Lack of involvement of mitochondrial factors in caspase activation in a Drosophila cell-free system

Abstract

Although mitochondrial proteins play well-defined roles in caspase activation in mammalian cells, the role of mitochondrial factors in caspase activation in Drosophila is unclear. Using cell-free extracts, we demonstrate that mitochondrial factors play no apparent role in Drosophila caspase activation. Cytosolic extract from apoptotic S2 cells, in which caspases were inhibited, induced caspase activation in cytosolic extract from normal S2 cells. Mitochondrial extract did not activate caspases, nor did it influence caspase activation by cytosolic extract. Silencing of Hid, Reaper, or Grim reduced caspase activation by apoptotic cell extract. Furthermore, a peptide representing the amino terminus of Hid was sufficient to activate caspases in cytosolic extract, and this activity was not enhanced by addition of mitochondria or mitochondrial lysate. The Hid peptide also induced apoptosis when introduced into S2 cells. These results suggest that caspase activation in Drosophila is regulated solely by cytoplasmic factors and does not involve any mitochondrial factors.

Viral fibroblast growth factor, matrix metalloproteases, and caspases are associated with enhancing systemic infection by baculoviruses

“…For caspase activity assays, hemolymph was centrifuged at 960 × g for 5 min at 4°C to separate cells from hemolymph. Cells were resuspended in caspase buffer (24) and hemolymph was diluted 1:1 with caspase buffer. Protein concentration was determined using the BCA Protein Assay Kit (Thermo Scientific), and equal amounts of protein were used.…”

The Drosophila retinoblastoma protein, Rbf1, induces a debcl and drp1-dependent mitochondrial apoptosis.

“…Although early studies did not emphasize a crucial role of mitochondria during apoptosis in fly (Dorstyn et al, 2004;Means et al, 2006;Zimmermann et al, 2002), more recent data show that this organelle has a more substantial role. First, key players of Drosophila apoptosis are localized to mitochondria, including the caspases Dronc and Drice (Dorstyn et al, 2002) or the pro-apoptotic proteins Reaper (Freel et al, 2008;Olson et al, 2003;Thomenius et al, 2011), Hid (Abdelwahid et al, 2007;Morishita et al, 2013) and Grim (Claveria et al, 2002).…”

Caspase function in programmed cell death

“…In response to many apoptotic insults, Drosophila cells fail to show cytochrome c release and extensive RNAi, expression and biochemical data show that cytochrome c is not required for caspase activation and apoptosis in Drosophila cells. 42,[63][64][65][66] ARK can assemble into a large apoptosome complex in the presence of dATP. 67 However, cytochrome c is not required for the apoptosome assembly and fails to bind the complex.…”