Ca2+-dependent autophagy is enhanced by the pharmacological agent PK11195 Pharmacological tools in autophagy

The 1-(2-Chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide, PK11195, is a proven enhancer of apoptotic cell death in a variety of cellular models. Recently, we have shown that by targeting the oncogene Bcl-2, PK11195 increases the [Ca2+] in the endoplasmic reticulum ([Ca2+](er)) as well as IP3 induced mitochondrial ([Ca2+](m)) and cytosolic ([Ca2+](c)) Ca2+ transients in HeLa cervix carcinoma cells. Here, in the same cells, we have investigated PK11195 contribution to models of pharmacologically induced macroautophagy. To do so, we have monitored the pattern of LC3 (the mammalian orthologue of yeast Atg8) distribution and post-transcriptional modifications after challenging with Ca2+ dependent (ATP, vitamin D3) and independent (rapamycin and H2O2) stimuli for autophagy execution. We found that PK11195 plays a pro-autophagy role if associated with ATP and vitamin D3 to be ineffective if co-incubated with rapamycin and H2O2. Notably, Bcl-2 deletion abolished PK11195 effects, thus suggesting a selective way of action against the oncogene. By these means, PK11195 is proposed as a facilitator of Ca2+-mediated autophagy and a tool to ascertain the Bcl-2 contribution to the onset and unfolding of this essential catabolic process for cellular homeostasis.