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ALS and Ubiquilin‐2: Effects of ALS Mutations on Ubiquilin‐2 Structure and Function
Author(s) -
Castaneda Carlos,
Dao Thuy
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.914.11
Subject(s) - microbiology and biotechnology , endoplasmic reticulum associated protein degradation , mutant , mutation , ubiquitin , endoplasmic reticulum , biology , chemistry , unfolded protein response , biochemistry , gene
Amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases are caused by malfunctions in ubiquitin‐mediated protein degradation pathways. Ubiquilin‐2 is a 624‐amino acid multi‐domain adaptor protein critical for maintaining protein homeostasis through the ubiquitin‐proteasome system, the endoplasmic reticulum‐associated protein degradation (ERAD) pathway and autophagy. Mutations in ubiquilin‐2 have recently been shown to cause dominant x‐linked inheritance of ALS and ALS/dementia. Moreover, wild‐type ubiquilin‐2 is present in protein inclusions found in patients diagnosed with either familial or sporadic ALS, further linking ubiquilin‐2 to the pathogenesis of ALS. Interestingly, most ALS‐linked mutations are localized to the proline‐rich repeat (Pxx) region that is unique to ubiquilin‐2 and not present in the other members of the ubiquilin protein family. The consequences of these mutations (specifically to residues P497, P506, P509, P525 and P533) on ubiquilin‐2's structure and function remain unknown. Towards that end, we are using biomolecular NMR spectroscopy and other biophysical techniques to characterize the Pxx region of ubiquilin‐2. 13 C‐detect NMR experiments have allowed for the direct and necessary observation of the prolines as well as aided in resonance assignment for a significant portion of this ubiquilin‐2 region. Significantly, even though the Pxx region is intrinisically disordered, we observed sequence‐distant perturbations in several ALS‐linked mutants. Serendipitously, similar to some other ALS‐linked proteins such as TDP‐43 and hnRNPA1, our ubiquilin‐2 constructs exhibit salt and temperature dependent liquid‐like phase‐separation, a behavior that is also affected by ALS mutations. Our data suggest that the C‐terminal region of ubiquilin‐2 is important for modulating phase separation behavior. We are working towards modeling the structure of ubiquilin‐2 containing the Pxx region, as well as identifying protein‐binding surfaces involving the Pxx region. Support or Funding Information ALS Association Starter Grant to C.A.C.