Collapsin response mediator protein-2 hyperphosphorylation is an early event in Alzheimer's disease progression (original) (raw)
Related papers
Brain, 2007
Neuritic abnormalities are a major hallmark of Alzheimer's disease (AD) pathology. Accumulation of b-amyloid protein (Ab) in the brain causes changes in neuritic processes in individuals with this disease. In this study, we show that Ab decreases neurite outgrowth from SH-SY5Y human neuroblastoma cells. To explore molecular pathways by which Ab alters neurite outgrowth, we examined the activation and localization of RhoA and Rac1 which regulate the level and phosphorylation of the collapsin response mediator protein-2 (CRMP-2). Ab increased the levels of the GTP-bound (active) form of RhoA in SH-SY5Ycells. This increase in GTP-RhoA correlated with an increase in an alternatively spliced form of CRMP-2 (CRMP-2A) and its threonine phosphorylated form. Both a constitutively active form of Rac1 (CA-Rac1) and the Rho kinase inhibitor,Y27632, decreased levels of the CRMP-2A variant and decreased threonine phosphorylation caused by Ab stimulation. The amount of tubulin bound to CRMP-2 was decreased in the presence of Ab but Y27632 increased the levels of tubulin bound to CRMP-2. Increased levels of both RhoA and CRMP-2 were found in neurons surrounding amyloid plaques in the cerebral cortex of the APP(Swe) Tg2576 mice. We found that there was an increase in threonine phosphorylation of CRMP-2 inTg2576 mice and the increase correlated with a decrease in the ability of CRMP-2 to bind tubulin. The results suggest that Ab-induced neurite outgrowth inhibition may be initiated through a mechanism in which Ab causes an increase in Rho GTPase activity which, in turn, phosphorylates CRMP-2 to interfere with tubulin assembly in neurites.
Neuroscience Research, 2013
Alzheimer's disease (AD) is characterized by amyloid- (A) protein and tau deposition in the brain. Numerous studies have reported a central role of A in the development of AD, but the pathogenesis is not well understood. Collapsin response mediator protein 2 (CRMP2), an intracellular protein mediating a repulsive axon guidance molecule, Semaphorin3A, is also accumulated in neurofibrillary tangles in AD brains. To gain insight into the role of CRMP2 phosphorylation in AD pathogenesis, we investigated the effects of A neurotoxicity in CRMP2 phosphorylation-deficient knock-in (crmp2 ki/ki ) mice, in which the serine residue at 522 was replaced with alanine. Intracerebroventricular (i.c.v.) injection of A 25-35 peptide, a neurotoxic fragment of A protein, to wild-type (wt) mice increased hippocampal phosphorylation of CRMP2. Behavioral assessment revealed that i.c.v. injection of A 25-35 peptide caused impairment of novel object recognition in wt mice, while the same peptide did not in crmp2 ki/ki mice. In electrophysiological recording, wt and crmp2 ki/ki mice have similar input-output basal synaptic transmission and paired-pulse ratios. However, long-term potentiation was impaired in hippocampal slices of A 25-35 peptide-treated wt but not those of crmp2 ki/ki . Our findings indicate that CRMP2 phosphorylation is required for A-induced impairment of cognitive memory and synaptic plasticity.
Molecular Neurodegeneration, 2011
Background: Recent studies suggest that the pathogenic process in neurodegenerative disorders may disrupt mature neuronal circuitries and neurogenesis in the adult brain. Abnormal activation of CDK5 is associated with neurodegenerative disorders, and recently a critical role for CDK5 in adult neurogenesis has been identified. We have developed an in vitro model of abnormal CDK5 activation during adult hippocampal neurogenesis, and here we used this model to investigate aberrantly phosphorylated downstream targets of CDK5. Results: Abnormal CDK5 activation in an in vitro model of adult neurogenesis results in hyperphosphorylation of collapsin-response mediator protein-2 (CRMP2) and impaired neurite outgrowth. Inhibition of CDK5, or expression of a non-phosphorylatable (S522A) CRMP2 construct reduced CRMP2 hyperphosphorylation, and reversed neurite outgrowth deficits. CRMP2 plays a role in microtubule dynamics; therefore we examined the integrity of microtubules in this model using biochemical and electron microscopy techniques. We found that microtubule organization was disrupted under conditions of CDK5 activation. Finally, to study the relevance of these findings to neurogenesis in neurodegenerative conditions associated with HIV infection, we performed immunochemical analyses of the brains of patients with HIV and transgenic mice expressing HIV-gp120 protein. CDK5-mediated CRMP2 phosphorylation was significantly increased in the hippocampus of patients with HIV encephalitis and in gp120 transgenic mice, and this effect was rescued by genetic down-modulation of CDK5 in the mouse model.
increases neuronal CRMP-2 phosphorylation
2016
Neuritic abnormalities are a major hallmark of Alzheimer's disease (AD) pathology. Accumulation of b-amyloid protein (Ab) in the brain causes changes in neuritic processes in individuals with this disease. In this study, we show that Ab decreases neurite outgrowth from SH-SY5Y human neuroblastoma cells. To explore molecular pathways by which Ab alters neurite outgrowth, we examined the activation and localization of RhoA and Rac1 which regulate the level and phosphorylation of the collapsin response mediator protein-2 (CRMP-2). Ab increased the levels of the GTP-bound (active) form of RhoA in SH-SY5Ycells. This increase in GTP-RhoA correlated with an increase in an alternatively spliced form of CRMP-2 (CRMP-2A) and its threonine phosphorylated form. Both a constitutively active form of Rac1 (CA-Rac1) and the Rho kinase inhibitor,Y27632, decreased levels of the CRMP-2A variant and decreased threonine phosphorylation caused by Ab stimulation. The amount of tubulin bound to CRMP-2 was decreased in the presence of Ab but Y27632 increased the levels of tubulin bound to CRMP-2. Increased levels of both RhoA and CRMP-2 were found in neurons surrounding amyloid plaques in the cerebral cortex of the APP(Swe) Tg2576 mice. We found that there was an increase in threonine phosphorylation of CRMP-2 inTg2576 mice and the increase correlated with a decrease in the ability of CRMP-2 to bind tubulin. The results suggest that Ab-induced neurite outgrowth inhibition may be initiated through a mechanism in which Ab causes an increase in Rho GTPase activity which, in turn, phosphorylates CRMP-2 to interfere with tubulin assembly in neurites.
