Global Shifts in Protein Sumoylation in Response to Electrophile and Oxidative Stress

The neurodegenerative disorder spinal and bulbar muscular atrophy or Kennedy disease is caused by a CAG trinucleotide repeat expansion within the androgen receptor (AR) gene. The resulting expanded polyglutamine tract in the N-terminal region of the receptor renders AR prone to ligand-dependent misfolding and formation of oligomers and aggregates that are linked to neuronal toxicity. How AR misfolding is influenced by post-translational modifications, however, is poorly understood. AR is a target of SUMOylation, and this modification inhibits AR activity in a promoter context-dependent manner. SUMOylation is up-regulated in response to multiple forms of cellular stress and may therefore play an important cytoprotective role. Consistent with this view, we find that gratuitous enhancement of overall SUMOylation significantly reduced the formation of polyglutamine-expanded AR aggregates without affecting the levels of the receptor. Remarkably, this effect requires SUMOylation of AR itself because it depends on intact AR SUMOylation sites. Functional analyses, however, indicate that the protective effects of enhanced AR SUMOylation are not due to alterations in AR transcriptional activity because a branched protein structure in the appropriate context of the N-terminal region of AR is necessary to antagonize aggregation but not for inhibiting AR transactivation. Remarkably, small ubiquitin-like modifier (SUMO) attenuates AR aggregation through a unique mechanism that does not depend on critical features essential for its interaction with canonical SUMO binding motifs. Our findings therefore reveal a novel function of SUMOylation and suggest that approaches that enhance AR SUMOylation may be of clinical use in polyglutamine expansion diseases.Spinal and bulbar muscular atrophy (SBMA), 2 or Kennedy disease, is an inherited degenerative disorder of lower motor neurons (1, 2). SBMA is characterized by muscle cramps and fasciculations followed by progressive weakness and atrophy of the proximal limb and bulbar muscles (3-5). The causative genetic alteration is an expansion in the length of a CAG trinucleotide repeat within the coding sequence of the androgen receptor (AR) gene, leading to an expanded polyglutamine tract in the N-terminal transcriptional regulatory domain of the receptor. A similar expansion within the coding sequence of a set of additional genes is responsible for other members of the polyglutamine class of protein folding diseases (6, 7), which include Huntington disease, several autosomal dominant spinocerebellar ataxias (SCAs) (8), and dentatorubral-pallidoluysian atrophy (9, 10).The length of the CAG repeat within AR is correlated to the severity of SBMA. Although the normal repeat length is highly polymorphic and ranges between 9 and 36 copies, overt disease is associated with lengths in the range of 38 -62 repeats. The presence of an expanded polyglutamine tract within AR renders the protein prone to hormone-dependent misfolding, oligomerization, and aggregation and to the formation of microscopica...

Section: Resultsmentioning

confidence: 99%

Small Ubiquitin-like Modifier (SUMO) Modification of the Androgen Receptor Attenuates Polyglutamine-mediated Aggregation

Mukherjee¹,

Thomas

Dadgar

et al. 2009

“…Arsenite treatment induces SUMOylation and degradation of PML-RARA fusion protein in leukemic cells, which underlies its clinical implications in remissions of acute promyelocytic leukemia (36,37). Therefore, we used arsenite as an oxidative stress inducer and investigated its potential effect on nucleolin SUMOylation.…”

Section: Discovery Of Nucleolinmentioning

confidence: 99%

“…In terms of nucleolin, we did observe a weak presence of nucleolin SUMOylation without any stimulation, which might account for its steady nuclear sequestration. Meanwhile, the protein SUMO level is dynamically regulated under various stress conditions, including osmotic stress, hypoxia, heat shock, and oxidative stress (36,37,48). On one hand, a low or moderate level of oxidative stress inhibits SUMOylation by oxidation of SUMO E1 and E2 enzymes, leading to disulfide bond formation between SAE1 and UBC9 (62).…”

mentioning

confidence: 99%

A Novel Post-translational Modification of Nucleolin, SUMOylation at Lys-294, Mediates Arsenite-induced Cell Death by Regulating gadd45α mRNA Stability

Zhang

Liang

Xie

et al. 2015

Background: Nucleolin is a multifunctional protein, but nucleolin-SUMO is unexploited. Results: Nucleolin-SUMO at Lys-294 facilitated binding with mRNA substrate gadd45␣ by maintaining its nuclear localization during cellular response to arsenite exposure. Conclusion: Nucleolin-SUMO promoted arsenite-induced apoptosis by increasing GADD45␣ expression. Significance: We identified a new modification of nucleolin and its contribution to the functional paradigm of nucleolin in mRNA stability regulation.

“…In contrast, SUMO2 and -3, referred to as SUMO2/3, are unconjugated but can rapidly convert to be conjugated in response to a variety of cellular stresses (2)(3)(4)(5)(6)(7). The progress of SUMOylation is reversible.…”

mentioning

confidence: 99%

SENP3-mediated De-conjugation of SUMO2/3 from Promyelocytic Leukemia Is Correlated with Accelerated Cell Proliferation under Mild Oxidative Stress

Han

Huang

Sun

et al. 2010

102

Small ubiquitin-like modifier (SUMO) 2/3 is known to conjugate to substrates in response to a variety of cellular stresses. However, whether and how SUMO2/3-specific proteases are involved in de-conjugation under cell stress is unclear. Here, we show that low doses of hydrogen peroxide (H 2 O 2 ) induce an increase of the SENP3 protein, which removes SUMO2/3 from promyelocytic leukemia (PML). Low dose H 2 O 2 causes SENP3 to co-localize with PML bodies and reduces the number of PML bodies in a SENP3-dependent manner. Furthermore, de-conjugation of SUMO2/3 from PML is responsible for the accelerated cell proliferation caused by low dose H 2 O 2 . Knocking down PML promotes basal cell proliferation as expected. This can be reversed by reconstitution with wild-type PML but not its mutant lacking SUMOylation, indicating that only the SUMOylated PML can play an inhibitory role for cell proliferation. Thus, SENP3 appears to be a key mediator in mild oxidative stress-induced cell proliferation via regulation of the SUMOylation status of PML. Furthermore, SENP3 is over-accumulated in a variety of primary human cancers including colon adenocarcinoma in which PML is hypo-SUMOylated. These results reveal an important role of SENP3 and the SUMOylation status of PML in the regulation of cell proliferation under oxidative stress.