NF-kB

The NALP family consists of cytoplasmic proteins within the larger CATERPILLER protein family. There exist in short forms (such as NALP4) and long forms (NALP1). NALP proteins include the apoptosis regulator apoptotic protease activating factor 1 (APAF1) and mammalian NOD-LRR proteins, and are thought to play a role in the inflammation and reproduction processes.

The innate immune system is responsible for reacting to viral infections through recognition of various viral components. Like toll-like receptor 3 (TLR3), MDA5 recognizes double-stranded (ds) RNA which is a molecular pattern indicative of viral infection. MDA5 and its relative RIG-1 recognize different types of dsRNA, with MDA5 recognizing poly (I:C). MDA5 is a member of the DEAD/DEAH-box RNA helicase family, which all contain the conserved DEAD motif of Asp-Glu-Ala-Asp.

Apoptosis, or programmed cell death, is a normal component of cellular differentiation and the development of multicellular organisms. Receptor activator of NF-kB (RANK) lacks significant homology with the other family members of the tumor necrosis factor receptor (TNFR) superfamily. The cytoplasmic domain of RANK interacts with the tumor necrosis factor receptor associated factors, adaptor proteins such as TRAF2, TRAF5 and TRAF6.