A Prickly Subject: Apoptotic Regulation by Hedgehog Morphogens

Morphogens, as intercellular signalling proteins, provide a non-cell-autonomous mechanism to impart positional information to cells and govern essential cellular processes such as apoptosis. Individual morphogen pathways utilise diverse strategies to regulate the assembly and activity of the pro-apoptotic multi-protein complexes – namely the apoptosome and the death-inducing signalling complex (DISC). This review aims to highlight the apoptotic regulatory mechanisms utilised by the Hedgehog (HH) morphogen pathway – with particular emphasis on a novel Caspase-9 activating complex and the utilisation of a pro-apoptotic autocrine-signalling loop.