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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 pCRMP1may be involved in the pathogenesis of axonopathy in ALS, leading to spheroid formation through the proximal progression of axonopathy. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Leukocyte common antigen related (LAR) class protein tyrosine phosphatases (PTPs) are critical for axonal guidance; however, their relation to specific guidance cues is poorly defined. We here show that PTP-3, LAR homologue in C. elegans, is involved in axon guidance regulated by Sema2A-signaling. PTPd, one of vertebrate LAR class PTPs, participates in Sema3A-induced growth cone collapse response of primary cultured dorsal root ganglion neurons from M. musculus embryos. In vivo, however, the contribution of PTPδ in Sema3A-regualted axon guidance was minimal. Instead, PTPδ played a major role in Sema3A-dependent cortical dendritic growth. Ptpδ-/- and Sema3a-/- mutant mice exhibited poor arborization of basal dendrites of cortical layer V neurons. This phenotype was observed in both male and female mutants. The double heterozygous mutants, Ptpδ+/-; Sema3a+/-, also showed a similar phenotype, indicating the genetic interaction. In Ptpδ-/- brains, Fyn and Src kinases were hyperphosphorylated at their C-terminal Tyr527 residues. Sema3A-stimulation induced dephosphorylation of Tyr527 in the dendrites of wild-type cortical neurons but not of Ptpδ-/-. Arborization of cortical basal dendrites was reduced in Fyn-/- as well as in Ptpδ+/-; Fyn+/- double heterozygous mutants. Collectively, PTPδ mediates Sema3A-signaling through the activation of Fyn by C-terminal dephosphorylation. [ABSTRACT FROM AUTHOR]

Semaphorin 3A (Sema3A), a secretory semaphorin, exerts various biological actions through a complex between neuropilin-1 and plexin-As (PlexAs). Sema3A induces retrograde signaling, which is involved in regulating dendritic localization of GluA2 (also known as GRIA2), an AMPA receptor subunit. Here, we investigated a possible interaction between retrograde signaling pathways for Sema3A and nerve growth factor (NGF). Sema3A induces colocalization of PlexA4 (also known as PLXNA4) signals with those of tropomyosin-related kinase A (TrkA, also known as NTRK1) in growth cones, and these colocalized signals were then observed along the axons. The timelapse imaging of PlexA4 and several TrkA mutants showed that the kinase and dynein-binding activity of TrkAwere required for Sema3A-induced retrograde transport of the PlexA4--TrkA complex along the axons. The inhibition of the phosphoinositide 3-kinase (PI3K)--Akt signal, a downstream signaling pathway of TrkA, in the distal axon suppressed Sema3A-induced dendritic localization of GluA2. The knockdown of TrkA suppressed Sema3A-induced dendritic localization of GluA2 and that suppressed Sema3A-regulated dendritic branching both in vitro and in vivo. These findings suggest that by interacting with PlexA4, TrkA plays a crucial role in redirecting local Sema3A signaling to retrograde axonal transport, thereby regulating dendritic GluA2 localization and patterning. [ABSTRACT FROM AUTHOR]

Semaphorin 3A (Sema3A), originally identified as a potent growth cone collapsing factor in developing sensory neurons, is now recognized as a key player in immune, cardiovascular, bone metabolism and neurological systems. Here we established an anti-Sema3A monoclonal antibody that neutralizes the effects of Sema3A both in vitro and in vivo. The anti-Sema3A neutralization chick IgM antibodies were screened by combining an autonomously diversifying library selection system and an in vitro growth cone collapse assay. We further developed function-blocking chick-mouse chimeric and humanized anti-Sema3A antibodies. We found that our anti-Sema3A antibodies were effective for improving the survival rate in lipopolysaccharide-induced sepsis in mice. Our antibody is a potential therapeutic agent that may prevent the onset of or alleviate symptoms of human diseases associated with Sema3A. [ABSTRACT FROM AUTHOR]

Reorganization of the actin cytoskeleton is an early cellular response to various extracellular signals. Sema3A, a repulsive axon guidance molecule, induces the reorganization of actin cytoskeleton in the growth cones. Collapsin response mediator protein 1 (CRMP1) mediates the intracellular Sema3A signalling through its Ser522 phosphorylation. Here we show that UNC-33, CRMP1 C. elegans homologue, interacts with FLN-1, an actin-binding Filamin-A orthologue. In nematodes, this interaction participates in the projection of DD/VD motor neurons. CRMP1 binds both the actin-binding domain and the last immunoglobulin-like repeat of Filamin-A. The alanine mutants of Filamin-A or CRMP1 in their interacting residues suppress the Sema3A repulsion in neurons. Conversely, a phosphor-mimicking mutant CRMP1(Ser522Asp) enhances the Sema3A response. Atomic-force microscopy analysis reveals that the V-shaped Filamin-A changes to a condensed form with CRMP1(Ser522Asp). CRMP1(Ser522Asp) weakens the F-actin gelation crosslinked by Filamin-A. Thus, phosphorylated CRMP1 may remove Filamin-A from the actin cytoskeleton to facilitate its remodelling. [ABSTRACT FROM AUTHOR]

