Identification of Low-Density Lipoprotein Receptor-Related Protein 1 as a CXCL14 Receptor Using Chemically...

Area of Science:

• Immunology
• Chemical Biology
• Proteomics

Background:

• CXCL14 is a chemokine that facilitates CpG oligodeoxynucleotides (ODN) uptake into immune cells, activating Toll-like receptor 9 (TLR9).
• The precise mechanism of CXCL14-CpG ODN complex internalization into cells remains unclear.
• Identifying CXCL14 receptors is crucial for understanding its role in innate immunity.

Purpose of the Study:

• To synthesize CXCL14-derived photoaffinity probes for identifying its cellular receptors.
• To elucidate the molecular mechanism of CXCL14-CpG ODN complex entry into immune cells.
• To discover novel receptors for CXCL14 using chemical proteomics.

Main Methods:

• Chemical synthesis of site-specifically modified CXCL14-based photoaffinity probes using native chemical ligation and maleimide-thiol coupling.
• Incorporation of a photoreactive 2-aryl-5-carboxytetrazole (ACT) and a hydrazine-labile cleavable linker into the probes.
• Application of probes in quantitative proteomic experiments, including competitive proteome profiling, in RAW264.7 cells.

Main Results:

• Synthesized CXCL14 probes demonstrated comparable bioactivity to native CXCL14 in binding CpG ODN to immune cells.
• Quantitative proteomics identified numerous candidate receptors for CXCL14.
• Low-density lipoprotein receptor-related protein 1 (LRP1) was identified as a novel receptor for CXCL14.
• Disruption of LRP1 function impaired the uptake of the CXCL14-CpG ODN complex.

Conclusions:

• Synthetic CXCL14 photoaffinity probes are powerful tools for discovering novel receptors.
• LRP1 is a newly identified receptor for CXCL14, mediating the uptake of the CXCL14-CpG ODN complex.
• This research advances the understanding of CXCL14's molecular functions and innate immune system mechanisms.