Vesicle trafficking and RNA transfer add complexity and connectivity to cell-cell communication

Cell-cell communication, either in direct proximity or at a distance, generally occurs by receptor-ligand engagement and subsequent activation of downstream intracellular signaling cascades. This conventional, largely protein-based, model has long been considered necessary and sufficient to explain coordinate tissue and organismal function. Intriguing recent work indicates that many cells can also transfer RNA directly via cell-cell trafficking of nanometer-sized, lipid-bilayer vesicles. The distinct biogenesis pathways that give rise to the different vesicle types described to date are just beginning to be elucidated. Notwithstanding their diverse origin, all types of vesicles seem to contain a broad, cell-specific, nonrandom representation of cellular protein and RNA species. The cell-cell trafficking of coding and small noncoding RNAs in particular constitutes a new paradigm for the direct phenotypic modulation of cells in the local microenvironment and in distal organs. Here, we review the current understanding of RNA vesicle trafficking and its emerging role in cell-cell signaling.