Microscopic co-distributions of myosin, actin, alpha-actinin and vinculin in human neutrophils during movement.

Human neutrophils initiate their characteristic ameboid movement in response to external stimuli via a mechanochemical system of contractile proteins using mechanical energy derived from hydrolysis of adenosine triphosphate. We have visualized contractile proteins, including myosin, filamentous actin (F-actin), alpha-actinin, tropomyosin, and vinculin in human neutrophils during movement by fluorescence microscopy using double immunofluorescence staining procedures of fluorescein isothiocyanate-labeled antibodies, rhodamine-labeled antibodies, or rhodamine-conjugated phalloidin. From dual color images, both myosin and F-actin, both alpha-actinin and F-actin, both vinculin and F-actin showed co-localization, both myosin and alpha-actinin showed a partial co-localization, at the leading edge in the lamellipodia, and both vinculin and alpha-actinin were co-localized at the leading edge and appeared reciprocally at regular intervals in the lamellipodia. Our observations indicate that most of myosin, F-actin, alpha-actinin, and vinculin are focused in order to reorganize dynamically at the leading edge in the lamellipodia, and a motile apparatus is reconstituted there, when neutrophils start to move toward external substances.