Rsp5/NEDD4 and ESCRT regulate TDP-43 toxicity and turnover via an endolysosomal clearance mechanism

Sep 30, 2026

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Cytoplasmic mislocalization and aggregation of TDP-43, a nuclear RNA-binding protein, is a hallmark of most amyotrophic lateral sclerosis (ALS) cases, and enhanced clearance of cytoplasmic TDP-43 can reduce toxicity. The regulation of this clearance remains unclear. An unbiased high-throughput yeast dot blot screen identified ESCRT complex genes and K63-ubiquitination-linked factors, including Rsp5/NEDD4, as drivers of endolysosomal TDP-43 turnover. Rsp5/NEDD4 and ESCRT proteins bind and colocalize with TDP-43; their disruption increases aggregation, stability, and toxicity.

LanguageEnglish

CategoryHealthcare

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Pages28

Reading Time1 h 11 min

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Introduction

TDP-43 pathology in ALS

Proteostasis and known degradation pathways

Debated mechanisms for TDP-43 degradation

ARTICLE Rsp5/NEDD4 and ESCRT regulate TDP-43 toxicity and turnover via an endolysosomal clearance mechanism Aaron Byrd1,2*􀀁, Lucas J. Marmorale1*􀀁, Sophia Marcinowski1􀀁, Megan M. Dykstra3􀀁, Vanessa Addison1􀀁, Sami J. Barmada3􀀁, and J. Ross Buchan1􀀁 A pathological hallmark in >97% of amyotrophic lateral sclerosis (ALS) cases is the cytoplasmic mislocalization and aggregation of TDP-43, a nuclear RNA-binding protein, in motor neurons. Driving clearance of cytoplasmic TDP-43 reduces toxicity in ALS models, though how TDP-43 clearance is regulated remains controversial. We conducted an unbiased yeast screen using high-throughput dot blotting to identify genes that affect TDP-43 levels. We identified ESCRT complex genes, which induce membrane invagination (particularly at multivesicular bodies; MVBs) and genes linked to K63 ubiquitination (particularly cofactors of the E3 ubiquitin ligase Rsp5; NEDD4 in humans), as drivers of TDP-43 endolysosomal clearance. TDP-43 colocalized and bound Rsp5/NEDD4 and ESCRT proteins, and perturbations to either increased TDP-43 aggregation, stability, and toxicity. NEDD4 also ubiquitinates TDP-43. Lastly, TDP-43 accumulation induces giant MVB-like vesicles, within which TDP-43 accumulates in a NEDD4-dependent manner. Our studies shed light on endolysosomal-mediated cytoplasmic protein clearance, a poorly understood proteostasis mechanism, which may help identify novel ALS therapeutic strategies. Introduction Amyotrophic lateral sclerosis (ALS) is an age-related neurodegenerative disease that affects motor neurons and support cells of the brain and spinal cord. ALS is characterized by progressive degeneration and death of motor neurons, muscle weakness, and fatal paralysis due to respiratory∼ failure that typically occurs 2– 5 years after diagnosis. While 5–10% of cases exhibit a hereditary component, most ALS cases are sporadic and are not associated with a specific gene mutation. Many familial ALS mutations are in genes that impact RNA metabolism and proteostasis, indicating a likely role for these processes in ALS pathology. However, the molecular mechanisms underlying ALS onset and disease progression are still unknown, and no effective treatments for ALS exist (Taylor et al., 2016). Regardless of disease etiology, a common pathological feature that unites >97% of all ALS cases is the cytoplasmic mislocalization, accumulation, and often aggregation of a nuclear RNA-binding protein, TAR DNA-binding protein 43 (TDP-43)(Ling et al., 2013) . TDP-43 preferentially binds UG-rich sequences and functions in many mRNA metabolic processes, including regulation of alternative splicing, mRNA localization, and mRNA stability. TDP-43 mislocalization and accumulation within the cytoplasm results in a toxic gain-of-function, which could reflect TDP-43 aggregates sequestering key RNAs and proteins, as well as a nuclear loss-of-function, in which TDP-43 nuclear depletion may impair the performance of its various nuclear roles (Cascella et al., 2016). Failure to effectively clear cytoplasmic TDP-43 may facilitate the pathology of ALS. Indeed, many proteins involved in proteostasis mechanisms such as autophagy and the ubiquitin– proteasome system (UPS), including SQSTM1 (Fecto et al., 2011), VCP (Watts et al., 2004), UBQLN2 (Deng et al., 2011), and OPTN (Maruyama et al., 2010), are mutated in rare familial ALS cases. Also, ALS disease phenotypes can be recapitulated by overexpressing TDP-43 in numerous models (yeast [Johnson et al., 2008], flies [Li et al., 2010], and human cells [Bilicanet al., 2012]), indicating that accumulation of TDP-43 is pathogenic. Additionally, increasing TDP-43 degradation by driving bulk, nonselective autophagy can reverse toxicity associated with TDP-43 accumulation and/or mislocalization (Wang et al., 2012; Barmada et al., 2014). Therefore, increasing clearance of TDP-43 may be a broadly applicable therapeutic strategy for diseases with cytoplasmic TDP-43 proteinopat

FAQs

What is the main pathological feature of TDP-43 in ALS described here?

The text describes cytoplasmic mislocalization and aggregation of TDP-43 in motor neurons, occurring in the majority of ALS cases.

How did the study identify genes involved in TDP-43 clearance?

It used an unbiased yeast screen with high-throughput dot blotting to find genes that affect TDP-43 levels.

Which molecular systems regulate TDP-43 turnover in an endolysosomal route according to the study?

The study implicates ESCRT complex genes and K63-ubiquitination-linked factors, particularly Rsp5/NEDD4, as drivers of endolysosomal clearance of TDP-43.

Sep 30, 2026

Uploaded by Aran