad as well as the expression of p-Jak, p-Stat3, and cyclin D1 in vitro and in vivo. In addition, BHD upregulated Hes1 and downregulated cav-1 in vitro and in vivo. Taken together, these results suggest that BHD has neuroprotective effects and neurogenesis-promoting effects via activating PI3K/Akt/Bad and Jak2/Stat3/Cyclin D1 signaling pathways. Graphical Abstract Buyang Huanwu Decoction (BHD) activates the PI3K-AKT-BAD pathway in the ischemic brain for neuroprotection. BHD also activates JAK2/STAT3/Cyclin D1 signaling cascades for promoting neurogenesis in the hippocampus of post-ischemic brains. Moreover, BHD inhibits the expression of caveolin-1 and increases the expression of HES1 for promoting neuronal differentiation. The neuroprotective and neurogenesis-promoting effects in the hippocampus of post-ischemic brains promote learning ability.

Neuroprotective and neuroregenerative effects of CRMP-5 on retinal ganglion cells in an experimental in vivo and in vitro model of glaucoma

Purpose

To analyze the potential neuro-protective and neuro-regenerative effects of Collapsin-response-mediator-protein-5 (CRMP-5) on retinal ganglion cells (RGCs) using in vitro and in vivo animal models of glaucoma.

Methods

Elevated intraocular pressure (IOP) was induced in adult female Sprague-Dawley (SD) rats by cauterization of three episcleral veins. Changes in CRMP-5 expression within the retinal proteome were analyzed via label-free mass spectrometry. In vitro, retinal explants were cultured under elevated pressure (60 mmHg) within a high-pressure incubation chamber with and without addition of different concentrations of CRMP-5 (4 μg/l, 200 μg/l and 400 μg/l). In addition, retinal explants were cultured under regenerative conditions with and without application of 200 μg/l CRMP-5 after performing an optic nerve crush (ONC). Thirdly, an antibody against Protein Kinase B (PKB) was added to examine the possible effects of CRMP-5. RGC count was performed. Number and length of the axons were determined and compared. To undermine a signal-transduction pathway via CRMP-5 and PKB microarray and immunohistochemistry were performed.

Results

CRMP-5 was downregulated threefold in animals showing chronically elevated IOP. The addition of CRMP-5 to retinal culture significantly increased RGC numbers under pressure in a dose-dependent manner and increased and elongated outgrowing axons in retinal explants significantly which could be blocked by PKB. Especially the number of neurites longer than 400 μm significantly increased after application of CRMP-5. CRMP-5 as well as PKB were detected higher in the experimental than in the control group.

Conclusion

CRMP-5 seems to play an important role in an animal model of glaucoma. Addition of CRMP-5 exerts neuro-protective and neuro-regenerative effects in vitro. This effect could be mediated via activation of PKB affecting intra-cellular apoptosis pathways.

Lithium-associated transcriptional regulation of CRMP1 in patient-derived olfactory neurons and symptom changes in bipolar disorder

There is growing evidence that lithium used in the treatment of bipolar disorder (BD) affects molecular targets that are involved in neuronal growth, survival, and maturation, but it remains unclear if neuronal alterations in any of these molecules predict specific symptom changes in BD patients undergoing lithium monotherapy. The goals of this study were to (a) determine which molecular changes in the olfactory neurons of symptomatic patients receiving lithium are associated with antimanic or antidepressant response, and (b) uncover novel intraneuronal regulatory mechanisms of lithium therapy. Twenty-two treatment-naïve non-smoking patients, with symptomatic BD underwent nasal biopsies for collection of olfactory tissues, prior to their treatment and following a 6-week course of lithium monotherapy. Sixteen healthy controls were also biopsied. Combining laser capture microdissection with real-time polymerase chain reaction, we investigated baseline and treatment-associated transcriptional changes in candidate molecular targets of lithium action in the olfactory neuroepithelium. Baseline mRNA levels of glycogen synthase kinase 3 beta (GSK3β) and collapsin response mediator protein 1 (CRMP1) genes were significantly associated with BD status and with severity of mood symptoms. Among BD subjects, treatment-associated downregulation of CRMP1 expression was most predictive of decreases in both manic and depressive symptoms. This study provides a novel insight into the relevance of CRMP1, a key molecule in semaphorin-3A signaling during neurodevelopment, in the molecular mechanism of action of lithium, and in the pathophysiology of BD. It supports the use of human-derived olfactory neuronal tissues in the evaluation of treatment response of psychiatric disorders.

