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Increased phosphorylation of collapsin response mediator protein-2 at Thr514 correlates with β -amyloid burden and synaptic deficits in Lewy body dementias

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ABSTRACT

Collapsin response mediator protein-2 (CRMP2) regulates axonal growth cone extension, and increased CRMP2 phosphorylation may lead to axonal degeneration. Axonal and synaptic pathology is an important feature of Lewy body dementias (LBD), but the state of CRMP2 phosphorylation (pCRMP2) as well as its correlations with markers of neurodegeneration have not been studied in these dementias. Hence, we measured CRMP2 phosphorylation at Thr509, Thr514 and Ser522, as well as markers of β-amyloid (Aβ), tau-phosphorylation, α-synuclein and synaptic function in the postmortem neocortex of a longitudinally assessed cohort of LBD patients characterized by low (Parkinson’s disease dementia, PDD) and high (dementia with Lewy bodies, DLB) burden of Alzheimer type pathology. We found specific increases of pCRMP2 at Thr514 in DLB, but not PDD. The increased CRMP2 phosphorylation correlated with fibrillogenic Aβ as well as with losses of markers for axon regeneration (β-III-tubulin) and synaptic integrity (synaptophysin) in LBD. In contrast, pCRMP2 alterations did not correlate with tau-phosphorylation or α-synuclein, and also appear unrelated to immunoreactivities of putative upstream kinases glycogen synthase kinase 3β and cyclin-dependent kinase 5, as well as to protein phosphatase 2A. In conclusion, increased pCRMP2 may underlie the axonal pathology of DLB, and may be a novel therapeutic target. However, antecedent signaling events as well as the nature of pCRMP2 association with Aβ and other neuropathologic markers require further study.

Electronic supplementary material: The online version of this article (doi:10.1186/s13041-016-0264-9) contains supplementary material, which is available to authorized users.

No MeSH data available.


Decreased CDK5 activator, p25 in DLB parietal cortex. a Representative immunoblots and b bar graphs of p25, p35 and total CDK5 immunoreactivities (mean ± SEM in arbitrary units), with GAPDH used as a loading control. Available N for control (C) = 19; PDD (P) = 19 and DLB (D) = 20. **p < 0.01, significant difference for multiple pair-wise comparisons (one-way ANOVA with Bonferroni post-hoc tests)
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Fig5: Decreased CDK5 activator, p25 in DLB parietal cortex. a Representative immunoblots and b bar graphs of p25, p35 and total CDK5 immunoreactivities (mean ± SEM in arbitrary units), with GAPDH used as a loading control. Available N for control (C) = 19; PDD (P) = 19 and DLB (D) = 20. **p < 0.01, significant difference for multiple pair-wise comparisons (one-way ANOVA with Bonferroni post-hoc tests)

Mentions: To investigate whether the increased pThr514 CRMP2 may be associated with changes in upstream kinases, we measured total CDK5 and GSK3β as well as indicators of activation (p25, p35, pTyr216 GSK3β) and inactivation (pSer9 GSK3β). Furthermore, given that PP2A can dephosphorylate CRMP2 at Thr514 [14], the catalytic C-subunit of PP2A was also assessed. Figure 5 shows that while CDK5 levels were unchanged in LBD, there was a loss of p25 in DLB, while p35 showed similar trends not reaching statistical significance. In contrast, GSK3β levels were reduced in both PDD and DLB (Fig. 6), together with decreases of GSK3β phosphorylation at both Tyr216 (PDD and DLB) and Ser9 (PDD). However, when normalized to total GSK3β, neither pTyr216 GSK3β/GSK3β nor pSer9 GSK3β/GSK3β was significantly different between the groups (Fig. 6), indicating the loss of total GSK3β immunoreactivity rather than changes in activation status. Lastly, no alterations of PP2A C-subunit was observed in LBD (Additional file 7: Figure S7), suggesting that altered pThr514 CRMP2 may not be related to changes in dephosphorylation activity.Fig. 5


