Background: Identifying the underlying pathogenic mechanisms and disease-modifiers capable of altering the course of amyotrophic lateral sclerosis (ALS) is vital for the development of new therapies. One such candidate is the WW domain-containing oxidoreductase (WWOX), which plays a role in DNA damage repair, oxidative stress, neuronal differentiation, and neurodegeneration.
Objective: To determine whether and how alterations in WWOX signaling may contribute to ALS pathogenesis.
Results: Our findings demonstrate a significant decrease in WWOX levels in a large cohort of ALS post-mortem motor cortex (mCTX). Furthermore, genetic analysis of Project MinE data revealed several rare variants in WWOX in ALS patients that were completely absent in gnomAD. Four of these variants were associated with a high Combined Annotation Dependent Depletion score (CADD) (>25), including rWWOXG57E in the WW2 domain, WWOXSTOP261E in the mitochondria binding region of the short-chain alcohol dehydrogenases (SDR) domain, and rWWOXSTOP353Q and rWWOXA363P in the D3 region containing a pro-apoptotic tail. Interestingly, the SDR domain may regulate the mitochondrial electron transport chain (mtETC). Therefore, we assessed mtETC proteins in post-mortem ALS mCTX samples. Our results revealed a significant decrease in the levels of the ATP synthase subunit alpha of complex V (ATP5A) and the cytochrome c oxidase of complex IV (COX II or MTCO2) in ALS mCTX, consistent with previous findings. Additionally, co-immunoprecipitation experiments revealed that WWOX interacts with ATP5A in ALS post-mortem mCTX. Lastly, treatment of SH-SY5Y cells with the mutant rWWOX proteins reduced cell viability, and treatment with rWWOXSTOP261E specifically altered the levels of several mtETC proteins as well as ATP and reactive oxygen species (ROS) production in SH-SY5Y cells.
Conclusions: Collectively, our findings suggest that alterations in WWOX signaling may lead to mitochondrial dysfunction in ALS.