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Modulation of aberrant CDK5 signaling rescues impaired neurogenesis in models of Alzheimer's disease.

Crews L, Patrick C, Adame A, Rockenstein E, Masliah E - Cell Death Dis (2011)

Bottom Line: Neurodegeneration in AD has been associated with aberrant signaling through the cyclin-dependent kinase-5 (CDK5) pathway via its activators p35/p25; however, the role of CDK5 in the mechanisms of defective adult neurogenesis in AD is unknown.These conditions resulted in impaired maturation and neurite outgrowth in vitro, and these effects were reversed by pharmacological or genetic inhibition of CDK5.Moreover, potential therapeutic approaches could focus on modulating the aberrant activity of CDK5 to target the neurogenic and neurodegenerative alterations in AD.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093-0624, USA.

ABSTRACT
Recent studies show that in Alzheimer's disease (AD), alterations in neurogenesis contribute to the neurodegenerative process. Neurodegeneration in AD has been associated with aberrant signaling through the cyclin-dependent kinase-5 (CDK5) pathway via its activators p35/p25; however, the role of CDK5 in the mechanisms of defective adult neurogenesis in AD is unknown. First, to study AD-like abnormal activation of CDK5 signaling in an in vitro model of neurogenesis, neuronal progenitor cells (NPCs) were infected with a viral vector expressing p35, and exposed to amyloid-β protein (Aβ(1-42)). These conditions resulted in impaired maturation and neurite outgrowth in vitro, and these effects were reversed by pharmacological or genetic inhibition of CDK5. Similarly, neurogenesis was impaired in a transgenic mouse model of AD that expresses high levels of amyloid precursor protein (APP), and this effect was reversed in transgenic mice crossed with a CDK5 heterozygous-deficient mouse line. A similar rescue effect was observed in APP transgenic mice treated with Roscovitine, a pharmacological inhibitor of CDK5. Taken together, these data suggest that the CDK5 signaling pathway has a critical role in maintaining the integrity of NPCs and neuronal maturation in the adult hippocampus. Moreover, potential therapeutic approaches could focus on modulating the aberrant activity of CDK5 to target the neurogenic and neurodegenerative alterations in AD.

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Downmodulation of abnormal CDK5 activity in vitro rescues neuronal maturation. Differentiating NPCs were pretreated on day 2 with the pharmacological inhibitor Roscovitine (Rosco) or transfected with siRNA against CDK5 (siCDK5, 5 nM), and then infected 6 h later with adenovirus expressing p35, followed by treatment with Aβ on day 3 for 24 h. On day 4, NPC-derived neural progeny were briefly extracted and fixed with glutaraldehyde for β-tubulin immunofluorescence and neurite outgrowth analysis. Cell nuclei were co-stained with DAPI reagent. (a–c) Compared with controls (a), uninfected NPC-derived neural progeny treated with Rosco (b) or siCDK5 (c) showed only a mild reduction in the lengths of β-tubulin-positive neurites. (d–f) NPC-derived neural progeny with p35/Aβ treatment showed a notable decrease in the lengths of β-tubulin-positive neurites (d); this was rescued by treatment with Rosco (e) or siCDK5 (f). (g) Neurite outgrowth measurements using NeuronJ showed a 50% reduction in neurite lengths in p35/Aβ-treated cells, and this effect was reversed in cultures pretreated with Rosco or transfected with siCDK5. Scale bar=10 μm. *P<0.05 compared with vehicle-treated controls by one-way ANOVA with post hoc Dunnett's test (N=3). #P<0.05 compared with p35/Aβ-treated NPCs by one-way ANOVA with post hoc Tukey–Kramer test (N=3)
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fig3: Downmodulation of abnormal CDK5 activity in vitro rescues neuronal maturation. Differentiating NPCs were pretreated on day 2 with the pharmacological inhibitor Roscovitine (Rosco) or transfected with siRNA against CDK5 (siCDK5, 5 nM), and then infected 6 h later with adenovirus expressing p35, followed by treatment with Aβ on day 3 for 24 h. On day 4, NPC-derived neural progeny were briefly extracted and fixed with glutaraldehyde for β-tubulin immunofluorescence and neurite outgrowth analysis. Cell nuclei were co-stained with DAPI reagent. (a–c) Compared with controls (a), uninfected NPC-derived neural progeny treated with Rosco (b) or siCDK5 (c) showed only a mild reduction in the lengths of β-tubulin-positive neurites. (d–f) NPC-derived neural progeny with p35/Aβ treatment showed a notable decrease in the lengths of β-tubulin-positive neurites (d); this was rescued by treatment with Rosco (e) or siCDK5 (f). (g) Neurite outgrowth measurements using NeuronJ showed a 50% reduction in neurite lengths in p35/Aβ-treated cells, and this effect was reversed in cultures pretreated with Rosco or transfected with siCDK5. Scale bar=10 μm. *P<0.05 compared with vehicle-treated controls by one-way ANOVA with post hoc Dunnett's test (N=3). #P<0.05 compared with p35/Aβ-treated NPCs by one-way ANOVA with post hoc Tukey–Kramer test (N=3)

