Stress granules (SGs) are transient ribonucleoprotein (RNP) aggregates that form during cellular stress and are increasingly implicated in human neurodegeneration. To study the proteome and compositional diversity of SGs in different cell types and in the context of neurodegeneration-linked mutations, we used ascorbate peroxidase (APEX) proximity labeling, mass spectrometry, and immunofluorescence to identify ∼150 previously unknown human SG components. A highly integrated, pre-existing SG protein interaction network in unstressed cells facilitates rapid coalescence into larger SGs. Approximately 20% of SG diversity is stress or cell-type dependent, with neuronal SGs displaying a particularly complex repertoire of proteins enriched in chaperones and autophagy factors. Strengthening the link between SGs and neurodegeneration, we demonstrate aberrant dynamics, composition, and subcellular distribution of SGs in cells from amyotrophic lateral sclerosis (ALS) patients. Using three Drosophila ALS/FTD models, we identify SG-associated modifiers of neurotoxicity in vivo. Altogether, our results highlight SG proteins as central to understanding and ultimately targeting neurodegeneration.

Highlights d CeFra-seq applied to a range of cell types reveals basic rules of RNA localization d Transient stress disrupts subcellular mRNA and protein localization landscapes d Stress alters RNA binding of RBPs, including TDP-43, and alters splicing of STMN2 d Stress induces persistent RNA localization changes and cell death in ALS neurons

Stress granules (SGs) are transient ribonucleoprotein (RNP) aggregates that form in response to proteotoxic stress. Although SGs are distinct from aggregates observed in neurodegenerative disorders, they share protein components. We used APEX-mediated proximity labeling combined with quantitative mass spectrometry and high-throughput imaging to identify >100 previously unknown SG proteins in human cells, about 10% of which localize to SGs in a cell type-or stress type-dependent manner.Supporting a link between SG proteins and neurodegeneration, we demonstrate aberrant SG composition and subcellular distribution in iPSC-derived motor neurons from ALS patients, and identify several known and previously unidentified SG proteins that modify toxicity of mutant FUS and TDP-43 overexpression in Drosophila. We show that even in an unstressed steady-state, SG proteins form a densely-connected protein interaction network (PIN) and propose a model in which existing RNPs coalesce rapidly into microscopically visible granules that can act as gateways to pathological protein aggregation.

Stress granules (SGs) are transient ribonucleoprotein (RNP) aggregates that form during cellular stress and are increasingly implicated in human neurodegeneration. To study the proteome and compositional diversity of SGs in different cell types and in the context of neurodegeneration‐linked mutations, we used APEX proximity labeling, mass spectrometry and immunofluorescence to identify ~150 previously unknown human SG components. SG proteins form a dense interaction network in unstressed cells, facilitating rapid coalescence into larger SGs. About 20% of SG diversity is stress‐ or cell type‐dependent, with neuronal SGs displaying a particularly complex repertoire of proteins enriched in chaperones and autophagy factors. Strengthening the link between SGs and neurodegeneration, we demonstrate aberrant dynamics, composition and subcellular distribution of SGs in cells from ALS patients. Using three Drosophila ALS/FTD models, we identify ~30 SG‐associated modifiers of neurotoxicity in vivo. Altogether, our results highlight SG proteins as central to understanding and ultimately targeting neurodegeneration.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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