Amyloid-beta-dependent phosphorylation of collapsin response mediator protein-2 dissociates kinesin in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles. Prior to the development of these characteristic pathological hallmarks of AD, anterograde axonal transport is impaired. However, the key proteins that initiate these intracellular impairments remain elusive. The collapsin response mediator protein-2 (CRMP-2) plays an integral role in kinesin-1-dependent axonal transport and there is evidence that phosphorylation of CRMP-2 releases kinesin-1. Here, we tested the hypothesis that amyloid-beta (Aβ)-dependent phosphorylation of CRMP-2 disrupts its association with the kinesin-1 (an anterograde axonal motor transport protein) in AD. We found that brain sections and lysates from AD patients demonstrated elevated phosphorylation of CRMP-2 at the T555 site. Additionally, in the transgenic Tg2576 mouse model of familial AD (FAD) that exhibits Aβ accumulation in the brain with age, we found substantial co-localization of pT555CRMP-2 and dystrophic neurites. In SH-SY5Y differentiated neuronal cultures, Aβ-dependent phosphorylation of CRMP-2 at the T555 site was also elevated and this reduced the CRMP-2 association with kinesin-1. The overexpression of an unphosphorylatable form of CRMP-2 in neurons promoted the re-establishment of CRMP-2-kinesin association and axon elongation. These data suggest that Aβ-dependent phosphorylation of CRMP-2 at the T555 site may directly impair anterograde axonal transport protein function, leading to neuronal defects.

Stable isotope metabolic labeling suggests differential turnover of the DPYSL protein family

PURPOSE

In this work, we discuss how in vivo ¹⁵ N metabolic labeling in combination with MS simultaneously provides information on protein expression and protein turnover.

EXPERIMENTAL DESIGN

We metabolically labeled mice with the stable nitrogen isotope ¹⁵ N using a ¹⁵ N-enriched diet and analyzed unlabeled (¹⁴ N) versus ¹⁵ N-labeled brain tissue with LC-MS/MS. We then compared the ¹⁴ N versus ¹⁵ N peptide isotopologue clusters of ¹⁴ N and ¹⁵ N-labeled dihydropyrimidinase-related (DPYSL) proteins.

RESULTS

We present a workflow assessing protein expression and turnover at different time points of mouse brain development. Our data demonstrate distinct protein turnover patterns of DPYSL3 and DPYSL5 compared to other quantified proteins. We report the presence of two DPYSL3 and DPYSL5 populations with different ¹⁵ N incorporation rates, indicating altered protein turnover during development.

CONCLUSIONS AND CLINICAL RELEVANCE

In vivo ¹⁵ N metabolic labeling allows the simultaneous investigation of protein expression and turnover, enabling detailed protein dynamics studies. We report for the first time protein turnover data for the DPYSL2, DPYSL3, and DPYSL5 protein family members. As DPYSL proteins have important functions for nervous system maturation, our data provide useful information on their molecular fate during brain development.

Deletion of collapsin response mediator protein 4 results in abnormal layer thickness and elongation of mitral cell apical dendrites in the neonatal olfactory bulb

Collapsin response mediator protein 4 (CRMP4), a member of the CRMP family, is involved in the pathogenesis of neurodevelopmental disorders such as schizophrenia and autism. Here, we first compared layer thickness of the olfactory bulb between wild-type (WT) and CRMP4-knockout (KO) mice. The mitral cell layer (MCL) was significantly thinner, whereas the external plexiform layer (EPL) was significantly thicker in CRMP4-KO mice at postnatal day 0 (PD0) compared with WTs. However, differences in layer thickness disappeared by PD14. No apoptotic cells were found in the MCL, and the number of mitral cells (MCs) identified with a specific marker (i.e. Tbx21 antibody) did not change in CRMP4-KO neonates. However, DiI-tracing showed that the length of mitral cell apical dendrites was greater in CRMP4-KO neonates than in WTs. In addition, expression of CRMP4 mRNA in WT mice was most abundant in the MCL at PD0 and decreased afterward. These results suggest that CRMP4 contributes to dendritic elongation. Our in vitro studies showed that deletion or knockdown of CRMP4 resulted in enhanced growth of MAP2-positive neurites, whereas overexpression of CRMP4 reduced their growth, suggesting a new role for CRMP4 as a suppressor of dendritic elongation. Overall, our data suggest that disruption of CRMP4 produces a temporary alteration in EPL thickness, which is constituted mainly of mitral cell apical dendrites, through the enhanced growth of these dendrites.

Neuronal networks in mental diseases and neuropathic pain: Beyond brain derived neurotrophic factor and collapsin response mediator proteins

The brain is a complex network system that has the capacity to support emotion, thought, action, learning and memory, and is characterized by constant activity, constant structural remodeling, and constant attempt to compensate for this remodeling. The basic insight that emerges from complex network organization is that substantively different networks can share common key organizational principles. Moreover, the interdependence of network organization and behavior has been successfully demonstrated for several specific tasks. From this viewpoint, increasing experimental/clinical observations suggest that mental disorders are neural network disorders. On one hand, single psychiatric disorders arise from multiple, multifactorial molecular and cellular structural/functional alterations spreading throughout local/global circuits leading to multifaceted and heterogeneous clinical symptoms. On the other hand, various mental diseases may share functional deficits across the same neural circuit as reflected in the overlap of symptoms throughout clinical diagnoses. An integrated framework including experimental measures and clinical observations will be necessary to formulate a coherent and comprehensive understanding of how neural connectivity mediates and constraints the phenotypic expression of psychiatric disorders.

