G3BP1 inhibits ubiquitinated protein aggregations induced by p62 and USP10

Sergei Anisimov,Akiyoshi Kakita,Yoshinori Katsuragi,Taichi Kakihana,Hiroki Kitaura,Lu Zhang,Masahiko Takahashi,Masahiro Fujii

doi:10.1038/s41598-019-46237-1

Sergei Anisimov, Akiyoshi Kakita + Show 6 more

Open Access

https://doi.org/10.1038/s41598-019-46237-1

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Journal: Scientific Reports	Publication Date: Sep 9, 2019
Citations: 25	License type: open-access

Affiliation: Niigata University

Abstract

The aberrant accumulation of ubiquitinated protein aggregates in cells plays a critical role in the pathogenesis of several degenerative diseases, including Parkinson disease (PD) and cystic fibrosis (CF). In this study, we found that Ras GTPase-activating protein-binding protein 1 (G3BP1) inhibits ubiquitinated protein aggregations induced by p62 and USP10 in cultured cells. p62 is a ubiquitin receptor, and p62 and its binding partner USP10 have been shown to augment ubiquitinated protein aggregation. G3BP1 interacted with p62 and USP10 and inhibited p62/USP10-induced protein aggregation. The G3BP1 inhibition of protein aggregations targeted two aggregation-prone proteins, α-synuclein and CFTR-ΔF508, which are causative factors of PD and CF, respectively. G3BP1 depletion increased the amounts of ubiquitinated α-synuclein and CFTR-ΔF508 protein. A proteasome reporter indicated that G3BP1 depletion inhibits the proteasome activity. We herein present evidence that G3BP1, p62 and USP10 together control ubiquitinated protein toxicity by controlling both ubiquitination and aggregation. Taken together, these results suggest that G3BP1, p62 and USP10 could be therapeutic targets for ubiquitinated protein aggregation disorders, including PD and CF.

Highlights

The aberrant accumulation of ubiquitinated protein aggregates in cells is a common cause of many degenerative diseases, such as α-synuclein in Parkinson’s disease (PD) and CFTR-ΔF508 in cystic fibrosis (CF)1–3. α-synuclein is a causative factor of familial and sporadic PD4. α-synuclein is aggregation-prone, and α-synuclein-associated Parkinson disease (PD) is characterized by intracellular deposition of ubiquitinated α-synuclein aggregates as a Lewy body in neurons in brain lesions[4,5]
G3BP2-KD did not show stimulatory activity on the amount of ubiquitinated protein. These results suggested that G3BP1 but not G3BP2 reduces the amount of ubiquitinated proteins in HeLa cells
The existence of distinct binding specificities of G3BP1 mutants to p62 and USP10 suggests that G3BP1 and G3BP2 interact with p62 and USP10 by different mechanisms. These results suggested that G3BP1 inhibits p62/USP10-induced protein aggregation by interacting with p62 and/or USP10, and interactions of G3BP1 and G3BP2 with p62 and USP10 might explain the antagonistic activities of G3BP1-KD and G3BP2-KD against CFTR-ΔF508 aggregation

Summary

Introduction

The aberrant accumulation of ubiquitinated protein aggregates in cells is a common cause of many degenerative diseases, such as α-synuclein in Parkinson’s disease (PD) and CFTR-ΔF508 in cystic fibrosis (CF)1–3. α-synuclein is a causative factor of familial and sporadic PD4. α-synuclein is aggregation-prone, and α-synuclein-associated PD is characterized by intracellular deposition of ubiquitinated α-synuclein aggregates as a Lewy body in neurons in brain lesions[4,5]. CFTR-ΔF508 is ubiquitination-prone, and ubiquitinated CFTR-ΔF508 is degraded by the ubiquitin-proteasome system and reduces the amount of functional CFTR8 Precisely how such cells control the ubiquitinated protein aggregations and how such pathogenic inclusions are formed in degenerative diseases remains poorly understood. Many ubiquitination/aggregation-prone proteins, including α-synuclein and CFTR-ΔF508, share one notable characteristic: they are localized in aggresomes in cultured cells[9,10]. Aggresomes are large cytoplasmic protein aggregates induced by various stress inducers, such as proteasome inhibitor[8,9,11] Aggresomes contain both ubiquitinated and non-ubiquitinated proteins, autophagy-associated proteins, chaperons and others. USP10 has two functions: to promote protein aggregation and aggresome formation[14] It interacts with p62 and augments p62-induced protein aggregation. G3BP1 knockout mice develop neurodegeneration accompanied by neuronal cell death[23], suggesting that G3BP1 plays a critical role in the neuronal cell survival

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