“A negative feedback loop mediated by the NR4A family of nuclear hormone receptors restrains expansion of B cells that receive signal one in the absence of signal two”

Abstract

CCL4Running title: NR4A family renders B cells dependent upon a second signal ABSTRACT Ag stimulation (signal 1) triggers B cell activation and proliferation, and primes B cells to recruit, engage, and respond to T cell help (signal 2). However, failure to receive signal 2 within a defined window of time results in an abortive round of proliferation, followed by anergy or apoptosis. Although the molecular basis of T cell help has been extensively dissected, the mechanisms that restrain Ag-stimulated B cells, and enforce dependence upon co-stimulation, are incompletely understood. Nr4a1-3 encode a small family of orphan nuclear receptors that are rapidly induced by B cell receptor (BCR) stimulation, yet little is known about their function in humoral immune responses. Here we use germline and conditional loss-of-function mouse models to show that Nr4a1 and Nr4a3 play partially redundant roles to restrain both the survival and proliferation of B cells that receive signal 1 in the absence of co-stimulatory signals, and do so in part by repressing expression of BATF and consequently c-MYC. Correspondingly, Ab responses to TI-2 immunogens are enhanced in the absence of Nr4a1, but are unaltered in response to immunogens that incorporate co-stimulatory signals.Unexpectedly, we also identify a role for the NR4A family in restraining B cell access to T cell help by repressing expression of the T cell chemokines CCL3/4, as well as CD86 and ICAM1, and show that this is relevant under conditions of competition for limiting T cell help. Our studies collectively reveal a novel negative feedback loop mediated by the NR4A family that increases B cell dependence upon T cell help and restrains stronglyAg-activated B cell clones from monopolizing limiting amounts of T cell help. We speculate that this imposes B cell tolerance and dampens immunodominance to facilitate preservation of clonal diversity during an immune response.were from The Jackson Laboratory 32-38 . TCRalpha-/-were obtained from the Weiss lab 39 . Nr4a3-/-mice were generated via electroporation of gRNA and Cas9 mRNA. In brief, Cas9 protein (40µM) and Nr4a3 gRNAs (80µM) were mixed and electroporated into C57BL/6 zygotes. The sequence of Nr4a3 exon 3 (containing start ATG) targeted for deletion is shown in Fig 4E. 15 founder lines with the targeted deletion were identified through a screen for PCR amplicon size, and confirmed via sequencing of cloned PCR products. Two founder lines were chosen for further analysis and were backcrossed for at least 4 generations onto the C57BL/6J genetic background. All other strains were fully backcrossed to the C57BL/6J genetic background for at least 6 generations. All mice were housed in a specific pathogen-free facility at UCSF according to University and National Institutes of Health guidelines.Antibodies and Reagents.

NR4A1 Deletion in Marginal Zone B Cells Exacerbates Atherosclerosis in Mice—Brief Report

“…This is in agreement with a recent finding that NR4A1 regulates B-cell survival in a T cell–independent response but not in a T cell–dependent response. 23 In our models, we could not study the potential contribution of NR4A1 in B1 cells because these cells do not reconstitute well after irradiation, and, therefore, further experiments are needed to elucidate the role of NR4A1 in B1 cells during atherosclerosis.…”

Curcuphenol possesses an unusual histone deacetylase enhancing activity that counters immune escape in metastatic tumours

“…FOXO1 is also a transcriptional regulator of MHC-II expression and mediates an anti-tumour effect in tumour-associated macrophages (Yang et al, 2018). In addition, the NR4A nuclear receptors, when expressed, act to reduce B lymphocyte responses to antigens when second signals are not present (Tan et al, 2020). Furthermore, PALB2 is a noted tumour suppressor (Pauty et al, 2017).…”