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The tau tubulin kinases TTBK1/2 promote accumulation of pathological TDP-43.

Liachko NF, McMillan PJ, Strovas TJ, Loomis E, Greenup L, Murrell JR, Ghetti B, Raskind MA, Montine TJ, Bird TD, Leverenz JB, Kraemer BC - PLoS Genet. (2014)

Bottom Line: TTBK1/2 overexpression drives phosphorylation and relocalization of TDP-43 from the nucleus to cytoplasmic inclusions reminiscent of neuropathologic changes in disease states.Furthermore, protein levels of TTBK1 and TTBK2 are increased in frontal cortex of FTLD-TDP patients, and TTBK1 and TTBK2 co-localize with TDP-43 inclusions in ALS spinal cord.These kinases may represent attractive targets for therapeutic intervention for TDP-43 proteinopathies such as ALS and FTLD-TDP.

View Article: PubMed Central - PubMed

Affiliation: Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, Washington, United States of America; Department of Medicine, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
Pathological aggregates of phosphorylated TDP-43 characterize amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP), two devastating groups of neurodegenerative disease. Kinase hyperactivity may be a consistent feature of ALS and FTLD-TDP, as phosphorylated TDP-43 is not observed in the absence of neurodegeneration. By examining changes in TDP-43 phosphorylation state, we have identified kinases controlling TDP-43 phosphorylation in a C. elegans model of ALS. In this kinome-wide survey, we identified homologs of the tau tubulin kinases 1 and 2 (TTBK1 and TTBK2), which were also identified in a prior screen for kinase modifiers of TDP-43 behavioral phenotypes. Using refined methodology, we demonstrate TTBK1 and TTBK2 directly phosphorylate TDP-43 in vitro and promote TDP-43 phosphorylation in mammalian cultured cells. TTBK1/2 overexpression drives phosphorylation and relocalization of TDP-43 from the nucleus to cytoplasmic inclusions reminiscent of neuropathologic changes in disease states. Furthermore, protein levels of TTBK1 and TTBK2 are increased in frontal cortex of FTLD-TDP patients, and TTBK1 and TTBK2 co-localize with TDP-43 inclusions in ALS spinal cord. These kinases may represent attractive targets for therapeutic intervention for TDP-43 proteinopathies such as ALS and FTLD-TDP.

No MeSH data available.


Related in: MedlinePlus

Reduced TTBK1 protects against TDP-43 phosphorylation.(A) NSC-34 cells treated with siRNA targeting TTBK1 exhibit reduced TDP-43 phosphorylation following induction of P-TDP-43 with ethacrynic acid (EA). (B) Quantitative analysis of band intensities from three independent replicate siRNA experiments. Band intensities are graphed in arbitrary units. *P = 0.025 versus control+EA, Student's t-test.
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pgen-1004803-g003: Reduced TTBK1 protects against TDP-43 phosphorylation.(A) NSC-34 cells treated with siRNA targeting TTBK1 exhibit reduced TDP-43 phosphorylation following induction of P-TDP-43 with ethacrynic acid (EA). (B) Quantitative analysis of band intensities from three independent replicate siRNA experiments. Band intensities are graphed in arbitrary units. *P = 0.025 versus control+EA, Student's t-test.

Mentions: Decreasing TTBK1/2 kinase activity may prevent TDP-43 phosphorylation. To test this hypothesis, we employed small interfering RNAs (siRNAs) to decrease levels of TTBK1 gene expression in mammalian cultured cells. We have modeled pathological TDP-43 phosphorylation in the mouse motor neuron-like NSC-34 cell line using the chemical trigger ethacrynic acid (EA). EA acts by depleting cytosolic and mitochondrial glutathione, resulting in robust TDP-43 phosphorylation [36], [37]. EA is a specific trigger of TDP-43 phosphorylation, because a variety of other cell stressors fail to induce phospho-TDP-43 (S6A Figure). NSC-34 cells were transfected with siRNAs targeting TTBK1, averaging 76% reduction in gene expression and 46% reduction in protein levels (S6B–D Figure). These cells were then treated with EA to induce TDP-43 phosphorylation. We observed a robust decrease in TDP-43 phosphorylation following treatment with TTBK1 siRNA (Fig. 3). We also tested siRNAs targeting TTBK2, but were unable to achieve significant reduction in gene expression.


