Neutrophils can generate their activator neutrophil-activating peptide 2 by proteolytic cleavage of platelet-derived connective tissue-activating peptide III.
We have investigated the conditions that lead to the generation of the neutrophil-activating peptide 2 (NAP-2) from its precursor, the platelet-derived connective tissue-activating peptide III (CTAP-III). Lysed platelets were found to contain predominantly CTAP-III in the cytosolic fraction, but further truncated derivatives, among these NAP-2, occurred tightly bound to the membrane fraction of fresh platelets. NAP-2 biological activity, as measured by the induction of enzyme release in human neutrophils [polymorphonuclear leukocytes (PMN)] was released by stimulated platelets to a low degree. Much higher activities were formed in the presence of peripheral blood leukocytes. Coincubation of CTAP-III with PMN resulted in the almost complete conversion of the precursor to NAP-2, as did incubation of CTAP-III with PMN-conditioned medium. In both situations, the generation of NAP-2 could be prevented by serine-protease inhibitor phenylmethylsulfonyl fluoride but not by inhibitors specific for Ca(2+)-dependent or thiol proteases. From several PMN-derived proteases tested, only cathepsin G had the capacity to cleave CTAP-III into NAP-2 with high specificity and in a relatively short period of time (30 min). Our data indicate that NAP-2, released by platelets in small quantities, could cause PMN to enter into a positive feedback cycle by initiating the secretion of serine proteases, which in turn could convert platelet-derived CTAP-III into biologically active NAP-2.
Brandt
E
E
Forschungsinstitut Borstel, Department of Immunology and Cell Biology, Germany.
Van Damme
J
J
Flad
H D
HD
D000595:Amino Acid Sequence; D001779:Blood Coagulation Factors / Q000737:chemistry / Q000378:metabolism; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D016209:Interleukin-8 / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism; D010455:Peptides; D012697:Serine Endopeptidases / Q000378:metabolism; D013347:Subcellular Fractions / Q000276:immunology / Q000378:metabolism
D001779:Blood Coagulation Factors; D016209:Interleukin-8; D010455:Peptides; C009862:connective tissue-activating peptide; C018329:low affinity platelet factor 4; D012697:Serine Endopeptidases