CASTOR1 regulates humoral immune responses and contributes to the pathogenesis of systemic lupus erythematosus

Kusuda T, Komai T, Itamiya T, Abe T, Okamura T, Fujio K · 2026 · Arthritis & Rheumatology · Atlas ID KUS2026

What this study shows

Gives the arginine sensor CASTOR1 a defined physiological job upstream of mTORC1: losing it de-represses mTORC1 in B cells and drives plasma-cell expansion, IgG and anti-dsDNA autoantibodies, and lupus-like glomerulonephritis. In human SLE, CASTOR1 expression in plasmablasts was inversely correlated with disease activity (r = -0.32, p = 0.00031). One of the few studies to tie a specific upstream amino-acid sensor to a human autoimmune phenotype rather than to cancer or growth.

Abstract

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CASTOR1 senses arginine and regulates mammalian target of rapamycin complex 1 (mTORC1), a central metabolic signaling molecule. This study aimed to elucidate the roles of CASTOR1 in humoral immune responses. We analyzed human B cell transcriptomes from healthy controls and patients with systemic lupus erythematosus (SLE) via correlation analysis and gene set variation analysis using our database, Immune Cell Gene Expression Atlas from the University of Tokyo (ImmuNexUT).

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At a glance

Evidence type	M Molecular — cells, biochemistry, structure Marked M because it is molecular or in-vitro work (model: Human B cells (ImmuNexUT transcriptomes, n=136 SLE patients) + whole-body and B cell-specific Castor1-knockout mice) rather than a whole-organism health-outcome study. That is often exactly where causal biology gets established -- the code says which system the finding was shown in, and nothing about how good the work is.
Study type	5 - Mechanistic / In Vitro
Model system	Human B cells (ImmuNexUT transcriptomes, n=136 SLE patients) + whole-body and B cell-specific Castor1-knockout mice
Journal	Arthritis & Rheumatology
Year	2026
Peer reviewed	Yes
Record last updated	2026-08-22
Source	DOI 10.1002/art.70314 · PMID 42695806

In the Atlas

Cite this paper

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Kusuda, T., Komai, T., Itamiya, T., Abe, T., Okamura, T., & Fujio, K. (2026). CASTOR1 regulates humoral immune responses and contributes to the pathogenesis of systemic lupus erythematosus. Arthritis & Rheumatology. https://doi.org/10.1002/art.70314

@article{KUS2026,
  author       = {Kusuda, T. and Komai, T. and Itamiya, T. and Abe, T. and Okamura, T. and Fujio, K.},
  title        = {{CASTOR1 regulates humoral immune responses and contributes to the pathogenesis of systemic lupus erythematosus}},
  journal      = {Arthritis & Rheumatology},
  year         = {2026},
  doi          = {10.1002/art.70314},
  note         = {PMID: 42695806},
}

Cite this Atlas record

The record is the Atlas's own work — the evidence label, the extracted findings and the links. It is cited as part of the dataset, not as the paper.

Barton, O. (2026). Oliver's mTOR Atlas (record KUS2026) [Data set]. https://mtor-atlas.org/study/KUS2026/ · Dataset DOI 10.5281/zenodo.22059963

@misc{atlas_KUS2026,
  author       = {Barton, Oliver},
  title        = {{Oliver's mTOR Atlas}, record KUS2026},
  howpublished = {Data set},
  year         = {2026},
  url          = {https://mtor-atlas.org/study/KUS2026/},
  doi          = {10.5281/zenodo.22059963}
}