Biological activities of a novel lectin derived from silkworm faeces: characteristic changes of mouse peritoneal macrophages by the lectin.
A novel lectin derived from silkworm faeces, named NUE, activates phagocytosis of mouse peritoneal macrophages. At this time, significant morphological changes of the cells take place. NUE-treated macrophages formed projection-like neurocytes within 12 hr of treatment, and appeared somewhat flat in shape with the activation of cell growth. Associated with the morphological changes, actin was organized in dot-like structures corresponding to cell-substratum contact sites in NUE-treated macrophages. Vinculin, a cytoskeletal protein involved in microfilament-membrane interaction, formed doughnut-like rings matching the actin-dots, called "podosomes". Furthermore, observation by interference reflection microscopy showed that NUE-treated macrophages adhered more strongly to the substratum at local areas. According to these changes, more proteins associated with cell-substratum contact sites became to detergent-resistant. It was shown that NUE changed adhesive form of mouse peritoneal macrophages structurally and qualitatively.