A 62-aa core of the cochlin LCCL domain induces macrophage M1 polarization in vitro

Abstract

BackgroundCochlin, encoded by the COCH gene, mediates innate immunity against bacterial infections by segregating pathogens and recruiting immune cells through its N-terminal LCCL domain. This domain is cleaved and secreted to attract macrophages and neutrophils, but its core motif has remained unclear.MethodsWe designed and synthesized a shortened core peptide of the LCCL domain (cLCCL; 62 amino acids) preserving the conserved structural motif. Structural stability was predicted by in silico modeling. The immunomodulatory effects of LCCL and cLCCL were evaluated in RAW264.7 macrophage cells using bulk RNA sequencing, quantitative PCR, Western blotting, flow cytometry, and immunocytochemistry.ResultsRNA sequencing in RAW264.7 cells showed that both LCCL and synthetic cLCCL peptides induced M1 polarization, with upregulation of TICAM2, CD40, and CD86. Flow cytometry demonstrated a significant increase in CD40(+)/CD86(+) M1-polarized macrophages following LCCL or cLCCL treatment, with comparable effects between the full-length and core peptides.ConclusionThe identified cLCCL appears to promote pro-inflammatory macrophage polarization, activate pro-inflammatory innate immune pathways, and warrants further evaluation in mechanistic and in vivo studies.