CPO is often found on the nuclear envelope and aggregates upon serum starvation.

MDCK cells stably expressing CPO were fixed and immunostained with an antibody to CPO (red in A, B and D; white in C, E,F) and with BODIPY 493/503 to detect lipid droplets (green in B and D). Both wild-type CPO (A) and the inactive W297L CPO mutant (B) were often detected in a reticular pattern on the nuclear envelope. This nuclear envelope association was dramatically increased upon serum starvation. Control cells presented the usual punctate pattern with some lipid droplet association (C, D), while serum starvation for 24 hours resulted in large aggregates of CPO on the nuclear envelope (see nuclear cross-section in E and nuclear surface in F).