Atypical (p105) NF-κB signaling pathway. Simplified scheme of the atypical (p105) NF-κB signaling pathway. Nomenclature: TNFα: tumor necrosis factor α; TNFR1: tumor necrosis factor receptor 1; IL-1: interleukin 1; ILR1: interleukin 1 receptor; LPS: lipopolysacharide; TLR4: toll-like receptor 4; MAPK3: mitogen-activated protein kinase 3 (ERK1); IKK complex: IκB kinase enzyme complex to upregulate the NF-κB signaling; IκBα: IκB kinase 1 (IKK1); IκBβ: IκB kinase 2 (IKK2); IκBγ: IκB kinase gamma, NEMO: NF-kappa-B essential modulator, regulatory scaffolding protein; P: phosphorylated; p105: p50 (NF-κB1) progenitor. Atypical (p105) NF-κB-complex is the inactive cytoplasmic form, consisting out of p105 and two p50. The NF-κB (p50-p50) homodimer is the active form entering into the nucleus; it can act as a transcriptional repressor and as an activator together with B-cell lymphoma 3-encoded protein (BCL3).