Endogenous peptide inhibitor of CXCR4, hSA(408-423) peptide
EPI-X4 (endogenous peptide inhibitor of CXCR4) is a fragment identified from a blood-derived peptide library, corresponding to residues 408-423 of human serum albumin (hSA). EPI-X4 is a highly specific endogenous CXCR4 antagonist which is evolutionarily conserved and generated from the albumin precursor by pH-regulated proteases under acidic conditions that are a hallmark of inflammation. EPI-X4 suppresses CXCR4 signaling and inhibits infection by CXCR4 tropic HIV-1 strains. EPI-X4 can also antagonize CXCL12-induced tumour cell migration, mobilise stem cells and suppress inflammatory responses in mice. EPI-X4 is abundant in the urine of patients with inflammatory kidney diseases and may serve as a biomarker.