Increased phosphorylation of collapsin response mediator protein-2 at Thr514 correlates with β -amyloid burden and synaptic deficits in Lewy body dementias
Decreased CDK5 activator, p25 in DLB parietal cortex. a Representative immunoblots and b bar graphs of p25, p35 and total CDK5 immunoreactivities (mean ± SEM in arbitrary units), with GAPDH used as a loading control. Available N for control (C) = 19; PDD (P) = 19 and DLB (D) = 20. **p < 0.01, significant difference for multiple pair-wise comparisons (one-way ANOVA with Bonferroni post-hoc tests)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5016931&req=5

Fig5: Decreased CDK5 activator, p25 in DLB parietal cortex. a Representative immunoblots and b bar graphs of p25, p35 and total CDK5 immunoreactivities (mean ± SEM in arbitrary units), with GAPDH used as a loading control. Available N for control (C) = 19; PDD (P) = 19 and DLB (D) = 20. **p < 0.01, significant difference for multiple pair-wise comparisons (one-way ANOVA with Bonferroni post-hoc tests)
Mentions: To investigate whether the increased pThr514 CRMP2 may be associated with changes in upstream kinases, we measured total CDK5 and GSK3β as well as indicators of activation (p25, p35, pTyr216 GSK3β) and inactivation (pSer9 GSK3β). Furthermore, given that PP2A can dephosphorylate CRMP2 at Thr514 [14], the catalytic C-subunit of PP2A was also assessed. Figure 5 shows that while CDK5 levels were unchanged in LBD, there was a loss of p25 in DLB, while p35 showed similar trends not reaching statistical significance. In contrast, GSK3β levels were reduced in both PDD and DLB (Fig. 6), together with decreases of GSK3β phosphorylation at both Tyr216 (PDD and DLB) and Ser9 (PDD). However, when normalized to total GSK3β, neither pTyr216 GSK3β/GSK3β nor pSer9 GSK3β/GSK3β was significantly different between the groups (Fig. 6), indicating the loss of total GSK3β immunoreactivity rather than changes in activation status. Lastly, no alterations of PP2A C-subunit was observed in LBD (Additional file 7: Figure S7), suggesting that altered pThr514 CRMP2 may not be related to changes in dephosphorylation activity.Fig. 5

View Article: PubMed Central - PubMed

ABSTRACT

Collapsin response mediator protein-2 (CRMP2) regulates axonal growth cone extension, and increased CRMP2 phosphorylation may lead to axonal degeneration. Axonal and synaptic pathology is an important feature of Lewy body dementias (LBD), but the state of CRMP2 phosphorylation (pCRMP2) as well as its correlations with markers of neurodegeneration have not been studied in these dementias. Hence, we measured CRMP2 phosphorylation at Thr509, Thr514 and Ser522, as well as markers of &beta;-amyloid (A&beta;), tau-phosphorylation, &alpha;-synuclein and synaptic function in the postmortem neocortex of a longitudinally assessed cohort of LBD patients characterized by low (Parkinson&rsquo;s disease dementia, PDD) and high (dementia with Lewy bodies, DLB) burden of Alzheimer type pathology. We found specific increases of pCRMP2 at Thr514 in DLB, but not PDD. The increased CRMP2 phosphorylation correlated with fibrillogenic A&beta; as well as with losses of markers for axon regeneration (&beta;-III-tubulin) and synaptic integrity (synaptophysin) in LBD. In contrast, pCRMP2 alterations did not correlate with tau-phosphorylation or &alpha;-synuclein, and also appear unrelated to immunoreactivities of putative upstream kinases glycogen synthase kinase 3&beta; and cyclin-dependent kinase 5, as well as to protein phosphatase 2A. In conclusion, increased pCRMP2 may underlie the axonal pathology of DLB, and may be a novel therapeutic target. However, antecedent signaling events as well as the nature of pCRMP2 association with A&beta; and other neuropathologic markers require further study.

Electronic supplementary material: The online version of this article (doi:10.1186/s13041-016-0264-9) contains supplementary material, which is available to authorized users.

No MeSH data available.