NOTCH1 Can Initiate NF-κB Activation via Cytosolic Interactions with Components of the T Cell Signalosome

Abstract

T cell stimulation requires the input and integration of external signals. Signaling through the T cell receptor (TCR) is known to induce formation of the membrane-tethered CBM complex, comprising CARMA1, BCL10, and MALT1, which is required for TCR-mediated NF-κB activation. TCR signaling has been shown to activate NOTCH proteins, transmembrane receptors also implicated in NF-κB activation. However, the link between TCR-mediated NOTCH signaling and early events leading to induction of NF-κB activity remains unclear. In this report, we demonstrate a novel cytosolic function for NOTCH1 and show that it is essential to CBM complex formation. Using a model of skin allograft rejection, we show in vivo that NOTCH1 acts in the same functional pathway as PKCθ, a T cell-specific kinase important for CBM assembly and classical NF-κB activation. We further demonstrate in vitro NOTCH1 associates physically with PKCθ and CARMA1 in the cytosol. Unexpectedly, when NOTCH1 expression was abrogated using RNAi approaches, interactions between CARMA1, BCL10, and MALT1 were lost. This failure in CBM assembly reduced inhibitor of kappa B alpha phosphorylation and diminished NF-κB–DNA binding. Finally, using a luciferase gene reporter assay, we show the intracellular domain of NOTCH1 can initiate robust NF-κB activity in stimulated T cells, even when NOTCH1 is excluded from the nucleus through modifications that restrict it to the cytoplasm or hold it tethered to the membrane. Collectively, these observations provide evidence that NOTCH1 may facilitate early events during T cell activation by nucleating the CBM complex and initiating NF-κB signaling.

Notch-1 signaling regulates astrocytic proliferation and activation after hypoxia exposure

“…These results indicate a crosstalk between that Notch-1 and NF-B pathway involved in regulating the responsiveness of astrocyte to hypoxia. This is consistent with a previous report, in which NF-B activation is also regulated by Notch-1 pathway in T cells [21].…”

Transient Blockade of Delta-like Notch Ligands Prevents Allograft Rejection Mediated by Cellular and Humoral Mechanisms in a Mouse Model of Heart Transplantation

“…Possible targets include germinal center B cells and plasma cells, consistent with the markedly decreased numbers of these cells in anti-Dll1/4-treated mice (33, 53-55). Alternatively, it is possible that anti-Dll1/4 antibodies but not DNMAML expression inhibit putative non-canonical effects of Notch signaling in T cells that are independent of transcriptional activation by CSL/RBP-Jk and MAML proteins (47, 56-58). Such non-canonical pathways could control T cell help beyond the effects of canonical Notch signaling.…”

The Notch Signaling Pathway Controls Short-Lived Effector CD8+ T Cell Differentiation but Is Dispensable for Memory Generation

“…Alternatively, Notch signaling may act in a noncanonical manner (without binding of the NICD to RBPJ) to regulate the production of these cytokines. Indeed, the NICD has been reported to interact with signaling components of the TCR (56)(57)(58), and thus, it is possible that Notch deficiency affects TCR signaling, which in turn influences cytokine production. Further studies are required to decipher the mechanism by which Notch signaling controls the production of IL-2 and TNF-a in CD8 + Te cells.…”