Signal Transduction and Targeted Therapy | RNF213 Regulates B Cell Receptor Signaling, Metabolism, and B Lymphocyte Development

This study reveals a novel mechanism by which the interferon-induced protein RNF213 regulates B cell receptor signaling, metabolism, and development through ubiquitination-mediated control of the transcription factor SPIB, thereby modulating the PIK3C3-PI3P-PTEN axis. This provides new insights into the connection between innate and humoral immunity.

 

Literature Overview

The article titled 'Ring finger protein 213 regulates B-cell receptor signaling, metabolism, and development in B lymphocytes,' published in Signal Transduction and Targeted Therapy, reviews and summarizes the critical regulatory role of RNF213 in B lymphocytes. The study finds that RNF213 mediates K11-linked ubiquitination of the transcription factor SPIB, promoting its proteasomal degradation and thereby suppressing Pik3c3 transcription. In Rnf213-deficient B cells, SPIB protein accumulates stably, upregulating Pik3c3 expression, leading to elevated PI3P levels, which recruit PTEN to early endosomes, promote PIP3 degradation, and ultimately inhibit the AKT-mTOR signaling pathway, affecting B cell metabolism and development. The study further confirms that Spib gene knockout or the PIK3C3 inhibitor SAR405 can reverse the developmental and functional defects in B cells caused by Rnf213 deficiency. Additionally, Rnf213 deficiency significantly impairs both T cell-dependent and T cell-independent antibody responses, highlighting its crucial role in humoral immunity. Overall, this research uncovers a novel ubiquitin-dependent regulatory circuit linking interferon signaling to transcriptional and metabolic control of B cell homeostasis. It also establishes RNF213 as a key bridge between innate immune sensing and dynamic regulation of lymphocytes. The paragraph is coherent and logical, ending with a Chinese period.

Background Knowledge

B lymphocytes are central components of adaptive immunity, responsible for antibody production, antigen presentation, and immune regulation. Their development and function depend on precise coordination of antigen receptor signaling, transcriptional networks, and metabolic reprogramming. In recent years, innate immune-related factors have been found to directly regulate B cell fate; for example, STING and IRF1 participate in marginal zone B cell differentiation, and STAT1 mediates marginal zone structure formation. Ubiquitination, as a key post-translational modification, plays important roles in immune cell development and signal transduction, yet the functions of interferon-induced E3 ubiquitin ligases in B cells remain poorly understood.

RNF213 is a giant interferon-induced RING finger E3 ubiquitin ligase associated with moyamoya disease (MMD), suggesting roles in vascular and immune homeostasis. Previous studies have shown that RNF213 participates in regulating interferon responses, antimicrobial defense, angiogenesis, and lipid droplet dynamics, and functions in T cells and dendritic cells. However, its mechanism of action in B cells remains unclear.

SPIB, an ETS family transcription factor, is dynamically expressed during B cell development and is essential for BCR signaling and Ig secondary responses, yet the mechanisms regulating its protein stability—particularly via ubiquitination—remain undefined. PIK3C3 (VPS34), a class III PI3K, generates PI3P and participates in endosomal trafficking, autophagy, and metabolic signaling regulation, but its role in B cells and crosstalk with transcription factors remain unclear. This study focuses on the RNF213-SPIB-PIK3C3 axis to explore its role in B cell development and function, filling a gap between innate immunity and metabolic regulation of B cells, and providing new mechanisms for understanding the molecular basis of humoral immunity.

 

 

Research Methods and Experiments

The research team utilized Rnf213 gene knockout mouse models combined with multi-omics and functional validation approaches—including flow cytometry, Western blot, co-immunoprecipitation, ubiquitination assays, RNA-seq, ATAC-seq, CUT&Tag, Seahorse metabolic analysis, TIRF microscopy imaging, and in vivo pharmacodynamics experiments—to systematically analyze the role of RNF213 in B cell development, signal transduction, and metabolism. By generating Spib and Rnf213 double-knockout mice, the genetic dependency of SPIB on the RNF213-deficient phenotype was validated. The PIK3C3-specific inhibitor SAR405 was used for in vivo and in vitro pharmacological interventions to assess its rescue effects on signaling pathways and metabolic functions. Additionally, NP-Ficoll and NP-KLH immunization models were used to evaluate the impact of Rnf213 deficiency on T cell-dependent and T cell-independent antibody responses.

