Human GRO alpha, GRO beta (MIP-2 alpha ), and GRO gamma (MIP-2 beta ) are products of three distinct, non-allelic human genes. GRO beta and GRO gamma share 90% and 86% amino acid (aa) sequence homology, respectively, with GRO alpha. All three human GROs are members of the alpha (C-X-C) subfamily of chemokines and are thought to be the homologs of the murine KC, and MIP-2.
The three GRO cDNAs encode 107 aa precursor proteins from which the N-terminal 34 aa residues are cleaved to generate the mature GROs. There are no potential N-linked glycosylation sites in the aa sequences. GRO expression is inducible by serum, PDGF and/or by a variety of inflammatory mediators, such as IL-1 and TNF, in monocytes, fibroblasts, melanocytes and epithelial cells. In certain tumor cell lines, GRO is expressed constitutively.
Similarly to other alpha chemokines, the three GRO proteins are potent neutrophil attractants and activators. In addition, these chemokines are also active toward basophils. All three GROs can bind with high affinity to CXCR2. The 69 aa variant of human GRO beta is approximately 3 times more active than the 73 aa variant (R&D Systems, Catalog # 276-GB) in inducing myeloperoxidase release from cytochalasin B treated neurotrophils.
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