Mentions: Next, we sought to determine whether pharmacological or genetic inhibition of CDK5 might protect against the maturation defects observed in NPC-derived neural progeny exposed to p35/Aβ. For this purpose, on day 2 of neuronal induction, differentiating NPCs were pretreated with Roscovitine, or transfected with siCDK5 for 6 h, followed by infection with adv-p35, and Aβ treatment (Figure 3). Neurite outgrowth studies of β-tubulin-positive processes revealed that modulating CDK5 with Roscovitine or siCDK5 reversed the neurite outgrowth deficits observed after p35/Aβ treatment (Figures 3a–g). Taken together, these results support the possibility that AD-related aberrant activation of CDK5 signaling impairs the maturation of adult hippocampal NPCs, and this effect can be reversed by modulation of CDK5 by pharmacological or genetic means.


Modulation of aberrant CDK5 signaling rescues impaired neurogenesis in models of Alzheimer's disease.

Crews L, Patrick C, Adame A, Rockenstein E, Masliah E - Cell Death Dis (2011)

Downmodulation of abnormal CDK5 activity in vitro rescues neuronal maturation. Differentiating NPCs were pretreated on day 2 with the pharmacological inhibitor Roscovitine (Rosco) or transfected with siRNA against CDK5 (siCDK5, 5 nM), and then infected 6 h later with adenovirus expressing p35, followed by treatment with Aβ on day 3 for 24 h. On day 4, NPC-derived neural progeny were briefly extracted and fixed with glutaraldehyde for β-tubulin immunofluorescence and neurite outgrowth analysis. Cell nuclei were co-stained with DAPI reagent. (a–c) Compared with controls (a), uninfected NPC-derived neural progeny treated with Rosco (b) or siCDK5 (c) showed only a mild reduction in the lengths of β-tubulin-positive neurites. (d–f) NPC-derived neural progeny with p35/Aβ treatment showed a notable decrease in the lengths of β-tubulin-positive neurites (d); this was rescued by treatment with Rosco (e) or siCDK5 (f). (g) Neurite outgrowth measurements using NeuronJ showed a 50% reduction in neurite lengths in p35/Aβ-treated cells, and this effect was reversed in cultures pretreated with Rosco or transfected with siCDK5. Scale bar=10 μm. *P<0.05 compared with vehicle-treated controls by one-way ANOVA with post hoc Dunnett's test (N=3). #P<0.05 compared with p35/Aβ-treated NPCs by one-way ANOVA with post hoc Tukey–Kramer test (N=3)
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fig3: Downmodulation of abnormal CDK5 activity in vitro rescues neuronal maturation. Differentiating NPCs were pretreated on day 2 with the pharmacological inhibitor Roscovitine (Rosco) or transfected with siRNA against CDK5 (siCDK5, 5 nM), and then infected 6 h later with adenovirus expressing p35, followed by treatment with Aβ on day 3 for 24 h. On day 4, NPC-derived neural progeny were briefly extracted and fixed with glutaraldehyde for β-tubulin immunofluorescence and neurite outgrowth analysis. Cell nuclei were co-stained with DAPI reagent. (a–c) Compared with controls (a), uninfected NPC-derived neural progeny treated with Rosco (b) or siCDK5 (c) showed only a mild reduction in the lengths of β-tubulin-positive neurites. (d–f) NPC-derived neural progeny with p35/Aβ treatment showed a notable decrease in the lengths of β-tubulin-positive neurites (d); this was rescued by treatment with Rosco (e) or siCDK5 (f). (g) Neurite outgrowth measurements using NeuronJ showed a 50% reduction in neurite lengths in p35/Aβ-treated cells, and this effect was reversed in cultures pretreated with Rosco or transfected with siCDK5. Scale bar=10 μm. *P<0.05 compared with vehicle-treated controls by one-way ANOVA with post hoc Dunnett's test (N=3). #P<0.05 compared with p35/Aβ-treated NPCs by one-way ANOVA with post hoc Tukey–Kramer test (N=3)