Mouse pups lacking collapsin response mediator protein 4 manifest impaired olfactory function and hyperactivity in the olfactory bulb

Members of the collapsin response mediator protein (CRMP) family are reported to be involved in the pathogenesis of various neuronal disorders, including schizophrenia and autism. One of them, CRMP4, is reported to participate in aspects of neuronal development, such as axonal guidance and dendritic development. However, no physiological or behavioral phenotypes in Crmp4 knockout (Crmp4-KO) mice have been identified, making it difficult to elucidate the in vivo roles of CRMP4. Focusing on the olfaction process because of the previous study showing strong expression of Crmp4 mRNA in the olfactory bulb (OB) during the early postnatal period, it was aimed to test the hypothesis that Crmp4-KO pups would exhibit abnormal olfaction. Based on measurements of their ultrasonic vocalizations, impaired olfactory ability in Crmp4-KO pups was found. In addition, c-Fos expression, a marker of neuron activity, revealed hyperactivity in the OB of Crmp4-KO pups compared with wild-types following exposure to an odorant. Moreover, the mRNA and protein expression levels of glutamate receptor 1 (GluR1) and 2 (GluR2) were exaggerated in Crmp4-KO pups relative to other excitatory and inhibitory receptors and transporters, raising the possibility that enhanced expression of these excitatory receptors contributes to the hyperactivity phenotype and impairs olfactory ability. This study provides evidence for an animal model for elucidating the roles of CRMP4 in the development of higher brain functions as well as for elucidating the developmental regulatory mechanisms controlling the activity of the neural circuitry.

CRMP1 Inhibits Proliferation of Medulloblastoma and Is Regulated by HMGA1

Many facets of the tumor biology of medulloblastoma (MB) have not been fully elucidated. Collapsin response mediator protein 1 (CRMP1) is a member of cytoplasmic family of proteins that regulate the development of central nervous system. Recent studies demonstrated that CRMP1 could function as an invasion suppressor. We reported previously that high mobility group AT-hook 1 (HMGA1) contributed to development of MB and regulated its growth and migration/invasion. Transcriptional profiling and quantitative RT-PCR revealed increased expression of CRMP1 in HMGA1-depleted cells, suggesting that CRMP1 may be a downstream target of HMGA1 in MB. In this study, we showed HMGA1 can bind CRMP1 promoter by chromatin immunoprecipitation (ChIP) assay. Luciferase assay demonstrated a marked enhancement of CRMP1 transcription activity in HMGA1-depleted cells. Furthermore, quantitative RT-PCR revealed a negative correlation between HMGA1 and CRMP1 in 32 MB samples. To investigate the biological roles of CRMP1 in MB pathogenesis, we established MB clones stably expressing CRMP1. Functional analysis revealed that expression of CRMP1 significantly inhibited proliferation, migration, invasion and formation of filopodia and intense stress fiber of MB cells. Our data suggest that HMGA1 regulates CRMP1 expression and CRMP1 is implicated in MB pathogenesis.

Crystal structure of human CRMP-4: correction of intensities for lattice-translocation disorder

Collapsin response mediator proteins (CRMPs) are cytosolic phosphoproteins that are mainly involved in neuronal cell development. In humans, the CRMP family comprises five members. Here, crystal structures of human CRMP-4 in a truncated and a full-length version are presented. The latter was determined from two types of crystals, which were either twinned or partially disordered. The crystal disorder was coupled with translational NCS in ordered domains and manifested itself with a rather sophisticated modulation of intensities. The data were demodulated using either the two-lattice treatment of lattice-translocation effects or a novel method in which demodulation was achieved by independent scaling of several groups of intensities. This iterative protocol does not rely on any particular parameterization of the modulation coefficients, but uses the current refined structure as a reference. The best results in terms of R factors and map correlation coefficients were obtained using this new method. The determined structures of CRMP-4 are similar to those of other CRMPs. Structural comparison allowed the confirmation of known residues, as well as the identification of new residues, that are important for the homo- and hetero-oligomerization of these proteins, which are critical to nerve-cell development. The structures provide further insight into the effects of medically relevant mutations of the DPYSL-3 gene encoding CRMP-4 and the putative enzymatic activities of CRMPs.