Key Conclusions and Perspectives

• RNF213 is highly expressed in splenic B cells, especially at later developmental stages. Its deficiency blocks marginal zone B cell (MZB) development while increasing the proportion of follicular B cells (FOB), indicating a critical regulatory role of RNF213 in B cell subset differentiation
• RNF213 deficiency significantly impairs BCR signal initiation, including BCR clustering, membrane recruitment of pSYK and pCD19, and activation of downstream PI3K-AKT-mTOR, NFκB, and STAT signaling pathways
• Transcriptomic and chromatin accessibility analyses show that RNF213 deficiency leads to widespread downregulation of metabolic pathways, reduced mitochondrial membrane potential and ROS production, and impaired glycolysis and OXPHOS, indicating its indispensable role in B cell metabolic adaptation
• RNF213 mediates proteasomal degradation of the transcription factor SPIB via K11-linked ubiquitination, thereby limiting its transcriptional activity. Rnf213 deficiency leads to SPIB protein stabilization, which in turn upregulates Pik3c3 expression
• SPIB directly binds to enhancer/promoter regions of Pik3c3 and activates its transcription, resulting in increased PI3P levels, promoting PTEN recruitment to EEA1+ early endosomes, leading to PIP3 degradation and inhibition of AKT-mTOR signaling
• Genetic deletion of Spib or pharmacological inhibition of PIK3C3 restores AKT-mTOR signaling, metabolic activity, and MZB development in Rnf213-deficient B cells, confirming that SPIB and PIK3C3 are key downstream effector molecules of RNF213
• Rnf213-deficient mice exhibit defects in antibody production during both T cell-dependent and T cell-independent immune responses, including reduced IgM and high-affinity IgG1, along with disorganized germinal center structures, indicating broad roles of RNF213 in humoral immunity
• This study reveals a novel ubiquitin-dependent regulatory axis—RNF213-SPIB-PIK3C3-PTEN-PIP3-AKT/mTOR—that links interferon signaling to metabolic and developmental regulation in B cells, providing a molecular mechanism for crosstalk between innate and adaptive immunity

Research Significance and Prospects

This study is the first to reveal the critical role of RNF213 in B cell biology, expanding its functional repertoire within the immune system. As an interferon-induced factor, RNF213 may be activated under conditions of infection or inflammation, thereby dynamically regulating B cell responses, suggesting potential roles in vaccine responses or autoimmune diseases.

This work establishes RNF213 as a molecular bridge linking innate immune sensing to lymphocyte development regulation, offering new perspectives on the non-canonical functions of interferon in humoral immunity. Targeting the RNF213-SPIB-PIK3C3 axis may provide new strategies for modulating B cell metabolism and antibody responses, particularly in immunodeficiencies or chronic inflammatory diseases.

Future studies could explore the function of RNF213 in human B cells, its expression and role in autoimmune diseases, lymphomas, or immune aging. Additionally, identifying the ubiquitin ligases and deubiquitinases responsible for SPIB modification and elucidating the spatial regulation mechanisms of PI3P in B cell signaling compartmentalization warrant further investigation.

 

 

Conclusion

This study systematically elucidates the central role of RNF213 in the development, signal transduction, and metabolic regulation of B lymphocytes. Through integrated multi-omics and functional validation, the study reveals that RNF213 mediates K11-linked ubiquitination of the transcription factor SPIB, promoting its proteasomal degradation and thereby suppressing Pik3c3 transcription. In Rnf213-deficient B cells, SPIB accumulation leads to PIK3C3 overexpression, elevated PI3P levels, and subsequent recruitment of PTEN to early endosomes, accelerating PIP3 degradation and ultimately inhibiting the AKT-mTOR signaling pathway, impairing metabolic adaptation and B cell development. Genetic or pharmacological interventions targeting SPIB or PIK3C3 reverse these defects, confirming the functional importance of this axis. Furthermore, Rnf213 deficiency significantly impairs both T cell-dependent and T cell-independent antibody responses, indicating its broad role in humoral immunity. This study not only uncovers a novel ubiquitin-dependent regulatory circuit linking interferon signaling to B cell homeostasis but also establishes RNF213 as a key node in the crosstalk between innate and adaptive immunity. These findings provide new perspectives on the molecular mechanisms governing B cell fate decisions and offer potential therapeutic targets for related immune disorders.

 

Ziyin Zhang, Nanshu Xiang, Qian Liu, Xiaopeng Qi, and Chaohong Liu. Ring finger protein 213 regulates B-cell receptor signaling, metabolism, and development in B lymphocytes. Signal Transduction and Targeted Therapy.