ALS-Linked Mutations Affect UBQLN2 Oligomerization and Phase Separation in a Position- and Amino Acid-Dependent Manner

Proteasomal shuttle factor UBQLN2 is recruited to stress granules and undergoes liquid-liquid phase separation (LLPS) into protein-containing droplets. Mutations to UBQLN2 have recently been shown to cause dominant X-linked inheritance of amyotrophic lateral sclerosis (ALS) and ALS/dementia. Interes...

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Bibliographic Details
Published in:Structure (London) 2019-06, Vol.27 (6), p.937-951.e5
Main Authors: Dao, Thuy P., Martyniak, Brian, Canning, Ashley J., Lei, Yongna, Colicino, Erica G., Cosgrove, Michael S., Hehnly, Heidi, Castañeda, Carlos A.
Format: Article
Language:English
Subjects:
Adaptor Proteins, Signal Transducing - chemistry
Adaptor Proteins, Signal Transducing - genetics
Adaptor Proteins, Signal Transducing - metabolism
aggregation
ALS
Amino Acids - chemistry
Amino Acids - genetics
Amino Acids - metabolism
Amyotrophic Lateral Sclerosis - genetics
Autophagy-Related Proteins - chemistry
Autophagy-Related Proteins - genetics
Autophagy-Related Proteins - metabolism
Humans
liquid-liquid phase separation
Mutation
oligomerization
Phase Transition
proline-rich
Protein Aggregates
Protein Aggregation, Pathological
Protein Multimerization
protein quality control
self-assembly
Stress, Physiological - genetics
ubiquilin-2
ubiquitin
Ubiquitins - genetics
Ubiquitins - metabolism
viscoelasticity
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Summary:Proteasomal shuttle factor UBQLN2 is recruited to stress granules and undergoes liquid-liquid phase separation (LLPS) into protein-containing droplets. Mutations to UBQLN2 have recently been shown to cause dominant X-linked inheritance of amyotrophic lateral sclerosis (ALS) and ALS/dementia. Interestingly, most of these UBQLN2 mutations reside in its proline-rich (Pxx) region, an important modulator of LLPS. Here, we demonstrated that ALS-linked Pxx mutations differentially affect UBQLN2 LLPS, depending on both amino acid substitution and sequence position. Using size-exclusion chromatography, analytical ultracentrifugation, microscopy, and NMR spectroscopy, we determined that those Pxx mutants that enhanced UBQLN2 oligomerization decreased saturation concentrations needed for LLPS and promoted solid-like and viscoelastic morphological changes to UBQLN2 liquid assemblies. Ubiquitin disassembled all LLPS-induced mutant UBQLN2 aggregates. We postulate that the changes in physical properties caused by ALS-linked Pxx mutations modify UBQLN2 behavior in vivo, possibly contributing to aberrant stress granule morphology and dynamics, leading to formation of inclusions, pathological characteristics of ALS. [Display omitted] •ALS-linked mutations in proline-rich region disrupt UBQLN2 phase separation (LLPS)•ALS-linked mutations promote UBQLN2 oligomerization and self-association•Hydrophobic mutations decrease saturation concentration necessary for UBQLN2 LLPS•Ubiquitin disassembles mutant UBQLN2 liquid and solid-like aggregates UBQLN2, part of protein quality control machinery in cells, phase separates under physiological conditions. Dao, Martyniak, et al. show that a subset of ALS-linked mutations in a C-terminal construct of UBQLN2 disrupt phase separation, promote oligomerization, and change the material properties of UBQLN2 droplets in vitro.
ISSN:0969-2126
1878-4186
DOI:10.1016/j.str.2019.03.012