title: High-content RNAi screening identifies the Type 1 inositol triphosphate receptor as a modifier of TDP-43 localization and neurotoxicity.
abstract: Cytosolic aggregation of the nuclear RNA-binding protein (RBP) TDP-43 (43 kDa TAR DNA-binding domain protein) is a suspected direct or indirect cause of motor neuron deterioration in amyotrophic lateral sclerosis (ALS). In this study, we implemented a high-content, genome-wide RNAi screen to identify pathways controlling TDP-43 nucleocytoplasmic shuttling. We identified ∼60 genes whose silencing increased the cytosolic localization of TDP-43, including nuclear pore complex components and regulators of G2/M cell cycle transition. In addition, we identified the type 1 inositol-1,4,5-trisphosphate (IP3) receptor (ITPR1), an IP3-gated, endoplasmic reticulum (ER)-resident Ca(2+) channel, as a strong modulator of TDP-43 nucleocytoplasmic shuttling. Knockdown or chemical inhibition of ITPR1 induced TDP-43 nuclear export in immortalized cells and primary neurons and strongly potentiated the recruitment of TDP-43 to Ubiquilin-positive autophagosomes, suggesting that diminished ITPR1 function leads to autophagosomal clearance of TDP-43. The functional significance of the TDP-43-ITPR1 genetic interaction was tested in Drosophila, where mutant alleles of ITPR1 were found to significantly extended lifespan and mobility of flies expressing TDP-43 under a motor neuron driver. These combined findings implicate IP3-gated Ca(2+) as a key regulator of TDP-43 nucleoplasmic shuttling and proteostasis and suggest pharmacologic inhibition of ITPR1 as a strategy to combat TDP-43-induced neurodegeneration in vivo.
authors.affiliation: Department of Human Oncology, University of Wisconsin-Madison, Madison, WI 53705, USA.
authors.forename: Sang Hwa
authors.initials: SH
authors.lastname: Kim
authors.forename: Lihong
authors.initials: L
authors.lastname: Zhan
authors.forename: Keith A
authors.initials: KA
authors.lastname: Hanson
authors.forename: Randal S
authors.initials: RS
authors.lastname: Tibbetts
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000633:toxicity; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D057166:High-Throughput Screening Assays; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D009154:Mutation; D010588:Phagosomes / Q000378:metabolism; D021381:Protein Transport; D034622:RNA Interference
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D004268:DNA-Binding Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors