Gene expression profile of Ba/F3 variant (#BEB1) cells that have binding ability to Ecrg4

Esophageal cancer-related gene 4 (Ecrg4) encodes a hormone-like peptide, and is thought to be involved in a variety of physiological phenomena including tumor suppressor function. Recent progress of Ecrg4 reveals that Ecrg4 peptides are pro-inflammatory and induce the expression of several cytokines and chemokines. However, detailed molecular mechanisms of Ecrg4 signaling, especially the receptors for Ecrg4 peptides, remain poorly understood. Here, using retrovirus-mediated expression cloning, we identified lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) as a membrane protein bound for amino acid residues 71-132 of Ecrg4, Ecrg4(71-132). Moreover, not only LOX-1 but also several scavenger receptors such as Scarf1, Cd36 and Stabilin-1 efficiently internalized Ecrg4(71-132) into cells. The broad scavenger receptor competitive inhibitor polyinosinic acid reduced both the internalization of Ecrg4(71-132) and activation of NF-kB in microglia. In addition, this activation is dependent on Myd88, an adaptor protein to recruit signaling proteins to TLR and IL-1R receptors with induction of several immune response. These data suggest that multiple scavenger receptors recognize Ecrg4(71-132) and transduce its signals along with TLR/IL-1R receptors in microglia. A variant strain of Ba/F3 (#BEB1) cells that have an ability to bind Ecrg4 was obtained after five round sorting using retrovirus expression library prepared from mRNA of CG4 cells.