Covey, L. R. | Search bioRxiv

bioRxiv2025

Lowering CD40L expression in Murine Lupus Results in an Increase in Disease Indicators in Female but not Male B6 mice

Our lab has previously described a mouse model (CD40L{Delta}5) that produces only 60% of WT CD40L due to a targeted deletion in an RNA binding site within the CD40L message. The CD40L{Delta}5 mutation, which destabilizes CD40L mRNA during T cell activation, causes disrupted germinal center (GC) formation leading to reduced levels of memory B cells and switched antibodies. In this study, we used our model of limited CD40L expression to investigate its effect on Systemic Lupus Erythematosus (SLE or lupus). Two mouse models of SLE were assessed: The first, termed PIL, used pristane to induce disease over a six-month period and the second utilized a chronic graft-versus-host disease (bm12-cGVHD) that resembles lupus based on multiple parameters and allowed us to monitor the early events in disease development. Importantly, we found that in both model systems female mice expressing the CD40L{Delta}5 mutation showed a consistent increase in elevated antibody secreting cells and autoantibody titers. Also, PIL female CD40L{Delta}5 mice had higher levels of immunocomplex deposition in the kidney compared to all other cohorts. In the bm12-cGVHD model, cellular increases in GC cells along with an altered cytokine profile of donor CD4+ T cells and host dendritic cells (DCs) reflected a significant skewing of CD40L{Delta}5 female CD4 T cells towards a Th2 phenotype. Overall, our results support a more nuanced role for CD40L in lupus than previously described and suggest a sex-determined threshold of CD40L-CD40 signaling that demarcates an interface between protection and exacerbation at the very early steps of disease progression.

immunology↗

bioRxiv2022

Polypyrimidine Tract-Binding Protein 1 (PTBP1) regulates CD4 T cell Activation independent of its role in proliferation

Our previous work found that the RNA binding protein polypyrimidine tract-binding protein (PTBP1) is critical for regulating multiple events in T cell activation including changes in proliferation, and expression of activation markers and cytokines. These changes corresponded to the regulation of the ERK1/2 and NF-{kappa}B pathways as well as through changes in steady-state RNA levels. Because proliferation is critical for driving T cell activation, it was unclear whether PTBP1 was required for optimal activation per se or whether changes were secondary to a requirement for initiating/sustaining proliferation. To address this question, the human T cell lymphoma cell line, Jurkat, which recapitulates many of the molecular events of TCR-induced activation, was used to understand how PTBP1 impacts early events in T cell activation with ongoing proliferation. Using two phenotypically distinct Jurkat subclones (D1.1 and B2.7), we first profiled global RNA expression patterns using RNAseq analysis and found marked differences between the two cell lines with the D1.1 line giving a more antigen-experienced phenotype. Reducing PTBP1 by shPTB expression, to 60% WT levels resulted in no significant decrease in proliferation in the two subclones. However, we observed that PTBP1 was required for both optimal expression of activation markers, CD25, CD38, CD69, and CD40L, and signaling through the ERK1/2, P38 and AKT pathways. Importantly, limiting PTBP1 had different effects on the activation signals for each cell line suggesting that the differentiation state of the cell is a critical factor in understanding the role of PTBP1 in T cell activation. This was further reinforced by our finding that PTBP1 regulated distinct groups of genes specific for each line. Together, our findings suggest that PTBP1 regulates specific T cell activation responses independent of its role in proliferation and that the initial phenotype of the T cell plays an essential role in the dependency of the cell on PTBP1 for driving these changes.

immunology↗