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  • Title: Connective tissue-activating peptide III desensitizes chemokine receptors on neutrophils. Requirement for proteolytic formation of the neutrophil-activating peptide 2.
    Author: Härter L, Petersen F, Flad HD, Brandt E.
    Journal: J Immunol; 1994 Dec 15; 153(12):5698-708. PubMed ID: 7989767.
    Abstract:
    The connective tissue-activating peptide III (CTAP-III), which is released from activated platelets, represents an inactive precursor of the chemokine neutrophil-activating peptide 2 (NAP-2). Leukocytes and leukocyte-derived proteases have been found to convert CTAP-III into NAP-2 by proteolytic cleavage at the N terminus. We demonstrate here that rapid and efficient formation of NAP-2 is mediated by neutrophil granulocytes (PMN) but not by monocytes or lymphocytes. However, as seen in a degranulation assay, neutrophils processing CTAP-III did not become activated by the generated NAP-2 and even exhibited decreased responsiveness to high doses of NAP-2 or IL-8, but not to FMLP. The desensitizing effect, being maximal already after 5 min of preincubation with CTAP-III, was not mediated through binding of the precursor to specific receptors but correlated with the rapid down-modulation of common NAP-2/IL-8 high affinity binding sites. A similar functional and receptor desensitization was observed in PMN pre-exposed to nonstimulatory doses of NAP-2. Specific inhibition of the CTAP-III-cleaving enzyme by the serine protease inhibitor aprotinin abrogated the CTAP-III, but not the NAP-2-mediated effects. Desensitization of PMN by CTAP-III was due to NAP-2 generated by proteolytic truncation of CTAP-III. Our results suggest that CTAP-III may regulate PMN activation by protecting processing cells from premature activation.
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