LIX ( Liposaccharide-Induced CXC chemokine, also GARG-8 and Cxcl5) is a secreted 8-9 kDa member of the Intercrine alpha (or CxC) family of chemokines. It is widely expressed, being produced by diverse cell types such as fibroblasts, thymic epithelium, platelets, vascular endothelium, hepatocytes, lung type II alveolar cells and ileal columnar epithelium. As a chemokine, LIX demonstrates chemokinetic properties. It induces the chemotaxis of neutrophils and endothelial cells, and also promotes TNF-alpha secretion from mast cells and macrophages. Notably, circulating LIX is not derived from fibroblasts, but platelets. This suggests that neutrophil homeostasis/chemotaxis is a function of local resident cell activation and LIX secretion, not generally circulating LIX. Mouse LIX is synthesized as a 132 amino acid (aa) precursor that contains a 40 aa signal sequence, a 78 aa mature region (aa 41-118), and a cleavable 14 aa C-terminus. The mature region possesses an ELR/GluLeuArg motif between aa 50-52, and an alpha-family characteristic CxC motif between aa 53-55. Although there are no known splice variants of mouse LIX, considerable proteolytic processing occurs at both the N-and C-termini over aa 41-132. This may reduce the MW in SDS-PAGE by as much as 3 kDa. The majority of LIX appears to start between aa 47-50, and this is positively correlated with an bioactivity. Over aa 41-118, mouse LIX shares 73% aa sequence identity with an rat LIX. Although not a strict ortholog, mouse LIX shares 63% aa sequence identity with an human GCP-2.