Mentions: Next, we sought to determine whether pharmacological or genetic inhibition of CDK5 might protect against the maturation defects observed in NPC-derived neural progeny exposed to p35/Aβ. For this purpose, on day 2 of neuronal induction, differentiating NPCs were pretreated with Roscovitine, or transfected with siCDK5 for 6 h, followed by infection with adv-p35, and Aβ treatment (Figure 3). Neurite outgrowth studies of β-tubulin-positive processes revealed that modulating CDK5 with Roscovitine or siCDK5 reversed the neurite outgrowth deficits observed after p35/Aβ treatment (Figures 3a–g). Taken together, these results support the possibility that AD-related aberrant activation of CDK5 signaling impairs the maturation of adult hippocampal NPCs, and this effect can be reversed by modulation of CDK5 by pharmacological or genetic means.

Bottom Line: Neurodegeneration in AD has been associated with aberrant signaling through the cyclin-dependent kinase-5 (CDK5) pathway via its activators p35/p25; however, the role of CDK5 in the mechanisms of defective adult neurogenesis in AD is unknown.These conditions resulted in impaired maturation and neurite outgrowth in vitro, and these effects were reversed by pharmacological or genetic inhibition of CDK5.Moreover, potential therapeutic approaches could focus on modulating the aberrant activity of CDK5 to target the neurogenic and neurodegenerative alterations in AD.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093-0624, USA.

ABSTRACT
Recent studies show that in Alzheimer's disease (AD), alterations in neurogenesis contribute to the neurodegenerative process. Neurodegeneration in AD has been associated with aberrant signaling through the cyclin-dependent kinase-5 (CDK5) pathway via its activators p35/p25; however, the role of CDK5 in the mechanisms of defective adult neurogenesis in AD is unknown. First, to study AD-like abnormal activation of CDK5 signaling in an in vitro model of neurogenesis, neuronal progenitor cells (NPCs) were infected with a viral vector expressing p35, and exposed to amyloid-β protein (Aβ(1-42)). These conditions resulted in impaired maturation and neurite outgrowth in vitro, and these effects were reversed by pharmacological or genetic inhibition of CDK5. Similarly, neurogenesis was impaired in a transgenic mouse model of AD that expresses high levels of amyloid precursor protein (APP), and this effect was reversed in transgenic mice crossed with a CDK5 heterozygous-deficient mouse line. A similar rescue effect was observed in APP transgenic mice treated with Roscovitine, a pharmacological inhibitor of CDK5. Taken together, these data suggest that the CDK5 signaling pathway has a critical role in maintaining the integrity of NPCs and neuronal maturation in the adult hippocampus. Moreover, potential therapeutic approaches could focus on modulating the aberrant activity of CDK5 to target the neurogenic and neurodegenerative alterations in AD.

Show MeSH
Related in: MedlinePlus