The intracellular distribution patterns of myosin and actin are different among human neutrophils and monocytes during locomotion

Abstract

BACKGROUND AND OBJECTIVE: Neutrophils and monocytes initiate their characteristic ameboid movement by using mechanochemical systems of contractile proteins. It is known that neutrophils and monocytes exhibit differing patterns of motility. We set out to determine whether these differences may be associated with the intracellular distribution of myosin and actin, the principle components of the cellular apparatus involved in motility. METHODS: Myosin and F-actin in human neutrophils and monocytes were observed at resting and motile stages by using a double-fluorescence staining procedure and a confocal laser scanning microscope. RESULTS: In motile neutrophils, myosin was distributed in the lamellipodia and the cytoplasm, observed as a speckled pattern, whereas F-actin was concentrated in the front of the lamellipodia and in the perinuclear area. In the motile monocytes, myosin was found in the wide lamellipodia and was seen to radiate from the cytoplasm towards the edges of the cell in a punctate pattern. F-actin was densely distributed along the leading edge of the wide lamellipodia as well as in the perinuclear region. No differences were apparent in the intracellular distribution of myosin and F-actin between the resting neutrophils and monocytes. INTERPRETATION AND CONCLUSIONS: Findings indicate that differing patterns of arrangement of myosin and actin in the lamellipodia and cytoplasm of neutrophils and monocytes may contribute to their movement, in vitro.