The tau tubulin kinases TTBK1/2 promote accumulation of pathological TDP-43.

Liachko NF, McMillan PJ, Strovas TJ, Loomis E, Greenup L, Murrell JR, Ghetti B, Raskind MA, Montine TJ, Bird TD, Leverenz JB, Kraemer BC - PLoS Genet. (2014)

Reduced TTBK1 protects against TDP-43 phosphorylation.(A) NSC-34 cells treated with siRNA targeting TTBK1 exhibit reduced TDP-43 phosphorylation following induction of P-TDP-43 with ethacrynic acid (EA). (B) Quantitative analysis of band intensities from three independent replicate siRNA experiments. Band intensities are graphed in arbitrary units. *P = 0.025 versus control+EA, Student's t-test.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4256087&req=5

pgen-1004803-g003: Reduced TTBK1 protects against TDP-43 phosphorylation.(A) NSC-34 cells treated with siRNA targeting TTBK1 exhibit reduced TDP-43 phosphorylation following induction of P-TDP-43 with ethacrynic acid (EA). (B) Quantitative analysis of band intensities from three independent replicate siRNA experiments. Band intensities are graphed in arbitrary units. *P = 0.025 versus control+EA, Student's t-test.
Mentions: Decreasing TTBK1/2 kinase activity may prevent TDP-43 phosphorylation. To test this hypothesis, we employed small interfering RNAs (siRNAs) to decrease levels of TTBK1 gene expression in mammalian cultured cells. We have modeled pathological TDP-43 phosphorylation in the mouse motor neuron-like NSC-34 cell line using the chemical trigger ethacrynic acid (EA). EA acts by depleting cytosolic and mitochondrial glutathione, resulting in robust TDP-43 phosphorylation [36], [37]. EA is a specific trigger of TDP-43 phosphorylation, because a variety of other cell stressors fail to induce phospho-TDP-43 (S6A Figure). NSC-34 cells were transfected with siRNAs targeting TTBK1, averaging 76% reduction in gene expression and 46% reduction in protein levels (S6B–D Figure). These cells were then treated with EA to induce TDP-43 phosphorylation. We observed a robust decrease in TDP-43 phosphorylation following treatment with TTBK1 siRNA (Fig. 3). We also tested siRNAs targeting TTBK2, but were unable to achieve significant reduction in gene expression.

Bottom Line: TTBK1/2 overexpression drives phosphorylation and relocalization of TDP-43 from the nucleus to cytoplasmic inclusions reminiscent of neuropathologic changes in disease states.Furthermore, protein levels of TTBK1 and TTBK2 are increased in frontal cortex of FTLD-TDP patients, and TTBK1 and TTBK2 co-localize with TDP-43 inclusions in ALS spinal cord.These kinases may represent attractive targets for therapeutic intervention for TDP-43 proteinopathies such as ALS and FTLD-TDP.

View Article: PubMed Central - PubMed

Affiliation: Geriatric Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, Washington, United States of America; Department of Medicine, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
Pathological aggregates of phosphorylated TDP-43 characterize amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-TDP), two devastating groups of neurodegenerative disease. Kinase hyperactivity may be a consistent feature of ALS and FTLD-TDP, as phosphorylated TDP-43 is not observed in the absence of neurodegeneration. By examining changes in TDP-43 phosphorylation state, we have identified kinases controlling TDP-43 phosphorylation in a C. elegans model of ALS. In this kinome-wide survey, we identified homologs of the tau tubulin kinases 1 and 2 (TTBK1 and TTBK2), which were also identified in a prior screen for kinase modifiers of TDP-43 behavioral phenotypes. Using refined methodology, we demonstrate TTBK1 and TTBK2 directly phosphorylate TDP-43 in vitro and promote TDP-43 phosphorylation in mammalian cultured cells. TTBK1/2 overexpression drives phosphorylation and relocalization of TDP-43 from the nucleus to cytoplasmic inclusions reminiscent of neuropathologic changes in disease states. Furthermore, protein levels of TTBK1 and TTBK2 are increased in frontal cortex of FTLD-TDP patients, and TTBK1 and TTBK2 co-localize with TDP-43 inclusions in ALS spinal cord. These kinases may represent attractive targets for therapeutic intervention for TDP-43 proteinopathies such as ALS and FTLD-TDP.

No MeSH data available.


Related in: MedlinePlus