Relationship between lysosomal wrapping mechanism (LWM) and cytoskeletal elements during autophagolysosome formation
Acta Histochemica et Cytochemica
The relation of cytoskeletal elements to the lysosomal wrapping mechanism (LWM) was investigated by using so-called tubulolytic agents (colchicine, vinblastine or nocodazole), a microfilament destabilizer (cytochalasin B) and a microfilament stabilizer (phalloidin) during autophagy in mouse subcutaneous histiocytes, which was induced by a subcutaneous injection of ovalbumin. Pretreatment with the tubulolytic agents not only did not inhibit an occurrence of the LWM following ovalbumin injection,
... valbumin injection, but induced the LWM even without ovalbumin injection. On the other hand, pretreatment with the destabilizer or the stabilizer of microfilaments prevented the occurrence of LWM induced by ovalbumin. The direct morphological connection between actin-like microfilaments and lysosomes performing the LWM was observed in histiocytes in specimens treated with sodium dodecyl sulfate or saponin. These results suggest that depolymerization or disorganization of microtubules induces or favors the occurrence of LWM, and that the presence of intact microfilaments, but not microtubules, is necessary for the occurrence of the LWM induced by ovalbumin. The lysosomal wrapping mechanism (LWM) is the process which can be observed in connection with the autophagolysosome formation during autophagy. It was initially observed in histiocytes in the subcutaneous tissue of mice injected with horseradish peroxidase subcutaneously in the lower abdominal region (21, 22) . The LWM is represented by a direct wrapping of the locally degenerating cytoplasmic area or organellae to be autophagocytozed by pre-existing primary or secondary lysosomes. In other words, pre-existing lysosomes form tail-or arm-like extensions, and extend or flatten thinly to wrap around the cytoplasmic area which 1.