Recombinant Human PRAT4A Protein, CF

PRAT4A (PRotein Associated with Toll-like receptor 4A), also called CNPY3 (Canopy homolog 3) or TNRC5 (trinucleotide repeat-containing 5) is a widely expressed 40 kDa protein that is an intracellular chaperone for Toll-like receptors (TLRs) (1-3). Human PRAT4A cDNA encodes 278 amino acids (aa), including an N-terminal hydrophobic sequence of 26-37 aa (putative signal sequence) and a 250-241 aa mature region (3). A potential 153 aa form has an alternate start site at aa 126. Human PRAT4A shares 90%, 90%, 94%, 95% and 96% aa sequence identity with mouse, rat, bovine, canine and porcine PRAT4A, respectively. A related protein, PRAT4B, shares approximately 40% aa sequence identity, is co‑expressed, and is reported to bind TLR4 only if it lacks mature glycosylated structures (4). PRAT4A resides in the endoplasmic reticulum (ER) and is a co‑chaperone that provides substrate-specificity to the chaperone gp96, an HSP90 paralog required for proper folding of TLRs (1‑3, 5, 6). It binds TLR4, enhances TLR4 N-linked glycosylation, and forms a heterotrimer with TLR4 and its co‑receptor, MD2 (6-8). PRAT4A is required for transfer of TLR4 from the ER to the plasma membrane where it recognizes its extracellular ligand, bacterial lipopolysaccharide (LPS) (1‑3, 6, 7). PRAT4A is also essential for maturation and trafficking of TLR9 from the ER to endolysosomes in response to its intracellular ligand, unmethylated DNA (1‑3, 5‑7, 9). PRAT4A deletion, knockdown, or specific mutation in mice abolishes or lowers surface expression of TLR4/MD2, TLR2, TLR1 and RP105/CD180, and abolishes production of RANTES in response to a TLR7 ligand (3, 6-8). PRAT4A enhances Th1 responses and production of inflammatory cytokines in response to TLR ligands, and thus contributes to endotoxic shock (2, 6‑8).