Toll-like receptors (TLRs) recognize microbial products and induce immune responses. Their subcellular distribution is believed to be optimized for their pathogen recognition. Little is known, however, about molecular mechanisms regulating the subcellular distribution of TLR. Lipopolysaccharide, a principal membrane component of the Gram-negative bacteria, is recognized by the receptor complex consisting of Toll-like receptor 4 (TLR4) and MD-2. We here show that a novel molecule, a PRotein Associated with Tlr4 (PRAT4B), regulates cell surface expression of TLR4. PRAT4B has a signal peptide followed by a mature peptide. PRAT4B is associated with the hypoglycosylated, immature form of TLR4 but not with MD-2 or TLR2. Downregulation of PRAT4B mRNA with small interfering RNA decreased cell surface TLR4 on HEK293 cells. These results suggest a novel mechanism regulating the subcellular distribution of TLR4.
Interacting selectively and non-covalently with one or more specific sites on a receptor molecule, a macromolecule that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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