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The endogenous inhibitor of Akt, CTMP, is critical to ischemia-induced neuronal death.

Miyawaki T, Ofengeim D, Noh KM, Latuszek-Barrantes A, Hemmings BA, Follenzi A, Zukin RS - Nat. Neurosci. (2009)

Bottom Line: We found that global ischemia in intact rats triggered expression and activation of the Akt inhibitor CTMP (carboxyl-terminal modulator protein) in vulnerable hippocampal neurons and that CTMP bound and extinguished Akt activity and was essential to ischemia-induced neuronal death.RNA interference-mediated depletion of CTMP in a clinically relevant model of stroke restored Akt activity and rescued hippocampal neurons.Our results indicate that CTMP is important in the neurodegeneration that is associated with stroke and identify CTMP as a therapeutic target for the amelioration of hippocampal injury and cognitive deficits.

View Article: PubMed Central - PubMed

Affiliation: Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Center, Albert Einstein College of Medicine, Bronx, New York, USA.

ABSTRACT
Dysregulation of Akt signaling is important in a broad range of diseases that includes cancer, diabetes and heart disease. The role of Akt signaling in brain disorders is less clear. We found that global ischemia in intact rats triggered expression and activation of the Akt inhibitor CTMP (carboxyl-terminal modulator protein) in vulnerable hippocampal neurons and that CTMP bound and extinguished Akt activity and was essential to ischemia-induced neuronal death. Although ischemia induced a marked phosphorylation and nuclear translocation of Akt, phosphorylated Akt was not active in post-ischemic neurons, as assessed by kinase assays and phosphorylation of the downstream targets GSK-3beta and FOXO3A. RNA interference-mediated depletion of CTMP in a clinically relevant model of stroke restored Akt activity and rescued hippocampal neurons. Our results indicate that CTMP is important in the neurodegeneration that is associated with stroke and identify CTMP as a therapeutic target for the amelioration of hippocampal injury and cognitive deficits.

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Preconditioning but not ischemia promotes Akt kinase activity and phosphorylation of Akt targets. (a) Akt activity plots of relative fluorescence units vs. time. Experimental animals were sacrificed 3 h after reperfusion. (b) Mean Akt kinase activity in CA1. n = 4 animals per group. (c) Mean Akt kinase activity in CA3. n = 4 animals per group. (d) Western blot for p-GSK-3β at Ser 9 in the cytosol. n = 4–6 animals per group. (e) Western blot for p-FOXO3A at Ser 256 in the cytosol. n = 4–6 animals per group. (f) Western blot for p-FOXO3A at Ser 256 in the nucleus. n = 4–6 animals per group. Error bars represent means ± SEM. Significance is as described in the legend to Fig. 1.
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Figure 2: Preconditioning but not ischemia promotes Akt kinase activity and phosphorylation of Akt targets. (a) Akt activity plots of relative fluorescence units vs. time. Experimental animals were sacrificed 3 h after reperfusion. (b) Mean Akt kinase activity in CA1. n = 4 animals per group. (c) Mean Akt kinase activity in CA3. n = 4 animals per group. (d) Western blot for p-GSK-3β at Ser 9 in the cytosol. n = 4–6 animals per group. (e) Western blot for p-FOXO3A at Ser 256 in the cytosol. n = 4–6 animals per group. (f) Western blot for p-FOXO3A at Ser 256 in the nucleus. n = 4–6 animals per group. Error bars represent means ± SEM. Significance is as described in the legend to Fig. 1.

Mentions: The results thus far demonstrate that ischemia enhances phosphorylation and nuclear localization of Akt in neurons destined to die, but do not address Akt functional activity. Toward this end, we undertook two experimental strategies. First, we performed Akt kinase assays on samples of CA1 (Fig. 2a,b) and CA3 (Fig. 2c) of control, preconditioning, preconditioning+ischemia and ischemic animals. Whereas preconditioning or preconditioning+ischemia, markedly increased kinase activity in CA1 (preconditioning, 137 ± 8% of control; preconditioning+ischemia, 139 ± 6% of control; Fig. 2a,b), ischemia did not significantly alter Akt kinase activity relative to that of control (Fig. 2a,b), as assessed by real-time kinase activity assays. The effects were subfield-specific in that neither preconditioning nor ischemia significantly altered Akt kinase activity in the resistant CA3. These findings indicate that although ischemia enhances the phosphorylation status of Akt in CA1 (Fig. 1), it does not significantly alter Akt activity.


