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RanBP9 at the intersection between cofilin and Aβ pathologies: rescue of neurodegenerative changes by RanBP9 reduction.

Woo JA, Boggess T, Uhlar C, Wang X, Khan H, Cappos G, Joly-Amado A, De Narvaez E, Majid S, Minamide LS, Bamburg JR, Morgan D, Weeber E, Kang DE - Cell Death Dis (2015)

Bottom Line: In this study, we found that endogenous RanBP9 positively regulates SSH1 levels and mediates Aβ-induced translocation of cofilin to mitochondria and induction of cofilin-actin pathology in cultured cells, primary neurons, and in vivo.Endogenous level of RanBP9 was also required for Aβ-induced collapse of growth cones in immature neurons (days in vitro 9 (DIV9)) and depletion of synaptic proteins in mature neurons (DIV21).Therefore, these results underscore the critical importance of endogenous RanBP9 not only in Aβ accumulation but also in mediating the neurotoxic actions of Aβ at the level of synaptic plasticity, mitochondria, and cofilin-actin pathology via control of the SSH1-cofilin pathway in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, Tampa, FL, USA.

ABSTRACT
Molecular pathways underlying the neurotoxicity and production of amyloid β protein (Aβ) represent potentially promising therapeutic targets for Alzheimer's disease (AD). We recently found that overexpression of the scaffolding protein RanBP9 increases Aβ production in cell lines and in transgenic mice while promoting cofilin activation and mitochondrial dysfunction. Translocation of cofilin to mitochondria and induction of cofilin-actin pathology require the activation/dephosphorylation of cofilin by Slingshot homolog 1 (SSH1) and cysteine oxidation of cofilin. In this study, we found that endogenous RanBP9 positively regulates SSH1 levels and mediates Aβ-induced translocation of cofilin to mitochondria and induction of cofilin-actin pathology in cultured cells, primary neurons, and in vivo. Endogenous level of RanBP9 was also required for Aβ-induced collapse of growth cones in immature neurons (days in vitro 9 (DIV9)) and depletion of synaptic proteins in mature neurons (DIV21). In vivo, amyloid precursor protein (APP)/presenilin-1 (PS1) mice exhibited 3.5-fold increased RanBP9 levels, and RanBP9 reduction protected against cofilin-actin pathology, synaptic damage, gliosis, and Aβ accumulation associated with APP/PS1 mice. Brains slices derived from APP/PS1 mice showed significantly impaired long-term potentiation (LTP), and RanBP9 reduction significantly enhanced paired pulse facilitation and LTP, as well as partially rescued contextual memory deficits associated with APP/PS1 mice. Therefore, these results underscore the critical importance of endogenous RanBP9 not only in Aβ accumulation but also in mediating the neurotoxic actions of Aβ at the level of synaptic plasticity, mitochondria, and cofilin-actin pathology via control of the SSH1-cofilin pathway in vivo.

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RanBP9 reduction rescues neuroinflammation and synaptic protein depletion in APP/PS1 transgenic mice. (a-e) Brains from 8-month-old WT, APP/PS1, and APP/PS1;RanBP9+/− mice subjected to immunohistochemistry for GFAP (activated astrocyte marker), Iba1 (activated microglia marker), Synapsin I (presynaptic marker), and PSD95 (postsynaptic marker) in the anterior cortex (CTX) and/or hippocampus (HIPP). (a) Representative images showing RanBP9 reduction rescues neuroinflammation (GFAP and Iba1) and synaptic protein loss (Synapsin I and PSD95) in APP/PS1 mice. (b) Quantitation of PSD95 intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of synapsin I intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the hippocampus (ANOVA, post-hoc Tukey, *P<0.05, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the anterior cortex (ANOVA, post-hoc Tukey, **P=<0.005, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Quantification of Iba1 intensity in the hippocampus (ANOVA, post-hoc Tukey, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Error bars represent S.E.M. on graphs
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fig5: RanBP9 reduction rescues neuroinflammation and synaptic protein depletion in APP/PS1 transgenic mice. (a-e) Brains from 8-month-old WT, APP/PS1, and APP/PS1;RanBP9+/− mice subjected to immunohistochemistry for GFAP (activated astrocyte marker), Iba1 (activated microglia marker), Synapsin I (presynaptic marker), and PSD95 (postsynaptic marker) in the anterior cortex (CTX) and/or hippocampus (HIPP). (a) Representative images showing RanBP9 reduction rescues neuroinflammation (GFAP and Iba1) and synaptic protein loss (Synapsin I and PSD95) in APP/PS1 mice. (b) Quantitation of PSD95 intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of synapsin I intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the hippocampus (ANOVA, post-hoc Tukey, *P<0.05, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the anterior cortex (ANOVA, post-hoc Tukey, **P=<0.005, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Quantification of Iba1 intensity in the hippocampus (ANOVA, post-hoc Tukey, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Error bars represent S.E.M. on graphs

