Turning ON Caspases with Genetics and Small Molecules

Abstract

Caspases, aspartate-specific cysteine proteases, have fate-determining roles in many cellular processes including apoptosis, differentiation, neuronal remodeling, and inflammation (for review, see Yuan & Kroemer, 2010). There are a dozen caspases in humans alone, yet their individual contributions toward these phenotypes are not well understood. Thus, there has been considerable interest in activating individual caspases or using their activity to drive these processes in cells and animals. We envision that such experimental control of caspase activity can not only afford novel insights into fundamental biological problems but may also enable new models for disease and suggest possible routes to therapeutic intervention. In particular, localized, genetic, and small-molecule-controlled caspase activation has the potential to target the desired cell type in a tissue. Suppression of caspase activation is one of the hallmarks of cancer and thus there has been significant enthusiasm for generating selective small-molecule activators that could bypass upstream mutational events that prevent apoptosis. Here, we provide a practical guide that investigators have devised, using genetics or small molecules, to activate specific caspases in cells or animals. Additionally, we show genetically controlled activation of an executioner caspase to target the function of a defined group of neurons in the adult mammalian brain.

Medial Amygdalar Aromatase Neurons Regulate Aggression in Both Sexes

“…We first ablated these neurons in adult mice via bilateral targeted delivery to the MeA of an AAV encoding a genetically modified caspase-3 whose activation requires Cre recombinase (Figure 2A) (Yang et al, 2013). Activation of this caspase-3 triggers apoptosis exclusively in Cre+ cells without bystander toxicity to neighboring cells not expressing Cre (Morgan et al, 2014; Nelson et al, 2014; Yang et al, 2013). Only those aro Cre males with a substantive loss (>50% loss bilaterally) of aromatase+ MeApd neurons were included for analysis of behavioral performance (Figure 2B–D, S1A–F).…”

“…However, we consistently observed only a few weakly expressing mCherry+ neurons within the MeApd of aro Cre/IPIN females (data not shown), presumably reflecting the lower levels of aromatase in the female brain. Given that caspase-3 is extremely cytotoxic (Morgan et al, 2014), it is not surprising that despite the lower efficiency of Cre recombination in females, we succeeded in ablating aromatase+ MeApd neurons. In any event, our findings demonstrate that aromatase+ MeApd neurons are required for WT-levels of maternal aggression.…”

Genetic dissection of neural circuits underlying sexually dimorphic social behaviours

“…Importantly, this caspase-3-induced apoptosis is restricted to Cre-expressing neurons and spares neighbouring neurons that do not express aromatase (Cre) [37][38]121]. Ablation of these neurons in males significantly reduced specific components of male-typical aggression while male-typical mating behaviours were unaffected, whereas ablation of these neurons in females significantly reduced specific components of maternal aggression while maternal care and femaletypical mating behaviours were unaffected.…”

“…Aromatase itself is required for the normal display of male-typical mating and aggression behaviours [117 -120]. To study the functional significance of the aromatase-expressing neuronal subpopulation within the MeApd, we specifically ablated these neurons in adult mice [38], using a virally encoded Cre-dependent designer executioner caspase-3 [37,121]. These studies were done in genetically modified mice that we generated in order to express Cre in aromatase-expressing cells (aro cre mice).…”

Induction of apoptosis and erythroid differentiation of human chronic myelogenous leukemia K562 cells by low concentrations of lidamycin

“…The most important factor in the mechanism of apoptosis is the activation of caspases. Caspases are proteases that participate in the control of cell growth and apoptosis (22). Caspase-8 and caspase-9 are caspases upstream of the apoptosis signal transduction process, while caspase-3 is downstream, and all of these are effector molecules of cell apoptosis (23).…”