SMOCs: supramolecular organizing centres that control innate immunity

The diverse receptor families of the innate immune system activate signal transduction pathways that are important for host defence, but common themes to explain the operation of these pathways remain undefined. In this Opinion article, we propose - on the basis of recent structural and cell biological studies - the concept of supramolecular organizing centres (SMOCs) as location-specific higher-order signalling complexes in which increased local concentrations of signalling components promote the intrinsically weak allosteric interactions that are required for enzyme activation. We suggest that SMOCs are assembled on various membrane-bound organelles or other intracellular sites, which may assist signal amplification to reach a response threshold and potentially define the specificity of cellular responses that are induced in response to infectious and non-infectious insults.