GCP-2 (granulocyte chemotactic protein-2) also known as CXCL6, is a CXC chemokine initially isolated as a neutrophil chemoattractant from the MG-63 osteosarcoma cell line. Among human CXC chemokines, GCP-2 is most closely related to ENA-78 (78% amino acid (aa) sequence identity in the mature peptide region and 86% identity in the signal sequence). The structure and sequence of the genes for human GCP-2 and ENA-78 also exhibit close similarity suggesting the two genes may have originated from a gene duplication. LIX (LPS-induced CXC chemokine) was initially cloned as a gene induced by LPS in mouse fibroblasts. The predicted LIX protein sequence is identical to a previously purified mouse protein designated mouse GCP-2 based on its amino sequence similarity (60% sequence identity) to human GCP-2. Mouse GCP-2/LIX is also 54% identical with human ENA-78 at the amino acid sequence level.
Human GCP-2 cDNA encodes a propeptide of 114 amino acid residues with a predicted 37 aa residue signal peptide and 77 aa residue mature protein. Several forms of natural GCP-2 have been isolated from MG-63 conditioned media, indicating that GCP-2 undergoes limited processing at both the N- and C-termini. Human GCP-2 is a primary response gene whose induction by cytokines is attenuated by dexamethasone.
Human GCP-2 and mouse GCP-2/LIX have been shown to chemoattract and activate neutrophils, but not eosinophils and monocytes. It is likely that GCP-2 activities are mediated via the human or mouse CXCR2.
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