H-7-induced apoptosis in the cells of a Drosophila neuronal cell line through affecting unidentified H-7-sensitive substance(s).

The present study was undertaken to reveal underlying mechanisms of apoptosis in neurons using clonal neuronal cells, ML-DmBG2-c2, derived from Drosophila larval central nervous system 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine (H-7), a protein kinase inhibitor, induced cell death with typical features of apoptosis such as internucleosomal DNA fragmentation, nuclear condensation and apoptotic bodies in the cells. Though H-7 is known to inhibit cAMP-dependent protein kinase (PKA), protein kinase C (PKC), cGMP-dependent protein kinase (PKG), myosin light chain kinase (MLCK), and casein kinase I (CKI), specific inhibitors for these kinases such as H-89, calphostin C, ML-9, or CKI-7 did not induce apoptosis in the cells. Other kinases such as tyrosine kinase. PI3-kinase and Ca2+/CaM kinase II so far examined in the present study were interpreted not to be involved in the apoptotic cascade. Therefore, it is concluded that an H-7-sensitive substance(s) other than these kinases is responsible for the apoptosis in the neuronal cells. Caspase inhibitors prevented apoptosis in the cells treated with H-7. These results suggest that caspase(s) is involved downstream of the H-7-sensitive point in the cascade of the apoptosis.