PhD Candidate UT Hlth. San Antonio San Antonio, Texas, United States
Disclosure(s):
Milind Joshi: No financial relationships to disclose
Introduction/Rationale: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease marked by high-affinity, class-switched autoantibodies (autoAbs) produced by germinal center (GC) B cells with follicular helper T (Tfh) cell assistance. We previously used pharmacological inhibition with 6-Diazo-5-oxo-L-norleucine (DON) and T-cell-specific deletion of Gls1 (Gls1 KO) in Sle1b autoimmune mice and B6 controls, showing altered glutamine metabolism in SLE Tfh cells. Here, we investigate the mechanisms by which T-cell-intrinsic glutamine metabolism supports Tfh function and autoAb production.
Methods: B6 and Sle1b KO mice with controls were assessed ex vivo for autoAbs, class switching, GC responses, and Tfh markers by ELISA and flow cytometry. Seahorse metabolic assays, in vitro Tfh–B co-cultures, and RNA-seq assessed metabolic, functional, and transcriptional changes. Post-transcriptional proteasomal regulation was tested with MG132.
Results: Gls1 KO reduced Tfh cell function, autoAb production, and GC expansion in SLE-prone mice, underscoring the critical, T cell-intrinsic role of glutamine in pathogenic Tfh function. Seahorse assays showed reduced mitochondrial respiration, glycolysis, and spare respiratory capacity uniquely in Sle1b KO relative to Sle1b CD4+ T cells. In vitro Sle1b KO Tfh cells induced lower Ab production and class switching from co-cultured B6 B cells. ICOS expression was downregulated in DON-treated and Gls1 KO Tfh cells, linking glutaminolysis to its regulation and GC function. Tfh RNA-seq revealed broad transcriptional changes on the Sle1b background, indicating autoimmune-specific reliance on glutamine. Yet, Icos transcripts were unchanged, suggesting post-transcriptional regulation. Proteasome inhibition did not restore ICOS expression.
Conclusion: These findings identify glutaminolysis as a key metabolic pathway driving SLE Tfh function and autoAb production. Glutaminolysis regulates ICOS post-transcriptionally, revealing a novel proteasome-independent glutamine-dependent regulation of ICOS.
