There has been a growing
interest in nonvesicular pathways, which are particularly
important for mitochondria, plastids, and lipid droplets
since they receive little or no lipid by vesicular trafficking.
It is becoming increasingly clear that regions of close
apposition of organelle membranes, often called membrane
contact sites (MCSs), play critical roles in nonvesicular
lipid trafficking.
These zones, where
organelles typically come within 30 nm of one another,
are not only important for lipid trafficking but have long
been known to play important roles in calcium and other
signaling events.
Recent findings have revealed additional functions of MCSs in organelle inheritance, organelles
division and autophagy .