Insights into the oligomerization of CRMPs: crystal structure of human collapsin response mediator protein 5

Collapsin response mediator protein-5 (CRMP-5) is the latest identified member of the CRMP cytosolic phosphoprotein family, which is crucial for neuronal development and repair. CRMPs exist as homo- and/or hetero-tetramers in vivo and participate in signaling transduction, cytoskeleton rearrangements, and endocytosis. CRMP-5 antagonizes many of the other CRMPs' functions either by directly interacting with them or by competing for their binding partners. We determined the crystal structures of a full length and a truncated version of human CRMP-5, both of which form a homo-tetramer similar to those observed in CRMP-1 and CRMP-2. However, solution studies indicate that CRMP-5 and CRMP-1 form weaker homo-tetramers compared with CRMP-2, and that divalent cations, Ca(2+) and Mg(2+), destabilize oligomers of CRMP-5 and CRMP-1, but promote CRMP-2 oligomerization. On the basis of comparative analysis of the CRMP-5 crystal structure, we identified residues that are crucial for determining the preference for hetero-oligomer or homo-oligomer formation. We also show that in spite of being the CRMP family member most closely related to dihydropyrimidinase, CRMP-5 does not have any detectable amidohydrolase activity. The presented findings provide new detailed insights into the structure, oligomerization, and regulation of CRMPs.

CRMP-2 is involved in axon growth inhibition induced by RGMa in vitro and in vivo

Repulsive guidance molecule-a (RGMa) is associated with axon growth inhibition in different central nervous system (CNS) injuries, but its signaling pathways remain unclear. We examined the involvement of collapsin response mediator protein-2 (CRMP-2), a common downstream target of Rho-kinase and GSK-3β, in vitro by culturing neonatal rat primary cortical neurons with RGMa protein, Rho-kinase inhibitor (Y-27632), and GSK-3β inhibitor. We examined CRMP-2 in vivo by suppressing RGMa expression using recombinant adenovirus (rAd-shRGMa) in a rat MCAO/reperfusion model. RGMa induced neurite retraction and CRMP-2 phosphorylation in vitro, which were reversed by either Rho-kinase or GSK-3β inhibitors. After MCAO/reperfusion in rats, pCRMP-2 protein was greatly increased in the ischemic cortex, axons were damaged severely, Neurofilament-200 (NF-200) expression was significantly decreased, and neurological deficits were significant, which were all improved by down-regulating RGMa. We concluded RGMa inhibits axon growth by phosphorylating CRMP-2 via both Rho-kinase and GSK-3β signaling pathways.

Insight into the role of CRMP2 (collapsin response mediator protein 2) in T lymphocyte migration: the particular context of virus infection

Lymphocyte migration into the central nervous system is a critical step in the physiopathology of a variety of neurological diseases, including multiple sclerosis and virus-induced neuroinflammation. To better understand the molecular mechanisms involved in cells migration, we focused our studies on collapsin response mediator proteins (CRMPs), a group of phosphoproteins that mediate neural cell motility. There is now evidence that collapsin response mediator protein 2 (CRMP2) plays critical roles in the polarization (uropod formation) of T lymphocytes and their subsequent migration. CRMP2 was known to respond to semaphorin, ephrin and neurotrophin signaling in neurons. The link between the chemokine CXCL12, CRMP2 activity and cell migration has been demonstrated in T lymphocytes. These observations and comparisons of the activity of CRMPs in immune and non-immmune cells are summarized here. The ability of a human retrovirus to enhance lymphocyte migration through the modulation of CRMP2 activity is also discussed. In conclusion, viruses have the ability to manipulate the lymphocyte motility machinery, intensifying neural tissue invasion in infected patients.

Age-related proteomic changes in the subventricular zone and their association with neural stem/progenitor cell proliferation

In the mammalian central nervous system, generation of new neurons persists in the subventricular zone (SVZ) throughout life. However, the capacity for neurogenesis in this region declines with aging. Recent studies have examined the degree of these age-related neurogenic declines and the changes of cytoarchitecture of the SVZ with aging. However, little is known about the molecular changes in the SVZ with aging. In this study, we dissected the SVZs from rats aged postnatal day 28, 3 months, and 24 months. The SVZ tissues were processed for 2-D gel electrophoresis to identify protein changes following aging. Protein spots were subsequently subjected to mass spectrometry analysis to compare age-related alterations in the SVZ proteome. We also examined the level of cell proliferation in the SVZ in animals of these three age groups by using bromodeoxyuridine labeling. We found significant age-related changes in the expression of several proteins that play critical roles in the proliferation and survival of neural stem/progenitor cells in the SVZ. Among these proteins, glial fibrillary acidic protein, ubiquitin carboxy terminal hydrolase 1, glutathione S-transferase omega, and preproalbumin were increased with aging, whereas collapsin response-mediated protein 4 (CRMP-4), CRMP-5, and microsomal protease ER60 exhibited declines with aging. We have also observed a significant decline of neural stem/progenitor cell proliferation in the SVZ with aging. These alterations in protein expression in the SVZ with aging likely underlie the diminishing proliferative capacity of stem/progenitor cells in the aging brain.

