THE CYTOSKELETON OF DROSOPHILA-DERIVED SCHNEIDER LINE-1 AND KC23 CELLS UNDERGOES SIGNIFICANT CHANGES DURING LONG-TERM CULTURE

Insect cell cultures derived from Drosophila melanogaster are increasi ngly being used as an alternative system to mammalian cell cultures, a s they are amenable to genetic manipulation. Although Drosophila cells are an excellent tool for the study of genes and expression of protei ns, culture conditions have to be considered in the interpretation of biochemical results. Our studies indicate that significant differences occur in cytoskeletal structure during the long-term culture of the D rosophila-derived cell lines Schneider Line-1 (S1) and Kc23. Scanning, transmission-electron, and immunofluorescence microscopy studies reve al that microfilaments, microtubules, and centrosomes become increasin gly different during the culture of these cells from 24 h to 7-14 days . Significant cytoskeletal changes are observed at the cell surface wh ere actin polymerizes into microfilaments, during the elongation of lo ng microvilli. Additionally, long protrusions develop from the cell su rface; these protrusions are microtubule-based and establish contact w ith neighboring cells. In contrast, the microtubule network in the int erior of the cells becomes disrupted after four days of culture, resul ting in altered transport of mitochondria. Microtubules and centrosome s are also affected in a small percent of cells during cell division, indicating an instability of centrosomes. Thus, the cytoskeletal netwo rk of microfilaments, microtubules, and centrosomes is affected in Dro sophila cells during long-term culture. This implies that gene regulat ion and post-translational modifications are probably different under different culture conditions.