CDK5 protects from caspase‐induced Ataxin‐3 cleavage and neurodegeneration

Abstract

Spinocerebellar ataxia type 3 (SCA3) is one of at least nine inherited neurodegenerative diseases caused by an expansion of a polyglutamine tract within corresponding diseasespecific proteins. In case of SCA3, mutation of Ataxin-3 results in aggregation of misfolded protein, formation of intranuclear as well as cytosolic inclusion bodies and cell death in distinct neuronal populations. Since cyclin-dependent kinase-5 (CDK5) has been shown to exert beneficial effects on aggregate formation and cell death in various polyglutamine diseases, we tested its therapeutic potential for SCA3. Our data show increased caspase-dependent Ataxin-3 cleavage, aggregation, and neurodegeneration in the absence of sufficient CDK5 activity. This disease-propagating effect could be reversed by mutation of the caspase cleavage site in Ataxin-3. Moreover, reduction of CDK5 expression levels by RNAi in vivo enhances SCA3 toxicity as assayed in a Drosophila model for SCA3. In summary, we present CDK5 as a potent neuroprotectant, regulating cleavage and thereby toxicity of Ataxin-3 and other polyglutamine proteins.

Physiological and Pathological Roles of Cdk5: Potential Directions for Therapeutic Targeting in Neurodegenerative Disease

“…Cdk5–p35 has been shown to mitigate mHTT aggregation via phosphorylation of mHTT at Ser434, significantly reducing polyQ cleavage, accumulation, and subsequent toxicity . This caspase blocking activity is further supported by a more recent study in which inhibition of Cdk5 correlated with increased fragment aggregation and cell death in spinocerebellar ataxia type3 positive cells, another neurodegenerative polyQ protein disease . Additionally, Cdk5 was shown to phosphorylate mHTT at Ser1181 and Ser1201 in response to DNA damage in vivo and in vitro , preventing polyQ-induced p53 mediated toxicity and cell death in striatal neurons .…”

Physiological and Pathological Roles of Cdk5: Potential Directions for Therapeutic Targeting in Neurodegenerative Disease

“…Cdk5–p35 has been shown to mitigate mHTT aggregation via phosphorylation of mHTT at Ser434, significantly reducing polyQ cleavage, accumulation, and subsequent toxicity . This caspase blocking activity is further supported by a more recent study in which inhibition of Cdk5 correlated with increased fragment aggregation and cell death in spinocerebellar ataxia type3 positive cells, another neurodegenerative polyQ protein disease . Additionally, Cdk5 was shown to phosphorylate mHTT at Ser1181 and Ser1201 in response to DNA damage in vivo and in vitro , preventing polyQ-induced p53 mediated toxicity and cell death in striatal neurons .…”

CRISPR/Cas9-mediated genetic correction reverses spinocerebellar ataxia 3 disease-associated phenotypes in differentiated cerebellar neurons

“…Next, we investigated whether the formation of ataxin-3 spontaneous aggregates in cerebellar neurons involved calpain or caspase, which was thought to cleave ataxin-3 to induce aggregate formation [ 7 , 8 , 27 , 28 ]. The activity of calpain and caspase relies on intracellular Ca 2+ , the level of which can be elevated by treatment with l -glutamate (100 μM) in differentiated neurons ( Fig.…”

“…Our study showed that the spontaneous ataxin-3 aggregation in SCA3 cerebellar neurons was essentially different from excitation-induced ataxin-3 aggregation in SCA3 pan-neurons. The formation of spontaneous ataxin-3 aggregates in SCA3 cerebellar neurons is effected by Ca 2+ -related pathways but may not be caused by calpain and caspase, which had been thought to play important roles in ataxin-3 aggregation [ 7 , 8 , 27 , 28 ]. This contradictory result may be explained by the use of cerebellar region-specific neurons in our experiments, which contains many glutamatergic neurons.…”

Ronin overexpression induces cerebellar degeneration in a mouse model of ataxia

“…It is also noteworthy that Ronin was discovered as a caspase-3 target that has a functional caspase-3 cleavage site following the polyglutamine repeat ( Fujita et al, 2017 ). Caspase cleavage products have been shown to contribute to the development of SCAs ( Berke et al, 2004 ; Liman et al, 2014 ; Guyenet et al, 2015 ) and other neurological disorders ( Graham et al, 2006 ). Thus, in light of the induction of caspase-3 activation we observed at the transcriptional level ( ), it is possible that caspase-3-mediated cleavage might lead to the accumulation of Ronin fragments, which could contribute to the ataxic phenotype.…”

Physiological and Pathological Roles of Cdk5: Potential Directions for Therapeutic Targeting in Neurodegenerative Disease

