Ubiquitination of G3BP1 mediates stress granule disassembly in a stress-specific manner

Gwon, Youngdae; Maxwell, Brian A.; Kolaitis, Regina-Maria; Zhang, Peipei; Kim, Hong Joo; Taylor, J. Paul

doi:10.1101/2021.04.22.440930

Cited by 12 publications

(13 citation statements)

References 38 publications

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“…To prior efforts of how de-mixing RNA/RBP condensates are disassembled in cells 23,111,112 , our demonstration that HSPB1 facilitates disassembly of TDP-43 de-mixed droplets (Figure 5) offers what we believe is strong evidence for the proposal that binding of HSPB1 to TDP-43 in gel/solid structures acts to maintain TDP-43 in a refolding-capable state that facilitates its refolding. After removal of a provoking stress and restoration of ATP levels, it enhances droplet resolution (Supplemental Figure 11; Figure 7g) acting in conjunction with the HSP70 family chaperones, BAG2, BAG3, and HSP40 (e.g., DNAJB1 but not DNAJA1 [in line with recent report of the unique function DNAJB family proteins 113 ]).…”

Section: Discussionmentioning

confidence: 55%

Heat-shock chaperone HSPB1 regulates cytoplasmic TDP-43 phase separation and liquid-to-gel transition

Arogundade

et al. 2022

Nat Cell Biol

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While the RNA binding protein TDP-43 reversibly phase separates within nuclei into complex droplets (anisosomes) with TDP-43-containing liquid outer shells and liquid centers of HSP70 family chaperones, cytoplasmic aggregates of TDP-43 are hallmarks of multiple neurodegenerative diseases, including ALS. Here we show that transient oxidative stress, proteasome inhibition, or inhibition of HSP70's ATP-dependent chaperone activity provokes reversible cytoplasmic TDP-43 de-mixing and transition from liquid to gel/solid, independent of RNA binding or stress granules. Isotope labeling mass spectrometry is used to identify that phase separated cytoplasmic TDP-43 is primarily bound by the small heat shock protein HSPB1. Binding is direct, mediated through TDP-43's RNA binding and low complexity domains. HSPB1 partitions into TDP-43 droplets, inhibits TDP-43 assembly into fibrils, and is essential for disassembly of stress-induced, TDP-43 droplets. Decrease of HSPB1 promotes cytoplasmic TDP-43 de-mixing and mislocalization. HSPB1 depletion is identified within ALS-patient spinal motor neurons containing aggregated TDP-43. These findings identify HSPB1 to be a regulator of cytoplasmic TDP-43 phase separation and aggregation.

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Section: Discussionmentioning

confidence: 55%

Heat-shock chaperone HSPB1 regulates cytoplasmic TDP-43 phase separation and liquid-to-gel transition

Arogundade

et al. 2022

Nat Cell Biol

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“…Notably, in addition to eIF4A, other ATPases have also been shown to regulate SG dynamics. For example, recent studies have suggested a role for VCP, an AAA ATPase functioning as a segregase, in eliminating SGs through either the ubiquitin-proteasome or autophagy pathway 14,72 . Thus, reductions in ATP levels may regulate eSG/SG dynamics by affecting additional ATPases.…”

Section: Discussionmentioning

confidence: 99%

Intracellular Energy Controls Dynamics of Stress-induced Ribonucleoprotein Granules

Wang

Tian

Jang

et al. 2022

Preprint

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Energy metabolism and membraneless organelles have been implicated in human diseases including neurodegeneration. How energy stress regulates ribonucleoprotein particles such as stress granules (SGs) is still unclear. Here we identified a unique type of granules formed under energy stress and uncovered the mechanisms by which the dynamics of diverse stress-induced granules are regulated. Severe energy stress induced the rapid formation of energy-associated stress granules (eSGs), whereas moderate energy stress delayed the clearance of conventional SGs. The formation of eSGs or the clearance of conventional SGs was regulated by the mTOR-4EBP1-eIF4E pathway or eIF4A1, involving eIF4F complex assembly or RNA condensation, respectively. In ALS patients' neurons or cortical organoids, the eSG formation was enhanced, and conventional SG clearance was impaired. These results reveal a critical role for intracellular energy in the regulation of diverse granules and suggest that an imbalance in these dynamics may contribute to the pathogenesis of relevant diseases.

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“…UBQLN2 expression levels are negatively correlated to the number and sizes of stress granules (Alexander et al, 2018), indicating a role for UBQLN2 in regulating the disassembly of stress granules. Stress granules are cleared either following the removal of K63-linked polyubiquitinated G3BP1, a stress granule core protein, or by autophagy, depending on the stressor types and length of exposure (Buchan et al, 2013;Gwon et al, 2021). Through differential modulation of UBQLN2 LLPS by different polyUb chains, UBQLN2 may facilitate these different stress granule clearance processes (Fig.…”

Section: Discussionmentioning

confidence: 99%

Mechanistic insights into the enhancement or inhibition of phase separation by polyubiquitin chains of different lengths or linkages

Dao

Yang

Presti

et al. 2021

Preprint

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SummaryUbiquitin-binding shuttle UBQLN2 mediates crosstalk between proteasomal degradation and autophagy, likely via interactions with K48- and K63-linked polyubiquitin chains, respectively. UBQLN2 is recruited to stress granules in cells and undergoes liquid-liquid phase separation (LLPS) in vitro. However, interactions with ubiquitin or multivalent K48-linked chains eliminate LLPS. Here, we found that, although some polyubiquitin chain types (K11-Ub4 and K48-Ub4) did generally inhibit UBQLN2 LLPS, others (K63-Ub4, M1-Ub4 and a designed tetrameric ubiquitin construct) significantly enhanced LLPS. Using nuclear magnetic resonance (NMR) spectroscopy and complementary biophysical techniques, we demonstrated that these opposing effects stem from differences in chain conformations, but not in affinities between chains and UBQLN2. Chains with extended conformations and increased accessibility to the ubiquitin binding surface significantly promoted UBQLN2 LLPS by enabling a switch between homotypically to partially heterotypically-driven phase separation. Our study provides mechanistic insights into how the structural and conformational properties of polyubiquitin chains contribute to heterotypic phase separation with ubiquitin-binding shuttles and adaptors.HighlightsUbiquitin or short polyubiquitin chains bind to phase separation-driving stickers on UBQLN2 and inhibit its phase separation whereas longer chains provide the multivalency needed to enhance UBQLN2 phase separation.Compact K11- and K48-linked Ub4 chains destabilized UBQLN2 phase separation, while extended M1- and K63-linked Ub4 promoted UBQLN2 phase separation.Chain conformation and accessibility of the Ub interacting surface is a driving factor of UBQLN2/polyUb co-phase separation.UBQLN2 condensates assemble during in vitro enzymatic assembly of K63-linked polyUb chains as free ubiquitin is depleted.

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Ubiquitination of G3BP1 mediates stress granule disassembly in a stress-specific manner

Cited by 12 publications

References 38 publications

Heat-shock chaperone HSPB1 regulates cytoplasmic TDP-43 phase separation and liquid-to-gel transition

Heat-shock chaperone HSPB1 regulates cytoplasmic TDP-43 phase separation and liquid-to-gel transition

Intracellular Energy Controls Dynamics of Stress-induced Ribonucleoprotein Granules

Mechanistic insights into the enhancement or inhibition of phase separation by polyubiquitin chains of different lengths or linkages

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