Lipid trafficking sans vesicles: where, why, how?

Eukaryotic cells possess a remarkable diversity of lipids, which distribute among cellular membranes by well-characterized vesicle trafficking pathways. However, transport of lipids by alternate, or "nonvesicular," routes is also critical for lipid synthesis, metabolism, and proper membrane partitioning. In the past few years, considerable progress has been made in characterizing the mechanisms of nonvesicular lipid transport and how it may go awry in particular diseases, but many fundamental questions remain for this rising field.