that membrane tubules facilitate the sorting of membrane-bound
cargo destined for recycling away from soluble cargo [18–20],
and previous studies have shown that PLA2 antagonists inhibit
the formation of membrane tubules containing Tf/TfR [13]. The
accumulation of Tf and LDLR in SEs in the presence of 10 lMantagonist
is consistent with the idea that membrane tubules are involved
in trafficking from SEs to the ERC. The inhibition of Tf/TfR
and LDLR export from the ERC by a low concentration of antagonist
suggests that PLA2-dependent membrane tubules are involved in
this export step. In addition, the fact that export from SE and ERC
is sensitive to different concentrations of antagonists suggests that
different PLA2 enzymes may operate at each location. Future studies
are aimed at identifying specific cytoplasmic PLA2 enzymes involved
in each of these steps.