Human CXCL7, amino acids Ala59-Asp128 (Accession# NM_002704.3) was expressed in E. coli.
The 70 amino acid recombinant protein has a predicted molecular mass of approximately 7.6 kD. The DTT-reduced and non-reduced protein migrate at approximately 11 and 13 kD by SDS-PAGE respectively. The N-terminal amino acid is Ala.
0.22 µm filtered protein solution is in PBS.
Less than 0.01 ng per µg cytokine as determined by the LAL method.
10 and 25 µg sizes are bottled at 100 µg/mL.
Storage & Handling:
Unopened vial can be stored between 2°C and 8°C for three months, at -20°C for six months, or at -70°C for one year. For maximum results, quick spin vial prior to opening. Stock solutions should be prepared at no less than 10 µg/mL in sterile buffer (PBS, HPBS, DPBS, and EBSS) containing carrier protein such as 1% BSA or HSA. After dilution, the cytokine can be stored between 2°C and 8°C for one month or from -20°C to -70°C for up to 3 months. Avoid repeated freeze/thaw cycles.
Bioactivity was measured by its property to chemoattract human neutrophils in a dose dependent manner.
CXCL7 is an ERL+ chemokine that is secreted by activated platelets, neutrophils, lymphocytes, and macrophages as a precursor. Pro-platelet basic protein or leukocyte derived grow factor (PPBP/LDGF) (a protein of ~14 kD) is modified by post-transcriptional cleavage to give rise to connective tissue activating peptide (CTAP-III), CXCL7, β-thromboglobulin (β-TG), and two variants of thrombocidin (TC-1 and TC-2). CTAP-III is activated by enzymatic proteolysis performed by cell surface-bound cathepsin G (CathG), a chymotryptic serine protease found in primary neutrophil granules. In this way, neutrophils are the mayor cells that convert CTAP-III into CXCL7. In addition, monocytes and mast cells can proteolytically modify CTAP-III to produce CXCL7. In fact, CathG has been detected in mast cells in addition to chymase, another chymotryptic enzyme. Further C-terminal truncations, that eliminate the last four and seven amino acids in CXCL7, generate two additional natural isoforms; these variants are more potent neutrophils activators.
High levels of CTAP-III have been detected in plasma of patients with lung cancer. In fact, it has been suggested as a biomarker for early lung cancer detection. An increase in positive immunostained cells has been detected in the bronchial submucosa of patients with stable severe chronic obstructive pulmonary disease. Also, studies with premalignant breast cancer cells transfected with CXCL7 showed that these cells became as invasive as malignant breast cancer cells. In addition, CXCL7 induces stimulation of the lymphangiogenic factors VEGF-C and VEGF-D in human breast cancer cells, suggesting an important role for CXCL7 in tumor invasion.
CXCL7 stimulates chemotaxis and degranulation in neutrophils, induces transendothelial migration and neutrophil adhesion to activated endothelial cells, and has angiogenic activity. LPS induces the precursor in PBMCs.
1. Iida N, et al. 1996. FASEB J. 10:1336. 2. Schenk BI, et al. 2002. J. Immunol. 169:2602. 3. El-Gedaily A, et al. 2004. J. Leukoc. Biol. 75:495. 4. Schiemann F, et al. 2006. Blood 107:2234.
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