Collapsin response mediator protein 1 (CRMP1) is one of the CRMP family members that are involved in various aspects of neuronal development such as axonal guidance and neuronal migration. Here we provide evidence that crmp1-/- mice exhibited behavioral abnormalities related to schizophrenia. The crmp1-/- mice exhibited hyperactivity and/or impaired emotional behavioral phenotype. These mice also exhibited impaired context-dependent memory and long-term memory retention. Furthermore, crmp1-/- mice exhibited decreased prepulse inhibition, and this phenotype was rescued by administration of chlorpromazine, a typical antipsychotic drug. In addition, in vivo microdialysis revealed that the methamphetamine-induced release of dopamine in prefrontal cortex was exaggerated in crmp1-/- mice, suggesting that enhanced mesocortical dopaminergic transmission contributes to their hyperactivity phenotype. These observations suggest that impairment of CRMP1 function may be involved in the pathogenesis of schizophrenia. We propose that crmp1-/- mouse may model endophenotypes present in this neuropsychiatric disorder. [ABSTRACT FROM AUTHOR]

Collapsin response mediator proteins (CRMPs) are intracellular proteins that mediate signals for several extracellular molecules, such as Semaphorin3A and neurotrophins. The phosphorylation of CRMP1 and CRMP2 by Cdk5 at Ser522 is involved in axonal guidance and spine development. Here, we found that the Ser522-phosphorylated CRMP1 and/or CRMP2 are enriched in the dendrites of cultured cortical neurons and P7 cortical section. To determine the physiological role of CRMPs in dendritic development, we generated CRMP2 knock-in mutant mice (crmp2ki/ki) in which the Ser residue at 522 was replaced with Ala. Strikingly, the cortical basal dendrites of double mutant crmp2ki/ki and crmp1-/- mice exhibited severe abnormal dendritic patterning, which we defined as "curling phenotype." These findings demonstrate that the function of CRMP1 and CRMP2 synergistically control dendritic projection, and the phosphorylation of CRMP2 at Ser522 is essential for proper dendritic field organization in vivo. [ABSTRACT FROM AUTHOR]

The abilityto detect harmful chemicals rapidly is essentialforthe survival of all animals. In Caenorhabditis elegans(C. elegans), repellents trigger an avoidance response, causing animals to move away from repellents. Dihydrocaffeic acid (DHCA) is a water-soluble repellent and nonflavonoid catecholic compound that can be found in plant products. Using a Xenopus laevis(X. laevis) oocyte expression system, we identified a candidate dihydrocaffeic acid receptor (DCAR), DCAR-1. DCAR-1 is a novel seven-transmembrane protein that is expressed in the ASH avoidance sensory neurons of C. elegans. dcar-1 mutant animals are defective in avoidance response to DHCA, and cell-specific expression of dcar-1 in the ASH neurons of dcar-1 mutant animals rescued the defect in avoidance response to DHCA. Our findings identify DCAR-1 as the first seven-transmembrane receptor required for avoidance of a water-soluble repellent, DHCA, in C. elegans. [ABSTRACT FROM AUTHOR]

Semaphorin3A (Sema3A) is a secreted type of axon guidance molecule that regulates axon wiring through complexes of neuropilin-1 (NRP1) with PlexinA protein receptors. Sema3A regulates the dendritic branching through tetrodotoxin (TTX)-sensitive retrograde axonal transport of PlexA proteins and tropomyosin-related kinase A (TrkA) complex. We here demonstrate that Nav1.7 (encoded by SCN9A), a TTX-sensitive Na+ channel, by coupling with collapsin response mediator protein 1 (CRMP1), mediates the Sema3A-induced retrograde transport. In mouse dorsal root ganglion (DRG) neurons, Sema3A increased co-localization of PlexA4 and TrkA in the growth cones and axons. TTX treatment and RNAi knockdown of Nav1.7 sustained Sema3A-induced colocalized signals of PlexA4 and TrkA in growth cones and suppressed the subsequent localization of PlexA4 and TrkA in distal axons. A similar localization phenotype was observed in crmp1-/- DRG neurons. Sema3A induced colocalization of CRMP1 and Nav1.7 in the growth cones. The half maximal voltage was increased in crmp1-/- neurons when compared to that in wild type. In HEK293 cells, introduction of CRMP1 lowered the threshold of co-expressed exogenous Nav1.7. These results suggest that Nav1.7, by coupling with CRMP1, mediates the axonal retrograde signaling of Sema3A. [ABSTRACT FROM AUTHOR]