The endogenous inhibitor of Akt, CTMP, is critical to ischemia-induced neuronal death.

Miyawaki T, Ofengeim D, Noh KM, Latuszek-Barrantes A, Hemmings BA, Follenzi A, Zukin RS - Nat. Neurosci. (2009)

Preconditioning but not ischemia promotes Akt kinase activity and phosphorylation of Akt targets. (a) Akt activity plots of relative fluorescence units vs. time. Experimental animals were sacrificed 3 h after reperfusion. (b) Mean Akt kinase activity in CA1. n = 4 animals per group. (c) Mean Akt kinase activity in CA3. n = 4 animals per group. (d) Western blot for p-GSK-3β at Ser 9 in the cytosol. n = 4–6 animals per group. (e) Western blot for p-FOXO3A at Ser 256 in the cytosol. n = 4–6 animals per group. (f) Western blot for p-FOXO3A at Ser 256 in the nucleus. n = 4–6 animals per group. Error bars represent means ± SEM. Significance is as described in the legend to Fig. 1.
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Related In: Results  -  Collection

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Figure 2: Preconditioning but not ischemia promotes Akt kinase activity and phosphorylation of Akt targets. (a) Akt activity plots of relative fluorescence units vs. time. Experimental animals were sacrificed 3 h after reperfusion. (b) Mean Akt kinase activity in CA1. n = 4 animals per group. (c) Mean Akt kinase activity in CA3. n = 4 animals per group. (d) Western blot for p-GSK-3β at Ser 9 in the cytosol. n = 4–6 animals per group. (e) Western blot for p-FOXO3A at Ser 256 in the cytosol. n = 4–6 animals per group. (f) Western blot for p-FOXO3A at Ser 256 in the nucleus. n = 4–6 animals per group. Error bars represent means ± SEM. Significance is as described in the legend to Fig. 1.
Mentions: The results thus far demonstrate that ischemia enhances phosphorylation and nuclear localization of Akt in neurons destined to die, but do not address Akt functional activity. Toward this end, we undertook two experimental strategies. First, we performed Akt kinase assays on samples of CA1 (Fig. 2a,b) and CA3 (Fig. 2c) of control, preconditioning, preconditioning+ischemia and ischemic animals. Whereas preconditioning or preconditioning+ischemia, markedly increased kinase activity in CA1 (preconditioning, 137 ± 8% of control; preconditioning+ischemia, 139 ± 6% of control; Fig. 2a,b), ischemia did not significantly alter Akt kinase activity relative to that of control (Fig. 2a,b), as assessed by real-time kinase activity assays. The effects were subfield-specific in that neither preconditioning nor ischemia significantly altered Akt kinase activity in the resistant CA3. These findings indicate that although ischemia enhances the phosphorylation status of Akt in CA1 (Fig. 1), it does not significantly alter Akt activity.

Bottom Line: We found that global ischemia in intact rats triggered expression and activation of the Akt inhibitor CTMP (carboxyl-terminal modulator protein) in vulnerable hippocampal neurons and that CTMP bound and extinguished Akt activity and was essential to ischemia-induced neuronal death.RNA interference-mediated depletion of CTMP in a clinically relevant model of stroke restored Akt activity and rescued hippocampal neurons.Our results indicate that CTMP is important in the neurodegeneration that is associated with stroke and identify CTMP as a therapeutic target for the amelioration of hippocampal injury and cognitive deficits.

View Article: PubMed Central - PubMed

Affiliation: Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Center, Albert Einstein College of Medicine, Bronx, New York, USA.

ABSTRACT
Dysregulation of Akt signaling is important in a broad range of diseases that includes cancer, diabetes and heart disease. The role of Akt signaling in brain disorders is less clear. We found that global ischemia in intact rats triggered expression and activation of the Akt inhibitor CTMP (carboxyl-terminal modulator protein) in vulnerable hippocampal neurons and that CTMP bound and extinguished Akt activity and was essential to ischemia-induced neuronal death. Although ischemia induced a marked phosphorylation and nuclear translocation of Akt, phosphorylated Akt was not active in post-ischemic neurons, as assessed by kinase assays and phosphorylation of the downstream targets GSK-3beta and FOXO3A. RNA interference-mediated depletion of CTMP in a clinically relevant model of stroke restored Akt activity and rescued hippocampal neurons. Our results indicate that CTMP is important in the neurodegeneration that is associated with stroke and identify CTMP as a therapeutic target for the amelioration of hippocampal injury and cognitive deficits.

Show MeSH
Related in: MedlinePlus