Inside Out: How Cellular Localisation Shapes cGAS Functions in Health and Disease

The function of innate immune sensors is intricately shaped by their spatial distribution within cells. cGAS (cyclic GMP-AMP synthase), a key cytosolic DNA sensor, illustrates this principle through its unexpected localisation to diverse organelles-including the nucleus, micronuclei, mitochondria, and plasma membrane. In these compartments, cGAS assumes distinct regulatory states and executes specialised functions. For instance, chromatin-bound nuclear cGAS remains inactive under homeostasis but contributes to genome maintenance during genotoxic stress, whereas mitochondrial or micronuclear cGAS links damage signals to inflammation and cell death. This review synthesises recent advances in the spatial regulation of cGAS, focusing on mechanisms such as membrane interactions and post-translational modifications. We further reframe cGAS as a multifunctional regulator in infection, cancer, autoimmunity, and ageing, and introduce a unifying 'location code' framework. This framework proposes that the combined influence of PTMs, protein interactions, and membrane affinities dictates cGAS localisation, functional output, and pathological outcomes, thereby paving the way for spatially informed therapeutic interventions.