Recombinant Rat Protein S100-A8 (S100a8)

Function

S100A8 is a calcium- and zinc-binding protein which plays a prominent role in the regulation of inflammatory processes and immune response. It can induce neutrophil chemotaxis and adhesion. Predominantly found as calprotectin (S100A8/A9) which has a wide plethora of intra- and extracellular functions. The intracellular functions include: facilitating leukocyte arachidonic acid trafficking and metabolism, modulation of the tubulin-dependent cytoskeleton during migration of phagocytes and activation of the neutrophilic NADPH-oxidase. Also participates in regulatory T-cell differentiation together with CD69. Activates NADPH-oxidase by facilitating the enzyme complex assembly at the cell membrane, transferring arachidonic acid, an essential cofactor, to the enzyme complex and S100A8 contributes to the enzyme assembly by directly binding to NCF2/P67PHOX. The extracellular functions involve pro-inflammatory, antimicrobial, oxidant-scavenging and apoptosis-inducing activities. Its pro-inflammatory activity includes recruitment of leukocytes, promotion of cytokine and chemokine production, and regulation of leukocyte adhesion and migration. Acts as an alarmin or a danger associated molecular pattern (DAMP) molecule and stimulates innate immune cells via binding to pattern recognition receptors such as Toll-like receptor 4 (TLR4) and receptor for advanced glycation endproducts (AGER). Binding to TLR4 and AGER activates the MAP-kinase and NF-kappa-B signaling pathways resulting in the amplification of the pro-inflammatory cascade. Has antimicrobial activity towards bacteria and fungi and exerts its antimicrobial activity probably via chelation of Zn(2+) which is essential for microbial growth. Can induce cell death via autophagy and apoptosis and this occurs through the cross-talk of mitochondria and lysosomes via reactive oxygen species (ROS) and the process involves BNIP3. Can regulate neutrophil number and apoptosis by an anti-apoptotic effect; regulates cell survival via ITGAM/ITGB and TLR4 and a signaling mechanism involving MEK-ERK. Its role as an oxidant scavenger has a protective role in preventing exaggerated tissue damage by scavenging oxidants. The iNOS-S100A8/A9 transnitrosylase complex is proposed to direct selective inflammatory stimulus-dependent S-nitrosylation of multiple targets such as GAPDH, ANXA5, EZR, MSN and VIM by recognizing a [IL]-x-C-x-x-[DE] motif; S100A8 seems to contribute to S-nitrosylation site selectivity (By similarity)

Subcellular Location

Secreted; Cytoplasm; Cytoplasm, cytoskeleton; Cell membrane (Peripheral membrane protein)

Subunit

Homodimer. Preferentially exists as a heterodimer or heterotetramer with S100A9 known as calprotectin (S100A8/A9). S100A8 interacts with AGER, ATP2A2 and with the heterodimeric complex formed by TLR4 and LY96. Calprotectin (S100A8/9) interacts with CEACAM3 and tubulin filaments in a calcium-dependent manner. Heterotetrameric calprotectin (S100A8/A9) interacts with ANXA6 and associates with tubulin filaments in activated monocytes. S100A8 and calprotectin (S100A8/9) interact with NCF2/P67PHOX, RAC1 and RAC2. Calprotectin (S100A8/9) interacts with CYBA and CYBB (By similarity). Calprotectin (S100A8/9) interacts with NOS2 to form the iNOS-S100A8/A9 transnitrosylase complex (By similarity). Calprotectin (S100A8/9) interacts with CD69 (By similarity)

• Imamichi T. et al. Expression and cloning of migration inhibitory factor-related protein (MRP)8 and MRP14 in arthritis-susceptible rats. — Biochem. Biophys. Res. Commun. (1993)
• Raftery M.J. et al. Identification of posttranslational modifications and cDNA sequencing errors in the rat S100 proteins MRP8 and 14 using electrospray ionization mass spectrometry. — Anal. Biochem. (1998)
• Koike A. et al. Dynamic mobility of immunological cells expressing S100A8 and S100A9 in vivo: a variety of functional roles of the two proteins as regulators in acute inflammatory reaction. — Inflammation (2012)