Are novel genes for early-onset Alzheimer's disease to be expected?
Neurobiol Aging, 2000
I produces a phosphoprotein that is a substrate for the mitotic regulator, Pin], and that binding of Pin1 to phosphothr 231 tau alters the conformation of the protein, as assessed by the ability to promote microtubule assembly. There is good evidence that this phosphorylation of tau occurs very early in the course of Alzheimer neurodegeneration and is probably the result of cdc2-like activity. There is also evidence that Pin] is associated with paired helical filaments (PHF) of tau, both after isolation and in situ. One hypothesis that appears reasonable proposes that confomxttional changes in tau produced by Pin1 prolyl isomerization facilitates aggregation of phosphotau into PHF. This aggregation may require or be enhanced by additional phosphorylation events, particularly those in the C-terminus of tau. We have discovered that the amyloid precursor protein (APP) also has a phosphoepitope to which Pin] will bind with high affinity. Cdc2 phosphorylation of APP on threonine 668 creates a site at which Pin1 binds with very similar kinetics to the binding to phosphothr 231 of tau. These two phosphoepitopes appear to have a strikingly similar conformation: monoclonal antibodies raised to the phosphoAPP epitope react with phosphothr 231 of tau, and vice versa. These antibodies do not react with a large number of other phosphopeptides. Monoclonal antibodies which appear to be specttic for the phosphothr 668 of APP have also been produced. Staining of AD brain tissues with these antibodies reveals the occurrence of this epitope in hippocampal and coliical neurons, and staining appears to be limited to those neurons in which phosphothr 23 I of tau can also be detected. This work raises the posrihihty that both tau and APP are phoaphorylated by cdc2 OT a related enzyme early in the course of AD neurodegeneration. For tau, this phoaphorylation appears to lead to Pm I binding and conformational changes. The consequences of this phosphorylation (and perhaps Pin] binding) for APP are not yet clear.
Genes to Cells, 2005
Collapsin response mediating protein-2 (CRMP2) has been identified as an intracellular protein mediating Semaphorin3A (Sema3A), a repulsive guidance molecule. In this study, we demonstrate that cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3β β β β (GSK3β β β β ) plays a critical role in Sema3A signalling. In In vitro kinase assay, Cdk5 phosphorylated CRMP2 at Ser522, while GSK3β β β β did not induce any phosphorylation of CRMP2. Phosphorylation by GSK3β β β β was exclusively observed in Cdk5-phosphorylated CRMP2, but barely in CRMP2T509A. These results indicate that Cdk5 primarily phosphorylates CRMP2 at Ser522 and GSK3β β β β secondarily phosphorylates at Thr509. The dual-phosphorylated CRMP2, but not non-phosphorylated or single-phosphorylated CRMP2, is recognized with the antibody 3F4, which is highly reactive with the neurofibrillary tangles of Alzheimer's disease. 3F4 recognized the CRMP2 in the wild-type but not cdk5 − − − − /− − − − mouse embryonic brain lysates. The phosphorylation of CRMP2 at Ser522 caused reduction of its affinity to tubulin. In dorsal root ganglion neurones, Sema3A stimulation enhanced the levels of the phosphorylated form of CRMP2 detected by 3F4. Over-expression of CRMP2 mutant substituting either Ser522 or Thr509 to Ala attenuates Sema3A-induced growth cone collapse response. These results suggest that the sequential phosphorylation of CRMP is an important process of Sema3A signalling and the same mechanism may have some relevance to the pathological aggregation of the microtubule-associated proteins.
Genes To Cells, 2005
Collapsin response mediating protein-2 (CRMP2) has been identified as an intracellular protein mediating Semaphorin3A (Sema3A), a repulsive guidance molecule. In this study, we demonstrate that cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3β β β β (GSK3β β β β ) plays a critical role in Sema3A signalling. In In vitro kinase assay, Cdk5 phosphorylated CRMP2 at Ser522, while GSK3β β β β did not induce any phosphorylation of CRMP2. Phosphorylation by GSK3β β β β was exclusively observed in Cdk5-phosphorylated CRMP2, but barely in CRMP2T509A. These results indicate that Cdk5 primarily phosphorylates CRMP2 at Ser522 and GSK3β β β β secondarily phosphorylates at Thr509. The dual-phosphorylated CRMP2, but not non-phosphorylated or single-phosphorylated CRMP2, is recognized with the antibody 3F4, which is highly reactive with the neurofibrillary tangles of Alzheimer's disease. 3F4 recognized the CRMP2 in the wild-type but not cdk5 − − − − /− − − − mouse embryonic brain lysates. The phosphorylation of CRMP2 at Ser522 caused reduction of its affinity to tubulin. In dorsal root ganglion neurones, Sema3A stimulation enhanced the levels of the phosphorylated form of CRMP2 detected by 3F4. Over-expression of CRMP2 mutant substituting either Ser522 or Thr509 to Ala attenuates Sema3A-induced growth cone collapse response. These results suggest that the sequential phosphorylation of CRMP is an important process of Sema3A signalling and the same mechanism may have some relevance to the pathological aggregation of the microtubule-associated proteins.