Knockdown of transactive response DNA-binding protein (TDP-43) downregulates histone deacetylase 6

Abstract

TDP-43 is an RNA/DNA-binding protein implicated in transcriptional repression and mRNA processing. Inclusions of TDP-43 are hallmarks of frontotemporal dementia and amyotrophic lateral sclerosis. Besides aggregation of TDP-43, loss of nuclear localization is observed in disease. To identify relevant targets of TDP-43, we performed expression profiling. Thereby, histone deacetylase 6 (HDAC6) downregulation was discovered on TDP-43 silencing and confirmed at the mRNA and protein level in human embryonic kidney HEK293E and neuronal SH-SY5Y cells. This was accompanied by accumulation of the major HDAC6 substrate, acetyl-tubulin. HDAC6 levels were restored by re-expression of TDP-43, dependent on RNA binding and the C-terminal protein interaction domains. Moreover, TDP-43 bound specifically to HDAC6 mRNA arguing for a direct functional interaction. Importantly, in vivo validation in TDP-43 knockout Drosophila melanogaster confirmed the specific downregulation of HDAC6. HDAC6 is necessary for protein aggregate formation and degradation. Indeed, HDAC6-dependent reduction of cellular aggregate formation and increased cytotoxicity of polyQ-expanded ataxin-3 were found in TDP-43 silenced cells. In conclusion, loss of functional TDP-43 causes HDAC6 downregulation and might thereby contribute to pathogenesis.

A role for calpain-dependent cleavage of TDP-43 in amyotrophic lateral sclerosis pathology

“…The results from Tg mice expressing wild-type human and mouse TDP-43 are consistent with respect to the loss of nuclear TDP-43 but not cytoplasmic mislocalization 1,35,53,54 . In addition to generating aggregation-prone fragments, the cleavage of TDP-43's C-terminal disrupts binding to hnRNP A1, histone deacetylase 6 and fused in sarcoma/translocated in liposarcoma 2,55,56 . How neurons bearing TDP-43 pathology undergo neuronal death remains to be elucidated, but the present results on AR2 and AR2H mice indicate that the motor neurons expressing Q/R site-unedited GluA2 (refs 18, 25) exhibit loss of TDP-43 in the nucleus but not necessarily abnormal cytoplasmic inclusions during the process to death.…”

“…The disease course is rapidly progressive, and the eventual respiratory muscle weakness results in death within a few years of onset. The cause of ALS is largely unknown, but transactive response DNA-binding protein 43 (TDP-43), a nuclear protein involved in the regulation of RNA processing [1][2][3][4][5][6][7] , has recently attracted interest as a molecule relevant to the pathogenesis of this disease. TDP-43 is absent from the nucleus in which it normally resides but localizes in abnormal cytoplasmic inclusions in a considerable proportion of spinal cord motor neurons in the majority of sporadic ALS patients [8][9][10] .…”

“…TDP-43 is absent from the nucleus in which it normally resides but localizes in abnormal cytoplasmic inclusions in a considerable proportion of spinal cord motor neurons in the majority of sporadic ALS patients [8][9][10] . As TDP-43 is indispensable for embryonic development and neuronal cell survival in cell culture [2][3][4]7 and genetically modified animals 1 , abnormal localization of TDP-43 in ALS motor neurons is believed to have a pathogenic role in ALS.…”

Mutant induced pluripotent stem cell lines recapitulate aspects of TDP-43 proteinopathies and reveal cell-specific vulnerability

“…As determined by qRT-PCR, M337V and control iPSC lines expressed similar levels of TARDBP, the pluripotency markers TERT and REX1, and histone deacetylase 6 (HDAC6) mRNA (Fig. 3A), the latter of which is regulated by TDP-43 (30). Western blotting revealed that two independent M337V iPSC clones had higher levels of full-length TDP-43 in the soluble fraction and C-terminal TDP-43 fragments in the detergent-resistant fraction than controls (Fig.…”

Staurosporine Induced Apoptosis Rapidly Downregulates TDP-43 in Glioma Cells

“…To investigate the role of TDP-43 in STS-induced apoptosis in U87, we used TDP-43 siRNA specifically targeted for 3' UTR region of human TDP-43 mRNA (Fiesel et al, 2009) to knockdown endogenous TDP-43 before subjecting to STS (0.5uM) for 40 hours. Immunoblot was performed to exam the knockdown efficiency of siRNA ( Figure 4B).…”