“…Cdk5–p35 has been shown to mitigate mHTT aggregation via phosphorylation of mHTT at Ser434, significantly reducing polyQ cleavage, accumulation, and subsequent toxicity . This caspase blocking activity is further supported by a more recent study in which inhibition of Cdk5 correlated with increased fragment aggregation and cell death in spinocerebellar ataxia type3 positive cells, another neurodegenerative polyQ protein disease . Additionally, Cdk5 was shown to phosphorylate mHTT at Ser1181 and Ser1201 in response to DNA damage in vivo and in vitro , preventing polyQ-induced p53 mediated toxicity and cell death in striatal neurons .…”

CRISPR/Cas9-mediated genetic correction reverses spinocerebellar ataxia 3 disease-associated phenotypes in differentiated cerebellar neurons

“…Next, we investigated whether the formation of ataxin-3 spontaneous aggregates in cerebellar neurons involved calpain or caspase, which was thought to cleave ataxin-3 to induce aggregate formation [ 7 , 8 , 27 , 28 ]. The activity of calpain and caspase relies on intracellular Ca 2+ , the level of which can be elevated by treatment with l -glutamate (100 μM) in differentiated neurons ( Fig.…”

“…Our study showed that the spontaneous ataxin-3 aggregation in SCA3 cerebellar neurons was essentially different from excitation-induced ataxin-3 aggregation in SCA3 pan-neurons. The formation of spontaneous ataxin-3 aggregates in SCA3 cerebellar neurons is effected by Ca 2+ -related pathways but may not be caused by calpain and caspase, which had been thought to play important roles in ataxin-3 aggregation [ 7 , 8 , 27 , 28 ]. This contradictory result may be explained by the use of cerebellar region-specific neurons in our experiments, which contains many glutamatergic neurons.…”

Ronin overexpression induces cerebellar degeneration in a mouse model of ataxia

“…It is also noteworthy that Ronin was discovered as a caspase-3 target that has a functional caspase-3 cleavage site following the polyglutamine repeat ( Fujita et al, 2017 ). Caspase cleavage products have been shown to contribute to the development of SCAs ( Berke et al, 2004 ; Liman et al, 2014 ; Guyenet et al, 2015 ) and other neurological disorders ( Graham et al, 2006 ). Thus, in light of the induction of caspase-3 activation we observed at the transcriptional level ( ), it is possible that caspase-3-mediated cleavage might lead to the accumulation of Ronin fragments, which could contribute to the ataxic phenotype.…”

Physiological and Pathological Roles of Cdk5: Potential Directions for Therapeutic Targeting in Neurodegenerative Disease

“…Cdk5–p35 has been shown to mitigate mHTT aggregation via phosphorylation of mHTT at Ser434, significantly reducing polyQ cleavage, accumulation, and subsequent toxicity . This caspase blocking activity is further supported by a more recent study in which inhibition of Cdk5 correlated with increased fragment aggregation and cell death in spinocerebellar ataxia type3 positive cells, another neurodegenerative polyQ protein disease . Additionally, Cdk5 was shown to phosphorylate mHTT at Ser1181 and Ser1201 in response to DNA damage in vivo and in vitro , preventing polyQ-induced p53 mediated toxicity and cell death in striatal neurons .…”

CRISPR/Cas9-mediated genetic correction reverses spinocerebellar ataxia 3 disease-associated phenotypes in differentiated cerebellar neurons

“…Next, we investigated whether the formation of ataxin-3 spontaneous aggregates in cerebellar neurons involved calpain or caspase, which was thought to cleave ataxin-3 to induce aggregate formation [ 7 , 8 , 27 , 28 ]. The activity of calpain and caspase relies on intracellular Ca 2+ , the level of which can be elevated by treatment with l -glutamate (100 μM) in differentiated neurons ( Fig.…”

“…Our study showed that the spontaneous ataxin-3 aggregation in SCA3 cerebellar neurons was essentially different from excitation-induced ataxin-3 aggregation in SCA3 pan-neurons. The formation of spontaneous ataxin-3 aggregates in SCA3 cerebellar neurons is effected by Ca 2+ -related pathways but may not be caused by calpain and caspase, which had been thought to play important roles in ataxin-3 aggregation [ 7 , 8 , 27 , 28 ]. This contradictory result may be explained by the use of cerebellar region-specific neurons in our experiments, which contains many glutamatergic neurons.…”

Ronin overexpression induces cerebellar degeneration in a mouse model of ataxia

“…It is also noteworthy that Ronin was discovered as a caspase-3 target that has a functional caspase-3 cleavage site following the polyglutamine repeat ( Fujita et al, 2017 ). Caspase cleavage products have been shown to contribute to the development of SCAs ( Berke et al, 2004 ; Liman et al, 2014 ; Guyenet et al, 2015 ) and other neurological disorders ( Graham et al, 2006 ). Thus, in light of the induction of caspase-3 activation we observed at the transcriptional level ( ), it is possible that caspase-3-mediated cleavage might lead to the accumulation of Ronin fragments, which could contribute to the ataxic phenotype.…”