A Small Molecule that Induces Intrinsic Pathway Apoptosis with Unparalleled Speed

Apoptosis is generally believed to be a process thatrequires several hours, in contrast to non-programmed forms of cell death that can occur in minutes. Our findings challenge the time-consuming nature of apoptosis as we describe the discovery and characterization of a small molecule, named Raptinal, which initiates intrinsic pathway caspase-dependent apoptosis within minutes in multiple cell lines. Comparison to a mechanistically diverse panel of apoptotic stimuli reveals that Raptinal-induced apoptosis proceeds with unparalleled speed. The rapid phenotype enabled identification of the criticalroles of mitochondrial voltage-dependent anion channel function, mitochondrial membrane potential/coupled respiration, and mitochondrial complex I, III, and IV function for apoptosis induction. Use of Raptinal in whole organisms demonstrates its utility for studying apoptosis invivo for a variety of applications. Overall, rapid inducers of apoptosis are powerful tools that will be used in a variety of settings to generate further insight into the apoptotic machinery. Palchaudhuri etal. describe the discovery of a small molecule called "Raptinal" that induces unusually rapid apoptotic cell death via the intrinsic pathway. Their work describes the utility of Raptinal as a tool for apoptosis induction relative to other available small molecules

Selective Small Molecule Inhibition of Poly(ADP-Ribose) Glycohydrolase (PARG)

The poly­(ADP-ribose) (PAR) post-translational modification is essential for diverse cellular functions, including regulation of transcription, response to DNA damage, and mitosis. Cellular PAR is predominantly synthesized by the enzyme poly­(ADP-ribose) polymerase-1 (PARP-1). PARP-1 is a critical node in the DNA damage response pathway, and multiple potent PARP-1 inhibitors have been described, some of which show considerable promise in the clinic for the treatment of certain cancers. Cellular PAR is efficiently degraded by poly­(ADP-ribose) glycohydrolase (PARG), an enzyme for which no potent, readily accessible, and specific inhibitors exist. Herein we report the discovery of small molecules that effectively inhibit PARG <i>in vitro</i> and in cellular lysates. These potent PARG inhibitors can be produced in two chemical steps from commercial starting materials and have complete specificity for PARG over the other known PAR glycohydrolase (ADP-ribosylhydrolase 3, ARH3) and over PARP-1 and thus will be useful tools for studying the biochemistry of PAR signaling

A Small Molecule that Induces Intrinsic Pathway Apoptosis with Unparalleled Speed

Apoptosis is generally believed to be a process that requires several hours, in contrast to non-programmed forms of cell death that can occur in minutes. Our findings challenge the time-consuming nature of apoptosis as we describe the discovery and characterization of a small molecule, named Raptinal, which initiates intrinsic pathway caspase-dependent apoptosis within minutes in multiple cell lines. Comparison to a mechanistically diverse panel of apoptotic stimuli reveals that Raptinal-induced apoptosis proceeds with unparalleled speed. The rapid phenotype enabled identification of the critical roles of mitochondrial voltage-dependent anion channel function, mitochondrial membrane potential/coupled respiration, and mitochondrial complex I, III, and IV function for apoptosis induction. Use of Raptinal in whole organisms demonstrates its utility for studying apoptosis in vivo for a variety of applications. Overall, rapid inducers of apoptosis are powerful tools that will be used in a variety of settings to generate further insight into the apoptotic machinery