Combined age- and trauma-related proteomic changes in rat neocortex: a basis for brain vulnerability

This proteomic study investigates the widely observed clinical phenomenon, that after comparable brain injuries, geriatric patients fare worse and recover less cognitive and neurologic function than younger victims. Utilizing a rat traumatic brain injury model, sham surgery or a neocortical contusion was induced in 3 age groups. Geriatric (21 months) rats performed worse on behavioral measures than young adults (12-16 weeks) and juveniles (5-6 weeks). Motor coordination and certain cognitive deficits showed age-dependence both before and after injury. Brain proteins were analyzed using silver-stained two-dimensional electrophoresis gels. Spot volume changes (>2-fold change, p<0.01) were identified between age and injury groups using computer-assisted densitometry. Sequences were determined by mass spectrometry of tryptic peptides. The 19 spots identified represented 13 different genes that fell into 4 general age- and injury-dependent expression patterns. Fifteen isoforms changed differentially with respect to both age and injury (p<0.05). Further investigations into the nature and function of these isoforms may yield insights into the vulnerability of older patients and resilience of younger patients in recovery after brain injuries.

CRMP5 regulates generation and survival of newborn neurons in olfactory and hippocampal neurogenic areas of the adult mouse brain

The Collapsin Response Mediator Proteins (CRMPS) are highly expressed in the developing brain, and in adult brain areas that retain neurogenesis, ie: the olfactory bulb (OB) and the dentate gyrus (DG). During brain development, CRMPs are essentially involved in signaling of axon guidance and neurite outgrowth, but their functions in the adult brain remain largely unknown. CRMP5 has been initially identified as the target of auto-antibodies involved in paraneoplasic neurological diseases and further implicated in a neurite outgrowth inhibition mediated by tubulin binding. Interestingly, CRMP5 is also highly expressed in adult brain neurogenic areas where its functions have not yet been elucidated. Here we observed in both neurogenic areas of the adult mouse brain that CRMP5 was present in proliferating and post-mitotic neuroblasts, while they migrate and differentiate into mature neurons. In CRMP5(-/-) mice, the lack of CRMP5 resulted in a significant increase of proliferation and neurogenesis, but also in an excess of apoptotic death of granule cells in the OB and DG. These findings provide the first evidence that CRMP5 is involved in the generation and survival of newly generated neurons in areas of the adult brain with a high level of activity-dependent neuronal plasticity.

Proteomic analysis of zebrafish brain tissue following exposure to the pesticide prochloraz

The hypothalamus-pituitary-gonadal (HPG) axis plays a central role in the maintenance of homeostasis and disruptions in its function can have important implications for reproduction and other critical biological processes. A number of compounds found in aquatic environments are known to affect the HPG axis. In the present study, we used two-dimensional electrophoresis to investigate the proteome of female and male zebrafish brain after 96 h exposure to the fungicide prochloraz. Prochloraz has known effects on a number of key HPG molecules, including antagonism of Cyp17 and Cyp19 (aromatase). Twenty-eight proteins were shown to be differentially expressed in the brains of females and 22 in males. Proteins were identified using LC-MS/MS and identities were examined relative to brain function in the context of changing steroid hormone levels. There was little overlap between sexes in proteins exhibiting differential expression. Proteins with known roles in metabolism, learning, neuroprotection, and calcium regulation were determined to be differentially regulated. Relationships between identified proteins were also examined using Ingenuity Pathway Analysis, and females were shown to exhibit enrichment of several metabolic pathways. We used differentially expressed proteins to establish a putative classifier consisting of three proteins that was able to discriminate prochloraz-exposed from control females. Putatively impacted brain functions and specific protein changes that were observed have the potential to be generalized to other that similarly impact steroid hormone levels.

Proteomic analysis of a model fish species exposed to individual pesticides and a binary mixture

Pesticides are nearly ubiquitous in surface waters of the United States, where they often are found as mixtures. The molecular mechanisms underlying the toxic effects of sub-lethal exposure to pesticides as both individual and mixtures are unclear. The current work aims to identify and compare differentially expressed proteins in brains of male fathead minnows (Pimephales promelas) exposed for 72 h to permethrin (7.5 μg/L), terbufos (57.5 μg/L) and a binary mixture of both. Twenty-four proteins were found to be differentially expressed among all three treatments relative to the control using an ANOVA followed by a Dunnett's post hoc test (p ≤0.05). One protein was found to be differentially expressed among all treatment groups and one protein was in common between the terbufos and the mixture group. Fifteen spots were successfully sequenced using LC-MS/MS sequencing. Proteins associated with the ubiquitin-proteasome system, glycolysis, the cytoskeleton and hypoxia were enriched. As a second objective, we attempted to establish protein expression signatures (PES) for individual permethrin and terbufos exposures. We were unable to generate a useable PES for terbufos; however, the permethrin PES was able to distinguish between control and permethrin-exposed individuals in an independent experiment with an accuracy of 87.5%. This PES also accurately classified permethrin exposed individuals when the exposure occurred as part of a mixture. The identification of proteins differentially expressed as a result of pesticide exposure represent a step forward in the understanding of mechanisms of toxicity of permethrin and terbufos. They also allow a comparison of molecular responses of the binary mixture to single exposures. The permethrin PES is the first step in establishing a method to determine exposures in real-world scenarios.