Mentions: Given the robust upregulation of RanBP9 levels in APP/PS1 mice, we next determined whether genetic reduction in RanBP9 can prevent neuroinflammation and synapse loss associated with APP/PS1 transgenic mice. We performed immunohistochemistry for glial fibrillary acidic protein (GFAP) and Iba1 to detect activated astrocytes and microglia as well as Synapsin I and PSD95 to detect pre- and postsynaptic proteins from 8-month-old APP/PS1, APP/PS1;RanBP9+/−, and WT littermates. As expected, APP/PS1 mice demonstrated significantly increased GFAP and Iba1 immunoreactivities throughout the hippocampus and areas of the anterior cortex associated with Aβ accumulation as well as diminished PSD95 and Synapsin I immunoreactivities within the stratum lucidium (SL: synaptic terminating zone) of CA3 (Figures 5a and b). In contrast, APP/PS1;RanBP9+/− mice showed significantly reduced GFAP and Iba1 immunoreactivities in the hippocampus and anterior cortex, as well as significantly rescued Synapsin I and PSD95 immunoreactivities within the SL of CA3 compared with APP/PS1 littermate mice, essentially indistinguishable from WT mice (Figures 5a and b). As RanBP9 overexpression promotes Aβ production in cultured cells and in vivo,17, 18 we next examined whether endogenous RanBP9 reduction alters Aβ burden in the hippocampus and anterior cortex of 8-month-old APP/PS1 mice. Indeed, APP/PS1;RanBP9+/− mice demonstrated a significant decrease in both the area covered by total Aβ deposits and thioflavin S-positive fibrillar Aβ deposits within the hippocampus and anterior cortex compared with littermate APP/PS1 mice (Figures 6a and c). In addition, soluble Aβ levels were also significantly reduced in the hippocampus of APP/PS1;RanBP9+/− mice compared with littermate APP/PS1 mice (Figures 6d and e). These results show that RanBP9 reduction protects against Aβ accumulation, as well as neuroinflammation and synaptotoxicity in vivo.


RanBP9 at the intersection between cofilin and Aβ pathologies: rescue of neurodegenerative changes by RanBP9 reduction.

Woo JA, Boggess T, Uhlar C, Wang X, Khan H, Cappos G, Joly-Amado A, De Narvaez E, Majid S, Minamide LS, Bamburg JR, Morgan D, Weeber E, Kang DE - Cell Death Dis (2015)

RanBP9 reduction rescues neuroinflammation and synaptic protein depletion in APP/PS1 transgenic mice. (a-e) Brains from 8-month-old WT, APP/PS1, and APP/PS1;RanBP9+/− mice subjected to immunohistochemistry for GFAP (activated astrocyte marker), Iba1 (activated microglia marker), Synapsin I (presynaptic marker), and PSD95 (postsynaptic marker) in the anterior cortex (CTX) and/or hippocampus (HIPP). (a) Representative images showing RanBP9 reduction rescues neuroinflammation (GFAP and Iba1) and synaptic protein loss (Synapsin I and PSD95) in APP/PS1 mice. (b) Quantitation of PSD95 intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of synapsin I intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the hippocampus (ANOVA, post-hoc Tukey, *P<0.05, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the anterior cortex (ANOVA, post-hoc Tukey, **P=<0.005, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Quantification of Iba1 intensity in the hippocampus (ANOVA, post-hoc Tukey, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Error bars represent S.E.M. on graphs
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fig5: RanBP9 reduction rescues neuroinflammation and synaptic protein depletion in APP/PS1 transgenic mice. (a-e) Brains from 8-month-old WT, APP/PS1, and APP/PS1;RanBP9+/− mice subjected to immunohistochemistry for GFAP (activated astrocyte marker), Iba1 (activated microglia marker), Synapsin I (presynaptic marker), and PSD95 (postsynaptic marker) in the anterior cortex (CTX) and/or hippocampus (HIPP). (a) Representative images showing RanBP9 reduction rescues neuroinflammation (GFAP and Iba1) and synaptic protein loss (Synapsin I and PSD95) in APP/PS1 mice. (b) Quantitation of PSD95 intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of synapsin I intensity within the SL of CA3 (ANOVA, post-hoc Tukey, *P<0.05, **P<0.005, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the hippocampus (ANOVA, post-hoc Tukey, *P<0.05, n=4 mice per genotype, 2 F and 2 M). Quantitation of GFAP intensity in the anterior cortex (ANOVA, post-hoc Tukey, **P=<0.005, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Quantification of Iba1 intensity in the hippocampus (ANOVA, post-hoc Tukey, ***P<0.0005, n=4 mice per genotype, 2 F and 2 M). Error bars represent S.E.M. on graphs
Mentions: Given the robust upregulation of RanBP9 levels in APP/PS1 mice, we next determined whether genetic reduction in RanBP9 can prevent neuroinflammation and synapse loss associated with APP/PS1 transgenic mice. We performed immunohistochemistry for glial fibrillary acidic protein (GFAP) and Iba1 to detect activated astrocytes and microglia as well as Synapsin I and PSD95 to detect pre- and postsynaptic proteins from 8-month-old APP/PS1, APP/PS1;RanBP9+/−, and WT littermates. As expected, APP/PS1 mice demonstrated significantly increased GFAP and Iba1 immunoreactivities throughout the hippocampus and areas of the anterior cortex associated with Aβ accumulation as well as diminished PSD95 and Synapsin I immunoreactivities within the stratum lucidium (SL: synaptic terminating zone) of CA3 (Figures 5a and b). In contrast, APP/PS1;RanBP9+/− mice showed significantly reduced GFAP and Iba1 immunoreactivities in the hippocampus and anterior cortex, as well as significantly rescued Synapsin I and PSD95 immunoreactivities within the SL of CA3 compared with APP/PS1 littermate mice, essentially indistinguishable from WT mice (Figures 5a and b). As RanBP9 overexpression promotes Aβ production in cultured cells and in vivo,17, 18 we next examined whether endogenous RanBP9 reduction alters Aβ burden in the hippocampus and anterior cortex of 8-month-old APP/PS1 mice. Indeed, APP/PS1;RanBP9+/− mice demonstrated a significant decrease in both the area covered by total Aβ deposits and thioflavin S-positive fibrillar Aβ deposits within the hippocampus and anterior cortex compared with littermate APP/PS1 mice (Figures 6a and c). In addition, soluble Aβ levels were also significantly reduced in the hippocampus of APP/PS1;RanBP9+/− mice compared with littermate APP/PS1 mice (Figures 6d and e). These results show that RanBP9 reduction protects against Aβ accumulation, as well as neuroinflammation and synaptotoxicity in vivo.

