SCAN1-TDP1 trapping on mitochondrial DNA promotes mitochondrial dysfunction and mitophagy

Abstract

A homozygous mutation of human tyrosyl-DNA phosphodiesterase 1 (TDP1) causes the neurodegenerative syndrome, spinocerebellar ataxia with axonal neuropathy (SCAN1). TDP1 hydrolyzes the phosphodiester bond between DNA 3′-end and a tyrosyl moiety within trapped topoisomerase I (Top1)-DNA covalent complexes (Top1cc). TDP1 is critical for mitochondrial DNA (mtDNA) repair; however, the role of mitochondria remains largely unknown for the etiology of SCAN1. We demonstrate that mitochondria in cells expressing SCAN1-TDP1 (TDP1H493R) are selectively trapped on mtDNA in the regulatory non-coding region and promoter sequences. Trapped TDP1H493R-mtDNA complexes were markedly increased in the presence of the Top1 poison (mito-SN38) when targeted selectively into mitochondria in nanoparticles. TDP1H493R-trapping accumulates mtDNA damage and triggers Drp1-mediated mitochondrial fission, which blocks mitobiogenesis. TDP1H493R prompts PTEN-induced kinase 1–dependent mitophagy to eliminate dysfunctional mitochondria. SCAN1-TDP1 in mitochondria creates a pathological state that allows neurons to turn on mitophagy to rescue fit mitochondria as a mechanism of survival.

DNA and RNA Cleavage Complexes and Repair Pathway for TOP3B RNA- and DNA-Protein Crosslinks

“…Similarly, earlier publications show that TDP1 or TDP2 depletion increases TOP1ccs and TOP2ccs. Specifically, TDP1 depletion increases TOP1ccs in Tdp1−/− neural tissue ( Katyal et al, 2014 ) and TOP1MTccs in mitochondria ( Chiang et al, 2017 ; Ghosh et al, 2019 ). Two additional publications show that TDP2−/− cells accumulate more TOP2ccs ( Hoa et al, 2016 ; Sasanuma et al, 2018 ).…”

Top1-PARP1 association and beyond: from DNA topology to break repair

“…Cells from SCAN1 patients or TDP1 knockout mice are hypersensitive to camptothecin (CPT) that selectively trap nuclear Top1-DNA covalent complexes (Top1cc) ( 2 , 3 , 35 , 39 ). TDP1 is critical for mitochondrial DNA (mtDNA) repair ( 34 ), accordingly SCAN1-mutant TDP1 is trapped in the specific loci of mtDNA, which increases mitochondrial DNA damage, and mitochondrial fission that leads to neuronal damage associated with SCAN1 etiology ( 40 ). Loss of TDP1 also resulted in gradual age-related cerebellar atrophy in one of the mouse model ( 2 , 35 , 39 ).…”

Tang Luo Ning, a Traditional Chinese Compound Prescription, Ameliorates Schwannopathy of Diabetic Peripheral Neuropathy Rats by Regulating Mitochondrial Dynamics In Vivo and In Vitro

“…The mitochondria number and mitochondria coverage were quantified using ImageJ software (Dietrich et al, 2013). In addition, mitochondria was measured by incubating with MitoTracker Green FM (200 nM, M7154, Thermo Fisher) for 30 min at 37°C in the dark according to the manufacturer's instructions (Ghosh et al, 2019). After incubation, the cells were washed twice with pre-warmed DMEM.…”

“…Determination of ΔΨm was performed using TMRM (Ghosh et al, 2019). Cells were cultured in a 20-mm confocal dish and incubated with Image-iT ™ TMRM Reagent (200 nM, I34361, Thermo Fisher) and MitoTracker ™ Red FM (200 nM, M22425, Thermo Fisher) for 30 min at 37°C according to the manufacturer's instructions.…”