The deubiquitinase ataxin-3 requires Rad23 and DnaJ-1 for its neuroprotective role in Drosophila melanogaster

Abstract

Ataxin-3 is a deubiquitinase and polyglutamine (polyQ) disease protein with a protective role in Drosophila melanogaster models of neurodegeneration. In the fruit fly, wild-type ataxin-3 suppresses toxicity from several polyQ disease proteins, including a pathogenic version of itself that causes spinocerebellar ataxia type 3 and pathogenic huntingtin, which causes Huntington’s disease. The molecular partners of ataxin-3 in this protective function are unclear. Here, we report that ataxin-3 requires its direct interaction with the ubiquitin-binding and proteasome-associated protein, Rad23 (known as hHR23A/B in mammals) in order to suppress toxicity from polyQ species in Drosophila. According to additional studies, ataxin-3 does not rely on autophagy or the proteasome to suppress polyQ-dependent toxicity in fly eyes. Instead this deubiquitinase, through its interaction with Rad23, leads to increased protein levels of the co-chaperone DnaJ-1 and depends on it to protect against degeneration. Through DnaJ-1, our data connect ataxin-3 and Rad23 to protective processes involved with protein folding rather than increased turnover of toxic polyQ species.

Polyglutamine length-dependent toxicity from α1ACT inDrosophilamodels of spinocerebellar ataxia type 6

“…Still, a clear, age-dependent phenotype is observable phenotypically (disruption of internal eye structures; shorter life span) and biochemically (SDS-resistant species that become more prominent over time) when the protein is expressed selectively in fly retinae or in all tissues. Fly eyes have been used frequently and successfully to understand the biology of disease of various toxic proteins and to screen for modifiers of these diseases (Bilen and Bonini, 2007; Blount et al, 2014; Bonini and Fortini, 2003; Casci and Pandey, 2015; Lanson et al, 2011; McGurk and Bonini, 2012; Park et al, 2013; Tsou et al, 2013, 2015b); our finding that α1ACT leads to eye degeneration in a time- and polyQ length-dependent manner is of importance to future work in SCA6.…”

USP5 Is Dispensable for Monoubiquitin Maintenance in Drosophila

“…SDS-PAGE, Western Blotting, and Quantification-Larvae, pupae, or flies, as indicated in figures and legends, were homogenized in boiling SDS lysis buffer (50 mM Tris, pH 6.8, 2% SDS, 10% glycerol, and 100 mM DTT), sonicated, boiled for 10 min, centrifuged for 10 min at 13,000 ϫ g at room temperature, loaded onto SDS-PAGE gels, electrophoresed at 160 -170 V, and transferred onto PVDF membranes (Bio-Rad) for Western blotting, as previously described (19,(22)(23)(24)(25). 10 larvae, 5 pupae, or 5 adults were collected per group in 15 l of lysis buffer per larva, 20 l of lysis buffer per pupa, or 30 l of buffer per adult.…”

Structures of Rpn1 T1:Rad23 and hRpn13:hPLIC2 Reveal Distinct Binding Mechanisms between Substrate Receptors and Shuttle Factors of the Proteasome

“…hPLIC proteins are associated with protein quality control pathways through their connections to neurodegenerative diseases (Deng et al, 2011; Hiltunen et al, 2006; Mah et al, 2000; Stieren et al, 2011), cytoprotective activity during stress (Lu et al, 2009), aggresome formation (Heir et al, 2006), targeting of aggregated proteins to autophagosomes (N’Diaye et al, 2009; Rothenberg et al, 2010), and clearance of expanded polyglutamine proteins (Wang et al, 2006; Wang and Monteiro, 2007). Rad23 proteins are similarly associated with neuroprotection activities (Tsou et al, 2015), but are most well known for their function in nucleotide excision repair (Mueller and Smerdon, 1996; Watkins et al, 1993). hHR23b (a human ortholog of Rad23) is downregulated in highly invasive breast cancer cell lines (Linge et al, 2014), associated with risk of lung, laryngeal and bladder cancer (Abbasi et al, 2009; Chang et al, 2008; Chen et al, 2007), and substitution of A249 for valine in this protein is associated with increased esophageal cancer risk (Pan et al, 2009).…”