GALNT1 drives aggressive phenotypes of rheumatoid synoviocytes via NEK9 O-glycosylation
Yaoyao Zou, Haobo Lin, Jianling Su, Jieying Wang, Qin Zeng, Tianxiao Feng, Yunxia Lei, Jianda Ma, Hudan Pan, Hanshi Xu, Lie Dai, Yang Li
Yaoyao Zou, Haobo Lin, Jianling Su, Jieying Wang, Qin Zeng, Tianxiao Feng, Yunxia Lei, Jianda Ma, Hudan Pan, Hanshi Xu, Lie Dai, Yang Li
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Research Article Bone biology

GALNT1 drives aggressive phenotypes of rheumatoid synoviocytes via NEK9 O-glycosylation

Abstract

Fibroblast-like synoviocytes (FLSs) are crucial in driving synovial inflammation and joint damage in rheumatoid arthritis (RA). This study explored the functions and underlying mechanisms of GALNT1-mediated O-glycosylation, which is markedly upregulated in RA FLSs, in synovial aggression and subsequent experimental joint damage. Targeted suppression of GALNT1 effectively curtailed migration and invasion in RA FLSs and mitigated arthritis severity in a collagen-induced arthritis model in rats. Mechanistically, NEK9 was identified as a pivotal substrate and downstream effector of GALNT1, affecting the aggressive phenotype of RA FLSs. In vitro experiments further demonstrated that O-glycosylation of NEK9, mediated by GALNT1, promotes the pathogenic phenotype of RA FLSs by promoting cytoskeleton reorganization and restraining excessive ER stress activation. Our study provides mechanistic insights into the activation of RA FLSs and identifies GALNT1 as a potential therapeutic target for RA.

Authors

Yaoyao Zou, Haobo Lin, Jianling Su, Jieying Wang, Qin Zeng, Tianxiao Feng, Yunxia Lei, Jianda Ma, Hudan Pan, Hanshi Xu, Lie Dai, Yang Li

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Figure 5

NEK9 regulates cytoskeleton organization in RA FLS.

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NEK9 regulates cytoskeleton organization in RA FLS. (A) RNA-Seq was perf...
(A) RNA-Seq was performed on the NEK9-silenced group and the control group, followed by GO clustering analysis of the differentially downregulated genes. (B) Differentially expressed genes enriched in the GO term of actin cytoskeleton organization. (C) Expression levels of indicated genes in RA (n = 5) and HC (n = 5) groups (microarray). Data are log2-transformed normalized intensity. Differences were analyzed by 2-tailed t test with Benjamini-Hochberg FDR correction. (D) After silencing of NEK9 expression, qRT-PCR was used to detect the expression levels of mRNAs. Data were normalized to siNC and analyzed by 2-tailed 1-sample t test against 1. n = 3 independent experiments. (E) Staining of actin cytoskeleton by phalloidin. White arrows indicate lamellipodia; yellow arrows indicate filopodia. Scale bars: 20 μm (left). Original magnification, ×1000 (left). (F) RA FLSs were infected with vector or NEK9-OE or NEK9-mut and then analyzed by qRT-PCR. Data were normalized to vector control. NEK9-OE and NEK9-mut were compared with vector by 2-tailed paired t tests. n = 3 independent experiments. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001.