CTAP-III/CXCL7

CXCL7 is a platelet-derived growth factor that belongs to the ELR⁺ CXC chemokine family, functioning as a potent chemoattractant and activator of neutrophils through binding to its receptor CXCR2^[1].
CXCL7, a member of the CXC chemokine subfamily, is translated as a proprotein and cleaved into several smaller forms, each with particular functions. In humans, the CXCL7 gene is translated as a 14 kDa proprotein, designated leucocytederived growth factor (LDGF), which is cleaved into several smaller forms, platelet basic protein (PBP), connective tissue activating protein III (CTAP-III) and β-thrombogulin (β-TG), and NAP-2. The longest form, PBP or LDGF, is expressed in platelets and megakaryocytes and is reported to be a fibroblast mitogen. CTAP-III is a 85 amino acid protein and can be converted to 70 amino acid NAP-2 by enzymatic removal of 15 residues. CTAP-III is suggested to support megakaryocyte maturation and platelet production and is involved in resistance to mycobacteria by augmenting reactive oxygen production. NAP-2, the smallest protein in this series, is a neutrophil-activating mediator, stimulating functions such as lysosomal enzyme degranulation, but is reported to inhibit megakaryocytopoiesis^[2].
CXCL7 has been demonstrated to participate in a variety of cellular processes, such as DNA synthesis, glycolysis, mitosis, intracellular cAMP accumulation, prostaglandin E2 secretion, as well as the synthesis of hyaluronic acid and plasminogen activator. Moreover, it is also an antimicrobial protein with bactericidal and antifungal activity. Recently, CXCL7 has been found to be deregulated in human cancers, and plays a role in tumor growth. For instance, CXCL7 is found to promote the growth of clear cell renal cell carcinoma. The CXCL7/CXCR2 signaling plays a promoting role in several common malignancies, including lung, renal, colon, and breast cancer^[1].

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