Centriolar satellite biogenesis and function in vertebrate cells

Centriolar satellites are non-membranous cytoplasmic granules that concentrate in the vicinity of the centrosome, the major microtubule-organizing centre (MTOC) in animal cells. Originally assigned as conduits for the transport of proteins towards the centrosome and primary cilium, the complexity of satellites is starting to become apparent. Recent studies defined the satellite proteome and interactomes, placing hundreds of proteins from diverse pathways in association with satellites. In addition, studies on cells lacking satellites have revealed that the centrosome can assemble in their absence, whereas studies on acentriolar cells have demonstrated that satellite assembly is independent from an intact MTOC. A role for satellites in ciliogenesis is well established; however, their contribution to other cellular functions is poorly understood. In this Review, we discuss the developments in our understanding of centriolar satellite assembly and function, and why satellites are rapidly becoming established as governors of multiple cellular processes. We highlight the composition and biogenesis of satellites and what is known about the regulation of these aspects. Furthermore, we discuss the evolution from thinking of satellites as mere facilitators of protein trafficking to the centrosome to thinking of them being key regulators of protein localization and cellular proteostasis for a diverse set of pathways, making them of broader interest to fields beyond those focused on centrosomes and ciliogenesis.