ALS-Linked Mutations Affect UBQLN2 Oligomerization and Phase Separation in a Position- and Amino Acid-Dependent Manner
ALS-Linked Mutations Affect UBQLN2 Oligomerization and Phase Separation in a Position- and Amino Acid-Dependent Manner
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DOI：
10.1016/j.str.2019.03.012
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发表时间：
2019-06-04
期刊：
影响因子：
5.7
通讯作者：
Castaneda, Carlos A.
中科院分区：
文献类型：
--
作者：
Dao, Thuy P.;Martyniak, Brian;Castaneda, Carlos A.
蛋白酶体穿梭因子UBQLN 2被募集以应激颗粒并经历液-液相分离（LLPS）成含蛋白质的液滴。UBQLN 2的突变最近被证明会导致肌萎缩侧索硬化症（ALS）和ALS/痴呆的显性X连锁遗传。有趣的是，这些UBQLN 2突变中的大多数位于其富含脯氨酸（Pxx）的区域，这是LLPS的重要调节剂。在这里，我们证明了ALS连锁的Pxx突变差异影响UBQLN 2 LLPS，这取决于氨基酸取代和序列位置。使用尺寸排阻色谱，分析超离心，显微镜，和NMR光谱，我们确定，这些Pxx突变体，增强UBQLN 2寡聚化降低LLPS所需的饱和浓度，并促进固体样和粘弹性形态变化的UBQLN 2液体组件。泛素分解所有LLPS诱导的突变体UBQLN 2聚集体。我们推测ALS连锁Pxx突变引起的物理性质的变化改变了UBQLN 2在体内的行为，可能有助于异常的应力颗粒形态和动力学，导致形成包涵体，ALS的病理特征。
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.