Regulation of intracellular lysosomal movements by the cytoskeletal system in rat alveolar macrophages.

Abstract

Saltatory intracellular lysosomal movements were enhanced by both fluid-phase pinocytosis (horseradish peroxidase; HRP) and adsorptive pinocytosis (peroxidase anti-peroxidase; PAP) in cultured rat alveolar macrophages. To elucidate the role of cytoskeletal elements in the regulatory mechanism of lysosomal movements related to the autophagy and heterophagy, the effects of actin filament destabilizers (cytochalasin B, D) and antimicrotubular drugs (colchicine, nocodazole) on the lysosomal movement induced adsorptive pinocytosis of PAP were investigated by cytochemical electron microscopy.In the cultured alveolar macrophages, the pinocytosis of PAP promoted lysosomal movements and the extension of nematolysosomes (thread-like lysosomes) within the cytoplasm. The actin filament destabilizers inhibited these lysosomal movements and forming process of nematolysosomes, while the drugs had little or no inhibitory effect on pinocytosis of PAP. The antimicrotubular drugs also had an inhibitory effect on the appearance of nematolysosomes. Moreover, these drugs led to another type of lysosomal transformation, i.e., wrapping lysosomes which are thought to be one process of autophagy.The present study using actin filament destabilizers and antimicrotubular drugs clarifies two distinct types of lysosomal transformations, which are nematolysosomes and wrapping lysosomes. It is suggested that cytoskeletal elements play an important role in regulating the movement and transformation of lysosomes in the macrophages.