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YTHDF2 facilitates aggresome formation via UPF1 in an m⁶A-independent manner.

ABSTRACT: YTHDF2 has been extensively studied and typified as an RNA-binding protein that specifically recognizes and destabilizes RNAs harboring N⁶-methyladenosine (m⁶A), the most prevalent internal modification found in eukaryotic RNAs. In this study, we unravel the m⁶A-independent role of YTHDF2 in the formation of an aggresome, where cytoplasmic protein aggregates are selectively sequestered upon failure of protein homeostasis mediated by the ubiquitin-proteasome system. Downregulation of YTHDF2 in HeLa cells reduces the circularity of aggresomes and the rate of movement of misfolded polypeptides, inhibits aggresome formation, and thereby promotes cellular apoptosis. Mechanistically, YTHDF2 is recruited to a misfolded polypeptide-associated complex composed of UPF1, CTIF, eEF1A1, and DCTN1 through its interaction with UPF1. Subsequently, YTHDF2 increases the interaction between the dynein motor protein and the misfolded polypeptide-associated complex, facilitating the diffusion dynamics of the movement of misfolded polypeptides toward aggresomes. Therefore, our data reveal that YTHDF2 is a cellular factor involved in protein quality control.

SUBMITTER: Hwang HJ

PROVIDER: S-EPMC10558514 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature

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YTHDF2 facilitates aggresome formation via UPF1 in an m6A-independent manner.

Hwang Hyun Jung HJ Park Tae Lim TL Kim Hyeong-In HI Park Yeonkyoung Y Kim Geunhee G Song Chiyeol C Cho Won-Ki WK Kim Yoon Ki YK

Nature communications 20231006 1

YTHDF2 has been extensively studied and typified as an RNA-binding protein that specifically recognizes and destabilizes RNAs harboring N6-methyladenosine (m6A), the most prevalent internal modification found in eukaryotic RNAs. In this study, we unravel the m6A-independent role of YTHDF2 in the formation of an aggresome, where cytoplasmic protein aggregates are selectively sequestered upon failure of protein homeostasis mediated by the ubiquitin-proteasome syste ...[more]

PMID: 37803021

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Project description:BackgroundAdolescent idiopathic scoliosis (AIS) is characterized by low lean mass without vertebral deformity. The cause-and-effect relationship between scoliosis and paraspinal muscle imbalance has long puzzled researchers. Although FTO has been identified as a susceptibility gene for AIS, its potential role in the asymmetry of paraspinal muscles has not been fully elucidated.MethodsWe investigated the role of Fto in murine myoblast proliferation, migration, and myogenic differentiation. We examined its precise regulatory influence on murine muscle fiber remodeling in vitro and in vivo. We identified the downstream target gene of Fto by screening key regulators of murine muscle fiber remodeling and identified its m6A reader. Deep paraspinal muscle samples were obtained from the concave and convex sides of AIS patients with or without Schroth exercises, and congenital scoliosis served as a control group. We compared the content of type I fibers, expression patterns of fast- and slow-type genes, and levels of FTO expression.ResultsFTO contributed to maintain the formation of murine slow-twitch fibers both in vitro and in vivo. These effects were mediated by the demethylation activity of FTO, which specifically demethylated NFATC1 and prevented YTHDF2 from degrading it. We found a significant reduction in type I fibers, mRNA levels of MYH7 and MYH7B, and expression of FTO on the concave side of AIS. The percentage of type I fibers showed a positive correlation with the expression level of FTO. The asymmetric patterns observed in AIS were consistent with those seen in congenital scoliosis, and the asymmetry of FTO expression and fiber type in AIS was largely restored by Schroth exercises.ConclusionsFTO supports the formation of murine slow-twitch fibers in an NFATC1-YTHDF2 dependent manner. The consistent paraspinal muscle features seen in AIS and congenital scoliosis, as well as the reversible pattern of muscle fibers and expression of FTO in AIS suggest that FTO may contribute to the muscle fiber remodeling secondary to scoliosis.

Project description:BackgroundUbiquitin-proteasome-system-mediated clearance of misfolded proteins is essential for cells to maintain proteostasis and reduce the proteotoxicity caused by these aberrant proteins. When proteasome activity is inadequate, ubiquitinated proteins are sorted into perinuclear aggresomes, which is a significant defense mechanism employed by cells to combat insufficient proteasome activity, hence mitigating the proteotoxic crisis. It has been demonstrated that phosphorylation of SQSTM1 is crucial in regulating misfolded protein aggregation and autophagic degradation. Although SQSTM1 S403 phosphorylation is essential for the autophagic degradation of ubiquitinated proteins, its significance in proteasome inhibition-induced aggresome formation is yet unknown. Herein, we investigated the influence of SQSTM1 S403 phosphorylation on the aggresome production of ubiquitinated proteins during proteasome suppression.MethodsWe examined the phosphorylation levels of SQSTM1 S403 or T269/S272 in cells after treated with proteasome inhibitors or/and autophagy inhibitors, by western blot and immunofluorescence. We detected the accumulation and aggresome formation of ubiquitinated misfolded proteins in cells treated with proteasome inhibition by western blot and immunofluorescence. Furthermore, we used SQSTM1 phosphorylation-associated kinase inhibitors and mutant constructs to confirm the regulation of different SQSTM1 phosphorylation in aggresome formation. We examined the cell viability using CCK-8 assay.ResultsHerein, we ascertained that phosphorylation of SQSTM1 S403 did not enhance the autophagic degradation of ubiquitinated proteins during proteasome inhibition. Proteasome inhibition suppresses the phosphorylation of SQSTM1 S403, which facilitated the aggresome production of polyubiquitinated proteins. Interestingly, we found proteasome inhibition-induced SQSTM1 T269/S272 phosphorylation inhibits the S403 phosphorylation. Suppressing S403 phosphorylation rescues the defective aggresome formation and protects cells from cell death caused by unphosphorylated SQSTM1 (T269/S272).ConclusionsThis study shows that inhibition of SQSTM1 S403 phosphorylation facilitates the aggresome formation of ubiquitinated proteins during proteasome dysfunction. SQSTM1 T269/S272 phosphorylation inhibits the S403 phosphorylation, boosting the aggresome formation of ubiquitinated protein and shielding cells from proteotoxic crisis.

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YTHDF2 facilitates aggresome formation via UPF1 in an m⁶A-independent manner.

Publications

YTHDF2 facilitates aggresome formation via UPF1 in an m<sup>6</sup>A-independent manner.

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