Responses in the brain proteome of Atlantic cod (Gadus morhua) exposed to methylmercury

The molecular mechanisms underlying the neurotoxicity of methylmercury (MeHg), a ubiquitous environmental contaminant, are not yet fully understood. Furthermore, there is a lack of biomarkers of MeHg neurotoxicity for use in environmental monitoring. We have undertaken a proteomic analysis of brains from Atlantic cod (Gadus morhua) exposed to 0, 0.5 and 2 mg/kg MeHg administered by intraperitoneal injection. The doses were given in two injections, half of the dose on the first day and the second half after 1 week, and the total exposure period lasted 2 weeks. Using 2-DE coupled with MALDI-TOF MS and MS/MS, we observed the level of 71 protein spots to be 20% or more significantly altered following MeHg exposure, and successfully identified 40 of these protein spots. Many of these proteins are associated with main known molecular targets and mechanisms of MeHg-induced neurotoxicity in mammals, such as mitochondrial dysfunction, oxidative stress, altered calcium homeostasis and tubulin/disruption of microtubules. More interestingly, several of the affected proteins, with well-established or recently demonstrated critical functions in nervous system-specific processes, have not previously been associated with MeHg exposure in any species. These proteins include the strongest up-regulated protein, pyridoxal kinase (essential for synthesis of several neurotransmitters), G protein (coupled to neurotransmitter receptors), nicotinamide phosphoribosyl-transferase (protection against axonal degeneration), dihydropyrimidinase-like 5 (or collapsin response mediator protein 5, CRMP-5) (axon guidance and regeneration), septin (dendrite development), phosphatidylethanolamine binding protein (precursor for hippocampal cholinergic neurostimulating peptide) and protein phosphatase 1 (control of brain recovery by synaptic plasticity). The results of the present study aid our understanding of molecular mechanisms underlying MeHg neurotoxicity and defense responses, and provide a large panel of protein biomarker candidates for aquatic environmental monitoring.

Behavioral and quantitative mitochondrial proteome analyses of the effects of simvastatin: implications for models of neural degeneration

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, simvastatin, is used for lowering elevated low-density lipoprotein cholesterol concentrations. This translates into reduced cardiovascular disease-related morbidity and mortality, while the drugs' anti-oxidant and anti-inflammatory properties have earmarked it as a potential treatment strategy against various neurological conditions. Statins have been shown to protect neurons from degeneration in a number of animal models. Although no mechanism completely explains the multiple benefits exerted by statins, emerging evidence suggests that in some degenerative and brain injury models, mitochondrial impairment may play a contributive rate. However, [corrected] evidence lacks to support a directly influencing role for statins on mitochondria-related proteins and motor behavior. Mitochondrial dysfunction may increase oxygen free radical production, which in turn leaves cells susceptible to energy failure, apoptosis and related events [corrected] which could prove fatal. The potential link between simvastatin treatment and mitochondrial function would be supported if key mitochondrial proteins were altered by simvastatin exposure. Using mass spectroscopy (MS), we identified 24 mitochondrial proteins that differed significantly (P < 0.05) in relative abundancy as a result of simvastatin treatment. The identified proteins represented many facets of mitochondrial integrity, with the majority forming part of the electron transport chain machinery, which is necessary for energy production. In a follow-up study, we then addressed whether simvastatin is capable of altering sensorimotor function in a mitochondrial toxin-induced animal model. Rats were pre-treated with simvastatin for 14 days, followed by a single unihemispheric (substantia nigra; SN) injection of rotenone, a mitochondrial complex I (Co-I) inhibitor. Results showed that simvastatin improved motor performance in rotenone-infused rats. The data are consistent with the possibility that alteration of mitochondrial function may contribute to the beneficial effects associated with statin use.

Gene expression profiles of rat olfactory bulb at developmental stage

Microarray analysis may be a useful tool to identify some candidate genes related to the development of olfactory bulbs. In the present study, gene expression profiles of olfactory bulbs from postnatal day 1 (P1) rats and postnatal day 35 (P35) rats were analyzed by oligonucleotide-microarray and expression levels of some selected genes were also confirmed by RT-PCR and in situ hybridization. 9146 genes were commonly identified in six microarray chips. Among these genes, 76 were up-regulated and 130 were down-regulated three-folds or more at P1 olfactory bulbs. Out of these 76 up-regulated genes, 24 genes were annotated based on the NCBI database of reference sequences and expression levels of these 24 genes were confirmed by RT-PCR. Among them, 2 interesting genes (neurogenic differentiation 1 and retinoid acid receptor alpha) were localized in the P1 olfactory bulb by the use of in situ hybridization technique. Our results may provide basic information to identify genes associated with functional growth of olfactory bulbs.

