Changes in subcellular localization and surface expression of L-selectin, alkaline phosphatase, and Mac-1 in human neutrophils during stimulation with inflammatory mediators

Abstract

The localization of the adhesion protein L-selectin in human neutrophils was determined by sub-cellular fractionation and immunoelectron microscopy and compared with the localization of Mac-1 (α _m β _z ) and alkaline phosphatase, the marker for secretory vesicles. L-selectin was found to be localized exclusively on the plasma membrane of unstimulated cells and also of stimulated cells, although markedly diminished. This was in contrast to Mac-1, which was also localized in secretory vesicles and in specific/gelatinase granules as shown previously [Sengeiov, H., et al. J. Clin. Invest. (1993) 92, 1467–1476]. Stimulation of neutrophils with inflammatory mediators such as tumor necrosis factor (TNF), platelet-activating factor (PAF), or f-Met-Leu-Phe (fMLP), induced parallel up-regulation of the surface membrane content of alkaline phosphatase and Mac-1 and down-regulation of L-selectin, as evidenced by flow cytometry. Preimbedding immunoelectron microscopy confirmed that L-selectin was present mainly on tips of microvilli in unstimulated cells and showed that alkaline phosphatase and Mac-1 were randomly distributed on the surface membrane of fMLP-stimulated cells. These studies indicate that the transition of neutrophils from L-selectin-presenting cells to Mac-l-presenting cells induced by inflammatory mediators is mediated by incorporation of secretory vesicle membrane, rich in Mac-1 and devoid of L-selectin, into the plasma membrane. J. Leukoc. Biol. 56: 80–87; 1994.