Effects of diethyldithiocarbamate on calmodulin in neuroblastoma cells

Diethyldithiocarbamate (DDC) was used to treat the neuroblastoma cell line Neuro-2a. Cell injury caused by DDC affects the calcium-binding protein calmodulin (CaM) and alters copper homeostasis in these cells. Neuro-2a cells were treated with 1 x 10(-5) M DDC for 1 h and were harvested at various time points over a 24-h period. Light microscopy of control cells showed CaM deposited around the cell periphery and along the neuritic processes. Treated cells showed the same distribution until 3 h after treatment. Electron microscopy showed CaM deposited around the cell periphery and within the cytoplasm and nucleus of control cells. Treated cells showed a time-dependent localization of CaM in relation to cellular disorganization. Staining of electrophoretic transfers by ProtoGold showed that CaM was present in all control samples and treated samples through 6 h. Atomic absorption spectrophotometry showed no difference in calcium levels between control and treated samples, but copper levels were significantly elevated. This study indicated that degenerative changes induced by DDC altered calmodulin levels. These changes may have been caused by elevated copper content within the cells and subsequent cell injury.