Extensive expression of collapsin response mediator protein 5 (CRMP5) is a specific marker of high-grade lung neuroendocrine carcinoma

The diagnosis of high-grade neuroendocrine tumors has strong clinical relevance because it identifies patients at higher risk of an unfavorable outcome who should receive multimodal treatment. However, these tumors can be mistaken for poorly differentiated nonsmall cell carcinoma or carcinoid lung tumors. In fact, no immunohistochemical marker can currently distinguish between histologic lung subtypes. Because the collapsin response mediator protein (CRMP) family is involved in an autoimmune disease associated with small cell lung carcinoma, we explored the relationship between CRMP5 expression and lung tumor behavior. Using World Health Organization morphologic criteria, 123 lung neuroendocrine tumors and 41 randomly selected non-neuroendocrine tumors were classified. CRMP5 protein expression in tumors, metastases, and healthy lung tissue was assessed using immunostaining method. Strong and extensive CRMP5 expression was seen in 98.6% of high-grade neuroendocrine lung tumors, including small cell lung carcinoma and large cell lung neuroendocrine carcinoma, but not in any of the squamous cell carcinomas or lung adenocarcinomas in our series. In contrast, the majority of low-grade neuroendocrine lung tumors were negative for CRMP5 staining, although weak CRMP5 expression was seen in some, with 2 different staining patterns of either scattered positive cells or small foci of positive cells. Our findings point at CRMP5 as a novel marker for routine pathologic evaluation of lung tumors surgical samples in distinguishing between highly aggressive neuroendocrine carcinoma and the other lung cancers.

A comparative analysis of leucine-rich repeat kinase 2 (Lrrk2) expression in mouse brain and Lewy body disease

Pathogenic substitutions in leucine-rich repeat kinase 2 (LRRK2, Lrrk2) have been genetically linked to familial, late-onset Parkinsonism. End-stage disease is predominantly associated with nigral neuronal loss and Lewy body pathology, but patients may have gliosis, tau or ubiquitin inclusions (pleomorphic pathology). The anatomical distribution of Lrrk2 protein may provide insight into its function in health and neurodegeneration, thus we performed a comparative study with 'in-house' and commercially available Lrrk2 antibodies using brain tissue from wild type and human Lrrk2 transgenic bacterial artificial chromosome (BAC) mice, and from diffuse Lewy body disease (DLBD) patients. Lrrk2 protein was ubiquitously expressed and relatively abundant in most brain regions, including the substantia nigra, thalamus and striatum. Lrrk2 was not a major component of Lewy body or neuritic pathology associated with Parkinson's disease. However, selective loss of dopaminergic neurons in Lrrk2-associated Parkinsonism argues the protein may have regional-specific interactions. Lrrk2 immunohistochemical staining was present in the subventricular zone, a region containing stem cells that give rise to both neurons and glia. A role for Lrrk2 in neurogenesis might provide further insight into the aberrant role of mutant protein in age-associated neurodegeneration with pleomorphic pathology.

Mice deficient in collapsin response mediator protein-1 exhibit impaired long-term potentiation and impaired spatial learning and memory

Collapsing response mediator protein-1 (CRMP-1) was initially identified in brain and has been implicated in plexin-dependent neuronal function. The high amino acid sequence identity among the five CRMPs has hindered determination of the functions of each individual CRMP. We generated viable and fertile CRMP-1 knock-out (CRMP-1(-/-)) mice with no evidence of gross abnormality in the major organs. CRMP-1(-/-) mice exhibited intense microtubule-associated protein 2 (MAP2) staining in the proximal portion of the dendrites, but reduced and disorganized MAP2 staining in the distal dendrites of hippocampal CA1 pyramidal cells. Immunoreactivity to GAP-43 (growth-associated protein-43) and PSD95 (postsynaptic density-95) (a postsynaptic membrane adherent cytoskeletal protein) was also decreased in the CA1 region of the knock-out mice. These changes were consistent with the mutant mice showing a reduction in long-term potentiation (LTP) in the CA1 region and impaired performance in hippocampal-dependent spatial learning and memory tests. CRMP-1(-/-) mice showed a normal synapsin I labeling pattern in CA1 and normal paired-pulse facilitation. These findings provide the first evidence suggesting that CRMP-1 may be involved in proper neurite outgrowth in the adult hippocampus and that loss of CRMP-1 may affect LTP maintenance and spatial learning and memory.

Proteomic analysis of γ-butyrolactone-treated mouse thalamus reveals dysregulated proteins upon absence seizure

Absence seizure has been of interest because the symptom is related to sensory processing. However, the mechanism that causes the disease is not understood yet. To better understand the molecular mechanism related to the disease progress at protein level, we performed proteomic studies using the thalamus of mice for which absence seizure was induced by gamma-butyrolactone (GBL). Differential proteome expression between GBL-treated mice and control mice was examined by fluorescence 2D difference gel electrophoresis (DIGE) at three different time points (5, 10, and 30 min) after GBL-administration. We identified 16 proteins differentially expressed by >1.4-fold at any of the three time points. All proteins besides the serine protease inhibitor EIA were down-regulated in absence seizure-induced mice. The down-regulated proteins can be classified into five groups by their biological functions: cytoskeleton rearrangement, neuroprotection, neurotransmitter secretion, calcium binding, and metabolism. The maximum level of change was reached by 10 min after GBL-treatment, with the expression level returning back to the original at 30 min when mice were awakened from absence seizure thereby demonstrating the proteomic response is reversible. Our results suggest that absence seizures are associated with restricted functional sets of proteins, whose down-regulation may interfere with general function of neuronal cells.

