Subcellular distribution of annexins, gelsolin and filamentous actin in adherent human neutrophils during phagocytosis

• Subcellular elevations of cytosolic free calcium concentration ([ea2+];), are critical for certain functional responses within the neutrophil, such asfilamentous actin (F-actin) reorganization and phagolysosome fusion (PLF). During this event, an accumulation of phospholipid- and calciumbinding proteins, annexins, can be seen in the periphagosomal area. A prerequisite for phagolysosome fusion is the elimination of F-actin around the phagosomes to facilitate the membrane contact between lysosomes and phagosomes. Gelsolin is a protein that severs F:actin by binding to the barbed ends, and thereby affect further polymerization. In this study, we used immunofluorescence staining and immunogold technique to analyse the distribution of annexin I, annexin III and gelsolin, in relation to the rearrangement ofF-actin during phagocytosos of complement-opsonized yeast particles by adherent human neutrophils. Iu unchallenged cells, both the aunexins and gelsolin were evenly distributed throughout the cells, whereas F-actin was found mostly in the protruding pseudopodia. Upon phagocytosis an accumulation of both. annexin I and annexin III, and gelsolin could be seen w1thm the vicimty of the phagocytic cups and phagosomes where they colocalized with Factin around the ingested particle.In calcium-depleted cells, the subcellular distributions of annexins and gelsolin were unaffected. On the other hand, there was a total increase inF-actin polymerization.Our data may indicate that gelsolin is important for the rearrangement of F-actin and that annexin I and annexin III, which are present in high concentrations in neutrophils, may participate in the following calciumdependent PLF in human neutrophils.

Nyckelord

Annexins

Ca2

F-actin

gelsolin

phagocytosis

MEDICINE

MEDICIN

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vet (ämneskategori)

ovr (ämneskategori)