MAJOR COLOCALIZATION OF THE EXTRACELLULAR-MATRIX DEGRADATIVE ENZYMES HEPARANASE AND GELATINASE IN TERTIARY GRANULES OF HUMAN NEUTROPHILS

The expression of cell-surface adhesion proteins and the release of ex tracellular-matrix degradative enzymes constitute crucial processes fo r the attachment of neutrophils to the endothelium and for the subsequ ent extravasation of these cells through the endothelial layer. We hav e analysed in resting human neutrophils the subcellular localization o f heparanase, a heparan-sulphate-degrading endoglycosidase that can de grade basement-membrane components, thereby facilitating neutrophil pa ssage into the tissue during an inflammatory reaction. By subcellular fractionation of postnuclear supernatants from resting human neutrophi ls on continuous sucrose gradients, we have found that heparanase acti vity was mainly located in gelatinase-containing tertiary granules, Us ing a specific antibody, the 96-kDa heparanase protein was further loc ated in the gelatinase-rich subcellular fractions. Following immunoblo tting and immunoprecipitation analysis in the distinct subcellular fra ctions, we also found colocalization of heparanase and Mol (CD11b/CD18 ), a leucocyte integrin involved in the attachment of neutrophils to t he endothelium, in the fractions enriched in gelatinase-containing ter tiary granules. Treatment of human neutrophils with tumour necrosis fa ctor or granulocyte/macrophage colony-stimulating factor induced an in crease in the CD11b/CD18 cell-surface expression, as well as the relea se of both gelatinase (matrix metalloproteinase-9) and heparanase, but not of other granule markers, indicating a major co-localization of g elatinase, heparanase and CD11b/CD18 in the same organelle. Furthermor e, confocal laser scanning microscopy using specific antibodies agains t gelatinase and heparanase revealed a major co-localization of both e nzymes in intracellular cytoplasmic granules. The major localization o f heparanase and CD11b/CD18 in the gelatinase-containing tertiary gran ule supports the notion that mobilization of this organelle can regula te extravasation of human neutrophils.