The CRMP family of proteins and their role in Sema3A signaling

The CRMP proteins were originally identified as mediators of Sema3A signaling and neuronal differentiation. Much has been learned about the mechanism by which CRMPs regulate cellular responses to Sema3A. In this review, the evidence for CRMP as a component of the Sema3A signaling cascade and the modulation of CRMP by plexin and phosphorylation are considered. In addition, current knowledge of the function of CRMP in a variety of cellular processes, including regulation of the cytoskeleton and endocytosis, is discussed in relationship to the mechanisms of axonal growth cone Sema3A response. The secreted protein Sema3A (collapsin-1) was the first identified vertebrate semaphorin. Sema3A acts primarily as a repulsive axon guidance cue, and can cause a dramatic collapse of the growth cone lamellipodium. This process results from the redistribution of the F-actin cytoskeleton and endocytosis of the growth cone cell membrane. Neuropilin-1 (NP1) and members of the class A plexins (PlexA) form a Sema3A receptor complex, with NP1 serving as a high-affinity ligand binding partner, and PlexA transducing the signal into the cell via its large intracellular domain. Although the effect of Sema3A on growth cones was first described nearly 15 years ago, the intracellular signaling pathways that lead to the cellular effects have only recently begun to be understood. Monomeric G-proteins, various kinases, the redox protein, MICAL, and protein turnover have all been implicated in PlexA transduction. In addition, the collapsin-response-mediator protein (CRMP) family of cytosolic phosphoproteins plays a crucial role in Sema3A/NP1/PlexA signal transduction. Current knowledge regarding CRMP functions are reviewed here.

Transient alterations in granule cell proliferation, apoptosis and migration in postnatal developing cerebellum of CRMP1?/?mice

Collapsin response mediator proteins (CRMPs) consist of five homologous cytosolic proteins that participate in signal transduction involved in a variety of physiological events. CRMP1 is highly expressed during brain development; however, its functions remains unclear. To gain insight into its function, we generated CRMP1(-/-) mice with a knock-in LacZ gene. No gross anatomical changes or behavioral alterations were observed. Expression of CRMP1 was examined by the expression of the knocked-in LacZ gene, in situ hybridization with riboprobes and by imunohistochemistry. CRMP1 was found to be highly expressed in the developing the cerebellum, olfactory bulbs, hypothalamus and retina. In adults, expression level was high in the olfactory bulbs and hippocampus but very low in the retina and cerebellum and undetectable in hypothalamus. To study potential roles of CRMP1, we focused on cerebellum development. CRMP1(-/-) mice showed a decrease in the number of granule cells migrating out of explants of developing cerebellum, as did treatment of the explants from normal mice with anti-CRMP1 specific antibodies. CRMP1(-/-) mice showed a decrease in granule cell proliferation and apoptosis in external granule cell layers in vivo. Adult cerebellum of CRMP1(-/-) did not show any abnormalities.

Age-dependent alterations in CRMP2 and CRMP4 protein expression profiles in cat visual cortex

We monitored the protein expression profiles of collapsin response mediator protein 2 and 4 (CRMP2 and CRMP4) throughout cat primary visual area 17 at different postnatal ages. Single immunocytochemical stainings revealed a clear effect of cortical maturation on the spatial and laminar distribution profile of CRMP2 and CRMP4. In kittens of postnatal day 10 (P10) and 30 (P30), CRMP2 and CRMP4 immunoreactivity was exclusively present in fibers running perpendicular to the cortical surface and crossing all cortical layers, but was never found in neuronal cell bodies. The immunoreactive fibers were embedded in an intensely and homogeneously stained neuropil. In contrast, mature visual cortex immunocytochemistry located CRMP2 and CRMP4 in the somatodendritic compartment of neurons with a clear CRMP-specific lamination pattern. Similar to kitten, neuropil staining was clearly observed but showed a decreasing gradient from layer I to VI in adult area 17. Detailed analysis of cellular morphology and size classified the CRMP2- and CRMP4-immunopositive cells in distinct neuronal populations. Double labeling of CRMP2 or CRMP4 with the typical interneuron marker parvalbumin (PV) showed many double-labeled cells immunoreactive for CRMP4 and PV, but not for CRMP2 and PV, corroborating the cell type-specific character of each CRMP. Our present results clearly illustrate that CRMP2 and CRMP4 may play an important role in visual cortex, possibly providing different classes of neurons with the potential to form a functionally meaningful network, not only during development, but also in adulthood, coincident with the belief that CRMPs are involved in neurite growth and guidance.