Bottom Line: In this study, we found that endogenous RanBP9 positively regulates SSH1 levels and mediates Aβ-induced translocation of cofilin to mitochondria and induction of cofilin-actin pathology in cultured cells, primary neurons, and in vivo.Endogenous level of RanBP9 was also required for Aβ-induced collapse of growth cones in immature neurons (days in vitro 9 (DIV9)) and depletion of synaptic proteins in mature neurons (DIV21).Therefore, these results underscore the critical importance of endogenous RanBP9 not only in Aβ accumulation but also in mediating the neurotoxic actions of Aβ at the level of synaptic plasticity, mitochondria, and cofilin-actin pathology via control of the SSH1-cofilin pathway in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine, USF Health Byrd Alzheimer's Institute, Tampa, FL, USA.

ABSTRACT
Molecular pathways underlying the neurotoxicity and production of amyloid β protein (Aβ) represent potentially promising therapeutic targets for Alzheimer's disease (AD). We recently found that overexpression of the scaffolding protein RanBP9 increases Aβ production in cell lines and in transgenic mice while promoting cofilin activation and mitochondrial dysfunction. Translocation of cofilin to mitochondria and induction of cofilin-actin pathology require the activation/dephosphorylation of cofilin by Slingshot homolog 1 (SSH1) and cysteine oxidation of cofilin. In this study, we found that endogenous RanBP9 positively regulates SSH1 levels and mediates Aβ-induced translocation of cofilin to mitochondria and induction of cofilin-actin pathology in cultured cells, primary neurons, and in vivo. Endogenous level of RanBP9 was also required for Aβ-induced collapse of growth cones in immature neurons (days in vitro 9 (DIV9)) and depletion of synaptic proteins in mature neurons (DIV21). In vivo, amyloid precursor protein (APP)/presenilin-1 (PS1) mice exhibited 3.5-fold increased RanBP9 levels, and RanBP9 reduction protected against cofilin-actin pathology, synaptic damage, gliosis, and Aβ accumulation associated with APP/PS1 mice. Brains slices derived from APP/PS1 mice showed significantly impaired long-term potentiation (LTP), and RanBP9 reduction significantly enhanced paired pulse facilitation and LTP, as well as partially rescued contextual memory deficits associated with APP/PS1 mice. Therefore, these results underscore the critical importance of endogenous RanBP9 not only in Aβ accumulation but also in mediating the neurotoxic actions of Aβ at the level of synaptic plasticity, mitochondria, and cofilin-actin pathology via control of the SSH1-cofilin pathway in vivo.

Show MeSH
Related in: MedlinePlus