CXCL13 production by an established lymph node stromal cell line via lymphotoxin-beta receptor engagement involves the cooperation of multiple signaling pathways

Abstract

Non-hematopoietic mesenchymal stromal cells in secondary lymphoid organs play pivotal roles in tissue organization and immune responses by exhibiting specialized features such as the production of lymphoid homeostatic chemokines. However, the maturational process of stromal cells mediated by lymphotoxin-beta receptor (LTbetaR) signaling, a key for stromal maturation, remains unclear. Taking advantage of a stromal cell line established from mouse lymph node, which can produce a homeostatic chemokine, CXC chemokine ligand (CXCL) 13, by the engagement of LTbetaR but not by tumor necrosis factor (TNF) receptor (TNFR), we analyzed the details of intracellular signaling events during the maturational process. The activation of both canonical and non-canonical nuclear factor-kappaB (NF-kappaB) pathways was essential for CXCL13 induction; however, an excessive amount of non-canonical RelB-p52 complex was still insufficient for CXCL13 gene expression. Under RelB-p52-over-expressed conditions, TNFalpha could induce a markedly high amount of CXCL13 production, indicating that the downstream of TNFR contains an additional key component of signaling. We also found that protein kinase C activity plays a critical role in this process in addition to the NF-kappaB pathways. Taken together, it is suggested that the maturation of lymphoid stromal cells mediated by LTbetaR is accomplished by the cooperation of multiple signaling cascades.

Prediction of Novel Pathway Elements and Interactions Using Bayesian Networks

“…As another example, the Cxcl13 is a chemokine ligand in B cells with a C-X-C motif. It has already been established that Cxcl13 induction requires activation of canonical and non-canonical Nf-kB pathways (Suto, et al, 2009), which confirms the prediction of this gene in our network. These data strongly support the predictions generated by our analysis.…”

Classical NF-κB Activation Negatively Regulates Noncanonical NF-κB-dependent CXCL12 Expression

“…Contrasting with the negative regulation of CXCL12 expression in HUVEC, studies in lymph node stromal cells (12,14) and smooth muscle cells (13) showed that TNF stimulation enhanced LT␤R ligation-induced expression of CXCL13. We did not detect CXCL13 in HUVEC or dermal EC (11), suggesting that the expression profiles of NC NF-B-dependent genes are cell type-specific.…”

“…TNF markedly up-regulates p100 levels in EC via classical NF-B signaling, although it does not activate the NC pathway or induce CXCL12 expression (11). Previous studies demonstrated that TNF enhances expression of the NC gene CXCL13 induced by anti-LT␤R in lymph node stromal cells and aortic smooth muscle cells (12)(13)(14). Furthermore, antigen receptor ligation on B cells has been shown to increase p100 levels providing a pool of p100 for BLyS-induced NC signaling (15).…”

Distinct Developmental Requirements for Isolated Lymphoid Follicle Formation in the Small and Large Intestine

“…Growth of developing CPs relies on the continued cross talk between LTi cells, which express RANK, RANKL and CXCR5, and VCAM-1 ϩ organizer cells that express RANKL and CXCL13 upon LT␤R signaling. 34,35 Decreased LT␣ 1 ␤ 2 expression caused by absence of RANKL may lead to loss of CXCL13 expression, which in turn inhibits further CP development and prevents their maturation into ILFs.…”